Distributing water to famine refugees, many of whom walked hundreds of miles from their homes in the Horn of Africa. Source: Oxfam
The United Nations’ Intergovernmental Panel on Climate Change (IPCC) took a major step last week toward advancing the discussion of global climate change by confirming the growing body of evidence that global warming is in fact contributing to extreme weather events, and recognizing that many parts of the world have entered a new “normal” in which once rare events have and will continue to become more common.
In a 29-page summary document for policymakers, the IPCC’s Working Group II, charged with identifying potential impacts of climate change, evaluating vulnerability of at-risk populations and developing strategies for adapting to a changing climate, offered a preview of a more comprehensive report to be published next spring, titled, “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation.”
In many ways, the summary document represents a marked departure from previous IPCC reports, going so far as to redefine the term “climate change.”
Whereas the UN Framework Convention on Climate Change’s (UNFCCC) definition has been limited to change resulting from human activity above and beyond natural variations, the Working Group II’s report defines climate change as the net change regardless of cause.
Fort Calhoun Nuclear Reactor surrounded by Missouri River during spring 2011 floods that ravaged the US midwest.
Responding to past criticisms of IPCC assessments and predictions, the new report also acknowledges the uncertainty inherent in predicting the frequency or severity climate change impacts, as well as the variability in quality and quantity of currently available climate and weather-related data. As a result, predictions are quantitatively expressed as probabilities and qualitatively using defined terms such as “likely,” “very likely” or “virtually certain.” Similarly, assessments are accompanied by degree of confidence, expressed qualitatively as “low,” “medium” or “high.”
Contributing to the report were 220 authors from 62 countries, augmented by more than 18,000 reviewer comments.
Risk Assessment and Risk Management
Having integrated perspectives from traditionally separate fields of study, the IPCC summary document explores the interaction of climatic, geographic, environmental, economic, social, political, cultural and other factors that determine human and ecosystem exposure and vulnerability to extreme weather.
Socioeconomic development interacts with natural and human-caused climate variations to influence disaster risk. Source: IPCC
While the report recognizes the need for national and regional strategies, it emphasizes the need to focus efforts locally, since exposure, vulnerability and potential solutions vary significantly from one locale to another. Moreover, scientific, engineering and planning efforts are known to be most effective when informed by local knowledge, experience and culture.
The summary report includes six scenarios, each of which identifies the probability of various extreme weather events specific to a locale, risk factors associated with those events, and potential actions that can mitigate catastrophic impacts.
In Europe, for example, the report concludes that an increase in frequency of heat waves is likely (60-100% probability), while increases in day and nighttime temperatures are very likely (90-100% probability). Under such conditions, risk factors for heat-related health problems might include age of the population, lack of access to cooling, pre-existing health conditions, poverty, isolation or lack of infrastructure. Adaptation strategies might include providing for public cooling spaces, increasing urban green space, enhancements to social care networks, warning systems and modifications to urban infrastructure.
For tropical, small island developing countries, the effect of sea level rise to extreme coastal high water levels, such as storm surges, is considered very likely (90-100% probability). Here, risk factors may include such considerations as shore erosion, intrusion of saltwater into freshwater sources, number and percentage of population that lives on or near the coast, and the extent to which the economy depends upon tourism. Potential risk management strategies include early warning systems, maintenance of drainage systems, regional risk pooling and relocation.
In keeping with the Working Group II’s systematic approach to risk assessment, a broad range of risk-management approaches are outlined, beginning with those that provide immediate benefits apart from extreme weather events, while also serving to mitigate damage from extreme events in the future. Included are improvements in sustainable land and ecosystems management, improvements in water supply and sanitation, development and enforcement of better building codes, among others.
Probabilities of Extreme Weather Related to Climate Change
Among the Working Group II’s assessments of extreme weather events due to increased global temperature are the following:
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Over three days in April, 2011, 336 tornadoes swept across the Southern, Midwestern, and Northeastern US in the largest tornado outbreak ever recorded.
It is likely (66-100% probability) that the frequency of heavy precipitation will increase in the 21st century over many regions, but virtually certain (99-100% probability) that increases in the frequency of warm daily temperature extremes and decreases in cold extremes will occur throughout on a global scale.
- It is very likely (90-to 100% probability) that heat waves will increase in length, frequency, and/or intensity over most land areas.
- It is very likely that average sea level rise will contribute to upward trends in extreme sea levels in extreme coastal high water levels.
- It is likely (66-100% probability) that the average maximum wind speed of tropical cyclones will increase, although possibly not in every ocean basin, and that there will be a net decrease or no change in the number of tropical cyclones.
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Carcasses of dead sheep and goats litter the landscape in Somaliland, victims of severe and prolonged drought. Source: Oxfam
Due to a lack of observational data and the many factors that contribute to droughts, there is medium confidence in evidence indicating 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.
- 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.
Moving Forward and COP 17
With the summary document for policymakers released last week and the full report to come next year, the IPCC has effectively moved past questions of whether global warming is real, whether it’s the result of human or natural causes, whether recent extreme weather is related to climate change, and whether we can expect extreme events to become more severe and frequent in the future. The question now is what, if anything, are we going to do prevent more frequent and more severe weather extremes from becoming human and ecological catastrophes.
Just as important is that, by relating climate change to extreme weather, the Working Group II report brings a tangible sense of urgency to the often abstract threats of global of predictions cannot.
With the 17th Conference of the Parties (COP17) to the United Nations Framework Convention on Climate Change about to convene next week in Durban, South Africa, it will be interesting to see how deep that sense of urgency runs.
