The following is from yesterday's Washington Post.
Warmer Still: Extreme Climate Predictions Appear Most Accurate, Report Says
By Brian Vastag, Published: November 8, 2012
Climate scientists agree the Earth will be hotter by the end of the century, but their simulations don't agree on how much. Now a study suggests the gloomier predictions may be closer to the mark.
"Warming is likely to be on the high side of the projections," said John Fasullo of the National Center for Atmospheric Research in Boulder, Colo., a co-author of the report, which was based on satellite measurements of the atmosphere.
That means the world could be in for a devastating increase of about eight degrees Fahrenheit by 2100, resulting in drastically higher seas, disappearing coastlines and more severe droughts, floods and other destructive weather.
Such an increase would substantially overshoot what the world's leaders have identified as the threshold for triggering catastrophic consequences. In 2009, heads of state agreed to try to limit warming to 3.6 degrees, and many countries want a tighter limit.
Climate scientists around the world use supercomputers to simulate the Earth's atmosphere and oceans. Sophisticated programs attempt to predict how climate will change as society continues burning coal, oil and gas, the main sources of heat-trapping gases such as carbon dioxide.
But these simulations spit out a wide range of warming estimates. All foresee an overheated planet in 2100, but some predict just three degrees of warming while others estimate eight or more degrees of extra heat.
"This problem has been around for 30 years," Fasullo said. "As long as climate models have existed, there's been this spread in projections of the future."
One source of uncertainty involves the impact of cloud cover, especially clouds that form in the tropical and subtropical regions between about 30 degrees north and south of the equator.
"Tropical clouds are so important to climate," Fasullo said. "Small changes in clouds near the equator have a big effect on where you end up" for temperature predictions.
As sunlight pours onto the tropics, clouds bounce some of that heat back into space. Fewer clouds open up the atmosphere "like an iris," Fasullo said, allowing more heat to beam onto Earth's surface.
No supercomputer is powerful enough to predict cloud cover decades into the future, so Fasullo and colleague Kevin Trenberth struck on another method to test which of the many climate simulations most accurately predicted clouds: They looked at relative humidity. When humidity rises, clouds form; drier air produces fewer clouds. That makes humidity a good proxy for cloud cover.
Looking back at 10 years of atmospheric humidity data from NASA satellites, the pair examined two dozen of the world's most sophisticated climate simulations. They found the simulations that most closely matched humidity measurements were also the ones that predicted the most extreme global warming.
In other words, by using real data, the scientists picked simulation winners and losers.
"The models at the higher end of temperature predictions uniformly did a better job," Fasullo said. The simulations that fared worse — the ones predicting smaller temperature rises — "should be outright discounted," he said.
The most accurate climate simulations were run by the United Kingdom's Met Office, a consortium in Japan and a facility at the National Center for Atmospheric Research.
"The biggest benefit of this study is really just a reminder to go back" and see how well climate models match reality, said Jimmy Booth, a post-doctoral fellow at the NASA Goddard Institute for Space Studies in New York, who was not involved in the study. Booth works on a climate model called E2, and he said his team can now reexamine how well it simulates humidity in the tropics.
The study is part of a quickening trend to improve climate simulations. Over the past decade, these computer programs have become "tremendously more sophisticated," said Stephen Lord of the National Oceanic and Atmospheric Administration. International groups collaborate on simulations even as available computing power soars.
The first climate models, about 30 years old, simulated only the Earth's atmosphere. The latest generation add the effects of ocean currents, the dwindling planetary ice cover, and even how plants and animals take up and release carbon.
"As you make those improvements," Lord said, "the ability to simulate long-term climate gets better."
Scientists not involved in the research said the report, funded by NASA and scheduled for publication Friday in the journal Science, could improve the predictions made by the Intergovernmental Panel on Climate Change in its next comprehensive report, due in 2013. The panel is a world body organized by the United Nations to guide policymakers as they struggle to curb and adapt to climate change. The world has warmed by about 1.4 degrees Fahrenheit since 1880, a rise scientists nearly uniformly attribute to carbon pollution from fossil fuels.
© The Washington Post Company
Okay, here it is, almost a year later. The world's Climate Scientists have spoken (and it's not good). :eek:
Libby
~
The Washington Post
By Darryl Fears, Published: September 27, 2013
A panel of the world's leading climate scientists strongly asserted Friday that "it is extremely likely that human influence has been the dominant cause" of global warming since 1950 and warned of more rapid ice melt and rising seas if governments do not aggressively act to reduce the pace of greenhouse gas emissions.
