The Skeptic’s Case

David M.W. Evans:

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^oC x 3 = 3.3^oC.1

The direct effect of CO₂ is well-established physics, based on laboratory results, and known for over a century.2

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.3 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.4

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.5 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 CO₂ even while they got more detailed with more computer power.

• How well have the climate models predicted the temperature?
• Does the data better support the climate models or the skeptic’s view?

Air Temperatures

One of the earliest and most important predictions was presented to the US Congress in 1988 by Dr James Hansen, the “father of global warming”:

Figure 3: Hansen’s predictions to the US Congress in 1988,6 compared to the subsequent temperatures as measured by NASA satellites.7

Hansen’s climate model clearly exaggerated future temperature rises.

In particular, his climate model predicted that if human CO₂ emissions were cut back drastically starting in 1988, such that by year 2000 the CO₂ level was not rising at all, we would get his scenario C. But in reality the temperature did not even rise this much, even though our CO₂ emissions strongly increased — which suggests that the climate models greatly overestimate the effect of CO₂ emissions.

A more considered prediction by the climate models was made in 1990 in the IPCC’s First Assessment Report:8

Figure 4: Predictions of the IPCC’s First Assessment Report in 1990, compared to the subsequent temperatures as measured by NASA satellites.

It’s 20 years now, and the average rate of increase in reality is below the lowest trend in the range predicted by the IPCC.

Ocean Temperatures

The oceans hold the vast bulk of the heat in the climate system. We’ve only been measuring ocean temperature properly since mid-2003, when the Argo system became operational.9^,10 In Argo, a buoy duck dives down to a depth of 2,000 meters, measures temperatures as it very slowly ascends, then radios the results back to headquarters via satellite. Over 3,000 Argo buoys constantly patrol all the oceans of the world.

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