The 2010s may be remembered as the decade when the fight against harmful climate change was lost. In 2015, at the COP21 climate conference in Paris, 196 countries agreed to limit global warming to well below 2 degrees Celsius above pre-industrial levels. But global greenhouse-gas (GHG) emissions have continued to increase, atmospheric concentrations of carbon dioxide are at their highest levels in 800,000 years, and current policies will likely result in warming of about 3 degrees Celsius by 2100. Moreover, the recent COP25 negotiations in Madrid ended in failure, with governments squabbling over the value and allocation of “carbon credits” held over from a discredited previous policy regime.