A century's worth of records suggests that hurricanes are on the rise and a warming Atlantic is to blame

Using records dating back to 1855, hurricane researchers say they have uncovered an ongoing rise in the number of Atlantic hurricanes that tracks the increase in sea surface temperature related to climate change. Critics of such a link argue that this trend is merely because of better observations since the dawn of the satellite era in the 1970s. But the authors of the new study say the conclusion is hard to dodge.

"Even if we take the extreme of these error estimates, we are left with a significant trend since 1890 and a significant trend in major hurricanes starting anytime before 1920," say atmospheric scientists Greg Holland of the National Center for Atmospheric Research in Boulder, Colo., and Peter Webster of the Georgia Institute of Technology in Atlanta.

Update: You can read Holland and Webster's full paper here. [.pdf]. Chris Landsea (specialist with the National Hurricane Center) post a rebuttle here [.pdf] (interestinly enough, prior to the paper's release). Further discussion on both items can be found at Chris Mooney's blog, The Intersection.

More on this news item at National Geographic and New Scientist (UK). For further information, please see the links to the researchers' pages included above. Also, see Chris Mooney's recent book Storm World for more on the history of hurricane study, meteorology and climate science (my current reading).

[I'm going to be very strict in whatever I post here in the future. The public discussion for this seed is for related links and discussion of the science only. Non-related items, friendly or not, will be deleted unless relegated to a separate discussion. In other words, if you feel a need to comment on me or deny otherwise sound science, then clip this to some other group and start a new, private thread. Otherwise, your comment will be deleted. You have been warned. If you are in doubt, then don't post your comment.]

Forests, after all, cool the atmosphere by drinking in carbon dioxide from the air. A new study, however, published in Proceedings of the National Academy of Sciences reports that forests' other climatic effects can cancel out their carbon cleaning advantage in some parts of the world. Using a three-dimensional climate model, the research team mimicked full global deforestation and also studied the effects of clear-cutting in different regions of latitude, such as the tropics and boreal zones. Apparently, these natural carbon sinks only do their job effectively in tropical regions; in other areas, they have either no impact or actually contribute to warming the planet. In fact, according to this model, by the year 2100, if all the forests were cut and left to rot, the annual global mean temperature would decrease by more than 0.5 degree Fahrenheit.

Africa, the continent most vulnerable to the effects of climate change, is not acting urgently enough to stem the dire economic and environmental damage of greenhouse gas emissions, the UN cautioned Tuesday.

The warning came after the Intergovernmental Panel on Climate Change (IPCC) released a report Friday detailing the impacts of global warming, which, it said, will wreak the most havoc on the world's poor.

"This report is a drastic message about the impact of climate change on the economic development of this continent," UN Environment Programme chief Achim Steiner told a press conference in Nairobi.

"Africa is on the frontlines of having to cope with the reality of climate change – not in the future, but today," Steiner added.

The second report of the Intergovernmental Panel on Climate Change reveals that global warming impacts are already advancing, and will get worse

From space, climate change is obvious. For more than 20 years satellite images have shown springtime greenery bursting forth earlier and earlier in that season. Thanks to global warming, the growing season is lengthening in many parts of the world. And though this may boost crop yields in some areas, it will have a host of other, less benign impacts, such as transforming the eastern Amazon from rain forest to savanna, according to the second report from the Intergovernmental Panel on Climate Change (IPCC).

Spring is coming early to the western slope of Colorado's Rocky Mountains, providing continuing signs of a warming world, according to a conservation biologist.

"I'm anticipating there'll be some flowering again in April this year, which is something that never used to happen," said David Inouye, a professor at the University of Maryland in College Park.

This will be Inouye's 37th season at the Rocky Mountain Biological Laboratory (RMBL) in Gothic, outside the resort town of Crested Butte.

Dozens of scientists make the annual trek to a meadow at RMBL about 9,500 feet (2,900 meters) above sea level to study everything from wildflowers to marmots.

Many of the studies indicate a warming planet.

In addition to the early flowers, robins return earlier from their wintering grounds, and marmots, chipmunks, and ground squirrels emerge earlier from hibernation than they once did, the scientists say.

How might U.S. national security be threatened by mega-droughts, coastal flooding, killer hurricanes, food scarcity and the other ecological calamities scientists widely predict will occur if global warming continues apace?

No one knows, but Sens. Chuck Hagel, R-Neb., and Dick Durbin, D-Ill., think it's time to find out. Two weeks ago, the bipartisan duo introduced a bill that would require federal intelligence agencies to collaborate on a National Intelligence Estimate to evaluate the security challenges presented by climate change.

UK fungi season now longer in autumn, with an extra fruiting in spring.

Climate change could turn the autumnal fungus foray in Britain into a year-round event, say researchers who have recorded changes in fruiting patterns over the past half-century.

In the autumn, the UK mushroom season has doubled in length, from about 33 days in the 1950s, to nearly 75 days now, they say. Fungi are starting to fruit earlier, and finishing later.

And some species are fruiting in both spring and autumn — a unique development in response to rising temperatures, says Alan Gange of Royal Holloway, University of London. Although it has been shown that climate change is making birds nest and flowers bloom earlier, he knows of nothing else that has added a complete extra breeding season to its life cycle.

Global warming threatens to extinguish hundreds of millions of human lives and nearly a third of the planet's wildlife, an international panel of climate scientists said in a report issued today.

The Intergovernmental Panel on Climate Change (IPCC) warned that the world's poorer nations face spiraling rates of death and disease due to increased risk of droughts, floods, storms and other severe climate effects spurred by human-caused greenhouse gas emissions.

Up to 30 percent of animal and plant species could be wiped out by a global temperature rise of 2.7 to 4.5 degrees Fahrenheit (1.5 to 2.5 degrees Celsius), experts said.

The IPCC forecasts a rise of between 3.2 and 7.1 degrees Fahrenheit (1.8 and 4 degrees Celsius) by the end of this century.

The new findings, based on the work of some 2,500 scientists in more than 130 countries, follow an IPCC statement in February that global warming is "unequivocal" and that human activity is almost certainly the cause.

Climate change is not a future problem but a present one that must be tackled now, concludes the latest chapter of a major climate report.

The report details how different amounts of global warming, ranging from 0°C to 5°C will impact on human society. It also underlines that those who will be most affected are the poor people who are least responsible for increasing levels of greenhouse gas emissions in the atmosphere. Read the summary for policy makers (PDF).

The warming of other solar bodies has been seized upon by climate sceptics; but oh how wrong they are, says Oliver Morton.

If the shooting of fish in barrels offends you, look away. The publication this week of a Nature paper on global warming on Mars offers a fantastic opportunity to kill off one of the silliest climate-sceptic arguments, and I'm more than happy to be pointing the gun at the water.

The sceptical 'argument' — using the word loosely — in question is that global warming on Earth should be seen as a natural, as opposed to anthropogenic, phenomenon because other planets and moons in the Solar System are getting warmer, too (which, indeed, they are). Since what the planets have in common is the Sun, they say, it must thus be the Sun that is driving the warming.

But despite longstanding treaty commitments to help poor countries deal with warming, these industrial powers are spending just tens of millions of dollars on ways to limit climate and coastal hazards in the world's most vulnerable regions — most of them close to the equator and overwhelmingly poor.

But despite longstanding treaty commitments to help poor countries deal with warming, these industrial powers are spending just tens of millions of dollars on ways to limit climate and coastal hazards in the world's most vulnerable regions — most of them close to the equator and overwhelmingly poor.

There is evidence that the world is already feeling the effects of climate change and has been for the past decade. This is what hundreds of UN-backed scientists and politicians will say on Friday 6 April, a source involved in last-minute discussions taking place in Brussels, Belgium, told New Scientist.

The latest report of the Intergovernmental Panel on Climate Change (IPCC) is the first to be based on observations of recent changes in weather, rather than computer-model-based forecasts of future climate.

Dust storms and dark rocks are making the red planet hotter.

Mars is getting hotter. Measurements of the brightness of the planet's surface over the show that the thermometer has ratcheted up some 0.65 °C over a few decades.

Lori Fenton at the Carl Sagan Center, Mountain View, California, and colleagues looked at maps of Mars's 'albedo', a measure of how much light reflects off a surface. By comparing a map from 1976-78 with one from 1999-2000, they found "some pretty dramatic changes", says Fenton. In particular, the southern highlands region of Mars had darkened significantly.

Darkness and heat feed on each other in new simulations that predict a 20-year warming trend on the Red Planet

A darkening of the Martian surface may have slowly warmed the planet over the past 20 years. Based on a model of the Red Planet's climate, researchers report that the brightness or darkness of its sands have a strong effect on its atmospheric temperature. They found that the heat absorbed by dark rock kicks up winds that blow away shiny dust, leaving behind even darker rock. But the predicted warming is hard to confirm, researchers say, and could shift with the sands at any time.

Snapshots over the past three decades have shown vast regions of the Red Planet's surface have brightened or darkened by 10 percent or more, reflecting between 10 and 30 percent of incoming sunlight in total. To determine if albedo or reflectivity changes affect the climate, researchers compared Viking orbiter photos from 1976 to 1978, which mapped the planet's bright and dark spots, to those from 1999 to 2000, when the Mars Global Surveyor discovered a darker Mars.

The Arctic is melting. But is it really the result of global warming? And if global warming is happening, how do we know humans have had anything to do with it? How can we be sure?

Here are ten of the questions most frequently posed by people who are skeptical about whether or not global warming is happening. Some of the answers may surprise you.

The fossilised remains of an amphibian which lived more than 245 million years ago have been found in Antarctica, suggesting that the climate during much of the Triassic era was remarkably balmy.

