The Arctic's thick perennial sea ice typically survives the warmth of the summer and lasts through the year. But satellite images taken in late August show that up to 10 percent of the perennial sea ice has been fractured by summer storms. The surprising change involves an area larger than the size of the British Isles.

The striking openings in the pack ice were found north of Svalbard, Norway and extend to the Russian Arctic all the way to the North Pole. This condition is likely due to the thinning and extra mobility in the European section of the central Arctic ice pack seen in recent years.

"This situation is unlike anything observed in previous record low ice seasons," said Mark Drinkwater of the European Space Agency's Oceans/Ice Unit. "It is highly imaginable that a ship could have passed from Spitzbergen or Northern Siberia through what is normally pack ice to reach the North Pole without difficulty." The minimum ice extent—the lowest amount of ice recorded in the area annually—has shrunk from 3 million square miles in the early 1980's to less than 2 million square miles in 2005. A recent study showed that between 2004 and 2005, the ice shrunk by 14 percent, a decrease in area the size of Texas.

"If this anomaly trend continues, the North-East Passage or "Northern Sea Route" between Europe and Asia will be open over longer intervals of time, and it is conceivable we might see attempts at sailing around the world directly across.

California is forging ahead with the most aggressive U.S. program to reduce global warming -- a plan that pits Gov. Arnold Schwarzenegger against fellow Republican George W. Bush. Both the governor and his state's Democratic-led legislature want to make California -- the world's eighth largest economy -- a model to follow with caps in greenhouse gas emissions that the U.S. president rejects.

State politicians still are hammering out differences over the proposed Global Warming Solutions Act. If passed, it is likely to play a role in November's vote for governor and in national politics for years to come. Schwarzenegger -- branded "very green for a Republican" by the conservation group Sierra Club -- became an overnight hero for environmentalists a year ago by setting a goal to cut California's emissions to 1990 levels by 2020.

More recently, he accused fellow Republicans in Washington of lacking leadership on the environment as he signed a global warming accord with British Prime Minister Tony Blair. "We have a pretty brave governor who feels we should take the lead," said Linda Adams, a Democrat Schwarzenegger chose to run California's Environmental Protection Agency. The Democrats say their bill gives the governor's 2020 target "teeth" with an enforceable cap on emissions and mandatory reporting for top polluters like energy companies.

[O]cean researchers have found that the huge influx of carbon dioxide since 1800 is making oceans more acidic than they have been for millions of years. If not reversed, this trend could destabilize -- or even threaten --much of the world's marine life, particularly animals that can't adapt to living in a more corrosive environment.

So far, the ocean's pH (the commonly used scale of whether something is acidic or alkaline) has become about 30 per cent more acidic over the past 200 years because humans have added so much carbon dioxide to the atmosphere. Scientists say this change has never occurred in the recent history of the planet -- either in such a massive way, or so quickly.

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Although experts don't yet have a thorough understanding of all the implications of a more acidic ocean, they do know it has scary potential for all creatures that secrete calcium carbonate to build shells or skeletons, including corals, starfish, snails and many microscopic varieties of plankton. Should nothing be done to stop global warming, scientists predict that oceans could become acidic enough that the shells or skeletons of the most vulnerable marine animals may start to dissolve, possibly as early as 2050.

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The reason that oceans are becoming acidic is that carbon dioxide is water-soluble and easily passes from the air into the sea. Most of the carbon in the ocean is in the form of bicarbonate, a familiar ingredient in household baking soda. What is happening in the oceans is the reverse of the common high-school experiment in which vinegar, an acid, is poured on baking soda to produce a fizzy mass of carbon dioxide air bubbles. In this case, the ocean is holding the "baking soda," which is reacting with the influx of carbon dioxide to produce an acid.

"We may have less time than we think to do something (about the prospect of global warming)," Dr. Ira Leifer, a marine scientist at University of California Santa Barbara, said in an interview. Leifer is the main author of a study that looks at how "peak blowouts" of melting undersea formations called methane hydrates could release the potent greenhouse gas into the atmosphere. The study was published Thursday in Global Biogeochemical Cycles, a climate science publication.

The distribution of methane hydrates throughout the world is so vast that energy companies hope one day to tap the resource. The U.S. Department of Energy estimates that such formations could harbor as much as 200,000 trillion cubic feet of natural gas. Hydrate formations exist under hundreds of meters of water in places like the Gulf of Mexico and closer to the surface in permafrost areas of the Arctic. Methane, the main component of the fossil fuel natural gas, has two faces. When burned it releases less carbon dioxide, the main greenhouse gas that scientists believe are warming the earth, than any other fossil fuel. But if it escapes to the atmosphere without being burned, it can trap heat rapidly because it is a greenhouse gas at least 20 times stronger than carbon dioxide.

