Global warming will be worse in the future than previous predictions according to new research.
Two research teams used past records to predict how much global heat is rising.
They worked out that not only are natural gases making temperatures rise - but the heat causes even more greenhouse gases to be given out from areas such as forests.
Along with extra heat from the burning of fossil fuels, this means the Earth is getting hotter faster.
The scientists worked out that current estimates of the speed at which the earth is getting hotter are too low.
Margaret Torn of Lawrence Berkeley National Laboratory said: "It's the pace of change that will be one of the big problems"
Extra global warming
Global warming is partly caused by greenhouse gases which trap heat close to the earth. These are given out naturally but are also the result of humans burning fossil fuels like coal and petroleum.
The two scientific teams, from Europe and America admit that their work is not as precise as they would like and that more research needs to be done.
But they reckon that they have shown that the extra carbon dioxide from the burning of fossil fuels will push global temperatures higher than previous estimates.