The 60-centimetre (24-inch) piece of skull was teased out of thick sandstone at Fremouw Peak in the Transantarctic Mountains, just six degrees short of the South Pole.

Palaeontologists in Europe and the United States have identified the beast as a Parotosuchus, a two-metre-long (6.5-feet) giant salamander-like predator that lived 40 million years before the first dinosaurs, inhabiting lakes and rivers.

Worst-case warming scenario may bring totally new kinds of tropical climate and cause others to disappear

If global warming continues unabated, many of the world's climate zones may disappear by 2100, leaving new ones in their place unlike any that exist today, according to a new study. Researchers compared existing patterns of temperature and precipitation with those that may exist at the turn of the century, based on scenarios put forth in the recent report of the Intergovernmental Panel on Climate Change (IPCC). They found that if greenhouse gas emissions continue rising at the same rate, up to 39 percent of Earth's continental surface may experience totally new climates, primarily in the tropics and adjacent latitudes as warmer temperatures spread toward the poles.

So has Pacific Northwest snowpack declined? Emphatically yes. I say "emphatically yes" for three reasons. First, because Albright illustrates the supposed lack of a trend by comparing specific periods (e.g. 1940-1946 vs. 1997-2006), in which snowpack has increased in some locations. This is not very informative, because both the spatial and temporal variability is large, and any question of decline can only be correctly addressed using all the data together, and over a statistically significant time period (30 years or more would be preferred). According to a summary statement prepared by Dennis Hartman to try to clarify the situation for the media and government, the decline is quite evident when the analysis is done correctly. (Hartmann is currently Chair of the Atmospheric Sciences Department at the University of Washington).

The Bush administration has again been charged with interfering with federal climate science, in order to underplay the significance of global warming.

In a continuing investigation, the US House Committee on Oversight and Government Reform held its second hearing on the issue on Monday. Documents "appear to portray a systematic White House effort to minimise the significance of climate change", said a memo released by the committee.

As atmospheric carbon dioxide levels rise, scientists have counted on the ground beneath our feet to soak up some of this greenhouse gas. But fungi living in the soil could throw a wrench into that plan, according to a new study, which finds that the microbes could actually cause soil to lose carbon to the atmosphere.

Pollution from industrialized countries is heating the Arctic atmosphere faster than any region on Earth, a new study warns.

European researchers writing in today's issue of the journal Science report that temperature spikes in the Arctic are mainly caused by "human-induced emissions of long-lived greenhouse gases."

Ship emissions, smoke from summer forest fires, and air pollutants such as aerosols and ozone coming from the lower latitudes are contributing to "significant warming trends," the report authors say.

Surface air temperatures in the region have risen faster than the global average over the past few decades and "are predicted to warm by 5 degrees Celsius [9 degrees Fahrenheit] over a large part of the Arctic by the end of the 21st century," the authors note in their study.

Previous climate models have suggested that the Arctic's summer sea ice may completely disappear by 2040 if warming continues unabated.

"The Arctic is at risk because global warming is proceeding fastest there," said study co-author Andreas Stohl of the Norwegian Institute for Air Research.

"This is mainly a consequence of the increasing trends of long-lived greenhouse gases and feedbacks in the climate system, which are strongest in the Arctic."

Contrary to popular belief, the 'hot spots' of evolution are actually quite cool: a study suggests that new species emerge more frequently in temperate regions than in the tropics.

Scientists had assumed that new species develop faster in the tropics, since they are home to greater species diversity than at higher latitudes. But the researchers behind the new analysis say the explanation for this is that fewer species have gone extinct near the equator.

Jason Weir and Dolph Schluter at the University of British Columbia in Vancouver, Canada, compared how animal species across the Americas have evolved. They looked at pairs of 'sister species', which share an immediate common ancestor and so are the most closely related species.

Mountains are fountains. Humid air crashes into upthrusted rock and releases its water in the form of rain, snow or ice. But the tiny particles created when fuel is burned—aerosols—can interfere with this process by providing even more impurities in the air on which water can condense. The many more resulting smaller droplets collide less often, thus forming fewer raindrops and, ultimately, less rainfall. Or so the theory goes. And now, records stretching back 50 years for a mountaintop in China strongly support this idea.

Atmospheric scientist Daniel Rosenfeld of The Hebrew University of Jerusalem, Jin Dai and colleagues from the Meteorological Institute of Shaanxi Province in China and Zhanyu Yao of the Chinese Academy of Meteorological Sciences studied the records of precipitation and visibility at Mount Hua in central China. The site, one of five sacred mountains in China (familiar to many as a backdrop in martial arts films), has had a meteorological observatory on its peak since 1954.

A long-term strategy on energy policy, aimed at leading the world in the fight against global warming, was agreed by European Union heads of state on Friday.

The deal sets binding targets for slashing greenhouse gas emissions, developing renewable energy sources, promoting energy efficiency and using biofuels. It also lays down a challenge to the US and other major industrialised nations to follow suit.

Trying to save high-altitude glaciers? Then sprinkle them with dirt, say researchers, to increase the formation of ice spikes that shade large areas on the glaciers, slowing their melting.

Meredith Betterton of the University of Colorado at Boulder, US, and colleagues in France have been sprouting ice spikes in a lab freezer. They say the spikes mimic those found on mountain glaciers, notably above 4000 metres in the Andes. The real spikes can be up to 5 m high and are known as "penitentes" because they resemble precessions of white-hooded monks.

Betterton's replicas, however, are only a few centimetres high. She created them by putting blocks of snow in a freezer with a transparent lid and shining a spotlight onto them, mimicking sunlight. Within a few hours, sublimation of the snow had left spikes up to 5 centimetres high protruding from the surface (see image, top right).

When Charles Darwin first noticed penitentes while travelling through Chile, he noted that locals believed they were formed by strong winds. Betterton's lab experiments confirm what she had previously suggested after computer modelling: that sunlight forms the spikes independently of wind.

What's good for the ozone layer has been even better for Earth's climate. According to a new study, a 20-year-old ban on ozone-depleting chemicals has been extremely effective at curbing greenhouse gases as well. In fact, it has already had more impact than a fully implemented Kyoto Protocol would have accomplished, even though the protocol was specifically designed to target atmospheric warming. The findings, say the authors, emphasize the importance of ridding the planet of these powerful greenhouse substances.

Also in New Scientist

Simultaneous warming on Earth and Mars suggests that our planet's recent climate changes have a natural—and not a human-induced—cause, according to one scientist's controversial theory.

Earth is currently experiencing rapid warming, which the vast majority of climate scientists says is due to humans pumping huge amounts of greenhouse gases into the atmosphere.

In 2005 data from NASA's Mars Global Surveyor and Odyssey missions revealed that the carbon dioxide "ice caps" near Mars's south pole had been diminishing for three summers in a row.

Habibullo Abdussamatov, head of the St. Petersburg's Pulkovo Astronomical Observatory in Russia, says the Mars data is evidence that the current global warming on Earth is being caused by changes in the sun.

…

The conventional theory is that climate changes on Mars can be explained primarily by small alterations in the planet's orbit and tilt, not by changes in the sun.

"Wobbles in the orbit of Mars are the main cause of its climate change in the current era," [planetary physicist at Oxford University, Colin] Wilson explained.

"Mars has no moon, which makes its wobbles much larger, and hence the swings in climate are greater too," Wilson said.

Human Events hopes to undermine climate science by spreading their own myths. Color me shocked. No actual science publication supports these claims but of course that doesn't stop a conservative political magazine from publishing them. However, since someone has to set the record straight, I might as well try.

1. The U.S. is going it alone on Kyoto and global warming. – So far, the US isn't doing really anything on the issue of climate change. The notion that Kyoto is a "European Treaty" is false, as there are many non-European who have signed and ratified the agreement (something they forgot to tell you when they mentioned we signed it in this article). As for the claim that it's not working because in Europe, the statistic quoted doesn't really present the whole picture, unless it's already 2012.
2. Global-warming proposals are about the environment. – I'm not sure who is demanding energy rations, but it's not the people proposing solutions to climate change. The key is alternate energy and reducing energy needs. Being more efficient has nothing to do with going without. Of course, if you're "lifestyle" is all about throwing your own money down the toilet, then by all means don't let me tell you have to save money while helping the environment.
3. Climate change is the greatest threat to the world's poor. – Anyone who tells you that climate chang is "more accurately" described as weather is simply mistaken or lying to you; it's that simple. The only "adaption" we need in the way of technological advancements is in the form of alternate energy and more efficient energy uses. It's much harder to adapt to worsening drought or flooding.
4. Global warming means more frequent, more severe storms. – It certainly may, as is pointed out in the IPCC's Fourth Assessment. From the SPM:
   

   Based on a range of models, it is likely [greater than 66% confidence] that future tropical cyclones (typhoons and hurricanes) will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical SSTs.

   Oh, did I just quote that from where they said I couldn't? That's odd.

5. Global warming has doomed the polar bears! – Polar bears can swim, just not forever. Arctic ice is melting and that's where polar bears live. The melting ice has been driving them further south. As for the Arctic cooling, the Arctic is the fastest warming region on the entire planet and any local, short term annomolies will be just that.
6. Climate change is raising the sea levels. – The lie that somehow the IPCC report is distorted just doesn't hold water, especially when the level's rising. This remains a conservative and highly reviewed document, possibly the most peer-reviewed science document ever written. The fact that some opinion editors with no background in science would tell you otherwise means very little.
7. The glaciers are melting! – The global ice mass held is glaciers is receding. Period. You simply cannot point to a few outliers and claim that is science. Of course, there's really no science in this article, anyway.
8. Climate was stable until man came along. – Who even says that? Of course climate changes. The problem is that is currently changing at a rate an entire order of magnitude faster than previously known. Further, we are now most likely warmer than any time in the previous 1,300 years. Oh, the so-called "hockey stick" graph? It's still in the IPCC report, just in written format (sorry, but you have to read and not just look at pretty pictures):
   

   Paleoclimatic studies use changes in climatically sensitive indicators to infer past changes in global climate on time scales ranging from decades to millions of years. Such proxy data (e.g., tree ring width) may be influenced by both local temperature and other factors such as precipitation, and are often representative of particular seasons rather than full years. Studies since the TAR draw increased confidence from additional data showing coherent behaviour across multiple indicators in different parts of the world. However, uncertainties generally increase with time into the past due to increasingly limited spatial coverage. Paleoclimate information supports the interpretation that the warmth of the last half century is unusual in at least the previous 1300 years. … Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years.

