ONE TOWN SQUARE: at the intersection of peak oil, climate change, and land use

Scientists have recorded a massive spike in the amount of methane seeping from Arctic permafrost. Methane emissions from the Arctic increased by 31% from 2003-07. The increase represents about 1m extra tonnes of methane each year.

Sharply rising temperatures are to blame. Global warming is occurring twice as fast in the Arctic than anywhere else on Earth. Some regions have already warmed by 2.5C, and temperatures there are projected to increase by more than 10C by 2100 if carbon emissions continue to rise at current rates.

The new study supports scientists who warn that even modest levels of global warming could trigger huge increases in methane release from permafrost. Estimates of the amount of carbon trapped in shelf permafrost are in the range of 1,600 billion tonnes – roughly twice as much carbon as in the atmosphere now. Billions of tonnes of that sequestered carbon could be released by just a 2C average global rise, a positive feedback that could push Earth’s climate past a tipping point leading to catastrophic climate change.

The Guardian quotes Paul Palmer, a scientist at Edinburgh University who worked on the new study:

High latitude wetlands are currently only a small source of methane but for these emissions to increase by a third in just five years is very significant. It shows that even a relatively small amount of warming can cause a large increase in the amount of methane emissions.

Just over half of all methane emissions came from the tropics, with some 20m tonnes released from the Amazon River basin each year, and 26m tonnes from the Congo basin. Rice paddy fields across China and south and southeast Asia produced almost one-third of global methane, some 33m tonnes. Only 2% of global methane comes from Arctic latitudes, the study found, though the region showed the largest increases. The 31% rise in methane emissions there from 2003-07 was enough to help lift the global average increase to 7%.

The study is published in the journal Science.

At the meeting of the American Geophysical Union in San Francisco this week, scientists report that new data confirm that another positive feedback mechanism is at work. New temperature and water vapor observations have corroborated climate model predictions that the warming of our climate produced by carbon dioxide will be greatly exacerbated – more than doubled – by water vapor. As the climate warms, the atmosphere becomes more humid. Since water is a greenhouse gas, it serves as a powerful positive feedback to the climate system, amplifying the initial warming.

Here’s the abstract to the Science study:

Wetlands are the largest individual source of methane (CH4), but the magnitude and distribution of this source are poorly understood on continental scales. We isolated the wetland and rice paddy contributions to spaceborne CH4 measurements over 2003–2005 using satellite observations of gravity anomalies, a proxy for water-table depth {Gamma}, and surface temperature analyses TS. We find that tropical and higher-latitude CH4 variations are largely described by {Gamma} and TS variations, respectively. Our work suggests that tropical wetlands contribute 52 to 58% of global emissions, with the remainder coming from the extra-tropics, 2% of which is from Arctic latitudes. We estimate a 7% rise in wetland CH4 emissions over 2003–2007, due to warming of mid-latitude and Arctic wetland regions, which we find is consistent with recent changes in atmospheric CH4.