اگست 24, 2017
Evidence suggests that climate change has led to changes in climate extremes such as heat waves, record high temperatures and, in many regions, heavy precipitation in the past half century, the Intergovernmental Panel on Climate Change (IPCC) said on Wednesday.
Climate extremes, or even a series of non-extreme events, in combination with social vulnerabilities and exposure to risks can produce climate-related disasters, the IPCC said in its Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX).
While some extreme weather and climate events lead to disasters, others do not. Policies to avoid, prepare for, respond to and recover from the risks of disaster can reduce the impact of these events and increase the resilience of people exposed to extreme events, the IPCC shows in the new report.
At the same time, limits to resilience are faced when thresholds or tipping points associated with social and/or natural systems are exceeded, posing severe challenges for adaptation.
According to the report
* Observations since 1950 show changes in some extreme events, particularly daily temperature extremes, and heat waves.
* It is likely that the frequency of heavy precipitation will increase in the 21st century over many regions.
* It is virtually certain that increases in the frequency of warm daily temperature extremes and decreases in cold extremes will occur throughout the 21st century on a global scale. It is very likely—90 per cent to 100 per cent probability—that heat waves will increase in length, frequency, and/or intensity over most land areas.
* It is likely that the average maximum wind speed of tropical cyclones (also known as typhoons or hurricanes) will increase throughout the coming century, although possibly not in every ocean basin. However it is also likely—in other words there is a 66 per cent to 100 per cent probability—that overall there will be either a decrease or essentially no change in the number of tropical cyclones.
* There is evidence, providing a basis for medium confidence, that droughts will intensify over the coming century in southern Europe and the Mediterranean region, central Europe, central North America, Central America and Mexico, northeast Brazil, and southern Africa. Confidence is limited because of definitional issues regarding how to classify and measure a drought, a lack of observational data, and the inability of models to include all the factors that influence droughts.
* It is very likely that average sea level rise will contribute to upward trends in extreme sea levels in extreme coastal high water levels.
* Projected precipitation and temperature changes imply changes in floods, although overall there is low confidence at the global scale regarding climate-driven changes in magnitude or frequency of river related flooding, due to limited evidence and because the causes of regional changes are complex.
Talking about trends in disaster losses, the IPCC says
* Economic losses from weather- and climate-related disasters vary from year to year and place to place, but overall have increased (high confidence).
* Total economic losses from natural disasters are higher in developed countries (high confidence).
* Economic losses expressed as a proportion of Gross Domestic Product (GDP) are higher in developing countries (high confidence).
* Deaths from natural disasters occur much more in developing countries (high confidence). From 1970 to 2008 for example, more than 95% of deaths from natural disasters were in developing countries.
* Economic losses from weather- and climate-related disasters have been heavily influenced by increasing exposure of people and economic assets (high confidence).
Talking about managing the risk of disasters, the IPCC says
* An iterative process involving monitoring, research, evaluation, learning, and innovation can reduce disaster risk in the context of climate extremes (robust evidence, high agreement).
* Many measures for managing current and future risks have additional benefits, such as improving peoples’ livelihoods, conserving biodiversity, and improving human well-being (medium evidence, high agreement).
* Many measures, when implemented effectively, make sense under a range of future climates (medium evidence, high agreement). These “low regrets” measures include systems that warn people of impending disasters; changes in land use planning; sustainable land management; ecosystem management; improvements in health surveillance, water supplies, and drainage systems; development and enforcement of building codes; and better education and awareness.
* Effective risk management generally involves a portfolio of actions, from improving infrastructure to building individual and institutional capacity, in order to reduce risk and respond to disasters (high confidence).
* Post-disaster recovery and reconstruction provide an opportunity for reducing the risks posed by future weather- and climate-related disasters (robust evidence, high agreement). However, short-term measures to protect people from immediate risks can increase future risks, such as improvements in levees encouraging further development in flood plains (medium evidence, high agreement).
* Risk management works best when tailored to local circumstances. Combining local knowledge with additional scientific and technical expertise helps communities reduce their risk and adapt to climate change (robust evidence, high agreement).
* Actions ranging from incremental improvements in governance and technology to more transformational changes are essential for reducing risk from climate extremes (robust evidence, high agreement).
“The main message from the report is that we know enough to make good decisions about managing the risks of climate-related disasters. Sometimes we take advantage of this knowledge, but many times we do not,” said Chris Field of the Carnegie Institution for Science, Stanford, co-chair of IPCC’s Working Group II, which together with Working Group I produced the report. “The challenge for the future has one dimension focused on improving the knowledge base and one on empowering good decisions, even for those situations where there are lots of uncertainty.”
The IPCC released the Summary for Policymakers (SPM) of the report in November 2011. The full report offers a greater understanding of the human and economic costs of disasters and the physical and social patterns that cause them.
The report is the outcome of cross-disciplinary teamwork between scientists studying the physical aspects of climate change, scientists with expertise in impacts, adaptation and vulnerability as well as experts in disaster risk management.
“The report integrates these three areas of expertise as an IPCC product which has high policy relevance to countries and communities across the globe,” said R.K. Pachauri, Chairman of the IPCC. “The authors assess scientific and technical information from around the world to provide and communicate knowledge on what we know with confidence, as well as identifying areas on which greater scientific evidence is essential to gain deeper understanding.”
The environmental and social factors that influence the risk of disasters vary from region to region, but many of the effective strategies for dealing with disaster risk in a changing climate are similar. “The most effective measures tend to be those that aid sustainable development, provide a diverse portfolio of options, and represent “low regrets” strategies in the sense that they yield benefits across a wide range of climate futures,” said Field.
The authors have assessed many new studies, and new global and regional modelling results that were not available at the time of the Fourth Assessment Report in 2007, its last major assessment of climate change science. “The SREX provides an unprecedented level of detail regarding observed and expected changes in weather and climate extremes, based on a comprehensive assessment of over 1,000 scientific publications,” said Qin Dahe of China Meteorological Administration, Beijing, and co-chair of Working Group I.
“The report also provides improved differentiation of observed and projected changes in extremes of temperature, precipitation and drought across the continents,” said Thomas Stocker of University of Bern, Switzerland, the other co-chair of Working Group I.
“There are many options currently available that could improve preparation for effective response to extreme climate events and disasters, and enhance recovery from them, said Vicente Barros of the University of Buenos Aires, the other co-chair of Working Group II. “This report identifies lessons learned from extensive experience in disaster risk management and from the growing focus on climate change adaptation.”
The report’s 592 pages cite thousands of scientific studies and have been subjected to three rounds of review by experts and governments to ensure that the findings are firmly based in the underlying scientific and technical information. A total of 220 authors from 62 countries worked on the report, for which 18,784 outside expert and government review comments were received in the three rounds of formal review.