Smoke billows from a chimney of a heating plant as the sun sets in Beijing, China, in this file photo dated Feb. 13, 2012. President Donald Trump's executive order, signed Tuesday, March 28, 2017, will reduce the pressure on China and other countries to decrease carbon emissions under the 2016 Paris Agreement that Obama helped negotiate.
Alexander F. YuanAP
In this Oct. 30, 2013, file photo, people hold signs during a rally against hydraulic fracturing for natural gas, or fracking, in Albany, N.Y.
In this Aug. 29, 2003, file photo, one of two beluga whales that washed ashore in Turnagain Arm south of Anchorage, Alaska, lays on the beach. A national environmental group, the Center for Biological Diversity, has asked the National Marine Fisheries Service to block plans in Cook Inlet by an oil company for hydraulic fracturing, the extraction of oil and gas from rock by injecting high-pressure mixtures of water, sand or gravel and chemicals, because of possible harmful effects on endangered belugas.
This Nov. 16, 2015, photo shows a section of the Mississippi Power Co. carbon capture power plant in DeKalb, Miss. Carbon capture entails catching the carbon emissions from a power plant or cement or steel factory and injecting them underground for permanent storage.
Rogelio V. SolisAP
President Donald Trump's executive order, signed Tuesday, March 28, 2017, will end the moratorium on federal coal leasing on public lands. That change could lead to expanded coal mining on public lands, particularly in the western United States, if coal prices rise. In this April 4, 2013, file photo, Bruce Jones, general manager of the Spring Creek coal mine, explains work underway at the mine's repair shop near Decker, Mont.
This July 27, 2011, file photo shows a farmhouse in the background framed by pipes connecting pumps where the hydraulic fracturing process in the Marcellus Shale layer to release natural gas was underway at a Range Resources site in Claysville, Pa. In Pennsylvania’s fracking boom, new and more unconventional wells leaked far more than older and traditional wells, according to a study of inspections of more than 41,000 wells drilled. And that means that that methane leaks could be a problem for drilling across the nation, said the author of the study, which was funded in part by environmental activist groups and criticized by the energy industry. The study was published by the Proceedings of the National Academy of Sciences.
People protest outside the Aliso Canyon storage facility May 15, 2016, in the Porter Ranch section of Los Angeles. Homes located near the gas well blowout that spewed the nation's largest-known release of methane had higher levels of toxic metals that could have caused symptoms Los Angeles residents have suffered for months, public health officials said.
Jae C. HongAP
President Donald Trump's executive order, signed Tuesday, March 28, 2017, will end a White House requirement that federal agencies must consider climate change impacts when reviewing projects under the National Environmental Policy Act. That change will make it easier for the federal government to permit highways, power plants and other projects that could increase carbon emissions. The coal-fired Plant Scherer is shown in operation June 1, 2014, in Juliette, Ga.
Emilio Jimenez protests against the Southern California Gas Co. outside the Aliso Canyon storage facility May 15, 2016, in the Porter Ranch section of Los Angeles. Homes located near the gas well blowout that spewed the nation's largest-known release of methane had higher levels of toxic metals that could have caused symptoms Los Angeles residents have suffered for months, public health officials said.
Jae C. HongAP
In this March 29, 2013, file photo, workers tend to a well head during a hydraulic fracturing operation outside Rifle, in western Colorado.
Birds surround cattle in a feedlot at an ethanol plant in Mead, Neb., Jan. 18, 2007. Across the country, ethanol plants powered by methane instead of costly natural gas or coal are on the drawing board-- a movement that could be a win-win situation for the environment and the industry. Burning the methane will cut the amount of the greenhouse gas, which contributes to global warming released into the environment.
In this June 9, 2014, photo, drivers and their tanker trucks, capable of hauling water and fracking liquid line up near a natural gas burn off flame and storage tanks in Williston, N.D. The epicenter of the oil boom is a 45-mile stretch of U.S. Route 85 in North Dakota between the towns of Williston and Watford City.
Charles Rex ArbogastAP
In this Jan. 29, 2014, file photo, fracking opponents protest the New York State Department of Environmental Conservation hearing with Commissioner Joe Martens, in Albany, N.Y. Martens didn’t get out much as New York’s environmental commissioner, responsible for millions of acres of wilderness and other protected land, but by bicycling across the state he made up some lost ground before his departure from a job that also included overseeing the tumultuous debate over fracking.
The Total Port Arthur refinery, the largest oil refinery in the United States, is shown Dec. 2, 2009, in Port Arthur, Texas. Total Petrochemical's sprawling oil refinery in southeast Texas has sprayed tons of sulfuric acid and carbon monoxide into the sky. The French company's 62-year-old facility has also released cancer-causing benzene, regularly surpassed allowable pollution limits and failed to report dozens of emissions.
David J. PhillipAP
In this March 29, 2013, file photo, a worker helps monitor water pumping pressure and temperature, at a hydraulic fracturing and extraction site, outside Rifle, in western Colorado.
A vendor rides his tricycle near a coal-fired power plant in Beijing, China, on April 12, 2013. China, the world's largest producer of carbon dioxide, is directly feeling the man-made heat of global warming, scientists conclude in the first study to link the burning of fossil fuels to one country's rise in its daily temperature spikes.