Jonathan Chait: “Mitigating climate change is not a simple yes-no proposition. Holding temperature increases to 2.5 or 2.7 degrees Celsius may not be as good as holding them below 2 degrees, but it’s much better than holding them to 3.3 or 3.8 degrees. What’s more, the structure of the agreement is designed to produce additional reductions over time.”

“Obviously, such reductions will only happen if they are economically feasible. But recent history shows that political willpower and innovation feed off each other. Support for green energy in the United States (through the stimulus), Europe, China, and elsewhere spurred research and investment that have triggered a revolution in affordable solar and wind power, among other green-energy technologies. The green-energy revolution has made what was unaffordable in 2009 suddenly affordable. It is realistic to assume that the momentum from Paris will continue the virtuous cycle of political willpower and market innovation — the massive new market for reducing carbon emissions will spur more investment that will produce newer and more efficient technologies, allowing elected officials to make deeper emissions cuts.”

“It is hard to find any important accomplishment in history that completely solved a problem. The Emancipation Proclamation only temporarily and partially ended slavery; the 13th Amendment was required to abolish it permanently … Victories are hardly ever immediate or complete. The fight continues and history marches on. The climate agreement in Paris should take its place as one of the great triumphs in history.”