Former New York Mayor Michael Bloomberg speaks at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 27, 2016. Reuters On June 1, Donald Trump announced that the US will exit the Paris Agreement, an international effort aimed at curbing climate change by reducing global greenhouse gas emissions.

The move upset many states, climate scientists, and CEOs. But billionaire Michael Bloomberg, a vocal supporter of climate change mitigation, isn't phased.

To make up some of the $2 billion in lost funds toward climate action programs, the former New York City mayor's charitable organization, Bloomberg Philanthropies, is giving $15 million over the next two years to the UN Framework Convention on Climate Change. He's also leading a coalition, made up of three states, dozens of cities, and 80 university presidents, that vows to uphold the Paris Agreement.

Even before Bloomberg did all that, he and former Sierra Club executive director Carl Pope had already laid out a blueprint for fighting climate change. In their 2017 book "Climate of Hope," they argue it's most effective to take action on the local level.

Bloomberg and Pope offer small actions that companies and local governments can take toward boosting clean energy and reducing greenhouse-gas emissions. For example, building more bike lanes has been shown to reduce CO2 levels (since it encourages people to drive less often). Constructing public transit near housing has a similar effect.

Cities with large buildings that mandate energy-efficient upgrades to heating and cooling systems can minimize their carbon footprints and save on energy, Bloomberg says in the book. New York City's green building projects, for instance, are projected to lower greenhouse-gas emissions by 2.7 million tons — about the equivalent of kicking 560,000 cars off the road, according to CityLab.

Bloomberg and Pope also note that more investment in natural ecosystems can mitigate climate change.

"Here as elsewhere, the key to unlocking the climate puzzle is to realize that if we handle other pieces of our business better — in this case, stewardship of vital food, timber, and water sources like wetlands, mangroves, forests, prairies, and peat bogs — we will simultaneously make major strides toward a safer climate and a cooler world," the co-authors write. "Investment in ecosystems is vital if we want them to thrive and then do what they are superbly equipped to do — suck carbon out of the atmosphere and turn it into soil and vegetation."

There is also an increasing amount of scientific research into machines that can capture CO2 even after it's in the air. "Whether these pilots can, in a near future, be scaled at an affordable level is uncertain, but it seems only prudent to support the needed research to explore them," Bloomberg and Pope write.

Made up of 195 nations as of June 2017, the Paris Agreement aims to reduce greenhouse-gas emissions to fight rising global temperatures. As its contribution in 2014, the US pledged to lower its emissions by 26-28% below 2005 levels by 2025.

About 30 major US cities have vowed to uphold the Paris Agreement, despite the planned US withdrawal in late 2019. Pittsburgh Mayor Bill Peduto recently announced that the city plans to transition to 100% renewable-energy sources, by 2035.

Bloomberg and Pope say that new jobs at renewable energy projects can offset those lost at fossil fuel companies. They note that a number of US companies are already investing in clean energy projects, like wind and solar.

"The world economy will be a lot stronger if we solve climate than if we don't, even leaving aside the costs of climate," Pope told Business Insider.