



As methane intensifies greenhouse gas in the atmosphere – propelling average global temperatures higher toward the brink of no return – Cornell’s Robert Howarth briefed the White House’s Office of Science and Technology Policy May 27 on its dangers and solutions.

“In Paris at the COP21 [the 21st United Nations Climate Change Conference of the Parties] last December, the nations of the world came together to recognize that we need to keep our planet well below a 2 degrees Celsius temperature rise – compared to the pre-industrial baseline temperature for the Earth – and that anything above 1.5 degrees Celsius is dangerous,” said Howarth, the David R. Atkinson Professor of Ecology and Environmental Biology. “If we don’t, we’re at an increased risk of hitting tipping points in the climate system that will lead to runaway global warming.”

The 90-minute briefing, “Natural Gas and Methane After COP21,” was given to senior staff and scientists.

Howarth told the group Earth’s atmosphere is on target to raise the average atmospheric temperature by 1.5 degrees C in the next 10 to 15 years and by 2 degrees C within the next 35 to 40 years. “The only way to slow this rate of warming and meet the COP21 target is to reduce methane emissions,” he said. “Although we should reduce carbon dioxide emissions, reducing carbon dioxide alone will not slow global warming on the time scale of the next few decades. The climate system responds much more quickly to reducing methane emissions.”

Last October, Howarth published a scientific paper explaining how the U.S. Environmental Protection Agency (EPA) estimate for greenhouse gas emissions may be in error by a wide margin due to its computations accounting for natural gas, the so-called “bridge” fuel – a fuel considered transitional from full carbon energy like coal to renewable energy. “Methane emissions from the U.S. are much larger than is recognized by the EPA, according to a large and growing body of evidence,” he told the scientists.

“The agency relies on data that are questionable due to misuse of monitoring equipment, according to papers published last year,” he said. “Reliable data from satellite and airplane surveys show much higher emissions and indicate that global increases in methane in the atmosphere over the last decade may well be the result of increased emissions from the United States.”

Further, the EPA underestimates the importance of methane emissions on global warming, since they only compare methane and carbon dioxide for 100 years following emissions. This greatly discounts the importance of methane and is contrary to the guidance given by the Intergovernmental Panel of Climate Change. A better approach is to compare to the two greenhouse gases on the time scale of 10 to 20 years following emission, he said.

Statistically, carbon dioxide emissions from fossil fuel have fallen in the U.S. since 2007 due to the economic recession and switching to natural gas from coal to generate electricity, but, Howarth cautioned, “Total greenhouse gas emissions – after dipping slightly in 2007 – have been rising since at their most rapid rate ever, due to shale gas development and large methane emissions.

“If the U.S. wants to meet the COP21 target – to which we have agreed – we need to recognize that natural gas – and shale gas, in particular – is not a bridge fuel,” Howarth told the scientists. “We need to move aggressively move toward an economy based on renewable energy.”