At a meeting in Stockholm, where the panel released its latest assessmentof climate change, the scientists for the first time established a budget for the amount of carbon that can be released into the atmosphere. Even if that target is reached, carbon emissions will have a harmful impact on the environment well into the future.
"As the ocean warms, and glaciers and ice sheets reduce, global mean sea level will continue to rise but at a faster rate than we have experienced over the past 40 years," said Qin Dahe, a Chinese scientist who co-chaired the working group that produced the first of the report's three segments, a summary for government policymakers.
"As a result of our past, present and expected future emissions of [carbon dioxide], we are committed to climate change, and effects will persist for many centuries even if emissions . . . stop," said Thomas Stocker, a German scientist who served as the other leader of the working group.
Improved models
The 2,000-page report of the Intergovernmental Panel on Climate Change, appointed by the United Nations, will not be available until Monday, following a weekend of editing and corrections. But a summary highlighting 20 findings was provided early Friday.
Some key findingswere that the planet is warming at an accelerated pace without any doubt, that humans are causing it with 95 percent certainty and that the past three decades have been the hottest since 1850.
Carbon concentrations in the atmosphere have increased 40 percent since then, and carbon, methane and nitrous oxide are at levels unprecedented in at least 800,000 years.
Greenland and Antarctic ice sheets have steadily lost massin two decades, and glaciers are shrinking worldwide. Sea-level rise could reach three feet by 2100.
The panel expressed high confidence in its findings because climate models that help scientists observe surface temperature patterns have improved in the past six years, since its previous climate assessment. The current assessment is the IPCC's fifth since 1990.
Scientists arrived at their conclusions by drawing on more than 9,000 publications. They considered more than 54,000 comments from about 1,050 people in 52 nations.
Yet the summary did little to dissuade a small but forceful chorus of scholars who deny that humans cause significant global warming or that Earth is suffering from warming effects.
The Heartland Institute, a nonprofit group funded by individuals and corporations, denounced the IPCC's findings in a statement, citing a competing report called Climate Change Reconsidered II, released about a week ago by the Nongovernmental International Panel on Climate Change.
Consistent with the positions of the institute, which helped pay for it, the NIPCC found that "the human impact on climate is very small, and . . . any warming that may be due to human greenhouse gas emissions is likely to be so small as to be invisible," said the institute's president, Joseph Bast.
The IPCC comprises 800 scientists from around the globe, including workers at agencies such as NASA. The NIPCC has considerably fewer member scientists.
In the United States, officials reacted favorably to the report. Secretary of State John F. Kerry said that "climate change is real" and that the United States is determined to be a leader in curbing emissions.
Sen. Barbara Boxer (D-Calif.), chairman of the Committee on Environment and Public Works, called it a landmark study and said it underscores the Obama administration's recent efforts. "I will do everything in my power to support the administration in their efforts to address the dangerous impacts of climate disruption," Boxer said.
'A warning bell'
Frances Beinecke, president of the Natural Resources Defense Council, an environmental advocacy group, called the report "a warning bell to the world." She said the impacts are fierce wildfires, drought, floods and storms that will get worse with delay. "The science is clear: We are altering the climate," Beinecke said.
Critics have called climate computer modelsthat the IPCC and other climate scientists rely on into question, saying they have not taken a 15-year global warming slowdown into greater account.
Sen. James M. Inhofe (R-Okla.), a longtime climate skeptic, said the IPCC's summary "proves that the U.N. is more interested in advancing a political agenda than scientific integrity."
It "glossed over the ongoing 15-year pause in temperature increases and did nothing to suggest that their predictions might be wrong," he said.
Scientists on the panel retorted that their report gives greater weight to evidence of warming over a much longer period. "Certainly if we experience [a slowdown] for the next 20 years, we cannot be confident in the models," Stocker said at the Stockholm meeting, aired via a webcast.
On the other hand, he said: "The last three decades were the warmest in the last 150 years. The present decade indeed is the warmest one."
Using four scenarios based on different controls on greenhouse gas emissions, the report projected a rise in temperatures ranging from less than 1 degree to nearly 9 degrees.
Only the lowest scenario based on significant carbon emission cuts is likely to meet the limit of 3.6 degrees Fahrenheit above preindustrial temperatures agreed upon by IPCC member nations to avoid the worst impacts.
The White House recently acted to curb emissionsof future coal- and gas-fired power plants. The United States and China are the world's largest polluters.
For the first time, the report provided a carbon budget of 1 trillion tons of carbon released in the atmosphere to avoid the worst effects of climate change. More than half that amount has already been released. Up to 3 trillion tons are buried in the earth as fossil fuel.
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