Wood Romances

GMST in Various Datasets Since 2013 or so, it's been common to refer to global warming over the last 100 years or so as "real," "man-made" and "dangerous."[1]. To my knowledge, these terms were first used in political discussion, but I believe they can be useful categories for discussing whether it's happening (real), whether it's something we can correct (man-made) and whether it's a problem that needs correcting (dangerous). These three categories of claims do a good job of summarizing how a case can be built that we have a problem that we both can fix and need to fix. These categories are valuable because 1) we can only potentially have a climate warming problem if global warming is real. If it's 1) real and it's 2) man-made, then we have the capacity to fix it by changing what we're doing. If, however, it's mostly natural, then potentially there's nothing we could do to fix the problem, and that's really bad news...

The IPCC AR5 estimates that human activity is responsible for ~110% of the warming since 1951. This statement may seem far fetched to some, but a new paper from Gillett suggests that this actually may be a bit conservative. Gillett's work extends that analysis back to the latter half of the 19th century. The study concluded that "anthropogenic forcings caused 0.9 to 1.3 °C of warming in global mean near-surface air temperature in 2010–2019 relative to 1850–1900, compared with an observed warming of 1.1 °C. Greenhouse gases and aerosols contributed changes of 1.2 to 1.9 °C and −0.7 to −0.1 °C, respectively, and natural forcings contributed negligibly." In the above graph, you can see the that the impact of GHG and aerosol forcings dwarf the impact of other natural forcings. ' Observant readers may note that there are two relatively short-term temperature spikes in the instrumental record, one during the 1860s and another during the 1940s. But these warm years cooled ag...