The study measured the amount of methane that escaped to the atmosphere from a peak blowout from small volcanoes on the ocean floor off of California. It found that virtually all of the methane escaping from the deep water reached the atmosphere, countering some theories that methane seeps out in tiny bubbles that harmlessly dissolve in the ocean. Leifer said rising temperatures could warm the oceans, creating a feedback loop in which warm temperatures make global warming even worse.

According to the U.S. Geological Survey (USGS), 100,000 to 300 million trillion cu. ft. (tcf) of methane exists globally in hydrate form--most of it in the ocean floor. "There's more energy potential locked up in methane hydrate formations across the world than in all other fossil energy resources combined," says Brad Tomer, director of the Department of Energy's Strategic Center for Natural Gas and Oil.

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Methane bound in hydrates could provide the world with an astounding amount of natural gas--if it could be safely extracted.

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[I]f methane gas escapes directly to the atmosphere--as a byproduct of extraction, an earthquake or warming ocean waters--the consequences could be dire. Methane is a greenhouse gas 21 times more effective at trapping heat than carbon dioxide. Today, 3000 times more methane exists in hydrate deposits than in the atmosphere. Releasing even a fraction of this amount would amplify global warming. The decomposition of hydrates near the surface of the sea floor could even trigger tsunamis by causing landslides on the continental slope.

The Earth is the hottest it has been in at least 400 years, probably even longer. The National Academy of Sciences, reaching that conclusion in a broad review of scientific work requested by Congress, reported Thursday that the "recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia."

A panel of top climate scientists told lawmakers that the Earth is running a fever and that "human activities are responsible for much of the recent warming." Their 155-page report said average global surface temperatures in the Northern Hemisphere rose about 1 degree during the 20th century. The report was requested in November by the chairman of the House Science Committee, Rep. Sherwood Boehlert, R-N.Y., to address naysayers who question whether global warming is a major threat.

Last year, when the House Energy and Commerce Committee chairman, Rep. Joe Barton, R-Texas, launched an investigation of three climate scientists, Boehlert said Barton should try to learn from scientists, not intimidate them. The Bush administration also has maintained that the threat is not severe enough to warrant new pollution controls that the White House says would have cost 5 million Americans their jobs.

"Yet, a few weeks ago, when I - a NASA climate scientist - tried to talk to the media about these issues following a lecture I had given calling for prompt reductions in the emission of greenhouse gases, the NASA public affairs team - staffed by political appointees from the Bush administration - tried to stop me doing so. I was not happy with that, and I ignored the restrictions. The first line of NASA's mission is to understand and protect the planet."

"This new satellite data is a remarkable advance. We are seeing for the first time the detailed behaviour of the ice streams that are draining the Greenland ice sheet. They show that Greenland seems to be losing at least 200 cubic kilometres of ice a year. It is different from even two years ago, when people still said the ice sheet was in balance. Hundreds of cubic kilometres sounds like a lot of ice. But this is just the beginning. Once a sheet starts to disintegrate, it can reach a tipping point beyond which break-up is explosively rapid. The issue is how close we are getting to that tipping point. The summer of 2005 broke all records for melting in Greenland. So we may be on the edge."

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How far can it go? The last time the world was three degrees warmer than today - which is what we expect later this century - sea levels were 25m higher. So that is what we can look forward to if we don't act soon. None of the current climate and ice models predict this. But I prefer the evidence from the Earth's history and my own eyes. I think sea-level rise is going to be the big issue soon, more even than warming itself.

It's hard to say what the world will be like if this happens. It would be another planet. You could imagine great armadas of icebergs breaking off Greenland and melting as they float south. And, of course, huge areas being flooded.

How long have we got? We have to stabilise emissions of carbon dioxide within a decade, or temperatures will warm by more than one degree. That will be warmer than it has been for half a million years, and many things could become unstoppable. If we are to stop that, we cannot wait for new technologies like capturing emissions from burning coal. We have to act with what we have. This decade, that means focusing on energy efficiency and renewable sources of energy that do not burn carbon. We don't have much time left.

Researchers on a scientific expedition in the Atlantic Ocean measured the strength of the current between Africa and the east coast of America and found that the circulation has slowed by 30% since a previous expedition 12 years ago.