   The notion that the "hockey stick" graph is wrong was proven false last summer when the National Academy of the Sciences determined that it was in fact, correct. Too had Human Events doesn't bother to read the news. Then again, it's not like paleoclimate is the only reason that we know global warming is happening.

9. The science is settled -- CO2 causes global warming. – Man-made greenhouse gases have been determined to be the main cause of the recent changes in climate. The relation between the change in levels of CO₂ and global average temperature is complicated, not simply a one-to-one. However, a relationship has been clearly established and while there are certainly other sources for climate change, the world's body of climatologists are very confident (with greater than 90% certainty) that it is us (man) that is doing the major influencing on the climate.
10. It's hot in here! – It is most likely the warmest that it has been in over 1,300 years, based on paleoclimate proxies. Based on recorded temperatures, we are even more confident in the claim that it is hotter now than ever recorded. Playing shell games with what data you compare it to just doesn't change that. Pretending that being hot is so much better than an ice age is also a red-hearing; as is the case with saying that some problem you are not facing would be so much worse than the one you are doesn't make it go away.

Please consider this article to be on-going, as I'll add more information and links when I get the chance. For an even longer list of climate change myths, please see my previous article "25 Reasons Why You Should Understand Neil Boortz is Wrong."

Jason Coleman is a structural engineering who lives, practices, and writes in Richmond, VA, where he hope the truth wins out so his child will enjoy a better climate. This article is published under a Creative Commons Attribution- Noncommercial- Share Alike 3.0 License.

Residents of the western U.S. could be in for droughts worse than they have ever seen, a blue ribbon panel warned today. The severe, recurrent droughts that parched the region in past centuries could strike again--and could even be exacerbated by a regional warming trend.

Much of the western U.S. was gripped by drought from 2002 to 2005. During these years, water flow in the Colorado River--which supplies tens of millions of people in seven states--dropped to as low as a quarter of its usual value. That crisis spurred several federal and state water agencies to ask the National Academy of Science's National Research Council (NRC) to examine the state of science on the future of the river's water.

Moving satellites may have caused falling measurements of cloud cover.

Satellite evidence that cloud levels are decreasing could just be pie in the sky. The trend might simply be a result of where the satellites are positioned.

Data from the International Satellite Cloud Climatology Project (ISCCP) have shown that cloud levels have decreased by up to 4% over the past 20 years. Clouds increase the Earth's ability to reflect sunlight back into space, cooling the planet. So reduced cloud cover has been linked to global warming.

But Amato Evan at the University of Wisconsin at Madison and his colleagues have taken a closer look at the ISCCP data. Cloud cover decreases abruptly when satellites are moved, the team reports in Geophysical Research Letters1.

As more satellites were launched from the mid 1980s through the 1990s, each satellite could narrow its field of view, looking straight down rather than at an angle. And when observed straight on, clouds appear less cloudy.

When Rep. Bart Gordon gavels the House Science and Technology Committee to order Thursday morning, it will mark Congress's first hearings on the latest United Nations-sponsored report on global warming.

But even before several authors of the prestigious report discuss its findings, other authors say the process is too slow.

The problem: Climate science is moving too quickly for the ponderous reporting system to keep up, they argue. Besides receiving a written consensus once every six years, policymakers need some form of interim report to keep abreast of the science of global warming and make important decisions, they add.

"Some of us believe that going to some updates, especially as the science is changing very rapidly, might be a very good tack to take," says Linda Mearns, a scientist at the National Center for Atmospheric Research in Boulder, Colo., and one of 15 lead authors on the chapter dealing with projections of global warming's regional effects.

Updates could come from the UN-affiliated group itself, the Intergovernmental Panel on Climate Change (IPCC), or some other organization, such as the World Climate Research Program.

The World Bank is hiring experts in 'adaptation' to a warming world. Coastal planners are starting to take it into account.

At least in the developed world, the idea that people should start figuring out how to deal with the projected effects of warming – changing temperature and rainfall, shifts in growing seasons, more bouts of severe weather, and rising sea levels – has been overshadowed by calls to reduce carbon-dioxide emissions. Some environmentalists have viewed adaptation either as a white flag on the issue or as a refuge of contrarians who pooh-pooh the broad consensus that human activity is warming the climate.

But last week's release of a report on the science of global warming – with its projections of warming based on emissions already in the air, as well as on potential future emissions trends – has helped underscore the need. "Climate change is here and now," notes Ian Noble, a senior climate-change specialist at the World Bank. "We have to adapt."

Peru's "White Mountain Range" may soon have to change its name.

The ice atop Cordillera Blanca, the largest glacier chain in the tropics, is melting fast because of rising temperatures, and peaks are turning brown. The trend is highlighting fears of global warming and, scientists say, is endangering future water supplies to the arid coast where most Peruvians live.

Glaciologists consider the health of the world's glaciers an indicator of global warming and they warn that what is happening in the Andes signals trouble ahead.

"To me it's the rate of ice loss that's a real concern," because when melting accelerates, the ice cannot replenish itself, said Lonnie Thompson, a leading glacier expert at Ohio State University.

An emphatic and clear status report on global warming opens the way for action — presenting new risks.

The release of the 2007 report of the Intergovernmental Panel on Climate Change (IPCC) last Friday marks an important milestone. Following the scientific consensus that has been apparent for some time, a solid political consensus that acknowledges the problem finally seems to be within reach. But achieving this outcome brings its own risks.

Until quite recently (perhaps even until last week), the general global narrative of the great climate-change debate has been deceptively straightforward. The climate-science community, together with the entire environmental movement and a broad alliance of opinion leaders ranging from Greenpeace and Ralph Nader to Senator John McCain and many US evangelical Christians, has been advocating meaningful action to curtail greenhouse-gas emissions. This requirement has been disputed by a collection of money-men and some isolated scientists, in alliance with the current president of the United States and a handful of like-minded ideologues such as Australia's prime minister John Howard.

The IPCC report, released in Paris, has served a useful purpose in removing the last ground from under the climate-change sceptics' feet, leaving them looking marooned and ridiculous. However, this predicament was already clear enough. Opinion in business circles, in particular, has moved on. A report released on 19 January by Citigroup, Climatic Consequences — the sort of eloquently written, big-picture stuff that the well-informed chief executive reads on a Sunday afternoon — states even more firmly than the IPCC that anthropogenic climate change is a fact that world governments are moving to confront. It leaves no question at all that large businesses need to get to grips with this situation — something that many of them are already doing.

Today the world faces global warming, but 34 million years ago a distinctly chillier menace was sweeping our planet.

Average temperatures around the world plunged nearly 15 degrees Fahrenheit (8.2 degrees Celsius) during a span of hundreds of thousands of years, according to a new study.

The cooling was so severe that it likely led to the extinction of many of North America's reptiles and amphibians.

The cause of the temperature shift was a change in the level of greenhouse gases—specifically carbon dioxide—the study shows.

Researchers believe an increase in carbon dioxide is mainly responsible for the global warming occurring today.

This is an expanded copy of a comment I made in response to (a seed of) Neil Boortz' "Why Am I Skeptical About Man-Made Global Warming?" [Note: Good luck finding the article in the seeded link, you can find it here, tough]. That piece was so wrong as to be contemptible. Here are the facts with more links to back it up; something Boortz was incapable of providing. That's because he had to either make up stuff of just believe the lies of others to write that article.

Also, I've tried to point out which items are science and which items are policy (or political in nature), which are two different parts of the discussion. Simply because one disagrees with a proposed policy doesn't mean one need to reject the science; a concept which is sorely missing on the skeptic side of this 'debate.'

