Steven D. Allison , University of California, Irvine and Tyrus Miller , University of California, Irvine Large wildfires in the Arctic and intense heat waves in Europe are just the latest evidence that climate change is becoming the defining event of our time. Unlike other periods that came and went, such as the 1960s or the dot-com boom, an era of unchecked climate change will lead to complex and irreversible changes in Earth’s life support systems.