For a variety of reasons I have been limited in blogging, but here is a brief roundup of interesting stories related to the science of anthropogenic global warming.
- Even by the EPA’s own alarmist numbers, a reduction in man-made warming of 0.01C in the year 2100 would cost $78 billion per year. This is over $7 trillion a year per degree of avoided warming, again using even the EPA’s overly high climate sensitivity numbers. For scale, this is almost half the entire US GDP. This is why the precautionary principle was always BS – it assumed that the cost of action was virtually free. Sure it makes sense to avoid low-likelihood but high-cost future contingencies if the cost of doing so is low. But half of GDP?
- As I have written a zillion times, most of the projected warming from CO2 is not from CO2 directly but from positive feedback effects hypothesized in the climate. The largest of these is water vapor. Water is (unlike CO2) a strong greenhouse gas and if small amounts of warming increase water vapor in the atmosphere, that would be a positive feedback effect that would amplify warming. Most climate modellers assume relative humidity stays roughly flat as the world warms, meaning total water vapor content in the atmosphere will rise. In fact, this does not appear to have been the case over the last 50 years, as relative humidity has fallen while temperatures have risen. Further, in a peer-reviewed article, scientists suggest certain negative feedbacks that would tend to reduce atmospheric water vapor.
- A new paper reduces the no-feedback climate sensitivity to CO2 from about 1-1.2C/doubling (which I and most other folks have been using) to something like 0.41C. This is the direct sensitivity to CO2 before feedbacks, if I understand the paper correctly. without any reference to feedbacks. In that sense, the paper seems to be wrong in comparing this sensitivity to the IPCC numbers, which are including feedbacks. A more correct comparison is of the 0.41C to a number about 1.2C, which is what I think the IPCC is using. Never-the-less, if correct, halving this sensitivity number should halve the post-feedback number.
My hypothesis continues to be that the post feedback climate sensitivity to CO2 number, expressed as degrees C per doubling of atmospheric CO2 concentrations, is greater than zero and less than one.
- It is pretty much time to stick a fork in the hide-the-decline debate. This is yet another occasion when folks (in this case Mann, Briffa, Jones) should have said “yep, we screwed up” years ago and moved on. Here is the whole problem in 2 charts. Steve McIntyre recently traced the hide-the-decline trick (which can be summarized as truncating/hiding/obfuscating data that undermined their hypothesis on key charts) back to an earlier era.