There is evidence that climate extremes have changed as a result of greenhouse-gas emissions caused by human activities, says a report by the Intergovernmental Panel on Climate Change.
A summary of the “Special report on managing the risks of extreme events and disasters to advance climate change adaptation” was published for policymakers on 18 November.
The report finds that it is likely that anthropogenic influences have led to warming of extreme daily maximum and minimum temperatures, with probability estimated at 66 per cent at least.
It is “virtually certain”, it adds, that the magnitude and frequency of hot days will increase in the future and “very likely” that there will be an increase in heat waves over most land areas.
It also finds that there is at least a 66 per cent probability that there has been an anthropogenic influence on increasing extreme coastal high water due to rising sea levels. It cites small island settlements as likely to be especially vulnerable as a result of sea-level rise.
In addition, it says, greenhouse-gas emissions seem to have caused more intense and longer droughts in some regions, though it notes that the evidence is not conclusive.
The report highlights the difficulty of assessing how global warming impacts on certain extreme weather events, such as hurricanes and tornadoes. Since extreme events are rare, it adds, there is little data on which to base such assessments.
Speaking to the Guardian newspaper, the IPCC’s chairman, Rajendra Pachauri, said that although he was prepared for attacks from climate sceptics, he was confident that most of the world would accept the findings.
“Some find us inconvenient. We will always be opposed by vested interests, and if people still want to attack us, there’s nothing we can do about it,” he said.
The report also looks at how extreme climate events impact on society and concludes that economic losses from weather- and climate-related disasters have increased, although figures fluctuate from year to year.
Such economic losses are higher in developed countries, it adds, but deaths and economic losses as a proportion of GDP are higher in the developing world.
Commenting on the report, Simon Brown, climate extremes research manager at the Met Office Hadley Centre, said the review would be helpful in progressing science on the topic:
“This focus of the IPCC on extremes is very welcome as less emphasis has traditionally been given to these phenomena which are very likely to be the means by which ordinary people first experience climate change,” he said in a statement.
“Human susceptibility to weather mainly arises through extreme weather events so it is appropriate that we focus on these which, should they change for the worse, would have wide ranging and significant consequences,” he added.
Bob Ward, policy and communications director at the Grantham Research Institute at London School of Economics, said that governments should realise the risks of climate change as they were preparing for the United Nations climate change summit that starts in Durban, South Africa, this month.
“This expert review of the latest available scientific evidence clearly shows that climate change is already having an impact in many parts of the world on the frequency, severity and location of extreme weather events, such as heatwaves, droughts and flash floods. This is remarkable because extreme events are rare and it is difficult to detect statistically significant trends in such small sets of data.
“Governments must focus clearly on reaching a strong international agreement to strengthen their efforts to reduce emissions and to prepare their populations for those impacts of climate change that cannot now be avoided,” he said in the same statement.