Climatatologist Dr. Roy W. Spencer from University of Alabama raises tough questions regarding a supposed linear upward trend of global average surface temperature of the past 30 years, which is attributed to human activities with a confidence of 90%.

1) Why are ALL of the 20+ IPCC climate models more sensitive in their total cloud feedback than published estimates of cloud feedbacks in the real climate system (Forster and Gregory, J. Climate, 2006)? …

2) And regarding those observational estimates of (somewhat) positive cloud feedbacks: How do you know that the cloud changes that have been observed during temperature changes really are “feedbacks”? …

3) …we all agree that there has been strong global-average warming since the 1970’s. Well, how do you know this wasn’t the result of a small, natural change in cloud cover? Doesn’t it seem like (another) coincidence that the Pacific Decadal Oscillation (PDO) just happened to shift to a different mode in 1977, about the time that the warming started? …

The fact is, we DON’T know how much of recent warming is natural, simply because we don’t have good enough global cloud observations back to the 1970’s (and earlier) to measure any long-term changes in cloudiness to the required accuracy – 1% or less.

The same cause-versus-effect uncertainty is true of any other climate variable as well, for instance water vapor, our main greenhouse gas. A small change in precipitation …

…The very high level of certainty (90%) claimed by the IPCC for their manmade explanation for warming can not be justified based upon the scientific evidence, and is little more than an expression of their faith that they understand the causes of climate variability – which they clearly don’t…

Read the entire open letter here at icecap.us

Is it just coincidence? Two weeks ago, I questioned why the IPCC is 90% confident that the human impact during the warming of the second half of the 20th century is mostly caused by human activites (whereby rising CO2 levels are supposed to take the greatest part in this warming of the land and the ocean.) and how they are even 90% confident that the temperature will go up by at least 1.5°C by 2100., based on the observations of the recent decades of warming and based on the attributed climate sensitivity of accumulating CO2 levels.

Thank you Mr. Spencer for confirming that it just doesn’t add up. I take your rhetorical question (quote) “Doesn’t it seem like (another) coincidence that the Pacific Decadal Oscillation (PDO) just happened to shift to a different mode in 1977?” and wonder if PDO has just shifted back. Could such a climate shift be the reason why we got finally one of the strongest El Ninas resulting from upwelling cold water from the Pacific Ocean causing a different distribution of weather and temperature around the globe, and, in combination with a weak sun, resulting in a significant net cooling effect?

You bet!

http://icecap.us/images/uploads/THE_GREAT_PACIFIC_CLIMATE_SHIFT_II.pdf
Here is the original paper: http://www.pnas.org/cgi/reprint/101/12/4136.pdf