Last month, NASA issued a report that predicted 2010 would likely end up as the warmest year on record, due to the combintation of global warming and El Nino.

They say if recent trends in Pacific climate patterns persist, there is a strong chance that an El Nino pattern will emerge in the coming months.

"2010 was a bit cooler than 2009 mainly because a moderate El Nino in the equatorial Pacific Ocean during late 2009 and early 2010 has been replaced by a moderate La Nina," he said.

The El Nino phenomenon is an important factor in monitoring global warming, according to a paper by Hansen and colleagues published in the current Proceedings of the National Academy of Sciences.

Part of the warmth earlier this year may have been due to an El Nino event in the Pacific Ocean, which tends to warm the planet, but that event is no longer taking place.