A champion of the environment, McCarthy, known as Jim, was committed to both education and advocacy about climate change. “A profound lesson from the past few decades of scientific discovery across the Earth and life sciences is that the weight of the human footprint on essential life-supporting services of the Earth system has grown dramatically since the time of Darwin,” he wrote in 2009 in an article for the journal Science, “Reflections On: Our Planet and Its Life, Origins, and Futures.”