Levels of the main greenhouse gas in the atmosphere have risen to new highs in 2010 despite an economic slowdown in many nations that slowed down industrial output, according to the latest data. Carbon dioxide, measured at Norway's Zeppelin station on the Arctic Svalbard archipelago, rose to a median 393.71 parts per million of the atmosphere in the first two weeks of March from 393.17 in the same period of 2009, extending years of gains. "Looking back at the data we have from Zeppelin since the end of the 1980s it seems like the increase is accelerating," Johan Stroem, of the Norwegian Polar Institute, said of the data compiled with Stockholm University. The rise in concentrations, close to an annual peak before carbon-absorbing plants start to grow in the northern hemisphere spring, was below the average gain over the year of around two parts per million. "It still confirms the rise," Stroem said of the data from the first two weeks of March. Concentrations vary from week to week depending on the source of Arctic winds. Carbon concentrations have risen by more than a third since the Industrial Revolution ushered in wider use of fossil fuels. A 2009 study of the ocean off Africa indicated carbon levels in the atmosphere were at their highest in 2.1 million years. The data "seem to show that we continue to emit as if there was no tomorrow," Kim Holmen, director of research at the Norwegian Polar Institute, said of the carbon readings. Carbon concentrations at Svalbard peak in April after rotting plants release the gas through the winter � land areas in the northern hemisphere are far bigger than in the south. Levels decline when plant growth resumes in the northern spring. Stroem said there were signs that the rise in concentrations in late winter was becoming bigger than in late summer. He speculated that could be a side-effect of global warming. A gradual shrinking of ice and snow cover in the Arctic summer, he said, might mean more plants were able to grow and so absorb carbon, masking the rise in atmospheric carbon. The death of some of the extra vegetation in winter added to emissions.