"Many of the extreme events of 2013 were consistent with what we would expect as a result of human-induced climate change," Michel Jarraud, secretary general of the World Meterological Organization (WMO), said as he released his agency's annual climate report.
"We saw heavier precipitation, more intense heat, and more damage from storm surges and coastal flooding as a result of sea level rise — as Typhoon Haiyan so tragically demonstrated in the Philippines," he added.
While individual extremes cannot be pinned on man-made climate change alone, due to a complex web of factors, Jarraud said they are part of a clear trend.
He pointed to data from Australia showing that record heat there last year would have been "virtually impossible" without human emissions of heat-trapping greenhouse gases.
Other 2013 weather events flagged by the agency included extreme cold in Europe and the United States, floods in India, Nepal, northern China, Russia, central Europe, Sudan and Somalia, snow in the Middle East, and droughts in southern China, Brazil, southern Africa and the western United States.
'No standstill' in global warming
Extreme cold in no way undermines the idea of global warming, Jarraud said, noting that climate change by definition skews weather patterns.
"When some people say global warming has stopped, what is now a record cold year is actually warmer than any year before 1998," he said.
Phenomena such as volcanic eruptions or the El Nino and La Nina weather patterns in the Pacific have always influenced temperatures and sparked disasters, but human activity is an accelerator, Jarraud explained.
"There is no standstill in global warming," he said.
"Levels of these greenhouse gases are at record levels, meaning that our atmosphere and oceans will continue to warm for centuries to come.
The laws of physics are non-negotiable," he added.
The report said 2013 tied with 2007 as the sixth warmest on record.
The average global land and ocean surface temperature for the year was 14.5 degrees Celsius (58.1 degrees Fahrenheit) — 0.5 C (0.9 F) above the 1961-1990 average and 0.03 C (0.05 F) higher than the average for 2001-2010, which was already the warmest decade on record.
Thirteen of the 14 warmest years on record occurred in the 21st century, and each of the last three decades has been warmer than the last.
Researchers have long warned that the chance is ebbing fast to limit global warming to 2.0 C (3.6 F) over pre-Industrial Revolution levels — the UN target.
"We cannot say that there is a magic number where below it, everything is OK, and beyond, it's a disaster," warned Jarraud.
"The more the temperature increases, the more adaptation will be required and therefore the more expensive it will be, in particular the impact for the least developed countries who may not have the resources to adapt."
Denial 'no longer possible
But there is little agreement on how to slow emissions of greenhouse gases — notably carbon dioxide — pumped out by industry, transport and agriculture, compounded by deforestation.
"To people who still deny the human origin of climate change, I'm sorry to say, but it's no longer possible," Jarraud said.
"But while awareness is accelerating, it still hasn't been translated into decision making," he warned.
The Intergovernmental Panel on Climate Change, the UN's Nobel-winning group of scientists, says that global greenhouse gas emissions surged by an average 2.2 percent per year between 2000 and 2010.
This compared to 1.3 percent per year between 1970 and 2000.
Some experts say that on current trends, warming by 2100 could be 4.0 C (7.2 F) or higher, spelling more severe droughts, floods, storms and hunger for many millions of people.
"If you take a system like the earth's climate and give it as big a kick as we're giving it, we're going to have to be incredibly lucky to not see severe climate changes," Brian Hoskins, of Imperial College London, was quoted as saying by Britain's Science Media Centre.