Enter Picarro, a San Francisco-based start-up with a laser-based device that makes it possible to take rapid measurements of gas concentrations on any street, and so begin to plug the leak data gap. Picarro's cavity ring-down spectrometer can be mounted on a car, detects concentrations at the parts per billion level in a fraction of a second, and doesn't require the driver to slow down to take a measurement. As a result, it is possible to map a city centre in a day or two rather than weeks.
Picarro is collaborating with Phillips to map the otherwise invisible methane plumes in US cities. Data collected in recent months from Boston and San Francisco show concentrations of up to 30 parts per million, more than 15 times global background levels. Phillips says such concentrations are unusually large for unconfined spaces, though they are unlikely to be a health concern and are nowhere near the threshold for causing an explosion, which stands around 50,000 ppm.
Should methane leak into confined spaces like manholes, however, it can quickly build up. One of four manholes surveyed by Phillips and a former gas worker in June registered 70,000 ppm - an explosion risk. National Grid, which is responsible for the pipes running adjacent to the manhole, says it is aware of the problem and is addressing it.
Concentration data alone is not enough to assess the climate change risks associated with the leaks, though: you need to know the volume of leaking gas. Phillips has begun collecting these measurements, but it is slow work: leaks need to be monitored individually. So far he has measured the volume of three leaks in Boston. On average they emitted a minimum of 4.9 m3 per day - only slightly less than the 5.7 m3 an average American home uses daily, according to the EIA. In the next one to two years, Phillips hopes to develop a method to characterise representative leaks so he can then estimate total leak volumes for the entire system.
What's clear already is that the ageing gas infrastructure is leaking across large areas of major US cities. Phillips's and Picarro's gas sniffers are not the only ones to point in that direction. In recent months, the New England Gas Workers Association got hold of documents showing more than 20,000 non-explosive-hazard leaks from utility pipelines in Massachusetts alone. The documents, obtained from the Massachusetts Department of Public Utilities, show that just 13,000 of these leaks were responsible for an estimated annual loss of 32 million m3 of gas.
The IEA's figures show that Russia and the US, the two largest gas producers by far, are also the leakiest...
But perhaps the greatest concern is that many countries cannot be assessed, for want of data. The most glaring omission is Iran, the world's third largest producer of gas. China and India are also planning to use much more gas, but they are not UNFCCC signatories so there is no data on their systems.