The 21st century's first decade was the hottest on record, with temperatures rising at an unprecedented pace and weather extremes claiming over 370,000 lives, the United Nations said Wednesday.
In a new report on 2001-2010, the World Meteorological Organization (WMO) said land and sea temperatures averaged 14.47 degrees Celsius (58 degrees Fahrenheit).
This compares with the long-term average of 14 C (57.2 F), as measured from weather records dating back to 1881.
"This is the warmest decade of this whole period," said WMO chief Michel Jarraud.
When measured globally, every year of the decade except 2008 was among the 10 warmest on record, the report showed.
"The increase between the 1990s and the past decade is the largest since we have instrumental records," Jarraud added.
In 2001-2010, the average global temperature jumped 0.21 degrees (0.37F) over the previous decade. By comparison, warming rose by 0.14 C (0.25F) in the 1990s over the 1980s.
Global warming is blamed on human activity such as industrial emissions of heat-trapping greenhouse gases, chiefly carbon dioxide (CO2).
Sceptics, however, suggest temperatures should be even higher according to estimates based on CO2 levels and that global warming is therefore plateauing.
"There's no plateau. If you filter out the very short-term variability, the last decade was the warmest by a significant margin," Jarraud countered.
He backed suggestions that heat is being stored in the deep ocean, where it was bound to released in the future.
Some doubters also point to recent harsh winters, or the current sluggish start to the European summer, which feeds a natural human tendency to grumble about the weather.
"When you look at climate variability and climate change, it's very important not to focus on a particular part of the world or to concentrate on a particular year," said Jarraud.
Based on surveys of 139 countries, the WMO report showed that nearly 94 percent registered their warmest decade in 2001-2010, while 44 percent reported nationwide temperature records during the period.
Floods were the most frequent extreme event during the decade, such as those in 2010 in Pakistan that killed some 2,000 people and affected 20 million others, the WMO said.
The number of people killed by floods fell by 43 percent, and those who perished in storms by 16 percent over the decade, thanks to better early warning systems and increased preparedness.
Despite this, the first 10 years of the 21st century registered more than 370,000 deaths linked to weather extremes, up 20 percent from the previous decade.
The increase was mainly due to heatwaves in Europe in 2003 and in Russia in 2010, which helped push the global heatwave death toll to 136,000, compared to just 6,000 in the previous decade.
"When the question is asked, is it due to climate change, our traditional answer has been in most cases we cannot tell you, we cannot attribute a single event to climate change, because these events results from many complex interactions," said Jarraud.
"However, because of climate change, we expect these things to become more frequent, or more intense. Change has increased the probability," he said.