Ken Caldeira is a climate scientist at the Carnegie Institution for Science, where his job is “to make important scientific discoveries.” He also serves as a Professor (by courtesy) in the Stanford University Department of Earth System Science. Among Caldeira’s key contributions to science are his relatively early recognition of the threats posed by ocean acidification, his pioneering investigations into the environmental consequences of intentional intervention in the climate system (“geoengineering”), and the first peer-reviewed study to estimate near-zero-emission energy needs consistent with a 2°C climate stabilization target. He has also played a central role in helping to elucidate what our understanding of long-term geochemical cycles implies for the fate of today’s carbon dioxide emissions. Caldeira co-authored the 2015 U.S. National Academy of Sciences reports on climate geoengineering. In 2010, he was elected Fellow of the American Geophysical Union. Caldeira was coordinating lead author of the oceans chapter for the 2005 IPCC report on Carbon Capture and Storage. For the past decade, he has been meeting with Bill Gates a few times each year for learning sessions about climate change and energy. Bill Gates, in his 2016 end-of-year blog post, referred to Ken Caldeira as “my amazing teacher”.