A month after President Donald Trump pledged to pull the United States from the landmark 2015 Paris climate change pact meant to curb global carbon emissions, California Gov. Jerry Brown seized the leadership role and announced that San Francisco would host the Global Climate Action Summit (GCAS). Together, the global commitments that roughly 7,000 cities and 6,000 companies have made since Paris do pack a punch. The entities making pledges on clean energy, forests, oceans, and infrastructure represent $36 trillion, far larger than the US economy. In the US, actions by the subnational sector helped the country meet nearly half the commitment it made in Paris. An analysis this summer from Lab partner Rhodium Group found that existing policies in the US mean we are headed toward a reduction ranging from 12 to 20 percent of emissions by 2025, still falling short of its stated 26-28 percent goal. That still leaves some room for uncertainty, given the capacity of forests to absorb carbon and energy costs and the unclear future of many federal climate policies.