Vague carbon emission checks put deal in balance

CHINA is this week playing host to the last stage of preparatory climate talks before delegates gather at the annual United Nations climate change summit, in Cancún, Mexico, in December. They will attempt once again to reach a deal on limiting emissions of carbon dioxide and other greenhouse gases.

But any deal may fail because those emissions cannot yet be measured with sufficient accuracy. This has been a significant sticking point in talks. The world badly needs an independent carbon police to check the figures and catch the carbon frauds. Can science deliver?

Even the easiest emission to assess - CO2 from burning fossil fuels in developed nations - may only be known to within 10 per cent, according to Gregg Marland of the Oak Ridge National Laboratory in Tennessee. And a report by energy consultant Irving Mintzer for WWF, published in June, found that China does not record CO2 emissions from its small coal-burning factories and long-standing fires in mines, which may result in under-reporting by as much as 20 per cent.

The uncertainties for other greenhouse gases are even greater. Globally, declared nitrogen dioxide emissions are less than half those known to reach the atmosphere.

Verifying national emissions requires both "bottom-up" independent oversight of the inventories, and better "top-down" monitoring of the atmosphere, says Matthias Jonas of the International Institute for Applied Systems Analysis in Laxenberg, Austria.

The first step will be to add to the global network of some 150 stations measuring CO2 and other gases in the atmosphere, run by the World Meteorological Organization. This logs gas levels at places distant from major pollution sources, but what is now needed is the exact opposite - stations sniffing the air close to major sources. Such a network is being discussed by the WMO.

As well as this, there should be more research aircraft doing spot checks. This summer, the US National Oceanic and Atmospheric Administration flew aircraft downwind of refineries and power stations in California. Their preliminary results suggest that methane emissions from Los Angeles are a third higher than expected.

Also needed are more flights to remote regions. Last year, a research flight by the US National Center for Atmospheric Research discovered methane leaking out of the Arctic Ocean. The race is on to find out if the source is new gas fields off Alaska or melting permafrost.

A new climate treaty will also need carbon sniffers in tropical forests, especially in countries that sign up to a part of the deal called REDD (Reduced Emissions from Deforestation and Forest Degradation). REDD would offer cash to countries that conserve their forests so they can soak up atmospheric CO2. This means knowing how much carbon is actually being absorbed by the forests. In August, a study of Peruvian forests by Greg Asner of Stanford University, California, found existing estimates of carbon stored and released could be out by as much as 50 per cent.