California Gov. Jerry Brown today signed a first-of-its-kind agreement with international leaders from 11 other states and provinces, collectively representing more than $4.5 trillion in GDP and 100 million people, to limit the increase in global average temperature to below 2 degrees Celsius - the warming threshold at which scientists say there will likely be catastrophic climate disruptions. With 170 California birds at risk of extinction over the coming decades due to global warming, this can only help.