C. IPCC Admits CO2 Rise lags Temperature Increase.
In 2007 IPCC report at page 105, the IPCC admitted this lag relationship and changed its position to an enhancement theory.
“However, it now appears that the initial climatic change preceded the change in CO2 but was enhanced by it (Section 6.4)”
This is a 100 percent change from the IPCC position in 1990. In 1990, the IPCC stated at page 47 that water vapour is the most important greenhouse gas but it is considered a natural consequence of the warming and is thus a feedback from CO2 and other man-made Greenhouse Gases. The IPCC also classified “clouds” as a feedback because clouds are a consequence of water vapour. If the temperature increase/decrease occurs before CO2 rise/fall then it is the cause and not the result.
It appears that after the IPCC discovered that there were too many scientific publications showing that temperature preceded the CO2 changes, they did not abandon the Greenhouse Effect Hypothesis, but instead argued that CO2 enhanced the amount of Temperature increase referencing Section 6.4 in their assessment report. However, IPCC Section 6.4 did not provide any proof of this enhancement. It stated:
“it may be the result of increased ocean heat transports due to either an enhanced thermohaline circulation (citations) or increased flow of surface ocean currents.” (pg. 442);
“enhanced biological production and increased dustiness (iron supply) are coincident with CO2 concentration changes of 20 to 50 ppm” (pg 446); or
“precipitation-sensitive records and models indicate that summer monsoons in Africa, India and Southeast Asia were enhanced in the early to mid-Holocene due to orbital forcing,” pg. 464.
None of these quoted statements support the position that the temperature increase was enhanced by the CO2. One statement dealt with enhanced ocean thermohaline circulation, one dealt with enhanced biological production, and the other found that precipitation enhancement was caused by orbital forcings. That is not proof that the temperature that occurred first but went higher that it would have because of the CO2.
However Section 6.4 in IPCC Assessment Report (2007) at pg. 444 in Figure 6.3 shows a rejection of this enhancement theory. Figure 6.3 below shows that a rise in temperature (black line) occurred slightly before a rise in CO2 (red line), before N2O (green line) and significantly before a rise in methane (blue line). But it also shows that CO2 does not drop immediately after the temperature drops. This rejects the enhancement theory.