CHARLESTON, W.Va. -- New York City Mayor Michael Bloomberg said Thursday he was donating $50 million to help the Sierra Club try to replace a third of the nation's aging fleet of coal-fired plants with clean energy by 2020.The donation, from Bloomberg's charitable foundation, was announced by the mayor and by Sierra Club officials at an event outside an Alexandria, Va., power plant."If we are going to get serious about reducing our carbon footprint in the United States, we have to get serious about coal," Bloomberg said. "Ending coal power production is the right thing to do, because while it may seem to be an inexpensive energy source, the impact on our environment and the impact on public health is significant."Sierra Club Executive Director Michael Brune called the move by Bloomberg a "game changer," and said his group welcomed the mayor's "business savvy and track record for success" to the Sierra Club campaign."This partnership will help the Sierra Club to work with communities nationwide as they tell one coal plant after another that inflicting asthma and other diseases on their children is unacceptable and that they will not accept coal pollution in their neighborhoods," Brune said.Coal industry lobbyists and the United Mine Workers reacted strongly to the announcement."Although Mayor Bloomberg and his foundation can do whatever they want with his money, it's troubling that he is willing to spend $50 million to help the Sierra Club put Appalachian coal miners out of work and plunge their local economies into deeper recession," said UMW President Cecil Roberts. "In the mostly rural areas where America's coal miners live and work, coal jobs are the only ones that pay wages that allow miners and their families to live solid, middle-class lives."Bloomberg is worth an estimated $16 billion, according to Forbes magazine and through his Bloomberg Philanthropies has donated hundreds of millions of dollars to various causes, including public health issues such as anti-tobacco campaigns. A Boston native, the 69-year-old Bloomberg was a Wall Street trader who built his fortune with a business information system that grew into a nearly $7 billion software, media and data company.Sierra Club officials say their "Beyond Coal" campaign has helped to stop more than 150 new coal-fired power plants from being built, pushed utilities to retire older and more-polluting coal plants, and aided local citizen groups in slowing the issuance of new mountaintop removal permits to a trickle.The group said the $50 million from Bloomberg would "fill a significant portion of the campaign's projected $150 million four-year budget." The campaign will expand from 15 to 45 states and its full-time staff will increase to 200, the Sierra Club said.In the U.S., coal is the leading cause of greenhouse gas emissions, and coal's pollution contributes to four out of five of the leading causes of mortality -- heart disease, cancer, stroke and respiratory illness, the Sierra Club said.Coal emits almost half of all U.S. mercury pollution, which causes developmental problems in babies and young children, as well as being a major contributor to asthma attacks. Coal pollution causes $100 billion in health costs annually, the Sierra Club said.Hal Quinn, president of the National Mining Association, said that Bloomberg should have invested his money "in technologies that make coal cleaner to use and not in gestures that will consign our country to higher unemployment and households to higher utility bills."More specifically, Roberts of the UMW said Bloomberg should have donated his money toward the development of carbon capture and storage, or CCS, technology to reduce the greenhouse emissions from coal-fired power plants.Mary Anne Hitt, director of the Sierra Club campaign, said her group is skeptical that CCS "will ever be economically competitive with wind and solar."We have opposed some CCS projects and we have not opposed others," Hitt said. "I would not go so far as to call us supportive -- we are not. We would oppose any plant using MTR coal or with other local impacts or opposition."Sen Joe Manchin, D-W.Va., said he was disappointed by Bloomberg's decision."Rather than a strictly 'anti-coal' agenda, I would hope that individuals with financial resources like Mayor Bloomberg would choose a more balanced approach that recognizes the vital role that coal plays in our nation's energy portfolio both now and into the future," Manchin said.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.