Cloudy Days on the Global Warming Front

Advocates of anthropogenic global warming want you to believe that the science is settled and there is nothing left to debate. But this is the opposite of the truth; in fact, climate science is in its infancy and virtually every proposition relating to it is controversial.
A case in point: the computer programs that tell us that human activity will lead to catastrophic warming assume that warmer temperatures will give rise to more high-altitude clouds, which in turn will trap heat in the earth’s atmosphere and create a positive feedback loop. Recent research suggests, however, that increasing temperatures will have the opposite effect, reducing the incidence of high-altitude clouds and thereby creating a safety valve rather than reinforcing the original warming. The research was published in Geophysical Research Letters by Roy W. Spencer, William D. Braswell, John R. Christy and Justin Hnilo:

The widely accepted (albeit unproven) theory that manmade global warming will accelerate itself by creating more heat-trapping clouds is challenged this month in new research from The University of Alabama in Huntsville.
Instead of creating more clouds, individual tropical warming cycles that served as proxies for global warming saw a decrease in the coverage of heat-trapping cirrus clouds, says Dr. Roy Spencer, a principal research scientist in UAHuntsville’s Earth System Science Center.
“All leading climate models forecast that as the atmosphere warms there should be an increase in high altitude cirrus clouds, which would amplify any warming caused by manmade greenhouse gases,” he said. “That amplification is a positive feedback. What we found in month-to-month fluctuations of the tropical climate system was a strongly negative feedback. As the tropical atmosphere warms, cirrus clouds decrease. That allows more infrared heat to escape from the atmosphere to outer space.”
As the Earth’s surface warms – due to either manmade greenhouse gases or natural fluctuations in the climate system – more water evaporates from the surface. Since more evaporation leads to more precipitation, most climate researchers expected increased cirrus cloudiness to follow warming.
“To give an idea of how strong this enhanced cooling mechanism is, if it was operating on global warming, it would reduce estimates of future warming by over 75 percent,” Spencer said. “The big question that no one can answer right now is whether this enhanced cooling mechanism applies to global warming.”
“The role of clouds in global warming is widely agreed to be pretty uncertain,” Spencer said. “Right now, all climate models predict that clouds will amplify warming. I’m betting that if the climate models’ ‘clouds’ were made to behave the way we see these clouds behave in nature, it would substantially reduce the amount of climate change the models predict for the coming decades.”
The team analyzed six years of data from four instruments aboard three NASA and NOAA satellites. The researchers tracked precipitation amounts, air and sea surface temperatures, high and low altitude cloud cover, reflected sunlight, and infrared energy escaping out to space.
When they tracked the daily evolution of a composite of fifteen of the strongest intraseasonal oscillations they found that although rainfall and air temperatures would be rising, the amount of infrared energy being trapped by the cloudy areas would start to decrease rapidly as the air warmed. This unexpected behavior was traced to the decrease in cirrus cloud cover.
“Global warming theory says warming will generally be accompanied by more rainfall,” Spencer said. “Everyone just assumed that more rainfall means more high altitude clouds. That would be your first guess and, since we didn’t have any data to suggest otherwise …”
There are significant gaps in the scientific understanding of precipitation systems and their interactions with the climate, he said. “At least 80 percent of the Earth’s natural greenhouse effect is due to water vapor and clouds, and those are largely under the control of precipitation systems.
“Until we understand how precipitation systems change with warming, I don’t believe we can know how much of our current warming is manmade. Without that knowledge, we can’t predict future climate change with any degree of certainty.”

That’s a remarkable quote: “Everyone just assumed” that more rainfall means more high altitude clouds. That is the level of scientific certainty on which claims of catastrophic anthropogenic global warming rest.
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