1. The U.N. is anti-American? What about NASA, NOAA, NIST, EPA etc.? These are American science institutions who clearly have our nations best interest in mind. The fact that the IPCC, which was established by the U.N. (who if they said the sky was blue, Boortz would claim was red). Then again, I imagine that Boortz hates all the federal government agencies, too. However, that hardly makes them un-American nor does it make the IPCC, which is made up of many American scientists un-American. [policy]
2. Communist rhetoric aside, there's nothing stopping a free-market approach to solving global warming right now. Sure, we may have to enact some regulation, but that's nothing new to U.S. policy, especially when it comes to energy policy, and it hardly makes us Communists. [policy]
3. Solar forcing is widely researched in climate science. The sun plays a key In fact, solar forcing is mentioned as a partial component of warming on Page 2 of the IPCC Summary for Policy Makers (SPM, hereafter). [science]
4. There is no global warming on Mars (nor any other of our solar system's planets), at least not anything at all like what we have recorded on Earth. It's a tired myth that comes up all the time, and has yet to be true. [science]
5. I think this chart clearly shows that the 1930's were not warmer across the globe. Boortz is simply wrong here. [science]
6. Another tired old argument is the global cooling myth (more here). While some MSM publications did have some scary headlines, climate scientists were not the one's causing the alarm thirty years ago, and certainly not with any large consensus like we have now. This is just more reason to listen to what the scientists have to say instead of untrained journalist mouth-pieces (ex. - Neil Boortz). [science]
7. One degree doesn't sound like much, but it's an annual global mean. Just because we wouldn't notice (or even mind) in the short term doesn't mean it's not a huge deal. Remember, this is global warming and not just raising the thermostat in your house. Further, the arctic is rising at a much higher rate, melting arctic ice which proves problematic in the lower latitudes, even if the temperature here doesn't change as much. Otherwise, cute attempt at ignoring a problem. [science]
8. It's simply not true that the so-called "Hockey Stick" graph has been proven false. On the contrary, the National Academy of Sciences found that the so-called "Hockey Stick" graph was indeed accurate science, and the 4th Assessment from the IPCC appears to agree that the last 50 years were likely warmer than any in the previous thirteen centuries. Too bad for skeptics (and people who ignore the news). However, even if the graph was incorrect, which is highly doubtful, it wouldn't matter as it's far from the only evidence at hand. [science]
9. The policy of the Kyoto protocol has nothing to do with the cause of global warming. However, too many people are prematurely calling Kyoto failed (as in past tense) when we've not even finished the second phase yet. [policy]
10. However, the Kyoto protocols can also be seen as an initial attempt to curb greenhouse gases. One which clearly needs work and the support of the U.S. government. [policy]
11. One of the more recent argument's I've heard lately is with regards to climate scientists who lie or stretch facts in order to secure funds for future research. I think anyone who is familiar with the grant writing process would instantly recognize this is as ridiculous, but clearly this argument is for their benefit. First of all, research grants are not easy to come by, even for those who have secured them in the past. Secondly, are we then to distrust any research as a result of continued grant money? What about cancer research or quantum computing? Research in a multitude of fields is funded by federal (and some state) grant money and it is absurd to discount its validity based on that. Secondly, it is simply poor logic on one hand to demand more precise data and then on the other deny the people who seek to provide it. [policy]
12. I don't wish to "punish" anyone who disagrees with me, as Boortz and other militant skeptics might assert. I am trying to get them to see reason and understand the science. I just am astounded by some people's willingness to ignore sound science. Then again, I'm also astounded when people ignore the advice of their physicians, which is an appropriate analogy here. Neither is smart. However, that being said, I do wish to call out someone who is perpetuating myths and that is exactly what Neil Boortz is doing. He is either lying or mislead, but he is most definitely not right. [policy]
13. The Medieval Warm Period. Yet another popular myth. The short answer: it's global warming, not just European warming. [science]
14. One scientists said something that is taken out of context? This hardly proves anything other than someone's willingness to spin the comments of another. However, neither the so-called "Medieval Warm Period" nor the "Little Ice Age" disprove global warming. (Actually, nothing disproves global warming since it's clearly been observed.) Further, to accept those events as evidence, one must then accept our the science of paleoclimatology, as in "the Hockey stick." [science]
15. Portions of the Antarctic ice sheet are thickening, but yet loosing overall volume due to shrinking area. In short, global warming results in great air moisture which in turn results in more precipitation. Oh, what does it matter, Boortz didn't care about the science to begin with… This is cherry picking data at best and simply lieing at worst. Either way, we have a number of measurements (the most accurate is probably NASA's GRACE satellite measurements, which detect gravity changes) which point to a loss of Antarctic ice. [science]
16. Well, once again, It's global warming, not U.S. warming. The temperature difference isn't the same everywhere (particularly wrt latitude). However, the U.S. is definitely getting warmer along with the rest of the globe. [science]
17. Here's one of the Boortz' inconsistencies that a lot of people, myself included, picked up immediately. Interesting that in one sentence we can't know what's going on with the majority of the world's glaciers because we haven't visited them and in the next Boortz claims to know exactly what is happening with them. The fact is, most glaciers are losing volume (globally, glacial volume is decreasing) and we don't have to set foot on them to know this. We have satellites that take remarkably accurate measurements, in addition to other means of measurement. [science]
18. Again, a portion of the Antarctic ice increased. The author of this study has clearly stated that this cherry-picking of data represents nothing but a misleading use of science, which has happened before and at least one author has spoken out on. [science]
19. Yes. Sea levels change naturally as the Earth's climate changes. However, both are changing at a rapid and previously unrecorded rate. That's really kind of the concern here. A large part of climatology is to pick out what is natural, cyclic phenomena and what is not. In short, were the current global warming observations a result of natural cycles, we'd be able to see them in the paleoclimate data, which we do not. [science]
20. Like Antarctica, the total volume of ice is receding in Greenland. Further, it's doing so at nearly twice the pace previously though to be occuring. We recently discovered what was thought to be a peninsula was actually an island that had been connected by ice. It isn't anymore. [science]
21. While the margin of error in some studies may support the notion that there have been multiple ice ages in the past 3,000 years (most global temperature reconstructions are for only 2,000 years or less), the Earth is clearly warmer today than it has been in 400 years, and likely for more than 2,000 years (ref. item number 14 above). [science]
22. The Earth's temperature has decreased? Boortz has truly gone off the deep end. Global temperatures have most definitely not decreased. I honestly don't know of anyone who believes otherwise. If Boortz had provided any sort of reference, I might be able to address this one, but he didn't. Of course, he expects his readers (and listeners) to take everything he says as fact without bothering to check it out. All I can do is suppose this might be what he is talking about, which is shown to be incorrect. [science]
23. An NPR reported wouldn't interview a scientist is evidence of what? Much like Kyoto, the willingness of a journalist to interview a scientist has nothing to do with the science. If this is a crucial piece of evidence, why ever listen to a scientist in the first place? [policy, but that's even being kind]
24. More on grant money. Contrary to Boortz' claim, if these scientists are in it for the grant money, they are most certainly not saying it's settled. It can't be both. The fact is, most scientists are wanting to pin down the effects so we can back out a solution of what to do about it. This goes hand in hand with making sure the initial assumptions are right. This is science, and it's clearly something Boortz doesn't get. However, we do know enough about climate and what is happening to begin to enact some policy to try and curb the negative consequences. This goes directly to the common confusion about science versus policy. [policy]
25. More of that Ice Age stuff? Well, the point is, Time (and Newsweek) aren't peer-reviewed science journals and if you look at what those said at the time, there was not prediction of global cooling and most climatologists clearly said that there was no reason for alarm of cooling (ref. item number 6 above). Of course, as we see now, the mainstream press has a really hard time understanding what scientists are saying. The fact is, the greenhouse effect has been understood since the 1800's (yes, that's right) and climate science is a mature field which quite possibly has the most stringent review of any science in the world. The Fourth Assessment Report by the IPCC represents what may very well be the single most peer-reviewed science document in history. To ignore it with the psuedo-logic and poor understanding of science is nothing short of sad. [science]

Boortz' article clearly shows that he knows nothing of the subject he's claiming to be a skeptic about. However, I have not doubt that like many other radio mouthpieces who know nothing about science, his listeners and readers take it without doubt. Further, he continues to provide mis-information to feed doubt, even on some of the most ridiculous subjects. Most recently (note: that link may be bad in a few days, given his poor site management system) he claims that a recent cold spell in Chicago is somehow evidence that global warming isn't happening (common skeptic tactic is to confuse weather with climate) and further he provides a link to a petition which supposes to have a mass of scientists against global warming. Never mind that it's six years old and has widely been criticized as misleading and a fraud.

I believe I've clearly demonstrated what a fraud Boortz is when it comes to global warming and really, science in general. He's wrong on every account and simply doesn't understand what he's writing or talking about. I think it's high time that we all started calling this stuff what it is instead of pretending it's just the other hand of an equal debate. It's not. It's a bunch of mis-leading information meant to cast hard science in a poor light out of some fear of possible policy actions (Boortz is an adamant anti-federalist). There is no significant debate over whether man is causing climate change in scientific circles and the sooner the mas media understands this, the sooner we can all get to solving the problem.

Anyone who would like to read more should check out some of the following (I'll add more as I find time):

• Real Climate - Archive of Climate Scientists' blog
• Grist - How to Talk to a Climate Skeptic
• New Scientist (UK) - Special Web section on Climate Change
• NERC Climate Challenge - Skeptics ask, climatologists respond
• Scientific American - George Musser replies to skeptic arguments against global warming and all the related blog posts by the editors.
• Pew Center - Climate Change 101
• NASA on the difference between Climate and Weather
• Live Science - The History of Climate Change Science
• National Geographic - Global Warming Fast Facts and "What is Global Warming?"
• BBC's Environment correspondent, Richard Black: "Climate science: Sceptical about bias"

Most importantly, everyone should read the Summary for Policy Makers [.pdf] from the Fourth Assessment by the IPCC, published online last Friday. It's really hard to overstate just how important this document is. This document contains the state of the art in climate science.

Jason Coleman is a structural engineering who lives, practices, and writes in Richmond, VA, where he enjoyed last month's Indian summer but despises the currently cold political climate towards science. This article also appeared on Jason Coleman.net under a Creative Commons 2.5 license which applies to this here as well.

This 2004 incident, reported by Steven Amstrup of the U.S. Geological Survey's Alaska Science Center, was the first report of polar bear cannibalism in two decades of study in the Beaufort Sea area of northern Alaska, and in 30 years of studies in northwestern Canada. Since then, Amstrup has documented two additional cases.

…

Some prominent researchers suspect that changes in the climate are a leading threat to polar bear survival. Polar bears are especially vulnerable to rising Arctic temperatures because they hunt, mate and usually make their dens on sea ice. "There is no evidence they can survive on land without sea ice," Williams said.

