Both mitigation and adaptation are needed to address climate change risks, says MIT professor John Sterman. We have the ingenuity to successfully tackle this complex issue, and lessons from the past to guide us.Prof. John StermanImage courtesy of Flickr user 808armada.Whats the best way to address the risks of climate change? Mitigation or adaptation? Should the world cut greenhouse gas emissions to lower the risks of harm from climate change (mitigation), or should we just get used to it (adaptation), spending to build seawalls, move populations inland, and figure out how to grow food for more than 9 billion people in a world of higher temperatures, droughts, and extreme weather?Many people, including some I greatly respect, have lately argued that advocacy for mitigation isnt working, so we should shift to advocacy for adaptation. They say thats where the interest is after Superstorm Sandy, thats how to get people engaged, and thats where the money is. The frustration of climate activists around mitigation is understandable. The failure of the 2009 Copenhagen climate conference was deeply discouraging, and since then the international negotiations have stalled. Total pledges for emissions reductions under the UNFCCCs (United Nations Framework Convention on Climate Change) voluntary system, even if fully implemented, are nowhere near enough. With gridlock in the U.S. Congress and the erosion of climate commitments in other nations, more and more people are giving up on mitigation.Of course, adaptation is necessary. Weve already warmed the climate about 1.4 F (0.8 C) over preindustrial levels. Global CO2 emissions have reached new records every year since 2009. In May, atmospheric CO2 hit 400 ppm for the first time in human history. We are dumping CO2 into the atmosphere about twice as fast as nature can remove it. Even with the best imaginable policies, the climate will keep changing for decades, and sea level will keep rising for centuries. Adaptation is necessary.However, adaptation without mitigation is futile. Since Sandy, the focus has been on updating flood maps and building sea walls. But sea walls are the Maginot line of climate change. Sea walls wont help with ocean acidification, water shortage, drought, more frequent and more dangerous wildfires, declines in agricultural output, and the many other impacts of climate change, not to mention the climate refugees and risks of war those impacts create. However, when we point out that theres no adapting to the changes in the climate we are facing if we dont cut emissions dramatically, some adaptation advocates say, yes, but if we can convene people around adaptation, theyll soon see its limitations and will end up strongly advocating mitigation as part of their local adaptation plan.Im deeply skeptical. It is more likely that the current push for adaptation will consume all the resources, energy and attention around climate change, so mitigation wont be considered, or will become an afterthought. New York City just released its $20 billion climate resilience plan. The plan focuses on adaptation, and pays no attention to reducing the greenhouse gas emissions that create the need for adaptation in the first place. Nearly 50 mayors