For more than 100 years, climate scientists have fully understood that if all else were held constant, an increase in the atmospheric concentration of carbon dioxide (CO2) would lead to an increase in the near-surface air temperatures. The problem becomes a lot more complicated in the real world when we consider that “all else” cannot be held constant and there are a lot more changes occurring at any one time than just the concentration of CO2. Once the temperature of the Earth starts inching upward, changes immediately occur to atmospheric moisture levels, cloud patterns, surface properties, and on and on. Some of these changes, like the additional moisture, amplify the warming and represent positive feedback mechanisms. Other consequences, like the development of more low clouds, would act to retard or even reverse the warming and represent negative feedbacks. Getting all the feedbacks correct is critical to predicting future conditions, and these feedbacks are simulated numerically in global climate general circulation models (GCMs). Herein lies a central component of the great debate — some GCMs predict relatively little warming for a doubling of CO2, and others predict substantial warming for the same change in atmospheric composition.

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Back in 2001, Richard Lindzen and colleagues made quite a stir in the climate community when they published a paper in the Bulletin of the American Meteorological Society in which they describe having possibly identified an “adaptive infrared iris” that opens and closes to keep the earth’s temperature fairly steady even in light of increasing atmospheric carbon dioxide levels. It was proposed to work something like this—when the temperature in the tropical oceans begins to warm up, it causes in increase in the amount of low-level water clouds and an even greater decrease in total coverage of high-altitude ice clouds. Since ice clouds are net warmers (that is, they trap more outgoing longwave radiation (heat) than they reflect away incoming shortwave (solar) radiation) and water clouds are (generally) net coolers (reflecting back to space more incoming solar shortwave radiation than they absorb outgoing longwave radiation), more of the latter and a lot less of the former leads to a net cooling, and the temperatures of the tropical oceans decrease. However, cooler tropical ocean temperatures lead to less low-level (water) clouds and more high altitude ice clouds. This configuration tends to lead to a net radiation increase and to higher temperatures. And the cycle starts over again. Lindzen’s moniker “adaptive infrared iris” refers to the mechanism in which the tropical ice cloud cover opens and closes in response to tropical ocean temperatures to allow more heat to escape to space when the oceans are warm and less heat to escape to space when the oceans are relatively cool (much like the iris of an eye which opens and closes in response to varying light levels to try to maintain a constant level falling on the retina). Lindzen et al. proposed that the iris acts as a global thermostat that will keep the earth’s temperatures from rising very far even as atmospheric concentrations of greenhouse gases increase.

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A recent article in Geophysical Research Letters by Rutgers’ scientists Alan Robock and Haibin Li addresses the issue of global warming and reduced soil moisture levels in important agricultural areas. Every popular global warming presentation lays out the case that higher temperatures in the future will cause higher levels of evaporation that will overwhelm any changes in precipitation and force soil moisture levels to drop. Of course, crops will fail, we will have more frequent and severe droughts of longer duration, and it will have all been caused by elevated carbon dioxide (CO2) levels. You’ve heard the story a 1,000 times by now.

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The global warming scare comes largely, if not exclusively, from the outputs of numerical climate models. Some of the models are relatively simple in their design while other climate models are among the most sophisticated computer programs ever built. When the concentration of greenhouse gases is increased numerically, almost all models of climate show an increase in global temperature with the most warming occurring in the Northern Hemisphere’s highest latitudes. Predictions involving precipitation, drought, hurricanes, floods, changes in climate variability, and all the rest vary considerably from model to model. Many greenhouse advocates treat the 2 ×CO2 model simulations as predictions for the future with little regard for shortcomings in the way the models numerically represent the 1,000s of complex processes at work in the climate system.

The Intergovernmental Panel on Climate (IPCC) change warns in their Summary for Policymakers “models cannot yet simulate all aspects of climate (e.g., they still cannot account fully for the observed trend in the surface-troposphere temperature difference since 1979) and there a particular uncertainties associated with clouds and their interaction with radiation and aerosols.” Two articles have appeared in the scientific literature recently that further expose the weaknesses in the model simulations.

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For years now, we have been deluged with the news that the earth’s oceans are heating up as a result of changes in atmospheric composition resulting from the combustion of fossil fuels.

