A draft UN report three years in the making concludes that man-made climate change has boosted the frequency or intensity of heat waves, wildfires, floods and cyclones and that such disasters are likely to increase in the future.
The document being discussed by the world’s Nobel-winning panel of climate scientists says the severity of the impacts vary, and some regions are more vulnerable than others.
Hundreds of scientists working under the Intergovernmental Panel for Climate Change (IPCC) will vet the phonebook-sized draft at a meeting in Kampala of the 194-nation body later this month.
“This is the largest effort that has even been made to assess how extremes are changing,” said Neville Nicholls, a professor at Monash University in Melbourne, Australia, and a coordinating lead author of one of the review’s key chapters.
Mindful of an outcry by climate skeptics over flaws in an earlier IPCC text, those working on the document stress that the level of “confidence” in the findings depends on the quantity and quality of data available.
But the overall picture that emerges is one of enhanced volatility and frequency of dangerous weather, leading in turn to a sharply increased risk for large swathes of humanity in coming decades.
AFP obtained a copy of the draft report’s 20-page Summary for Policymakers, which is subject to revision by governments before release on November 18.
Its publication coincides with a series of natural catastrophes around the world that have boosted the need to determine whether such events are freaks of the weather or part of a long-term shift in climate.
In 2010, record temperatures fuelled devastating forest fires across Siberia, while parts of Pakistan and India reeled from unprecedented flooding.
This year, the United States has suffered from a record number of billion-dollar disasters ranging from flooding in the Mississippi and Missouri Rivers to Hurricane Irene to the ongoing Texas drought.
Large swathes of China are suffering from intense drought as well, even as central America and Thailand count their dead from recent diluvian rains.
Most of these events match predicted impacts of manmade global warming, which has raised temperatures, increased the amount of water in the atmosphere and warmed ocean surface temperatures — all drivers of extreme weather.
But teasing apart the role of natural fluctuations in the weather and rising levels of greenhouse gases in the atmosphere has proven devilishly difficult for scientists.
The nine-chapter Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, or SREX, pored over hundreds of recent scientific studies.
The new report’s main conclusions about future trends include:
– It is “virtually certain” — 99-100% sure — that the frequency and magnitude of warm daily temperature extremes will increase over the 21st century on a global scale;
– It is “very likely” (90-100% certainty) that the length, frequency and/or intensity of warm spells, including heat waves, will continue to increase over most land areas;
– Peak temperatures are “likely” (66-100% certainty) to increase — compared to the late 20th century — up to 3.0 degrees Celsius (5.4 degrees Fahrenheit) by 2050, and 5.0 C (9.0 F) by 2100;
– Heavy rain and snowfall is likely to increase over the next century over many regions, especially in the tropics and at high latitudes;
– At the same time, droughts will likely intensify in other areas, notably the Mediterranean region, central Europe, North America, northeastern Brazil and southern Africa.