The pledges that both US and China have taken in cutting carbon dioxide (CO2) emissions, won't be enough to stop a 2 degree Celsius warming, latest climate models have shown.
Just two weeks ago, there were widespread fears that the Copenhagen climate conference, which kicks off next week, would fail.
The Danish prime minister, who is hosting the talks, pleaded that the negotiators should at the very least offer quantitative promises to cut their countries' emissions.
The leaders of the US and China have now done so.
On November 26, Obama said that the US would cut emissions by 17 per cent from 2005 levels by 2020 and by 83 per cent by 2050.
The following day, China - which has long insisted it would not budge until the US did - pledged to cut the amount of carbon it releases per unit of GDP to 40 to 45 per cent below 2005 levels by 2020.
With pledges from most major emitters now on the table, the question is: will they be enough to limit the increase in global temperatures to 2 degree Celsius?
Many scientists predict that warming beyond this level will result in severe, and sometimes irreversible, environmental changes.
The indications are not promising.
According to a report in New Scientist, the pledges made so far translate into around 3 degree C warming by 2100, as determined by an international team of climate modellers.
Domestic politics in both China and the US make it difficult for either country's government to commit to bigger cuts.
Republicans in the US Congress have said that they will fight hard to defeat emissions cuts.
This makes it uncertain whether Obama will be able to deliver even on the pledge he will take to Copenhagen.
Chinese leaders are reluctant to commit to bigger emission savings for fear that this would slow the country's recent rapid increase in living standards.
These obstacles have led some climate campaigners to turn their attention to Europe, which has committed to a 20 per cent cut from 1990 levels by 2020.
"The impact of the recession now means that the European Union's 2020 goal is so unambitious that Europe would need to deliberately slow its reductions not to meet it," said Joss Garman, a climate campaigner with Greenpeace UK.
"There's a huge space for increased ambition that would move the world closer to what the science says is necessary," he added.