Preliminary data from the US government shows that carbon dioxide levels peaked last week at the highest levels on record

Carbon dioxide levels in the atmosphere have reached a new peak despite the economic recession in western countries and assurances from politicians that they intend to cut emissions, new research has shown.

Preliminary data from the US government's Earth Systems Research Laboratory at Mauna Loa in Hawaii, where measurements of CO2 have been continuously monitored for almost 50 years, show that 2011 CO2 levels peaked last week at 394.97ppm. This is an increase of nearly 1.6ppm on last year and the highest ever recorded.

The research comes after estimates from the International Energy Agency, revealed by the Guardian on Monday, that carbon-dioxide emissions from energy generation in 2010 were also the highest in history. About three-quarters of the energy emissions increase in 2010 came from developing countries, including China and India, said the IEA.

The continuing upward trend of CO2 concentration in the atmosphere is alarming climate scientists who say that levels must be held at or around 400ppm if we are to have any chance of avoiding serious climate change.

"This underlines the urgency of the problem. The CO2 figure continues to grow rapidly [and] can only accelerate while industrialising countries [such as China and India] do not decarbonise their economies because they have an increasingly large share of total emissions", said Dr Alice Bows, lecturer in Energy and climate change at Manchester university's Sustainable Consumption Institute.

The Mauna Loa monitoring station, run by the US government's National Oceanic and Atmospheric Administration (NOAA) – situated at 12,000ft and well away from major pollution sources in the middle of the Pacific – is considered the most reliable place to measure concentrations of gases in the atmosphere .

If present trends of a 1.5-2ppm annual increase in CO2 levels continue, there is little chance of stabilising greenhouse gas concentrations at 450 ppm. This would only result in a 50% likelihood of limiting global warming to 2C. Climate scientists say it would be necessary to achieve stabilisation well below 400 ppm to give a relatively high certainty of not exceeding 2C.

Two degrees is the point that scientists consider to be the threshold for "dangerous" climate change which, once passed, will leave millions exposed to drought, hunger and flooding.

"It's not too late to stop dangerous climate change if the world acts now – and fast. We need to save energy, reduce demand, and develop safe and renewable alternatives to polluting fossil fuels," said Mike Childs, head of climate at Friends of the Earth.

The new CO2 peak comes as 189 countries prepare to resume the UN climate talks in Bonn. No final agreement is expected this year because of continuing disagreements between rich and poor countries but progress is expected to be made on reducing emissions from forestry and securing cash to enable the poorest countries to adapt their economies to increasingly severe climatic events.