Future heat waves are likely to get even hotter and more frequent and heavier rainfall will trigger more floods as global temperatures increase, UN scientists warned today.
And the UN Intergovernmental Panel on Climate Change (IPCC) said it was "very likely" that emissions had led to an increase in daily maximum temperatures.
The Special Report, presented at the IPCC's 34th Session today in Kampala, Uganda, urged countries to come up with disaster management plans to adapt to the growing risk of extreme weather events linked to human-induced climate change.
It warned that emissions had also led some regions experiencing longer and more intense droughts and said extreme weather events are likely to increase based on future greenhouse gas scenarios.
"It is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes ... will occur in the 21st century on the global scale," the IPCC report said.
"It is very likely that the length, frequency and/or intensity of warm spells, or heat waves, will increase," it added.
"A 1-in-20 year hottest day is likely to become a 1-in-2 year event by the end of the 21st century in most regions," under one emissions scenario.
An exception is in very high latitudes, it said. Heat waves would likely get hotter by "1 degrees C to 3 degrees C by mid-21st century and by about 2 degrees C to 5 degrees C by late-21st century, depending on region and emissions scenario."
The details were outlined during a media briefing by the co-chairmen overseeing the compilation of two of the three segments of next IPCC assessment report.
Introducing the Summary for Policymakers of the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, IPCC chairman Rajendra Pachauri said: "It underlines the complexity and diversity of factors that are shaping human vulnerability to extremes."
The summary stated: "Extreme events are rare, which means there are few data available to make assessments regarding changes in their frequency or intensity."
However, it added: "There have been statistically significant trends in the number of heavy precipitation events in some regions."
On the possible change to hurricane patterns, it said: "Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins.
"It is likely that the global frequency of tropical cyclones will either decrease or remain essentially unchanged."
Rajendra Pachauri, Chair of the IPCC, said: “This summary for policymakers provides insights into how disaster risk management and adaptation may assist vulnerable communities to better cope with a changing climate in a world of inequalities."
“It also underlines the complexity and the diversity of factors that are shaping human vulnerability to extremes - why for some communities and countries these can become disasters whereas for others they can be less severe,” he added.
Qin Dahe, Co-chair of IPCC Working Group I, which together with Working Group II was responsible for the development and preparation of the report, said: “There is high confidence that both maximum and minimum daily temperatures have increased on a global scale due to the increase of greenhouse gases.”
“Changes in other extremes, such as more intense and longer droughts are observed in some regions, but the assessment assigns medium confidence due to a lack of direct observations and a lack of agreement in the available scientific studies. Confidence in any long-term trend in tropical cyclone intensity, frequency or duration is assessed to be low,” he added.
Regarding the future, the assessment concludes that it is virtually certain that on a global scale hot days become even hotter and occur more often. "For the high emissions scenario, it is likely that the frequency of hot days will increase by a factor of 10 in most regions of the world", said Thomas Stocker the other Co-chair of Working Group I. “Likewise, heavy recipitation will occur more often, and the wind speed of tropical cyclones will increase while their number will likely remain constant or decrease”.
“Nevertheless, there are many options for decreasing risk. Some of these have been implemented, but many have not. The best options can provide benefits across a wide range of possible levels of climate change.” said Vicente Barros, Co-chair of Working Group II.
Chris Field, the other Co-chair of Working Group II, added: “We hope this report can be a scientific foundation for sound decisions on infrastructure, urban development, public health, and insurance, as well as for planning—from community organizations to international disaster risk management.”
“I would like to thank the scientists and experts who served as authors and review editors as well as the many expert reviewers for producing a comprehensive and scientifically sound summary and report,” said Mr Pachauri.
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