On Tuesday, Representative Alexandria Ocasio-Cortez and Senator Bernie Sanders announced their proposal for a resolution declaring a national climate emergency. The timing was appropriate. Ten years ago, President Obama travelled to Denmark to pledge to the world that by 2020, through the Copenhagen Accord, the United States would reduce its greenhouse-gas emissions seventeen per cent below its 2005 levels. The pledge was on shaky ground, with no binding terms, but it was a start. Six years later, in 2015, Obama travelled to France to negotiate the Paris climate accord, joined by every country in the world but two (Syria and Nicaragua, who have both since signed), and promised that by 2025 the U.S. would reduce its emissions twenty-six to twenty-eight per cent. Although the U.S. target was modest, considering the urgency of the crisis and the U.S.'s historic contributions to climate change (the U.S. has, from 1750 until the beginning of this year, emitted vastly more carbon than any other country on the planet), it was an important step and presented a goal that would be tough but not impossible to meet. The agreement also included a stipulation that the world's countries would come together every five years to commit to higher targets.