The IPCC hasn't rushed to judgment on climate change. It took 600 authors from 40 countries 6 years to produce hundreds of pages, which in turn were scanned by 600 reviewers. Then the wording--but not the science--of the 21-page "Summary for Policy Makers" got worked over by 300 delegates from 113 governments this week in Paris. The bottom line is that "there's an irrefutable consensus that [global warming] is real," says geoscientist Michael Oppenheimer of Princeton University in New Jersey. And "there's an irrefutable consensus that it will get worse" if greenhouse emissions are not reined in.

The IPCC's heightened confidence flows from several developments of the past few years. More observations of climate--from satellites to tree rings--have been analyzed. More computer models have grown more realistic and been run multiple times. And the natural world has continued to behave as if it is warming under a strengthening greenhouse. So IPCC upgraded its 2001 statement that "most of the observed warming ... is likely to have been due to" rising greenhouse gases to the warming being "very likely" human-caused.

The world gets a wake-up call from Paris that climate change is man-made and likely will worsen without emissions curbs

For the first time, a panel of climate experts has confirmed that global warming is occurring and that it is "very likely"—90 percent certain—man-made. The Intergovernmental Panel on Climate Change (IPCC), a working group of some 3,000 delegates from 113 countries, today issued its final report here on the state of climate change -- and the findings were grim. "There can be no question that the increases in these greenhouse gases are dominated by human activity," says Susan Solomon, co-chair of the working group and an atmospheric scientist with the U.S. National Oceanic and Atmospheric Administration (NOAA). "Warming of the climate system is now unequivocal. That is evident in observations of air and ocean temperature as well as rising global mean sea level."

Tomorrow the United Nations-backed Intergovernmental Panel on Climate Change (IPCC) will release a major report with grim predictions about global warming for the coming decades, according to journalists who have seen draft versions of the paper.

If the IPCC's recent track record is any indication, the predictions will be no exaggeration, an analysis posted today on the Web site of the journal Science suggests.

The Science study compared actual climate measurements with the computer models from a 2001 IPCC report.

In recent years actual concentrations of carbon dioxide—a greenhouse gas linked to global warming—have followed almost exactly the projections of the 2001 IPCC report.

If anything, the IPCC may have underestimated some climate threats in 2001. For example, actual temperatures were at the high end of the predicted range. And sea levels have actually risen faster than predicted.

"The real climate system is changing as fast or in some components even faster than expected by [the] IPCC," Stefan Rahmstorf, an ocean physicist at Potsdam University in Germany, said by email.

Climate-change figures since 1990 offer test of IPCC projections.

Climate factors such as sea-level rise may be changing more rapidly than predicted, according to a new survey of global trends since 1990. The figures suggest that the Intergovernmental Panel on Climate Change (IPCC), which publishes a fresh assessment of climate change tomorrow, may have previously underestimated the changes that lie ahead.

Researchers led by Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany studied the most recent data for atmospheric carbon dioxide, global temperatures and sea level. They calculate that carbon dioxide levels are rising in line with predictions, but that temperatures are rising in line with the upper limit predicted by the IPCC, and that sea-level rises are on the very edge of the worst-case predictions of climate models.

Satellite data show that, since the early 1990s, sea levels have been rising by an average of 3.3 millimetres per year. The IPCC's Third Assessment Report, published in 2001, predicted that the annual rise was likely to be around 2 millimetres.

Scientists have spent the past six years combing the seas, skies, land and space for data on climate change

ix years is not a long time in science. Data may be collected, a paper or two published or a PhD earned. But in the six years since the last Intergovernmental Panel on Climate Charge (IPCC) report was released, the science and certainty of global warming has grown markedly. "In the first IPCC report in 1990 there were no real observations demonstrating that climate had changed, only a prognosis that it would change," says Herve Le Treut, atmospheric physicist at CNRS (France's National Center for Scientific Research) and a lead author of part of the fourth IPCC report set to be released on Friday. "By 2001, there were many signs that climate is changing and now we are already seeing the patterns described in the first IPCC report."

Simple observation confirms the basic science of climate change. "All six years since the last report (2001 to 2006) are among the seven warmest years on record," notes Kevin Trenberth, head of the Climate Analysis Section at the U.S. National Center for Atmospheric Research (NCAR) and another lead author. "Northern Hemisphere snow cover has decreased and Arctic Sea ice has been at record low levels in the past three years."

It's hard to believe that something as ephemeral as lightning could be frozen in time for thousands of years. But that's just what happens with fulgurites--glassy, hollow tubes that form when lightning melts sand. For the first time, researchers have successfully dated these unusual geological formations, and the findings are providing a unique insight into the long-ago climate and ecology of the Sahara desert.

Fulgurites record the past by providing direct evidence of thunderstorms and rain. But when Rafael Navarro-González, a chemist at the National Autonomous University of Mexico in Mexico City, came across an unusual specimen from the Sahara desert in southwestern Egypt, he realized that some fulgurites may have a much more interesting story to tell. Unlike most fulgurites, this one was rounder and solid, but what really caught his eye were tiny, embedded glass bubbles. He wondered if they might contain gas.

Predictions of how much sea-levels would rise due to climate change, made by a key UN report in 2001, were conservative, say researchers on the eve of the release of the new update of the report.

Stefan Rahmstorf at the Potsdam Institute for Climate Impact Research in Germany, and colleagues, compared the predictions made in the 2001 report of the Intergovernmental Panel on Climate Change with the actual subsequent data. The factors they compared were temperature, sea-level rise and concentrations of carbon dioxide in the atmosphere.

The researchers found that changes in CO2 concentrations between 1990 and 2005 followed the 2001 predictions of the computer models "almost exactly"

The growth of tiny plants at the base of the ocean food chain is tightly linked to changes in the climate, according to a recent study.

The finding shows that as temperatures warm, the growth of single-celled ocean plants called phytoplankton slows at Earth's mid and low latitudes. The plants' growth increases when the climate cools.

While the findings are related to short-term changes in climate, they help scientists predict how the ocean will respond to long-term climate change, according to Jorge Sarmiento, an atmospheric and ocean scientist at Princeton University in New Jersey.

"This is telling us we can expect reduced biological production [the ability to support life such as plants, fish, and wildlife] with global warming in many regions of the world," he said.

Sarmiento is a co-author of the study, which was published last month in the science journal Nature.

Michael Behrenfeld, a botanist at Oregon State University in Corvallis, was lead author of the study. He said the research demonstrates a solid link between climate change and marine life.

Members of the Intergovernmental Panel on Climate Change are negotiating what many observers believe will be their most dire report yet

Climate change is real, it is already here and its consequences may be worse than anticipated, say early drafts of an upcoming report from an international group of climate scientists. The Intergovernmental Panel on Climate Change (IPCC) is set to release a summary of the report—its fourth on the state of global warming since the group was formed by the World Meteorological Organization (WMO) and U.N. Environment Program (UNEP) in 1988—on Friday, and the news is bleak.

The body of several thousand atmospheric scientists, climatologists, glaciologists, oceanographers and other scientists, hailing from 154 countries, are more certain than ever that humanity is to blame for global warming, which may be linked to odd events like trees blossoming in the Luxembourg Garden here in the middle of winter. The consensus stems from new evidence—among other things, proxies that extend the climate record back in time and six more years among the hottest ever recorded—brought forward since the last assessment in 2001. And it is unanimous, including the U.S. and other previously skeptical governments.

In an indication of Democratic eagerness to investigate whether the Bush administration has interfered with federal global warming research, Representative Henry Waxman (D-CA) today charged the White House with "an orchestrated effort to mislead the public." Waxman, who this month became chair of the House Oversight and Government Reform committee, says his staff has found evidence that scientific reports were manipulated for political ends despite efforts by the Administration to block recent requests for information.

Mountain glaciers are retreating three times faster than they were in the 1980s, says the World Glacier Monitoring Service.

On average, they lost about 66 centimetres in depth in 2005, according to the latest report from the UN-affiliated body, released on 30 January. This loss rate is 1.6 times more than the annual average for the 1990s and three times the 1980s average.

While the rate of change is certainly alarming, it is not a surprise, says Michael Zemp of WGMS. He says it fits in with the accelerating trend of the past 25 years, and simply serves to "make it sharper".

The truly worrying observation, he says, comes when the past 150 years are analysed in the context of the past 10,000 years of glacial history. Mountain glaciers reached their maximum extent for 10,000 years in 1850. But since then they have lost 50% of their area and retreated to their minimum extent for 10,000 years.

There's a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core.

Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior. According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion. However, Ehrlich believed that slight variations should be possible.

America's addiction to gas-guzzlers is at last poised to receive some treatment. In his annual State of the Union address on Tuesday, President George W Bush announced a plan to cut US gasoline use by 20% over the coming decade.

"For too long our nation has been dependent on foreign oil," Bush told the US Congress. "It is in our vital interest to diversify America's energy supply, and the way forward is through technology."

Three quarters of the proposed cut would be achieved by requiring the use of 35 billion gallons of renewable and alternative fuels – including ethanol and hydrogen – by 2017. This is nearly five times larger than the current target, which must be met by 2012. The rest of the cut in gasoline use would be made by strengthening the Corporate Average Fuel Economy (CAFE) standards for new vehicles.

Glaciers are quickly disappearing from the Alps and will be all but gone by 2050, a climate expert said Monday. That's 50 years earlier than a July 2006 study predicted.

The loss would change the supply of drinking and irrigation water, lead to more falling rocks, and cripple the European ski industry.

On average about 3 percent of Alpine glacial ice is lost each year, said Roland Psenner, a fresh water scientist at the University of Innsbruck in Austria. That corresponds to about 3.3 feet (1 meter) of ice thickness.

Ten percent was lost in the record-breaking heat of 2003. Seven percent was lost in 2006, Psenner said.

"If the melting goes on at this pace, glaciers will be gone by 2030 to 2050—except some high-altitude sites in the French, Swiss, and Italian Alps," he wrote in an email to National Geographic News.