The current, which drives the Gulf Stream, delivers the equivalent of 1m power stations-worth of energy to northern Europe, propping up temperatures by 10C in some regions. The researchers found that the circulation has weakened by 6m tonnes of water a second. Previous expeditions to check the current flow in 1957, 1981 and 1992 found only minor changes in its strength, although a slowing was picked up in a further expedition in 1998. The decline prompted the scientists to set up a £4.8m network of moored instruments in the Atlantic to monitor changes in the current continuously.

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If the current remains as weak as it is, temperatures in Britain are likely to drop by an average of 1C in the next decade, according to Harry Bryden at the National Oceanography Centre in Southampton who led the study. "Models show that if it shuts down completely, 20 years later, the temperature is 4C to 6C degrees cooler over the UK and north-western Europe," Dr Bryden said.

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Uncertainties in climate change models mean that the overall impact on Britain of a slowing down in the current are hard to pin down. "We know that if the current slows down, it will lead to a drop in temperatures in Britain and northern Europe of a few degrees, but the effect isn't even over the seasons. Most of the cooling would be in the winter, so the biggest impact would be much colder winters," said Tim Osborn, of the University of East Anglia climatic research unit.

"The question is no longer whether we will need to address this problem, but when we will need to address the problem," said Kenneth Caldeira, an author of the study and a climate expert at the Carnegie Institution's Department of Global Ecology, based at Stanford University.

"We can either address it now, before we severely and irreversibly damage our climate, or we can wait until irreversible damage manifests itself strongly," Dr. Caldeira said. "If all we do is try to adapt, things will get worse and worse." The paper's lead author, Bala Govindasamy of the Energy Department's Lawrence Livermore National Laboratory, said it might take 20 or 30 years before the scope of the human-caused changes becomes evident, but from then on there is likely to be no debate.

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Consistent with many other studies, the model showed that the Arctic would see the most warming, with average annual temperatures in many parts of Arctic Russia and northern North America rising more than 25 degrees Fahrenheit around 2100. Antarctica would follow suit later, with temperatures there rising sharply around 2200. The impact on vegetation and landscapes would transform large areas of the earth. In the simulation, at least one ecosystem, the scrubby Arctic tundra largely vanishes as climate zones shift hundreds of miles north. Tundra would decline from about 8 percent of the world's land area to 1.8 percent. Alaska, in the model, loses almost all of its evergreen boreal forests and becomes a largely temperate state.

[S]cores of piranhas shook in spasms in two inches of water -- what was left of the once flowing Parana de Manaquiri river, an Amazon tributary. Thousands of rotting fish lined the its dry banks. The governor of Amazonas, a state the size of Alaska, has declared 16 municipalities in crisis as the two-month-long drought strands river dwellers who cannot find food or sell crops.

Some scientists blame higher ocean temperatures stemming from global warming, which have also been linked to a recent string of unusually deadly hurricanes in the United States and Central America. Rising air in the north Atlantic, which fuels storms, may have caused air above the Amazon to descend and prevented cloud formations and rainfall, according to some scientists. "If the warming of the north Atlantic is the smoking gun, it really shows how the world is changing," said Dan Nepstadt, an ecologist from the Massachusetts-based Woods Hole Research Institute, funded by the U.S. government and private grants. "The Amazon is a canary in a coal mine for the earth. As we enter a warming trend we are in uncertain territory," he said.

Deforestation may also have contributed to the drought because cutting down trees cuts moisture in the air, increasing sunlight penetration onto land. Other scientists say severe droughts were normal and occurred in cycles before global warming started.

For years, many scientists and regulators believed the oceans were so vast there was little risk of marine species dying out. Now, some suspect the world is on the cusp of what Ellen K. Pikitch, executive director of the Pew Institute for Ocean Science, calls "a gathering wave of ocean extinctions." Dozens of biologists believe the seas have reached a tipping point, with scores of species of ocean-dwelling fish, birds and mammals edging toward extinction. In the past 300 years, researchers have documented the global extinction of just 21 marine species -- and 16 have occurred since 1972.

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Although a number of previous extinctions involved birds and marine mammals, it is the fate of many fish that worries experts. The large-scale industrialization of the fishing industry after World War II, a global boom in oceanfront development and a rise in global temperatures are all causing fish populations to plummet.

"Extinctions happen in the ocean; the fossil record shows that marine species have disappeared since life began in the sea," said Elliott A. Norse, who heads the Marine Conservation Biology Institute in Redmond, Wash. "The question is, are humans a major new force causing marine extinctions? The evidence, and projections scientists are making, suggest that the answer is yes."

Anyone doubting the effects of human activity on global climate change should talk to the people it affects in Alaska and the Yukon, U.S. Sen. John McCain said Wednesday. Fresh from a trip to Barrow, America's northernmost city, McCain said anecdotes from Alaskans and residents of the Yukon Territory confirm scientific evidence of global warming.

