CO2 isn't the point of contention, it's feedbacks-Dr. David M.W. Evans

2/26/12, "The Skeptics Case," WUWT, Dr. David M. W. Evans, (republished here with permission, PDF link below)

"We check the main predictions of the climate models against the best and latest data. Fortunately the climate models got all their major predictions wrong. Why? Every serious skeptical scientist has been consistently saying essentially the same thing for over 20 years, yet most people have never heard the message – here it is, put simply enough for any lay reader willing to pay attention.

What the Government Climate Scientists Say

Figure 1: The climate models. If the CO₂ level doubles (as it is on course to do by about 2070 to 2100), the climate models estimate the temperature increase due to that extra CO₂ will be about 1.1°C × 3 = 3.3°C.ⁱ

The direct effect of CO₂ is well-established physics, based on laboratory results, and known for over a century.ⁱⁱ

Feedbacks are due to the ways the Earth reacts to the direct warming effect of the CO₂. The threefold amplification by feedbacks is based on the assumption, or guess, made around 1980, that more warming due to CO₂ will cause more evaporation from the oceans and that this extra water vapor will in turn lead to even more heat trapping because water vapor is the main greenhouse gas. And extra heat will cause even more evaporation, and so on. This amplification is built into all the climate models.ⁱⁱⁱ The amount of amplification is estimated by assuming that nearly all the industrial-age warming is due to our CO₂.

The government climate scientists and the media often tell us about the direct effect of the CO₂, but rarely admit that two thirds of their projected temperature increases are due to amplification by feedbacks.

What the Skeptics Say

Figure 2: The skeptic’s view. If the CO₂ level doubles, skeptics estimates that the temperature increase due to that extra CO₂ will be about 1.1°C × 0.5 ≈ 0.6°C.^iv

The serious skeptical scientists have always agreed with the government climate scientists about the direct effect of CO₂. The argument is entirely about the feedbacks....

The feedbacks dampen or reduce the direct effect of the extra CO₂, cutting it roughly in half.^v The main feedbacks involve evaporation, water vapor, and clouds. In particular, water vapor condenses into clouds, so extra water vapor due to the direct warming effect of extra CO₂ will cause extra clouds, which reflect sunlight back out to space and cool the earth, thereby reducing the overall warming.

There are literally thousands of feedbacks, each of which either reinforces or opposes the direct warming effect of the extra CO₂. Almost every long-lived system is governed by net feedback that dampens its response to a perturbation. If a system instead reacts to a perturbation by amplifying it, the system is likely to reach a tipping point and become unstable (like the electronic squeal that erupts when a microphone gets too close to its speakers). The earth’s climate is long-lived and stable— it has never gone into runaway greenhouse, unlike Venus — which strongly suggests that the feedbacks dampen temperature perturbations such as that from extra CO₂.

What the Data Says

The climate models have been essentially the same for 30 years now, maintaining roughly the same sensitivity to extra CO₂even while they got more detailed with more computer power."...

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Ed. note: From my reading, people who feel most strongly about the existence of catastrophic man-caused global warming include in that belief that US industry must be muted, and money must be taken from evil Americans and given to the poor or to the UN who will then allegedly give it to the poor. Climate science and social justice are not the same. I understand the continent of Africa has been told billions of dollars are on their way there from evil Americans. Most Americans are broke now and the middle class has become the new poor. Aside from that, slavery has more or less gone out. There are still many billionaires in the US. Try getting the cash from them. You're always free to sell all your belongings and turn the proceeds over to the UN. Have a nice day.


via Behind the Black, Robert Zimmerman. Charts from Dr. Evans article