Friday, August 31, 2007
By Steven Milloy
Runaway global warming, the climate alarmist fantasy let loose on the public, has not yet been captured, but it certainly appears to have at least been cornered by new data from researchers at the University of Alabama-Huntsville (UAH).
In a study published in the American Geophysical Union's Geophysical Research Letters on Aug. 9, the UAH researchers provide more real-world evidence of the atmosphere's self-regulating nature. If this particular self-regulatory mechanism is confirmed by additional research, it will represent yet another deal-breaker for the scientific hypothesis that has propped up climate alarmism thus far.
Global warmers claim that increasing levels of atmospheric greenhouse gases are raising global temperatures. But even if this claim was true — and there is ample reason to be skeptical — greenhouse gases by themselves could only warm the planet by so much.
One of the oft-cited predictions of potential warming is that a doubling of atmospheric carbon dioxide levels from pre-industrial levels — from 280 to 560 parts per million — would alone cause average global temperature to increase by about 1.2 °C.
But such a modest warming by itself is unlikely to cause catastrophic climate change. At a current atmospheric carbon dioxide level of 380 parts per million, we have already observed about half that predicted temperature change without experiencing any climatic chaos.
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Recognizing the ho-hum nature of such a temperature change, the alarmist camp moved on to hypothesize that even this slight warming will cause irreversible changes in the atmosphere that, in turn, will cause more warming. These alleged "positive feedback" cycles supposedly will build upon each other to cause runaway global warming, according to the alarmists.
Existing climate models, for example, assume that a warmer atmosphere will cause an increase in high-altitude cirrus clouds — a positive feedback into the climate system since cirrus clouds trap outgoing radiation emitted by the Earth.
When you feed the above-mentioned warming scenario — the doubling of atmospheric carbon dioxide levels causing 1.2 °C
of warming — into a climate model that has been turbo-charged with positive feedback, the resulting estimated warming increases by 250 percent to 3 °C.
Many have questioned the validity of the hypothetical positive feedback mechanism. Massachusetts Institute of Technology atmospheric physicist Richard Lindzen, for example, proposed in 2001 an explanation called the "iris effect" for why amplified warming has never materialized.
Based on a limited set of data, Lindzen hypothesized that cirrus clouds and associated moisture actually work in opposition to surface temperature changes. When the Earth's surface warms, Lindzen supposed, the clouds open up to allow heat to escape. A cooling surface, in turn, causes clouds to close and trap heat.
This elegant atmospheric self-regulatory mechanism was soon attacked for being based on limited data and the inability of other researchers to be able to identify the iris effect in other cloud and temperature data sets.
But the new research from the University of Alabama-Huntsville supports the validity of the iris effect.
Analyzing six years of data from four instruments aboard three NASA and NOAA satellites, the UAH researchers tracked precipitation amounts, air and sea surface temperatures, high- and low-altitude cloud cover, reflected sunlight and infrared energy escaping out to space.
Rather than the hypothesized positive feedback of the climate models, the UAH data actually shows a strong negative feedback. As the tropical atmosphere warms, cirrus clouds decrease, allowing infrared heat to escape from the atmosphere to outer space.
"To give an idea of how strong this enhanced cooling mechanism is, if it was operating on global warming, it would reduce [climate model-based] estimates of future warming by 75 percent," said UAH researcher Roy Spencer in a media release.
"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."
If you think about it for a moment, none of this should be surprising. As explained in greater detail at JunkScience.com, if positive feedback from warming was really a dominant climatic effect, then it should be very easy to identify by considering an unusual recent weather event — the 1997-98 El Niño event which caused temperatures to spike to the highest level since the 1930s.
But since the Earth cooled almost as abruptly as it warmed, we can only assume that no positive feedback occurred. Our El Niño experience indicates that the Earth is not precariously perched upon some critical temperature threshold beyond which a whole new type of physics takes over and runaway global warming becomes a self-perpetuating nightmare.
The seasonal heating of the hemispheres — quite a severe annual warming event — is also worthy of mention. Average surface temperature in the northern hemisphere, for example, warms by 3.8 °C
from January to July every year without triggering any self-perpetuating positive feedback.
It is, therefore, somewhat difficult to view ongoing global temperature change — amounting to an estimated 0.6 plus or minus 0.2 °C
over the past 120 years — as being dangerous.
No doubt the iris effect will require more research to confirm its existence. But at least real-world data encourage such research. That's a lot more than can be said for the imaginary notion of runaway climate and the climate models that are rigged to make-believe it exists.
Steven Milloy publishesJunkScience.comandDemandDebate.com. He is a junk science expert, and advocate of free enterprise and an adjunct scholar at the Competitive Enterprise Institute.
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