For those who have read my climate work or seen the video, the key question in climate science revolves around the feedback effects in the climate system to Co2 warming.
Skeptics, like alarmists, generally agree that a doubling of Co2 concentrations might warm the Earth about a degree Celsius, absent any other effects. But we can imagine all sorts of feedback effects, the most important of which are in water vapor and cloud formation. Warming that forms more clouds might have negative feedback, as clouds offset some of the warming. Warming that increases humidity could lead to more warming, as water vapor is a strong greenhouse gas.
The difference, then, between minor warming and catastrophe is in the feedbacks, and most importantly in clouds and water vapor. All the research the government is funding on whether warming will cause sterility in tree frogs is tangential to this key question.
And this question is far from decided. I won't get into all the arguments here, but to the extent there is any consensus, it is that man' CO2 is probably causing some warming. Whether this is a catastrophe or a nuisance depends on feedbacks which are not well understood.
This week there has been a lot of interesting back and forth over a paper by Roy Spencer several months ago arguing that cloud feedback was negative and would serve to limit the total amount of man-made warming. Just how central this issue is can be seen in the fuss this paper has caused, including editors forced to resign for even daring to publish such heresy, and the speed with which a counter-paper flew through peer review.
I won't get into the depths of this, except to show two charts. The first is from Dessler in the alarmist camp, the second is the same chart but using a different data series. I won't explain the axes, just trust the relationship between these two variables is key to diagnosing the size and direction of feedback.
So we get opposite results (the slope of the regression) simply by using temperature and radiative flux data from to different agencies. And note how thin the fit is in both -- basically drawing a line through a cloud. Neither of these likely has an R-squared higher than about .05.
So there you have it, the most important question in climate - really, the only important question associated with anthropogenic global warming. Settled science, indeed.