This year is on track to be the second warmest since records began in the 1860s and floods in Pakistan or a heatwave in Greece may herald worse disruptions in store from global warming, experts said on Friday.
"2007 is looking as though it will be the second warmest behind 1998," said Phil Jones, head of the Climatic Research Unit at Britain's University of East Anglia, which provides data to the UN's International Meteorological Organization.
"It isn't far behind ... it could change, but at the moment this looks unlikely," he told Reuters, based on temperature records up to the end of April.
Jones had predicted late last year that 2007 could surpass 1998 as the warmest year on record due to rising concentrations of greenhouse gases emitted mainly by burning fossil fuels and an El Nino warming of the Pacific.
Almost all climate experts say that the trend is towards more droughts, floods, heatwaves and more powerful storms. But they say that individual extreme events are not normally a sign of global warming because weather is, by its nature, chaotic.
"Severe events are going to be more frequent," said Salvano Briceno, director of the Geneva-based secretariat of the UN International Strategy for Disaster Reduction.
The 10 warmest years in the past 150 years have all been since 1990. Last year ranked number six according to the IMO. NASA, which uses slightly different data, places 2005 as warmest ahead of 1998.
Among extreme events, more than 500 people have died in storms and floods in Pakistan, Afghanistan and India in the past week.
Temperatures in Greece reached 46 degree celsius (114.80F) this week as part of a heatwave across parts of southern Europe. Parts of China have also had a heat wave in recent days.
And torrential rains have battered northern England and parts of Texas, where Austin has had its wettest year on record so far.
The UN climate panel, drawing on the work of 2,500 scientists, said this year that it was "very likely" that human activities led by use of fossil fuels were the main cause of a warming in the past half-century.
It gave a "best estimate" that temperatures will rise 1.8-4.0 Celsius (3.2 and 7.8 Fahrenheit) this century.
Briceno told Reuters that the world had to work out better policies to prepare for disasters, saying that climate change was adding to already increasing risks faced by a rising human population of about 6.6 billion people.
Irrespective of warming, many people were cramming into cities, for instance, settling in plains where there was already a risk of floods or moving to regions vulnerable to droughts.
"We need to reduce all the underlying risk factors, such as by locating communities out of hazard-prone areas," he said. "We now have a clearer picture of what is going to happen and it's urgent that governments give this higher priority."
In Germany, average temperatures for the 12 months to May 2007 smashed records for the past century, raising questions about whether climate change was quickening, the Potsdam Institute for Climate Impact Research said.
"If this trend continues in the near future, we will be experiencing an acceleration of global warming in Germany so far unexpected by climate scientists," it said in a statement.