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Cutting leaks of methane from natural gas pipelines and wells

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Vehicle fuel economy standards

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17%

On targetThe US can meet – and maybe even exceed – Obama’s target of cutting greenhouse gas emissions by 17 per cent, from 2005 levels, by 2020

10 | NewScientist | 2 February 2013

BARACK OBAMA is certainly talking the talk on climate change – promising to put the fight against global warming at the heart of his second term. What’s more surprising is that the US – historically, the world’s biggest emitter – actually seems to be walking the walk. It is on track to meet Obama’s 2009 pledge to cut US emissions by 17 per cent, from 2005 levels, by 2020. The target could even be exceeded, which may give a boost to the long-stalled international climate talks.

There’s no realistic possibility of passing new laws to curb US greenhouse gas emissions – Republican control of the House of Representatives will see to that. So some pundits were scratching their heads at Obama’s climate pledge in last week’s inaugural address. But independent analyses paint an upbeat picture of the progress he can make simply by using existing laws.

After the gloom that followed the failure, in Obama’s first term, to pass a national cap-and-trade scheme to cut emissions, the new mood of optimism may seem surprising. Yet it is backed by hard numbers, laid out in a report

released last October by Resources for the Future (RFF), a think tank based in Washington DC.

The group totted up emissions reductions likely to result from action taken by states and cities, and cuts that will occur through market forces as a glut of cheap natural gas encourages power utilities to burn gas instead of coal – which emits far more for the same amount of energy generated. Together, these get about a third of the way to Obama’s pledge.

But the biggest contribution comes from regulations under the Clean Air Act, including vehicle fuel economy standards that are already in place. Controls on emissions from power plants that are expected from the US Environmental Protection Agency make up the rest (see diagram, right). Given all this, RFF estimates that the US could cut emissions by 16.3 per cent by 2020.

“The US had been doing more than we’re given credit for,” says Matt Woerman, one of the report’s authors. “As an American citizen, I’m pleasantly surprised.”

“The 2020 target does seem to be in reach,” agrees Kevin Kennedy, who heads the US climate change initiative at World Resources Institute, also

in Washington DC. The think tank is expected to draw similar conclusions in a report due for release in early February.

According to Woerman, about two-thirds of the cuts outlined in the RFF report are already

Peter Aldhous

Yes, Obama can deliver on climate

THIS WEEK

Measured over a century, methane has 25 times the global warming potential of carbon dioxide – so the last thing the planet needs is for the stuff to be escaping into the atmosphere. Yet that’s happening on a massive scale in the US, through leaks from production wells and the pipes that distribute natural gas.

The US Environmental Protection Agency estimates total losses at

2.4 per cent of the gas being extracted, but the true figure could be higher. A survey in Colorado, led by the National Oceanic and Atmospheric Administration, last year suggested the region’s wells were losing some 4 per cent of what is produced.

Putting firmer numbers on the problem is the goal of a study led by the Environmental Defense Fund (EDF) in New York City. It should have

Fixing AmericA’s gAs leAk

“baked-in”. And emissions could be pushed down further still if the EPA is aggressive in regulating existing US power plants.

The RFF report assumed that the EPA would demand modest efficiency improvements for each type of plant. But the agency could get stronger cuts by setting a combined and more ambitious target for coal and gas-fired plants, and leave it to utilities and states to decide how to get there.

That would provide fresh incentives for power companies to ditch coal for natural gas. It could even bring in cap-and-trade by the back door, if companies and states decide schemes like the Regional Greenhouse Gas Initiative, launched by a coalition of north-east US

figures for production wells by the end of March, and for the entire distribution system by January 2014.

With better numbers in hand, the government could demand the leaks are plugged. “It is quite possible to produce natural gas with minimal ‘fugitive’ emissions,” says Mark Brownstein of the EDF. “It may just be a question of operational and maintenance practice.”

130202_N_p10_11.indd 10 29/1/13 17:52:37

2 February 2013 | NewScientist | 11

–Soon to be a thing of the past?–

FOR the first time, genes chemically silenced as a result of stress have been shown to stay switched off in eggs and sperm, so the effect is passed down to the next generation.

