The rising temperatures made northern icecaps melt and more extreme weather conditions ranging from drought to rainstorms were observed around the world, the World Meteorological Organisation (WMO) said in its annual statement on the global climate.
Since 1976, global surface temperatures have been rising at three times the average rate recorded over the past century. WMO experts admitted that they would not have forecast such temperature changes five to 10 years ago.
"The global temperature is accelerating. This increase is unprecedented in the 1,000-year record that includes ice core sampling, seabed mud and tree ring samples," Kenneth Davidson, head of the WMO's climate programme, said.
1998 was the warmest year on record since direct weather data was first gathered in 1860.
The WMO is adamant that the warmer temperatures are largely caused by pollution, notably by emissions which effectively add a layer of insulation in the upper atmosphere.
"If there is no further protective measure taken to prevent the release of greenhouse gases, then the trend will continue," WMO assistant secretary-general Hong Yan told reporters.
The Arctic ice cap shrank to its smallest area in September 2002 than any period since satellite observations started 24 years ago. Surface melting of the icecap in Greenland was also reported to be greater than in previous known records.
"It is part of a continuing downard trend in the Arctic sea ice," Matthew Manne of the US National Oceanic and Atmospheric Administration (NOAA) said.
Manne said changes in floating ice had little impact on sea levels but he warned that the decreasing ice cover did affect the way heat was transferred between the oceans and the atmosphere.
"It can have an impact on the regional climate especially and perhaps some impact on the global climate as well," he added.
WMO said 2002 was also marked by the start of a "moderate intensity" El Nino, a disruption of sea temperatures around the southern Pacific basin which triggers extreme weather across much of Asia, the Americas and sub-Saharan Africa.
"The El Nino conditions are expected to continue through April next year," Davidson said. He linked the onset of El Nino with drought in Australia that has caused massive bushfires, higher temperatures and heavy rain in East Africa and the fifth coldest spring in Canada.
Davidson forecast heavier than normal rainfall in northwestern parts of South America, drought across Argentina and Uruguay and more drought in southern Africa in coming months.
Other extreme weather events over the past year included heavy rain and flooding in parts of western and central Europe, as well as Sweden's warmest summer ever recorded.
Although a relatively small number of storms in the Atlantic developed into hurricanes, twice as many tropical storms -- eight -- reached the United States mainland than usual.
Annual rainfall was above normal in an area from central Asia to China and the Korean peninsula, due to warmer conditions, according to WMO.
Yet India experienced its first countrywide drought since 1987 and monsoon rains there were 19 percent below normal.
For the second summer in a row, excessively dry conditions had a "significant" impact on farming in central America.
Davidson admitted it was difficult to assert that rising temperatures were causing an increase in the number of extreme weather phenomena.
"We're not positive yet. I can only say that we have more extremes every year," he said.
Overall the worldwide mean surface temperature in 2002 rose by about 0.5 degrees compared to a 1961-1990 annual mean used as a reference point. This nudged out 2001, when mean surface temperature rose 0.42 degrees, as the second warmest year.
The overall rise in surface temperatures since 1900 now exceeds 0.6 degrees centigrade (33 degrees Farenheit).
The 10 warmest years on record have occurred since 1987, according to WMO.