Almost four years after donating $50 million to the Sierra Club's "Beyond Coal" campaign, former New York City Mayor Michael Bloomberg is back with another infusion of cash, pledging an additional $30 million through his Bloomberg Philanthropies foundation. 

“The single biggest reduction in carbon pollution in the U.S. has come by retiring and repurposing coal-fired power plants – and that’s the direct result of our Beyond Coal campaign,” Bloomberg said, adding that the U.S. last year led industrialized nations in carbon emissions. "But much more work remains, and today we are doubling down on what has proven to be an incredibly successful strategy for improving public health and fighting climate change.”

Since the partnership between the Sierra Club and Bloomberg kicked off, more than 185 coal plants have either been retired or transitioned to cleaner sources of energy. Coal dependence in the U.S. has also declined, with coal making up 38 percent of the energy mix compared to 52 percent in 2011. Funding increases have also allowed the Beyond Coal campaign to expand from 15 states to more than 40. With this new infusion of cash, the new goal will be to close or transition half of the nation's coal plants by 2017.

map of U.S. coal plants

Green markers indicate defeated coal plants, yellow progressing, and red active or upcoming plants. (Photo: Sierra Club)

“Mike Bloomberg’s continued commitment to clean air, water, and climate action demonstrate his understanding that we are at a critical turning point in our nation’s history when it comes to how we power our economy and ensure healthy families,” said Michael Brune, Sierra Club executive director.

Bloomberg's re-commitment to fighting Big Coal comes on the heels of a new push by the Obama administration linking climate change to personal health issues

"I think we've always known — or at least in the 20th century we've understood — that environment has an impact on public health," President Obama told CNN's Dr. Sanjay Gupta on Tuesday as part of a roundtable discussion for National Public Health Week.

"I remember when I first went to college in Los Angeles in 1979, the air was so bad that you couldn't go running outside," Obama said. "You'd have air quality alerts, and people who had respiratory problems or were vulnerable had to stay inside. We took action, and the air's a lot better."

There's no denying that air pollution has improved in the U.S. over the last several decades, but there are still many gains to be made. A 2012 study found that 40 percent of people live in areas with unhealthy levels of air pollution, with coal-fired plants by far the largest industrial source of airborne toxins. According to the Clean Air Task Force, closing a single plant can prevent 146 asthma attacks, 47 heart attacks, and 29 premature deaths each year. For every 50 gigawatts of coal taken offline in the U.S., the health care industry saves an estimated $2.5 billion in costs. 

Added Brune: “The Sierra Club and our 2.4 million members and supporters are proud to stand with Mr. Bloomberg today to continue building on the successes of the Beyond Coal campaign, and we look forward to more victories for public health and our planet that will be won state by state, city by city, and by dedicated people across America.”

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Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.

Michael Bloomberg gifts Sierra Club $30M to fund anti-coal efforts
Billionaire philanthropist says he's 'doubling down' on efforts to reduce carbon emissions and replace half the nation's coal fleet with clean energy by 2017.