Psenner's research was discussed Monday at an annual conference on the Alps in the Austrian mountain resort of Alpbach.

The government's ability to understand and predict hurricanes, drought and climate changes of all kinds is in danger because of deep cuts facing many Earth satellite programs and major delays in launching some of its most important new instruments, a panel of experts has concluded.

The two-year study by the National Academy of Sciences, released yesterday, determined that NASA's earth science budget has declined 30 percent since 2000. It stands to fall further as funding shifts to plans for a manned mission to the moon and Mars. The National Oceanic and Atmospheric Administration, meanwhile, has experienced enormous cost overruns and schedule delays with its premier weather and climate mission.

As a result, the panel said, the United States will not have the scientific information it needs in the years ahead to analyze severe storms and changes in Earth's climate unless programs are restored and funding made available.

The massive glaciers of the Himalayas, which hold one of Earth's largest reserves of snow and ice, have dwindled by one-fifth in the past 4 decades. A team of Indian geologists and remote sensing experts published the alarming news this week--a grim warning that if the trend continues, it could jeopardize the fresh water supply of more than 500 million people in India.

In this essay, I'd like to explain the science in the paper and give my answers to the most often asked questions.

In our paper, we examined the September Arctic sea ice cover in the 20th and 21st centuries in climate models, and found occasional decades of very rapid retreat. The most extreme case was a decrease from 6 to 2 million square kilometers in a decade (see Fig 1). This is about 4 times faster than the decline that has been observed in the past decade.

Dr. Cecilia Bitz, Assistant Professor of Atmospheric Sciences at the Univ. of Washington, provides some detailed answers to some of the questions she has been asked about a recent journal paper [.pdf] she co-authored in this guest commentary at Real Climate. This piece, as well as her univ. page, is a good place to learn about some of the techniques that go into the modeling of the planet's climate.

Two strong candidates for the 2008 US presidential elections have joined forces to address climate change.

On Friday, Republican John McCain and Democrat Barack Obama – plus independent senator Joe Lieberman - will present a bill in Congress calling for mandatory caps on greenhouse gas emissions from power plants, industry and oil refineries.

The legislation would require that US greenhouse gas emissions be cut by 2% every year. The senators say that as a result of these cuts, emissions would drop back to 2004 levels by 2012, and to 1990 levels by 2020.

[U]ntil yesterday, it appeared that no news release on annual climate trends out of the National Oceanic and Atmospheric Administration under the Bush White House had said unequivocally that a buildup of greenhouse gases was helping warm the climate.

The statement came in a release that said 2006 was the warmest year for the 48 contiguous states since regular temperature records began in 1895. It surpassed the previous champion, 1998, a year heated up by a powerful episode of the periodic warming of the tropical Pacific Ocean by El Niño. Last year, another El Niño developed, but this time a long-term warming trend from human activities was said to be involved as well.

It has now become all too common. Peculiar weather precipitates immediate blame on global warming by some, and equally immediate pronouncements by others (curiously, quite often the National Oceanic and Atmospheric Administration in recent years) that global warming can't possibly be to blame. The reality, as we've often remarked here before, is that absolute statements of neither sort are scientifically defensible. Meteorological anomalies cannot be purely attributed to deterministic factors, let alone any one specific such factor (e.g. either global warming or a hypothetical long-term climate oscillation).

Lets consider the latest such example. In an odd repeat of last year (the 'groundhog day' analogy growing ever more appropriate), we find ourselves well into the meteorological Northern Hemisphere winter (Dec-Feb) with little evidence over large parts of the country (most noteably the eastern and central U.S.) that it ever really began. Unsurprisingly, numerous news stories have popped up asking whether global warming might be to blame. Almost as if on queue, representatives from NOAA's National Weather Service have been dispatched to tell us that the event e.g. "has absolutely nothing to do with global warming", but instead is entirely due to the impact of the current El Nino event.

So what's really going on? The pattern so far this winter (admittedly after only 1 month) looks like a stronger version of what was observed last winter (note that these anomalies reflect differences relative to a relatively warm 1971-2000 base period, this tends to decrease the amplitude of positive anomalies relative to the more commonly used, cooler 1961-1990 base period). This poses the first obvious conundrum for the pure "El Nino" attribution of the current warmth: since we were actually in a (weak) La Nina (i.e., the opposite of 'El Nino') last winter, how is it that we can explain away the anomalous winter U.S. warmth so far this winter by 'El Nino' when anomalous winter warmth last year occured [sic.] in its absence?

When Mount Pinatubo erupted in 1991 it left a trail of evidence in the skies that is helping scientists decipher the workings of the global climate

Earth's climate cannot be replicated in a lab. So to understand how this critical component of the planet's heat regulation works, scientists must rely on "natural experiments." Such natural experiments take apocalyptic form, such as the eruption of Mount Pinatubo in the Philippines in June 1991 that sent 10 cubic kilometers of ash, gas and other materials sky high. By tracking how this eruption affected the global climate--and determining how to trace its footprint in other records--scientists have turned the catastrophe into a tool for comprehension. "The big problem with climate--and trying to study it--is you can't play with it in the lab," says atmospheric scientist Joanna Futyan of Columbia University. "We were trying to use this abrupt event as a natural experiment: something dramatic happened and you can look at how the atmosphere responds to it."

Futyan and physicist John Harries of Imperial College London analyzed how the atmosphere's humidity and temperature responded to the eruption as well as the overall radiative balance of the planet--in other words, the difference between the energy in sunlight absorbed by Earth versus the amount radiated back to space. The spectrum of this energy sent back into space from the surface (measured via satellite) has changed in the past 30 years as part of global warming, but the rate and magnitude of this change remain difficult to measure and rely on a variety of atmospheric processes, such as the amount of water vapor.

Remnants of volcanic smoke locked up in Antarctic ice could help geologists establish firmer links between ancient eruptions and climate changes.

Sulphur isotopes in the ice could show whether eruptions of dust and ash up to a million years ago were large enough to reach the upper atmosphere, and so block sunlight.

Mélanie Baroni, at the Université Joseph Fourier in St Martin d'Hères, France, and colleagues drilled ice cores to provide a record of historical eruptions. Particles from major eruptions spread across the globe, and are deposited as thin layers on the Antarctic snow, Baroni explains.

The Antarctic region is a particularly good place to study these layers because they tend to be well-preserved and are uncontaminated by human-made sulphur emissions, says Baroni.

Climate is a large-scale phenomenon that emerges from complicated interactions among small-scale physical systems. Yet despite the phenomenon's complexity, climate models have demonstrated some impressive successes.

Climate projections made with sophisticated computer codes have informed the world's policymakers about the potential dangers of anthropogenic interference with Earth's climate system. Those codes purport to model a large part of the system. But what physics goes into the models, how are the models evaluated, and how reliable are they?

The task climate modelers have set for themselves is to take their knowledge of the local interactions of air masses, water, energy, and momentum and from that knowledge explain the climate system's large-scale features, variability, and response to external pressures, or "forcings." That is a formidable task, and though far from complete, the results so far have been surprisingly successful. Thus, climatologists have some confidence that theirs isn't a foolhardy endeavor.

Statements often appear in the media about suggesting that more extreme mid-latitude storms will result from global warming. For instance, western Norway was recently battered by an unusually strong storm which triggered many such speculations. But scientific papers on how global warming may affect the mid-latitude storms give a more mixed picture. In a recent paper by Bengtsson & Hodges (2006), simulations with the ECHAM5 Global Climate Model (GCM) were analysed, but they found no increase in the number of mid-latitude storms world-wide. Another study by Leckebusch et al. (2006) showed that the projection of storm characteristics was model-dependent. (Note that the dynamics of tropical and mid-latitude (often called 'extra-tropical') storms involve different processes, and tropical storms have been discussed in previous posts here on RC: here, here, here, and here).

The factors that control this are often confounding and so make this a tricky prediction. Simple arguments based on the expected 'polar amplification' and the fact that the surface temperature gradient between the tropics and the poles will likely decrease would reduce the scope for 'baroclinic instability' (the main generator of mid-latitudes storms). However, there are also increases in the upper troposphere/lower stratospheric gradients (due to the stratosphere cooling and the troposphere warming) and that has been shown to lead to increases in wind speeds at the surface. And finally, although latent heat release (from condensing water vapour) is not a fundamental driver of mid-latitude storms, it does play a role and that is likely to increase the intensity of the storms since there is generally more water vapour available in warmer world. It should also be clear that for any one locality, a shift in the storm tracks (associated with phenomena like the NAO or the sea ice edge) will often be more of an issue than the overall change in storm statistics.

Dr. Rasmus E. Benestad, a physicist and author at Real Climate, provides some detailed information on the complexities of climate change and how it affects tropical storms.

Global warming is the greatest environmental threat that humanity has ever faced.

Caused mainly by the unprecedented levels of carbon dioxide pumped into the atmosphere by automobiles and industries, the rise in temperature is already starting to melt the polar ice caps and disrupt weather patterns.

The potential consequences for California are dire. At current rates of warming, state researchers project that the sea level will rise as much as three feet by the end of the century, flooding many low-lying areas and tainting important sources of fresh water like the San Joaquin-Sacramento River Delta. Higher temperatures will drastically shrink the Sierra snowpack that stores much of our water. They will increase smog, boost the risk of wildfires and upset California's vital agricultural industries.

Ocean sediment reveals the pattern behind the rise and fall of ice ages and the shape of Earth's orbit.

The useless shells of tiny ocean animals--foraminifera--drift silently down through the depths of the equatorial Pacific Ocean, coming to rest more than three miles (five kilometers) below the surface. Slowly, over time, this coating of microscopic shells and other detritus builds up. "In the central Pacific, the sedimentation rate adds between one and two centimeters every 1,000 years," explains Heiko Pälike, a geologist at the National Oceanography Center in Southampton, England. "If you go down in the sediment one inch, you go back in time 2,500 years."

