Al Gore starts his odyssey on global warming with the Keeling Curve - the chart of steadily increasing CO2 levels measured off the top of Mauna Loa. Very compelling and the cornerstone of the case for anthropogenic (man-made) global warming (AGW). Early this year, however, the annual rate of increase was the lowest measured, and on a monthly basis seemed to be coming to a dead stop - which means after seasonal adjustments would show a down trend. Now it appears there is a down trend in the CO2 levels. See chart. If this continues it spells the coup de grace for the goofy AGW case.

The core of the AGW case is industrial CO2 spews out and stays in the atmosphere, accumulating faster than natural processes can handle, and causing ever-increasing warming. Over the past few decades we have been emitting 4 ppm of CO2 per year, and the atmospheric levels have been increasing by 2 ppm. We continue to spew, but if CO2 levels drop, it means something else is going on.

Problems with CO2

I have discussed some of the problems with the CO2 case previously. The simplest rebuttal is that the vaunted ice core data that Al Gore touts shows CO2 lags warming. Also, CO2 is a trace gas, measured in parts per million. It isn't even the most important greenhouse gas - that honor goes to water vapor, which is 25x more prevalent and is measured in parts per thousand. This is why the theory of AGW has always been a bit goofy.

Another fact that is hard for the AGW theory to explain away is shown in this graphic: the models for the greenhouse effect require warming in the upper atmosphere where the greenhouse effect occurs, but satellite measurements say that isn't happening. Consequently, whatever has been warming the planet since the end of the Little Ice Age 250 years ago is NOT the greenhouse effect.



Climate Sensitivity

The IPCC climate models have a deep secret that the AGW advocates try to obscure: they do not assume the minute increase in CO2 itself (remember - parts per million) is directly causing the greenhouse effect; instead they add a 'climate sensitivity' to the models to make the CO2 increase fit the actual warming. A little CO2 goes a long way. Scarier is that the models have positive feedback so as more CO2 accumulates, the warming effect accelerates.

Here as well the theory is in deep trouble. This climate sensitivity can be measured, and not merely be a plug in a model to make it work. Prof. Lindzen of MIT has done the measurement, and found that the actual climate sensitivity is much less than in the models . This chart is a bit complex but the measured sensitivity is about 0.65 rather than 1.2 or higher as assumed by the models. This means (right axis) that the measured feedback is negative, not positive as in the models. This makes a huge difference - not only is warming less, but it will not become a runaway (positive feedback) process, like a nuclear bomb.

UPDATE 7/23: Lindzen has issued his analysis in a note, reported by WattsUpWithThat. Positive feedback is another reason why the AGW theory is goofy. We have had periods of much higher CO2 in the atmosphere than now, and not turned in a hothouse like Venus. Some natural process limits the greenhouse effect. These IPCC models need to assume a runaway feedback in order to take the minute increase in CO2 and make it cause warming.

Methane

Some AGW advocates have moved beyond CO2 to Methane (CH4) as an even more pernicious greenhouse gas, caused by SUVs, industrial activity and too many cows. Methane is measured in parts per billion, so is even more of a trace gas than CO2. Here again the AGW crowd is in trouble with their theory. While spewing of CH4 continues (although in the US at least at a lower rate), atmospheric CH4 has been plateauing.

Ocean Temperatures