Unsettled: What Climate Science Tells Us, What It Doesn’t, and Why It Matters

by Steven E. Koonin

Greenhouse gases alone caused a warming of 1.5ºC (2.7ºF) from 1900, which is partially offset by a cooling of about 0.6ºC (1.1ºF) from human-caused aerosols (solar variation and volcanic aerosols don’t have much long-term effect).