https://www.wsj.com/articles/media-climate-change-truth-degrees-warming-disaster-hurricanes-flooding-adaptation-infrastructure-united-nations-11630703058?mod=hp_opin_pos_3#cxrecs_s
If “news” is about how today differs from yesterday, the press missed a lot of news in the long-awaited new report from the United Nations Intergovernmental Panel on Climate Change that was issued a few weeks ago.
After 41 years of promoting a fuzzy and unsatisfying estimate of how much warming might result from a doubling of atmospheric CO2, the world’s climate science arbiter has finally offered the first real improvement in the history of modern climate science.
Through five previous U.N. assessment plus their predecessor, the 1979 Charney Report, the likely worst-case was a rise of 4.5 degrees Celsius. This came from averaging the result of inconsistent computer climate simulations about which the IPCC knew only one thing: They couldn’t all be right and perhaps none were.
Using real-world data, the new report now says the worst case is a 4-degree rise. More important, with much greater confidence than before, disastrous outcomes above 5 degrees are now found to be very unlikely.
In another departure, the U.N. panel now says the dire emissions scenario it promoted for two decades should be regarded as highly unlikely, with more plausible projections at least a third lower.
The report also notes, as the press never does, the full impact of these emissions won’t be manifested until decades, even a century, later. The ultimate likely worst-case effect of a doubling of CO2 might be 4 degrees, but the best estimate of the “transient climate response” this century is about 2.7 degrees, or 1.6 degrees on top of the warming experienced since the start of the industrial age.