Typical of these was a 2005 story titled “Where’s The Heat? Think Deep Blue,” from United Press International, describing a recent paper in Science by NASA climate modeler James Hansen. UPI wrote that “Over the past ten years, the heat content of the ocean has grown dramatically.” This study covered more than just the ocean surface temperature, which can fluctuate considerably from year to year. Rather, by considering a much deeper layer (the top 2,500 feet), Hansen could actually calculate the increasing amount of heat that is being stored. According to UPI’s story, this provided “a match” with computer model projections of global warming.

The ocean is a huge flywheel that integrates and stores long-term climate changes. Consequently, when computer models are driven with ever-increasing atmospheric carbon dioxide, the deep oceans warm, warm, and warm. But it takes time to start up, just like a big pot of water heated by a small match. Once the process starts, though, nothing should be able to stop it.

That’s the current wisdom of our climate models, but like current wisdom on so many other aspects of life, nature has behaved differently.

Within weeks, a paper is going to appear in the refereed journal Geophysical Research Letters, by John Lyman of the National Oceanic and Atmospheric Administration, showing that, globally, the top 2500 feet of the ocean lost a tremendous amount of heat between from 2003 through 2005—about 20% of all the heat gained in the last half-century.

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Juliet Eilperin’s latest headline in the Washington Post (January 29, 2006) about how global warming is destroying the earth was “Debate on Climate Shifts to Issue of Irreparable Change.” The Post, which has been news-editorializing this story for a couple of years now, featured her article above the fold in the top-right corner of the Sunday paper. Obviously they are exercised. Our response: cool it.
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Global sea level rise figures prominently in most climate doom and gloom stories. And, not surprisingly, good news is either ignored or mis-reported.

First, a little history. The Intergovernmental Panel on Climate Change estimated, in its Third Assessment Report (2001), that between 1990 and 2100, the global average sea level will rise somewhere between 3.5 and 34.6 inches, with a central value of 18.9 inches. Of course, the values falling near the low end of the range are usually left out of global warming scare stories, while the values near the high end are prominently featured (e.g. see here and here).
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Recently there have been several papers published that have attempted to use the evolution of the earth’s temperature after big volcanic eruptions as a determinate of the earth’s climate sensitivity—that is, how much the average temperature changes with a change in climate forcing (i.e. a change of energy input). Having a good understanding of the climate sensitivity is key to having a good understanding of future climate change.

Oftentimes, the sensitivity is reported as the temperature change resulting from an energy change that is equivalent to the one assumed for a doubling of the atmospheric carbon dioxide levels (from pre-industrial values). In its 2001 Third Assessment Report (TAR) the Intergovernmental Panel on Climate Change (IPCC) settled on a value of 3.7 watts per meter squared (W/m2) (see out last article for more information on energy units) for the energy change associated with a doubling of CO2. That’s the easy part. Figuring out how much the earth’s average temperature will change as a result has proven to be much more difficult.
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It seems that the longer NASA scientist Jim Hansen studies the climate, the more insensitive he, or should we say, his interpretation of the climate, becomes.

Climate “sensitivity” is the change in surface temperature expected for each additional Watt of energy that is re-radiated onto the earth’s surface and lower atmosphere by slight changes in the greenhouse effect. The main cause of these changes in the greenhouse effect, of course, is the increasing levels of atmospheric carbon dioxide caused by the combustion of fossil fuels.

You would think that it would be big news when Hansen—the guy who started all this mess with his incendiary 1988 congressional testimony—lowers his estimate for the sensitivity to two-thirds of the value he used back then.

After all, he does get a lot of ink. That’s what happened in October, 2004, when he traveled to hotly contested and environmentally sensitive Iowa the weekend before the election, and publicly berated his Boss’ global warming policy. Talk about insensitive!

Hansen’s most recent figure, just published in Sciencexpress, is that the surface temperature ultimately changes 0.67˚C per Watt per square meter (W/m2). In 1988 he said it was a full degree, and in 2001 he lowered it to 0.75.

The lower the climate sensitivity, the less that the global temperature will rise in the future (given the same amount atmospheric carbon dioxide) and the lower the threat of catastrophic climate change.
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Newly published results show that the degree to which sulfate aerosols lead to surface cooling is overestimated in current climate models. This result further undermines what little support remains for the IPCC’s high-end warming projections.
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