Plausible Scenarios for Global Warming
Judith Curry constructs an interesting global warming analysis by beginning with today’s climate as a baseline, and assessing the next 30 years, from 2020 to 2050:
In the midst of all the angst about 1.5oC or 2.0oC warming or more, as defined relative to some mythical time when climate was alleged to be ‘stable’ and (relatively) uninfluenced by humans, we lose sight of the fact that we have a better baseline period – now. One advantage of using ‘now’ as a baseline for future climate change is that we have good observations to describe the climate of ‘now’.
For this purpose, at least, Curry accepts the assumption that increasing levels of CO2 over the next 30 years will, ceteris paribus, increase global temperatures by somewhere between 0.35 and 0.7 degrees Centigrade by 2050. (The analysis is technical, I recommend reading it.) She then assesses the three main sources of natural variability: volcanoes, solar irradiance, and decadal-scale ocean circulation.
As it happens, all of those three natural variability factors are likely to lower global temperatures over the next 30 years. This chart sums up Curry’s conclusions (again, she is a top-notch scientist, and the explanations are all found at the link):
In other words, cooling trends reflecting natural variability are likely to cancel out, for the most part, any effects of increasing concentrations of CO2 over the next 30 years. This is an interesting conclusion. One interpretation is that climate disaster will strike after 2050, when natural variability may turn toward higher, rather than lower, temperatures. But by then, pretty much everyone will have given up on global warming hysteria. Which, in my view, will be a good thing no matter what happens after 2050, since global warming hysteria is all about power politics, not the environment.