Some of the world's top scientists are wrapping up a three-day, climate-change meeting in Copenhagen with a grim warning that global warming is arriving faster than previously expected.  

The Copenhagen meeting drew about 2,000 scientists from around the world, and the news they delivered was not encouraging as they warned of an increasingly warmer world with more frequent droughts, and food and health problems.

Intergovernmental Panel on Climate Change chairman Rajendra Pachauri summed up the fallout if temperatures increase.

"Even for a range of zero to one degree celsius [annual rise in temperature], we have problems with water availability.  We also have problems with ecosystems," he said.   "Food security would certainly be at growing risk.  Coastal areas are particularly vulnerable, and human health would also be affected by the impact of climate change."

Scientists warn the impact of climate change is hitting the world faster than previous predictions by Pachauri's IPCC, which amounts to a more conservative consensus of top world researchers.  

Climate change expert Konrad Steffen, of the University of Colorado in the United States, explained the impact of climate-induced sea level rises to coastal areas.

"The key finding of this meeting is that we have up to one-meter sea-level rise by 2100, based on our new insight of glaciers.  And that will affect up to 600 million people that are living close to the coastline and it will include major cities like New York," he said.  "We already know that New Orleans is in the same way, but also areas like Bangladesh or smaller areas of islands that will be flooded within that one-meter sea level rise."

World leaders of the top 20 economies are expected to discuss climate change during talks on the global economic downturn next month in London.  Late this year, scientists and politicians are to gather in Copenhagen for a key global climate-change summit in an effort to thrash out a consensus on cutting heat-trapping greenhouse gasses.