In a surprising turnaround, the amount of carbon dioxide being released into the atmosphere in the U.S. has fallen dramatically to its lowest level in 20 years, and government officials say the biggest reason is that cheap and plentiful natural gas has led many power plant operators to switch from dirtier-burning coal. Many of the world’s leading climate scientists didn’t see the drop coming, in large part because it happened as a result of market forces rather than direct government action against carbon dioxide, a greenhouse gas that traps heat in the atmosphere. Michael Mann, director of the Earth System Science Center at Penn State University, said the shift away from coal is reason for 'cautious optimism' about potential ways to deal with climate change
. He said it demonstrates that “ultimately people follow their wallets” on global warming. 'There’s a very clear lesson here. What it shows is that if you make a cleaner energy source cheaper, you will displace dirtier sources,' said Roger Pielke Jr, a climate expert at the University of Colorado.
In a little-noticed technical report, the US Energy Information Agency, a part of the Energy Department, said this month that energy related US CO2 emissions for the first four months of this year fell to about 1992 levels. Energy emissions make up about 98 percent of the total. The Associated Press contacted environmental experts, scientists and utility companies and learned that virtually everyone believes the shift could have major long-term implications for US energy policy. While conservation efforts, the lagging economy and greater use of renewable energy are factors in the CO2 decline, the drop-off is due mainly to low-priced natural gas, the agency said. A frenzy of shale gas drilling in the Northeast’s Marcellus Shale and in Texas, Arkansas and Louisiana has caused the wholesale price of natural gas to plummet from $7 or $8 per unit to about $3 over the past four years, making it cheaper to burn than coal for a given amount of energy produced. As a result, utilities are relying more than ever on gas-fired generating plants. Both government and industry experts said the biggest surprise is how quickly the electric industry turned away from coal. In 2005, coal was used to produce about half of all the electricity generated in the US. The Energy Information Agency said that fell to 34 percent in March, the lowest level since it began keeping records nearly 40 years ago. The question is whether the shift is just one bright spot in a big, gloomy picture, or a potentially larger trend.
Coal and energy use are still growing rapidly in other countries, particularly China, and CO2 levels globally are rising, not falling. Moreover, changes in the marketplace - a boom in the economy, a fall in coal prices, a rise in natural gas - could stall or even reverse the shift. For example, US emissions fell in 2008 and 2009, then rose in 2010 before falling again last year. Also, while natural gas burns cleaner than coal, it still emits some CO2. And drilling has its own environmental consequences, which are not yet fully understood.
The boom in gas production has come about largely because of hydraulic fracturing, or fracking. Large volumes of water, plus sand and chemicals, are injected to break shale rock apart and free the gas. Environmentalists say that the fluids can pollute underground drinking water supplies and that methane leaks from drilling cause serious air pollution and also contribute to global warming. The industry and many government officials say the practice is safe when done properly. But there have been cases in which faulty wells did pollute water, and there is little reliable data about the scale of methane leakage. 'The Sierra Club has serious doubts about the net benefits of natural gas,' said Deborah Nardone, director of the group’s Beyond Natural Gas campaign. 'Without sufficient oversight and protections, we have no way of knowing how much dangerous pollution is being released into Americans’ air and water by the gas industry. For those reason, our ultimate goal is to replace coal with clean energy and energy efficiency and as little natural gas as possible.' Wind supplied less than 3 percent of the nation’s electricity in 2011 according to EIA data, and solar power was far less. Estimates for this year suggest that coal will account for about 37 percent of the nation’s electricity, natural gas 30 percent, and nuclear about 19 percent. Some worry that cheap gas could hurt renewable energy efforts. 'Installation of new renewable energy facilities has now all but dried up, unable to compete on a grid now flooded with a low-cost, high-energy fuel,' two experts from Colorado’s Renewable and Sustainable Energy Institute said in an essay posted this week on Environment360, a Yale University website.
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