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SACRAMENTO, CA - MAY 19: (L-R) Winfried Kretschmann, Minister-President of Baden-Wuerttemberg, California Gov Jerry Brown and Baja California Governor Francisco A. Vega de Lamadrid sign a climate change bill during at bill signing event at the Leland Stanford Mansion on May 19, 2015 in Sacramento, California. California Gov Jerry Brown signed a first-of-its-kind agreement with leaders from 11 states and international provinces to limit the increase in global average temperature to below 2 degrees Celsius. (Photo by Justin Sullivan/Getty Images)

SACRAMENTO, CA - MAY 19:  (L-R) Winfried Kretschmann, Minister-President of Baden-Wuerttemberg, California Gov Jerry Brown and Baja California Governor Francisco A. Vega de Lamadrid sign a climate change bill during at bill signing event at the Leland Stanford Mansion on May 19, 2015 in Sacramento, California.  California Gov Jerry Brown signed a first-of-its-kind agreement with leaders from 11 states and international provinces to limit the increase in global average temperature to below 2 degrees Celsius.  (Photo by Justin Sullivan/Getty Images)