Pälike and his colleagues went considerably further than that, pulling a sediment core from the depths of the Pacific that stretched back 42 million years. Limiting their analysis to the Oligocene--a glacial time period that lasted between roughly 34 million and 23 million years ago--the researchers found that global climate responds to slight changes in the amount of sunlight hitting Earth during shifts in its orbit between elliptical and circular. "Of all the records so far, this is both the longest and, also, the clearest that most of the climatic variations between glacial and interglacial at that time [were] most likely related to orbital cycles," Pälike says.

NASA's climatologists have an enormous problem: when it comes to data on the atmosphere, they have too much of it.

To help understand climate change, NASA has created its Earth Observing System (EOS), made up of a dozen satellites plus a host of weather balloons and ground-based sensors that collect data such as air temperatures, water-vapour densities and aerosol concentrations. Terabytes of such measurements have been streaming in each day, and the agency was quickly swamped with so much data that all it could do was dump it on disc drives.

Now it has hit on a simple way to make that data accessible: software that superimposes it on the global 3D maps provided by Google Earth.

2006 was the Earth's sixth warmest year on record, averaging 0.4°C above the 1961 to 1990 average, according to the World Meteorological Organization. The records extend back to 1861. And the UK charted its warmest year ever – its records go back to 1659.

Advance figures for the Status of the Global Climate in 2006, released on Thursday, reveal that global temperatures have risen by 0.7°C since 1900. Most of this is due to a sharp rise (0.18°C per decade) since 1976. Final figures will be released in March 2007.

The report also finds that virtually no corner of the planet was spared from extreme weather events in 2006, many of which were record-breaking.

The US experienced its warmest January to September on record, and July in Europe was also the warmest on record, nearly 3°C above the norm. In the southern hemisphere, Brazil and Australia also experienced heat waves between January and March. The town of Bom Jesus in Brazil recorded 44.6°C on 31 January – one of the highest temperatures ever in the country.

Global warming is likely to affect cyclones and hurricanes, concludes a new statement from 125 experts, but they say the evidence for this to date is inconclusive.

"There could be an effect but it's impossible to say for sure," says Julian Heming of the UK Met Office. The statement was issued at the end of a workshop organised by the World Meteorological Organization (WMO).

The workshop concluded that the increasing economic damage caused by tropical cyclones is to a large extent the result of "increasing coastal populations […] and, perhaps, a rising sensitivity of modern societies to disruptions of infrastructure".

The influence of climate change on tropical cyclones – a term used to describe hurricanes, typhoons and cyclones – is a hotly contested debate. It gained public attention after 2004 and 2005 brought an unusual number of high-impact storms to Japan, China and the US. The events culminated in 1300 deaths, mainly through flooding in New Orleans, when Hurricane Katrina hit the US coast.

Temperature records and computer models suggest the warming climate will generate more frequent and powerful storms. But differences of opinion over the data and methods divide the scientific community.

Satellite images indicate marine life does not deal well with climate change

The web of life in Earth's oceans may rest on a more delicate balance than anyone had imagined. Researchers have discovered that even small rises in water temperatures are stifling photosynthesis by tiny marine organisms. If the warming continues, it could mean major changes for animals that feed on plankton and for global climate itself.

Phytoplankton, the microscopic plants that permeate the oceans, underlie the entire marine food chain. And they remove up to 50 billion tons of carbon dioxide per year from Earth's atmosphere--as much as all plant life on the planet's surface. That makes plankton a linchpin in keeping atmospheric CO2 under control.

Results hint that Europe may be in for a warm winter.

Do you still have roses in bloom in your English garden? Then you might not be surprised to hear that Europe is experiencing the warmest autumn since Columbus first sailed to America.

Preliminary analysis shows that continental mean temperatures in September and October were 11°C — that's 1.8 °C higher than the long-term average for these months. November was 2.5 °C higher than the average. The results show that 2006 has beaten the 'hottest' autumns of 1772, 1938 and 2000 by about a degree.

Previous research has shown that spring seems to be coming earlier around the world. But autumn climate trends have been generally less well investigated.

That's partly because warm autumns pose less stress on plants and animals than do temperature anomalies in spring, says Annette Menzel, a phenologist at the Technical University of Munich, Germany. But warm autumns come with their own problems.

Hundreds of people are dead or missing after the Philippines was hit by its fourth major storm in as many months.

Typhoon Durian tore through northern and central areas of the island country yesterday, causing torrential rains and dangerous flash floods (Philippines map).

"There are a lot of conflicting reports, but, looking at the trend, we could have about 300 to 400 people dead by tonight," Richard Gordon, a senator and head of the Philippine Red Cross, told local television, according to the Reuters news agency.

One of Australia's environment courts has ruled against the country's largest independent coal producer, saying that its assessment of the impacts of a new mine should have included an assessment of its impact on climate change.

The campaign group Greenpeace has called the ruling "historic". Greenpeace has been demonstrating against the proposal of the Centennial Coal Company to build a new mine in New South Wales.

Justice Nicola Pain ruled on Monday that the environmental assessment, previously approved by the government, was void. She cited "a sufficiently proximate link" between coal mining and greenhouse gas emissions for the latter to be considered in the mine's assessment.

Climate change appears to be increasing the risk of monsoon flooding on the Indian subcontinent.

The monsoon is the great life-giver and the great destroyer of the subcontinent. Without rain from these annual storms, crops wither, animals die and more than half the world's population suffers from potential famine. With too much rain, crops are inundated, animals drown and people suffer from floods and the diseases that follow in their wake. Observations of this critical climate system stretch back decades, and the overall level of rainfall has changed little over the years. But now researchers have discovered a trend within the annual measurements toward fewer, more extreme downpours--a trend that bodes ill for flooding and other natural disasters.

B. N. Goswami of the Indian Institute of Tropical Meteorology and his colleagues studied rain gauge data from 1,803 stations scattered throughout central India from 1951 to 2000. As expected there was a wide range of rainfall: from a maximum downpour of 58.2 centimeters in one day (nearly 23 inches) to none, with an average of just 5.7 millimeters (just under one quarter of an inch) a day during the season.

A slowing of the Gulf Stream--the Atlantic Ocean's massive warm-water current--may have been responsible for a minor ice age that occurred between 1200 and 1850 C.E. If true, the finding could have implications for tracking future climate change in the northern hemisphere.

Forest fires in northern countries may cause regional cooling and not warming, as was previously thought. Researchers say their new findings could mean that on a global scale, forest fires will not affect climate change one way or the other.

Unusually large fires have blazed across Canada, Alaska, Russia, Norway, Sweden and other northern countries over the past decade. Researchers have said that warmer climates, longer summers and generally drier conditions may be increasing their frequency.

It was thought releasing the large amounts of carbon dioxide stored in trees would mean that forest fires would contribute to the greenhouse effect and start a fiery feedback loop. Not so, says a team of 17 US and Australian researchers in Science.

The team took an overall look at the effects of a forest fire that burned about 6.7 hectares (16.5 acres) of the Donnely Flats in central Alaska in June 1999. Some researchers looked changes in how the area reflected radiation from the sun, while others looked at greenhouse gas emissions and changes in vegetation.

They then plugged all their data into a computer model and projected it 80 years forward to see how a single fire would affect climate in the short and medium term.

They found that while temperatures did warm for about one year after the fire, this was reversed within 10 to 15 years. Averaged over 80 years, the overall effect was a cooling of temperatures.

No breakthrough will happen next week in talks to extend the Kyoto pact on global warming, but a softening of stances will produce an agreement on next steps to take, senior negotiators have told Reuters.

Ready to debate a united response to the threat of climate change, 189 countries are scheduled to attend a 2-week conference in Nairobi.

The Kyoto Protocol has already taken a very small first step to curbing man's contribution to climate change, capping greenhouse-gas emissions by some industrialized nations. Scientists say much tougher caps are needed to avert catastrophic weather changes.

The long arm of global warming could reach down into the ocean floor, interrupting the flow of vital nutrients from shallow waters to deep ocean ecosystems.

These nutrients, in the form of sediment and organic matter, are funnelled down into the deep ocean through vast steep-sided submarine canyons. These flows were thought to be triggered by landslides and river floods.

World summary of emissions reveals continuing gains.

Global carbon emissions are now growing by 3.2% a year, according to results presented at an Earth science conference in Beijing on 9 November. That's four times higher than the average annual growth of 0.8% from 1990-99.

"We are not on any of the stabilization paths," says Michael Raupach, a carbon-cycle scientist with Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) in Canberra, who presented the Global Carbon Project results.

The result is not particularly surprising — there have been many reports of countries missing their national emissions targets. But the tally, using data up to 2005, drives home how far away we are from projections from the Intergovernmental Panel on Climate Change (IPCC) of the emissions levels needed to prevent damaging climate change.

Antarctic ice-drilling reveals linked cycle of warming and cooling.

Researchers trying to understand sudden, seesawing changes in the Arctic's prehistoric climate have found some answers in an unusual place: buried in the Antarctic ice, half a world away. Their work could help to predict the future consequences of sudden polar warming.

By digging more than 2,500 metres down into the Antarctic ice, climate scientists have shown that changes at one pole influence the other. This 'climate seesaw' moves heat from south to north along the length of the Atlantic Ocean.

Similar studies from Greenland have shown that the Arctic climate can warm by as much as 16 °C in just a few decades. The results from Antarctica confirm a theory that these warming episodes, and their subsequent cooling periods, swing back and forth between the poles.

Global warming could, quite literally, bring about a sea change.

