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Why isn't the atmosphere warming like the Earth's surface?

By Dennis T. Avery
web posted October 16, 2006

The Greenhouse Theory says the atmosphere above us should warm faster than the Earth's surface around us. But this doesn't seem to be happening. For example, compare California temperatures in the state's central farming valleys with the readings on the Sierra Nevada Mountains just above them.

John Christy, a native of the Valley now at the University of Alabama/Huntsville, has done just that. He recently led a team that digitized the old manual temperature records and adjusted for any change that could have altered the individual station records: location, instruments, paving, etc.

The adjusted record says the San Joaquin Valley's minimum summer-fall temperatures have risen about 3 degrees C since 1910 -- "a rise that is not detectable in the adjacent Sierra Nevada." Christy says the big reason for the mountain-valley differential is that the Central Valley today is irrigating an additional 1 million acres of farmland. "Human engineering of the environment has changed a [highly-reflective] desert into a darker, moister, vegetated plain" that absorbs more heat.

However, the big news from the more-accurate record is that Sierra Nevada Mountains show only a tiny warming trend--0.02 degrees C per decade from 1910–2003. Why didn't the Sierra Nevada warm more? The carefully adjusted records of the virtually undeveloped Sierra Nevada weather stations disagree with the global climate models. And high-altitude stations are where the Greenhouse Theory says the signs of human-induced warming should be clearest.

Then we have the discrepancies between the surface thermometers and the high-altitude balloons and satellites. Seven out of eight datasets on upper air temperatures in the tropics show much less warming in the atmosphere than on the Earth's surface, according to Christy's July 20, 2006 testimony before Congress. Christy points out that the tropics make up one-third of the planet's surface. He warns that seven datasets are very unlikely to differ from the eighth in the same way by random chance, he warns.

Christy's conclusion: "There is likely a significant difference between the surface and atmospheric trends, with the atmosphere being cooler. This is significant because all model simulations indicate the atmosphere should be warming faster than the surface if greenhouse influences are correctly included in climate models."

He believes that the earth is warming slowly, and that some part of the warming could be related to additional greenhouse gases. However, he says, we have no way to know how much of the 0.6 degree C warming of the 20th century has been natural.

Ice cores from Greenland and Antarctica brought up in the 1980s have told of a long, moderate, irregular 1500-year global warming cycle linked to the sun. It was too moderate and masked by too much natural climate variability to be discerned by primitive peoples without thermometers or written records. It has since been found in seabed sediments, tree rings, glacier retreats, stalagmites, pollen fossils, seashells, and prehistoric dwelling sites all over the world.

The current warming began about 1850, before much human-emitted CO2, and the record includes such erratic events as the global cooling from 1940 to 1975. The 1500-year cycle explains our warming better than the Greenhouse Theory. If we subtract the 0.5 degree C of warming that occurred before 1940 from the overall warming of 0.7-0.8 degrees C, that doesn't leave much to generate scary scenarios about human-emitted CO2. Christy's new paper strengthens the case for examining natural warming factors besides CO2, such as the broadly documented 1500-year cycle.

Christy says he is unimpressed by claims that today's weather is "unusual." In his experience, weather is always erratic and wildly variable -- and humans always think it's unusual. ESR

Dennis T. Avery was a senior policy analyst for the U.S. State Department, where he won the National Intelligence Medal of Achievement. He is the co-author, with atmospheric physicist Fred Singer, of the forthcoming book Unstoppable Global Warming -- Every 1500 Years, due in November from Rowman & Littlefield. Readers may write him at the Center for Global Food Issues, Post Office Box 202, Churchville, VA 24421.


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