Image caption Coal use in developing economies tends to make them less "carbon-efficient"

Carbon emissions fell in 2009 due to the recession - but not by as much as predicted, suggesting the fast upward trend will soon be resumed.

Those are the key findings from an analysis of 2009 emissions data issued in the journal Nature Geoscience a week before the UN climate summit opens.

Industrialised nations saw big falls in emissions - but major developing countries saw a continued rise.

The report suggests emissions will begin rising by 3% per year again.

"What we find is a drop in emissions from fossil fuels in 2009 of 1.3%, which is not dramatic," said lead researcher Pierre Friedlingstein from the UK's University of Exeter.

"Based on GDP projections last year, we were expecting much more.

"If you think about it, it's like four days' worth of emissions; it's peanuts," he told BBC News.

The headline figure masked big differences between trends in different groups of countries.

Broadly, developed nations saw emissions fall - Japan fell by 11.8%, the UK by 8.6%, and Germany by 7% - whereas they continued to rise in developing countries with significant industrial output.

China's emissions grew by 8%, and India's by 6.2% - connected to the fact that during the recession, it was the industrialised world that really felt the pinch.

Back on track

Before the recession, emissions had been rising by about 3% per year, with the growth having accelerated around the year 2000.

The new analysis suggests that after the recession, those rates of growth are likely to resume.

"Probably, we'll be back on the track of the previous decade, 2009 having been a small blip," said Dr Friedlingstein.

The figures come just a week before the start of the UN climate summit, held this year in Cancun, Mexico.

Little progress is expected, following what is widely regarded as the failure of last year's Copenhagen summit.

But the projections - produced by the Global Carbon Project, a network of researchers around the world - may focus delegates' minds anew on the enduring issue in tackling climate change: decoupling economic growth from carbon emissions.

Speaking last week at a meeting of Indian and British business leaders aiming to develop joint clean energy projects, UK climate minister Greg Barker conceded this was the missing ingredient.

Fundamentally, he said, the question was "whether a transition to a low-carbon economy is compatible with continued economic growth - and no-one knows the answer, because no country has made the transition yet".