Oceanographers have linked temperature changes in Greenland during the last ice age to abrupt changes in ocean salinity levels. Their research, published in the Oct. 5 issue of Nature, finds more evidence that global warming could affect ocean salinity levels in ways that could have far-reaching ramifications.

As part of their study, geologists Howard Spero, of the University of California, Davis, and Matthew Schmidt, of the Georgia Institute of Technology, recorded salinity levels in the North Atlantic Ocean between 45,000 and 60,000 years ago.

The rise of the Appalachian Mountains seems to have triggered an ice age 450 million years ago by sucking CO₂ from the atmosphere. Researchers report evidence that minerals from the mountain range washed into the oceans just before the cold snap, carrying atmospheric carbon dioxide with them. The result clarifies a long standing paradox in the historical relationship between CO₂ and climate, experts say.

The Greenland ice sheet is rapidly wasting away—but not as quickly as some recent studies have found, according to a new analysis.

Several recent studies have suggested that the island has been losing ice at a rate sufficient to push global sea levels up by 0.02 inch (0.5 millimeter) a year.

The new analysis cuts that rate in half, but the ice-mass loss is still happening fast enough to alarm scientists.

Greenland is losing each year 20 percent more mass than goes into the ice sheet as snowfall, said Jay Zwally, a glacier expert at the NASA Goddard Space Flight Center in Greenbelt, Maryland.

Zwally is a co-author of the new study, which is reported tomorrow in the journal Science.

Of late, the enormous glaciers that flow down to the sea from the interior of Greenland have been picking up speed. In the last few years, enough ice has come off the northern landmass to sustain the average flow of the Colorado River for six years or fill Lake Mead three times over or cover the state of Maryland in 10 feet of water, assuming it were perfectly flat. And whether it is the glaciers'' weight, speed or volume that is measured, a quickening of the their movement can be detected. In fact, the latest gravity-based measurements show that the glaciers lost roughly 101 gigatons of ice annually between 2003 and 2005, according to a paper published online in Science.

A dust layer sandwiched between layers of ice near Mars''s north pole suggests the planet''s climate has shifted dramatically in the past 100,000 years or so, reveal images recently obtained by NASA''s Mars Reconnaissance Orbiter (MRO).

Previous research has suggested that the tilt of Mars''s axis of rotation fluctuates from 10° to 40° with time, leading to major climate shifts.

Now MRO, which started returning close-up images of the Red Planet in late September 2006, has provided new evidence that Mars''s climate has undergone major shifts relatively recently.

Mammal species do not seem to last very long in the grand scheme of things, persisting for an average of 2.5 million years, according to the fossil record. By studying the fossilized teeth of rodents over a span of 22 million years, Jan van Dam of Utrecht University in the Netherlands and his colleagues confirmed this cycle of rodent species rise and fall. But they also found that it closely matched variations in Earth's orbit--and may have definitively linked the two. If you have seven or eight of these in a row all showing the same pattern, it becomes extremely unlikely that it can be reduced to chance, explains paleoecologist Paul Olsen of Columbia University.

Monsoons are critical to India's farmers. If the rains don't come, there can be serious consequences for the country's agriculture-driven economy. Predicting the severity of a drought has been a tricky business, but a new study suggests that the key to better forecasts depends on a detailed understanding of a warming of the Pacific Ocean, called El Niño.

Over the past 132 years, every Indian drought has come in an El Niño year. But not every El Niño has been accompanied by a drought. In 1997, a predicted drought never materialized. Worse, in both 2002 and 2004, unexpected and severe droughts surprised a completely unprepared country.

Industrial greenhouse-gas increase has been masked by natural declines.

Current projections of methane emissions are likely to be too optimistic, an international team of atmospheric scientists reports today in Nature.

Methane, which is less abundant in the atmosphere than carbon dioxide but 20 times more potent as a greenhouse gas, is thought to have been responsible for up to one-third of global warming since the industrial revolution.

Unlike CO₂, however, atmospheric methane concentrations stopped rising in the 1990s, probably as a result of the sharp decline of the Soviet Union's industrial power. Concentrations have remained relatively stable since 1999, giving the impression that human and natural methane sources and sinks may have reached a lasting balance.

But the most extensive study so far suggests this is not so: human-created sources are rising, but have been masked by natural declines.

Drastic climate change wasn't always our fault. In fact, wild swings in the average temperature of the Earth were going on in the time of the dinosaurs.

A study based on an analysis of ocean sediment that will appear in the October issue of Geology shows that the climate of ancient Earth was surprisingly fickle. During the Cretaceous period, ocean surface temperatures varied wildly, by as much as 6° C.

We get a switch, from warming then cooling, then warming then cooling, said Simon Brassell, a paleoclimatologist at Indiana University, Bloomington and lead author of the study. It's as if the Earth's climate responds not necessarily gradually, but more like a changing gear in a car. And that's something that many climatologists are concerned about—whether there is some threshold that will lead to us to a very different climate than we're experiencing now.

Satellite observations suggest vegetation encourages rainfall in Africa.

More rain makes for more plant growth: that much is obvious. But now a statistical study of satellite images has added weight to the reverse notion: more plants also make for more rain.

The result adds to the impetus to preserve green spaces in dry regions, in order to help prevent deserts from growing and encroaching on agricultural land.

Greenery can have a number of effects on a local climate. Plants are thought to transfer moisture from the soil into the air by evaporation from their leaves, and hold water in the soil close to the surface, where it can also evaporate. What is more, the darker surfaces of plants compared to sandy deserts also absorb more solar radiation, which, along with their rough texture, can create convection and turbulence in the atmosphere. This might create more — or less — rainfall.

All of these effects have been incorporated into climate models. But there has been disagreement about which effects were dominant and why, and how much impact it all has.

The new work concludes that vegetation effects account for around 30% of annual rainfall variation in Africa's Sahel region. The results are reported in Geophysical Research Letters.

A climate satellite is built and paid for. Nations offer to launch it for free. Scientists say it's an essential mission. So what's it doing in a box outside DC?

At a time when the Earth's climate is at the top of practically every nation's agenda, it might seem perplexing that there's a $100 million, fully completed climate-sensing satellite stored in a warehouse in Maryland.

The Deep Space Climate Observatory (DSCOVR) was supposed to be delivered five years ago to the L1 Lagrangian pointa gravity-neutral parking spot between the Earth and the sun that affords a continuous, sunlit view of the planet. From here, DSCOVR would measure the planet's energy balance and reflectivity, known as albedo, which is critical data for calibrating climate change models and monitoring the ozone layer. Yet the mission was quietly killed this year, so the satellite is sitting in a box at Goddard Space Flight Center.

Could the decision to kill DSCOVR have anything to do with the politics of climate science? For years, Republicans have claimed the need for more data before acting to curb global warming. A letter President Bush wrote to four Republican senators in March 2001 (after DSCOVR's endorsement by a National Academy of Sciences review panel) referred to the incomplete state of scientific knowledge of the causes of, and solutions to, global climate change. More recently, in a 2005 briefing, [former] White House Press Secretary Scott McClellan asserted that there is still a lot of uncertainty when it comes to the science of climate change. Dr. Kevin Trenberth, Head of the Climate Analysis Section at National Center for Atmospheric Research, said, It is as if the administration prefers to continue to hide behind lack of definitive data as an excuse for lack of action and leadership.

If overall global warming exceeds 5.5°F (3°C), many parts of the world are likely to see substantially increased risks of drought, floods, and wildfires, climate scientists say.

In addition, there will probably be large-scale changes in vegetation types, a U.K.-based research team reports in tomorrow's issue of the Proceedings of the National Academy of Science.

But if global warming is less than 3.5°F (2°C), the risks of such changes are much lower.

The most important message from the paper is that with stronger global warming, the risk of severe events becomes much more pronounced, said the study's lead author, Marko Scholze of the University of Bristol's QUEST (Quantifying and Understanding the Earth System) project.

Ten climate experts who are sharply divided over whether global warming is intensifying hurricanes say that this question, a focus of Congressional hearings, news reports and the recent Al Gore documentary, is a distraction from the main hurricane problem facing the United States.

That problem, the experts said yesterday in a statement, is an ongoing lemming-like march to the sea in the form of unabated coastal development in vulnerable places, and in the lack of changes in government policies and corporate and individual behavior that are driving the trend.

Whatever the relationship between hurricanes and climate, experts say, hurricanes are hitting the coasts, and houses should not be built in their path.

A recent conference presentation at AGU (reported here) while confirming that global sea level is indeed rising (in line with other estimates), showed that Arctic sea levels may actually be falling. On the face of it these preliminary results are a little puzzling (though note that this isn't yet a properly peer reviewed paper, and so may not reflect what ends up in the journal), but it does reveal some of the complexities in analysing sea level in relatively small enclosed basins and so a brief overview of the different factors involved is probably useful.

How sensitive is Earth's climate? Sufficient to warm by at least several degrees in response to greenhouse gas pollution but perhaps not as sensitive as some scientists have feared, according to a new study.

Climate sensitivity is a measure of how much the global temperature will warm in response to greenhouse gas emissions, explained Gabriele Hegerl, a climate scientist at Duke University in Durham, North Carolina.

'If [climate sensitivity is] high, we have a strong response not only to carbon dioxide but to any greenhouse gas. If it's low, we have a weak response. So we would really like to know what it is,' Hegerl said.

Hegerl and her team measured climate sensitivity by studying temperature changes in the Northern Hemisphere over the past 700 years.

The study's results refute recent research suggesting that the climate may be susceptible to extreme increases in temperature. But Hegerl cautions that the findings do not diminish the threat of global warming.

'[The finding] means the climate does react significantly to greenhouse gases,' she said.

'In other words,' she added, 'we have really detected greenhouse warming, and we are really concerned it is not small.'