A new El Nino has begun, which may lead to increased drought in Africa, India and Australia, and may make 2010 one of the hottest years on record, warn meteorologists.
El Nino is a periodic warming of the normally cold waters of the eastern tropical Pacific, the ocean region westwards out from South America along the line of the equator.
The 1997-98 El Nino combined with global warming to push 1998 into being the world's hottest year, and caused major droughts and catastrophic forest fires in South-east Asia which sent a pall of smoke right across the region.
At present, forecasters do not expect this El Nino to equal that of 1998, but it may be the second-strongest, and concerned groups, from international insurance companies to commodity traders, to aid agencies such as Oxfam, have begun to follow its progress anxiously.
Its potential for economic and social impact is considerable.
According to Professor Chris Folland, of the Met Office Hadley Centre for Climate Prediction and Research, "We are likely to see more global warming than we have seen in the past few years, which have been rather cool. In fact, we are already seeing it."
Since the Pacific is a heat reservoir that drives wind patterns around the world, the change in its temperature alters global weather.
An El Nino is defined by ocean surface temperatures rising by more than 0.5 degrees Celsius above the average.
This El Nino is well beyond that, according to the Climate Prediction Center of the US National Weather Service.
"Sea surface temperatures remain +0.5 to +1.5 above average across much of the equatorial Pacific Ocean," the center reported last week.
"Observations and dynamical model forecasts indicate El Nino conditions will continue to intensify and are expected to last through the northern hemisphere winter of 2009-10," it added.