A surge in atmospheric CO2 saw levels of greenhouse gases reach record levels in 2013, according to new figures.
Concentrations of carbon dioxide in the atmosphere between 2012 and 2013 grew at their fastest rate since 1984.
The World Meteorological Organisation (WMO) says that it highlights the need for a global climate treaty.
But the UK’s energy secretary Ed Davey said that any such agreement might not contain legally binding emissions cuts, as has been previously envisaged.
The WMO’s annual Greenhouse Gas Bulletin doesn’t measure emissions from power station smokestacks but instead records how much of the warming gases remain in the atmosphere after the complex interactions that take place between the air, the land and the oceans.
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It could be that the biosphere is at its limit but we cannot tell that at the moment”
About half of all emissions are taken up by the seas, trees and living things.
According to the bulletin, the globally averaged amount of carbon dioxide in the atmosphere reached 396 parts per million (ppm) in 2013, an increase of almost 3ppm over the previous year.
“The Greenhouse Gas Bulletin shows that, far from falling, the concentration of carbon dioxide in the atmosphere actually increased last year at the fastest rate for nearly 30 years,” said Michel Jarraud, secretary general of the WMO.
Atmospheric CO2 is now at 142% of the levels in 1750, before the start of the industrial revolution.
However, global average temperatures have not risen in concert with the sustained growth in CO2, leading to many voices claiming that global warming has paused.
“The climate system is not linear, it is not straightforward. It is not necessarily reflected in the temperature in the atmosphere, but if you look at the temperature profile in the ocean, the heat is going in the oceans,” said Oksana Tarasova, chief of the atmospheric research division at the WMO.
The bulletin suggests that in 2013, the increase in CO2 was due not only to increased emissions but also to a reduced carbon uptake by the Earth’s biosphere.
The scientists at the WMO are puzzled by this development. That last time there was a reduction in the biosphere’s ability to absorb carbon was 1998, when there was extensive burning of biomass worldwide, coupled with El Nino conditions.
“In 2013 there are no obvious impacts on the biosphere so it is more worrying,” said Oksana Tarasova.
“We don’t understand if this is temporary or if it is a permanent state, and we are a bit worried about that.”
“It could be that the biosphere is at its limit but we cannot tell that at the moment.”
The WMO data indicates that between 1990 and 2013 there was an 34% increase in the warming impact on the climate because carbon dioxide and other gases like methane and nitrous oxide survive for such a long time in the atmosphere.