California has joined a pact with 11 other states and countries to slash greenhouse gas emissions and tackle climate change. Gov. Jerry Brown signed an agreement Tuesday as part of a broader effort to pressure global leaders to adopt an aggressive emissions treaty at a United Nations-led summit in Paris later this year.

“This global challenge requires bold action on the part of governments everywhere,” Brown said in a statement. “It’s time to be decisive. It’s time to act.”

The 12-member agreement includes the U.S. states of Oregon, Washington and Vermont, as well as the Canadian provinces of British Columbia and Ontario. The Mexican states of Baja California and Jalisco also joined, along with the British country of Wales and states and provinces in Brazil, Germany and Spain. Together, the group represents more than 100 million citizens and $4.5 trillion in gross domestic product.

The signatories agreed to either reduce greenhouse gas emissions to at least 80 percent below 1990 levels by 2050, or to achieve an annual emission target of less than 2 metric tons per capita within the next four decades. Their goal is to limit the increase in global average temperature to below 2 degrees Celsius (3.2 degrees Fahrenheit) to avoid the most catastrophic consequences of climate change, including dramatic sea level rise, deadly heat waves and vanishing rainfall.

California is perhaps the most prominent member of the pact, with a $2 trillion economy and an ambitious slate of existing climate change policies. The state has a cap-and-trade system in place to curb emissions from power plants and industrial facilities, and a low-carbon fuel standard limits the “carbon intensity” of transportation fuels.

California also has an 80 percent target for 2050, which was set by former Gov. Arnold Schwarzenegger. Last month, Brown signed an executive order requiring California to cut its emissions to 40 percent below 1990 levels by 2030 to keep the state on track to meet the later target.

Brown separately proposed a series of climate change measures for the next 15 years, including a plan to get 50 percent of California’s electricity from wind, solar and other renewable energy sources by 2030, up from an existing target of 33 percent. California has already cut its per-person emissions by one-quarter over the 1990-2012 period, compared to a 17 percent reduction for the entire United States, according to the 2015 California Green Innovation Index released Monday.

As part of Tuesday’s agreement, California and other signatories agreed to recruit additional states and countries ahead of the UN climate conference in December.

Rhea Suh, president of the Natural Resources Defense Council, said she is hopeful the 12 signatories to the agreement will push leaders to negotiate a tougher emissions treaty. “As these states and provinces know so well, change begins at home. Regional leadership is an essential ingredient in the global response to climate change,” she said in a statement. Tuesday’s announcement, she added, “will build momentum for more ambitious national commitments at the international climate conference in Paris later this year.”