IT COULD be a rare piece of good news in the battle against global warming. The International Energy Agency (IEA), the world’s most prominent energy forecaster, said on March 16th that carbon-dioxide emissions from burning fossil fuels have remained flat for two years in a row. Emissions from the world’s two biggest polluters, America and China, have been falling. The world has not seen such a lull since the early 1980s.

The IEA’s provisional findings will fan a debate about whether global emissions have peaked. China, after all, is trying to rebalance its economy away from heavily polluting industries towards services. But analysts say two years is too short a period to be considered a lasting trend. What is more, the IEA is relying on data that many economists question. If China’s official growth figures are exaggerated, then it would not be becoming less carbon intensive as fast as it seems.

The IEA said the world’s energy-related emissions of carbon dioxide stood at 32.1 billion tonnes last year, for the second year running. This is the first time they have remained flat during a period of economic expansion in more than 40 years. Fatih Birol, the IEA’s director, says the three main drivers were a big growth of renewable-energy use in global power generation, led by wind turbines; a switch in America from coal-fired plants to natural-gas-fuelled ones after the shale revolution and a government-led effort in China to curb emissions due to concerns about pollution as well as climate change.

Mr Birol says the rapid deployment of renewables is good news; it tallies with the IEA’s best-case scenario for tackling global warming and shows emissions are “decoupling from economic growth”. But he expresses concern that the progress will be ephemeral: the low prices of natural gas and coal may undermine new investment in wind and solar power. They may also slow the trend toward improved energy efficiency.

The IEA’s most contentious finding is that emissions from China, the world’s biggest polluter, dropped 1.5% last year. Some experts will see this as evidence that China’s emissions will peak within a decade, if they haven’t already. The Chinese government, though, has insisted its emissions will continue to grow until 2030. In a report this month Fergus Green and Nicholas Stern of the London School of Economics said the official projections should be taken with a pinch of salt, since the government prefers “to under-promise and over-deliver.”

Richard Black of the Energy and Climate Intelligence Unit, a British think-tank, says the improvement in China represents a “huge turnaround”, and that its replacement of coal with renewable energy is likely to continue. However Michael Levi of America’s Council on Foreign Relations notes that the United States is still emerging from a period of deep economic weakness, China is restructuring and India is quickly developing, so the conditions that have brought emissions to a standstill may swiftly dissipate. He says that carbon dioxide emissions will need to fall to have a meaningful impact on climate change. “The first step towards reducing emissions is stabilising them, but it’s still only a first step.”