There is No Evidence

Let's break down the case for human-caused global warming logically:

1) There is plenty of evidence that global warming has been occurring recently.

2) There is ample evidence that carbon emissions causes warming and that the level of atmospheric carbon dioxide is increasing.

3) But there is no evidence that carbon dioxide emissions are the main cause of the recent global warming.

Read the document at http://sciencespeak.com/NoEvidence.pdf.

What Would Constitute Evidence?

There is good evidence to support the calculations of the warming caused by an increase in atmospheric CO2, without the effect of the climate feedbacks. We are much less certain about the total warming due to increasing CO2, which include the climate feedbacks that amplify or dampen this no-feedbacks warming due to CO2. IPCC climate theory assumes a strong positive, amplifying climate feedback, principally due to water vapor. Therefore, either:

• evidence of overall strong positive feedback in the climate, or
• evidence of a strongly positive water vapor feedback

would constitute evidence (that CO2 is the main cause of the recent global warming).

For example, if the radiosondes had detected the strong hotspot predicted by the IPCC climate models then that would have been strong evidence--but instead the observed lack of hotspot demonstrates that the water vapor feedback is weak or negative. Strong correlations and synchronized changes in trend directions between CO2 and temperature on all time scales would constitute evidence, but we know that it is not the case.

Otherwise we are looking for some new evidence from left field. Especially difficult for the CO2 theory is how to explain the counter evidence that is accumulating, which shows that the feedbacks are dampening not amplifying and that the climate sensitivity is a fraction of that assumed by the IPCC. It appears at this point that the CO2 theory is doomed, and it is only a matter of time before its bubble bursts.