"We are convinced that the overwhelming scientific evidence indicated that climate change is taking place and human activities play a very large role," McCain said.

McCain, accompanied by Sens. Hillary Rodham Clinton, D-N.Y., Susan Collins, R-Maine, and Lindsey Graham, R-S.C., spoke to villagers in Canada whose spruce trees are being attacked by the northward spread of spruce beetles. On Alaska's northern coast, they met Native Alaskans dealing with melting permafrost and coastal erosion.

"I don't think there is any doubt left for anyone who actually looks at the science," Clinton said. "There are still some holdouts, but they are fighting a losing battle. The science is overwhelming, but what is deeply concerning is that climate change is accelerating."

Graham, who declared himself "on the fence" about climate change legislation, said an academic debate about global warming is different in the North. "If you can go to the Native people and listen to their stories and walk away with any doubt that something's going on, I just think you're not listening," he said.

Question: Scott, on Philip Cooney, you said earlier today that the White House has been -- that he had been looking at other options for some time. With his move to Exxon, are there concerns now about at least an appearance of impropriety? Today you had Senate Minority Leader Harry Reid comment on this, saying that "the revolving door between the White House and big oil swung open again." Are you concerned that perhaps this is becoming, or could become a distraction from the President's agenda?

MR. McCLELLAN: I think it's unfortunate that some are trying to divert attention away from what is a strong record of addressing the long-term challenge we face from climate change. This administration has moved forward on initiatives to reduce greenhouse gas emissions. This administration has moved forward to reduce greenhouse gas intensity by 18 percent, come 2012. And we're on track to meet that commitment. This administration has worked with partners around the world to move forward in partnership on initiatives that would reduce greenhouse gas emissions. The President launched the methane-to-markets initiative. This is an initiative that will significantly reduce a greenhouse gas emission, and also provide cleaner burning electricity to people. Those are significant efforts.

We have invested billions of dollars in research when it comes to better understanding the science of climate change. We are investing in new technologies to reduce greenhouse gas emissions. So that's just simply someone trying to divert attention away from what is a strong record, when it comes to addressing climate change.

Question: But are you concerned at all that maybe this might gain some momentum, and perhaps become a larger distraction than it is right now?

MR. McCLELLAN: That what may gain some momentum? And what impropriety were you referring to?

Question: Well, Cooney's move to Exxon -- I'm asking if there is any concern about an appearance, at the very least, by some --

MR. McCLELLAN: Look, in terms of this individual, we wish him well. We appreciate his service.

Documents leaked to a whistle-blower project and published last week in New York Times showed that Mr Cooney repeatedly deleted warnings in official policy papers about climate change. He also emphasised doubts about the scientific research into greenhouse gases.

The revelation came just 24 hours after President George W. Bush said his administration viewed climate change as a "serious long-term" problem. The White House denied it was politicising science and said Mr. Cooney's changes were part of the normal policy review process.

In handwritten notes on drafts of several reports issued in 2002 and 2003, the official, Philip A. Cooney, removed or adjusted descriptions of climate research that government scientists and their supervisors, including some senior Bush administration officials, had already approved. In many cases, the changes appeared in the final reports.

The dozens of changes, while sometimes as subtle as the insertion of the phrase "significant and fundamental" before the word "uncertainties," tend to produce an air of doubt about findings that most climate experts say are robust.

Mr. Cooney is chief of staff for the White House Council on Environmental Quality, the office that helps devise and promote administration policies on environmental issues. Before going to the White House in 2001, he was the "climate team leader" and a lobbyist at the American Petroleum Institute, the largest trade group representing the interests of the oil industry. A lawyer with a bachelor's degree in economics, he has no scientific training[emphasis added].

In one instance in an October 2002 draft of a regularly published summary of government climate research, "Our Changing Planet," Mr. Cooney amplified the sense of uncertainty by adding the word "extremely" to this sentence: "The attribution of the causes of biological and ecological changes to climate change or variability is extremely difficult." In a section on the need for research into how warming might change water availability and flooding, he crossed out a paragraph describing the projected reduction of mountain glaciers and snowpack. His note in the margins explained that this was "straying from research strategy into speculative findings/musings."

Mr. Cooney's alterations can cause clear shifts in meaning. For example, a sentence in the October 2002 draft of "Our Changing Planet" originally read, "Many scientific observations indicate that the Earth is undergoing a period of relatively rapid change." In a neat, compact hand, Mr. Cooney modified the sentence to read, "Many scientific observations point to the conclusion that the Earth may be undergoing a period of relatively rapid change." [emphasis added]