The governor of California and Michael Bloomberg launched a new plan to fight climate change - with or without Trump

Two of the nation's foremost environmental leaders just launched a new plan for the US to fight climate change - with or without the federal government.

Governor Jerry Brown of California and former mayor of New York City Michael Bloomberg announced "America's Pledge" on Wednesday, an initiative aimed at keeping greenhouse gas emissions from US cities, states, and businesses consistent with the goals outlined in the Paris climate agreement.

The Obama administration set those benchmarks, along with nearly every nation in the world, in order to keep the planet from warming by more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels, a threshold that scientists say could keep the planet from launching into a tailspin of irreversible consequences. President Donald Trump had other plans, and withdrew the US from the global accord in June.

America's Pledge builds off movements like "We Are Still In," the Climate Mayors coalition of cities, and the US Climate Alliance group of states, which all popped up after Trump made his announcement. The pledge plans to track the efforts of those initiatives, so all of the groups who have promised to keep American emissions under the 26% to 28% of 2005 levels by 2025 can ensure they do so.

"Today we're sending a clear message to the world that America's states, cities and businesses are moving forward with our country's commitments under the Paris agreement - with or without Washington," Brown said in the press release.

The pledge will "provide a roadmap for increased climate ambition" over time, and offer a game plan to help organizations drive down their emissions. The initiative will also compare projected emissions from its members to those of "business as usual" emissions under the Trump administration's policies.

"In the US, emission levels are determined far more by cities, states, and businesses than they are by our federal government - and each of these groups is taking action because it's in their own best interest," Bloomberg said in the release.

"The American government may have pulled out of the Paris agreement," he added, "but American society remains committed to it - and we will redouble our efforts to achieve its goals. We're already halfway there."