The finding is based on DNA scans of developing mouse eggs and sperm. It backs up mounting but indirect evidence, from multigenerational studies, that the genetic impacts of environmental factors such as smoking, diet, famine and childhood stress can be passed on through a process called epigenetic inheritance. Many mainstream geneticists had considered this an impossibility.

Genes can be switched off by altering DNA through a process called methylation, in which enzymes respond to environmental factors by marking genes with methyl groups that prevent them from working.

But the idea that genes could retain these epigenetic markings when inherited is controversial. In previous studies, any markings added to genes were erased as sperm and eggs developed. If any marks did survive, it was thought they are wiped out when an egg is fertilised.

Now a team led by Jamie Hackett at the University of Cambridge has challenged this picture. The researchers extracted DNA from mouse primordial germ cells – the precursors to sperm and eggs – at various stages of their development and used markers to spot any methylated genes.

They found that a tiny number of methylated gene regions survived unerased: an average of just 233 out of about 25,000 genes in the germ cells. Still, the work clearly shows that traits resulting from the surviving markings can, in principle, be passed on. “What we’ve found is a potential way things can get through, whereas before, everything was considered to be erased,” says Hackett (Science, doi.org/kbj).

Do the markings survive simply because the erasure process may not always work properly, or are they

deliberately spared so that the information they carry is passed to the next generation? The finding “doesn’t solve this question”, says Hackett. “But it’s a proof of principle for one possible mechanism by which traits might be inherited epigenetically.”

Those sceptical of epigenetic inheritance are adamant that even if some methylated DNA makes it through, it is likely to be because of faulty erasure and will have little

impact on offspring. “The idea that what’s left carries information about the environment is sufficiently far‑fetched to demand much more evidence of its importance,” says Adrian Bird of the University of Edinburgh, UK. “I’d say [the erasure] is an inefficient process, and what’s left doesn’t matter.”

Researchers who claim to have demonstrated that epigenetic traits can be passed down were more enthusiastic. Isabelle Mansuy of the Swiss Federal Institute of Technology in Zurich has found that, in mice, the effects of stress in infancy can be passed from one generation to at least the next two.

“The paper demonstrates there are regions which do escape reprogramming,” Mansuy says. “This is fundamental to the idea of epigenetic inheritance of acquired traits that so many people are reluctant to accept, because it does indicate that it is possible to maintain some marks intact from parents to offspring.”

Hackett says that he and his colleagues plan to repeat the experiment in human cells. They also hope to resolve the question of whether gene markings that escape erasure do so by luck or by design. Andy Coghlan n

Stresses in your life may affect future generations

“ It backs indirect evidence that impacts of smoking, poor diet and childhood stress can be passed on”

For daily news stories, visit newscientist.com/news

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states, could help make the cuts. According to an analysis from

the Natural Resources Defense Council (NRDC), released in December, more aggressive policies like these could cut emissions from fossil fuel plants

by 26 per cent, from 2005 levels, by 2020 – equivalent to an additional 10 per cent shaved off total US emissions.

Other options open to Obama include an aggressive phase-out of hydrofluorocarbons – refrigerants that are potent greenhouse gases – and plugging methane leaks (see

“Fixing America’s gas leak”, left). No one has yet calculated the

amount by which the US could exceed Obama’s pledge, but Woerman is optimistic. “I think we can definitely blow past the target,” he says. “Maybe we could get to 25 per cent.”

Numbers like that would give Obama new authority in talks with other major polluters such as China, which have been reluctant to sign up for emissions cuts while the US seemed to drag its feet. “The US will have much more credibility and influence in the next international climate negotiations if it shows, by 2014 and 2015, that it is making good on the president’s pledge,” says David Doniger, climate policy director with the NRDC. n

“The US is on track to meet Obama’s pledge of cutting emissions by 17 per cent, from 2005 levels, by 2020”

130202_N_p10_11.indd 11 29/1/13 16:54:54