Managing the Risks of Extreme Events and Disasters

The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), which was completed in 2007 stated that: "Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level." It also stated that observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly in increases in temperature. Significantly, the AR4 found that since the mid-twentieth century most of the observed increase in global average temperatures is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. When the term "very likely" is used in this context, it denotes a probability level of 90 per cent or higher.

As a result of observed as well as projected climate change, some systems, sectors, and regions are likely to become especially affected by climate change. These include particular ecosystems including the tundra, boreal forest, and mountain regions because of sensitivity to warming, Mediterranean type ecosystems because of reduction in rainfalls, and tropical rainforests where precipitation declines. In addition, in coastal areas mangroves and salt marshes would be affected due to multiple stresses, as would also be the case with marine ecosystems including coral reefs. Impacts of climate change would also be significant for water resources in some dry regions at mid-latitudes and in the dry tropics due to changes in rainfall and evapo-transpiration, as well as in areas dependent on snow and ice melt. Impacts of climate change are also expected to be significant for agriculture in low latitudes due to reduced water availability, in low-lying coastal systems due to the threat of a sea level rise, increased risk from extreme weather events, as well as on human health in populations with low adaptive capacities. Some regions would also be affected significantly, such as the Arctic, because of the impacts of high rates of projected warming on natural systems and human communities. Africa would be affected because of low adaptive capacity and projected climate change impacts. The Asian and African mega deltas would also be vulnerable on account of large populations and high exposure to sea level rise, storm surges, and river flooding. Another major resource that is being affected by climate change is the ocean, wherein since 1750 the uptake of anthropogenic carbon has led to it becoming more acidic with an average decrease in pH of 0.1 units. Projections for the future indicate a worsening of this condition, and this progressive acidification of oceans is expected to have negative impacts on marine shell-forming organisms, such as corals and their dependent species.

More Focused Findings

Over and above these different impacts of climate change, the IPCC has now come up with a set of more focused findings in its Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). The character and severity of impacts from climate extremes depend not only on the extremes themselves, but also on exposure and vulnerability. Adverse impacts are considered disasters when they produce widespread damage and cause severe alterations in the normal functioning of communities or societies. Climate extremes, exposure, and vulnerability are influenced by a wide range of factors including anthropogenic climate change, natural climate variability, and socioeconomic development. Disaster risk management and adaptation to climate change focus on reducing exposure and vulnerability, and increasing resilience to the potential adverse impacts of climate extremes, even though risks cannot be eliminated fully. Exposure and vulnerability are dynamic, varying across temporal and spatial scales, and depend on economic, social, geographic, demographic, cultural, institutional, governance, and environmental factors. Settlement patterns, urbanization, and changes in socio-economic conditions have all influenced observed trends in exposure and vulnerability to climate extremes. For instance, coastal settlements, including in small islands and mega deltas and mountain settlements are exposed and vulnerable to climate extremes in both developed and developing countries, but with differences among regions and countries. Rapid urbanization and growth of mega cities, especially in developing countries, have led to the emergence of highly vulnerable urban communities, particularly through informal settlements and inadequate land management. Vulnerable populations also include refugees, internally displaced people, and those living in marginal areas.

The SREX determined that, based on evidence from observations gathered since 1950, there has been change in some extremes. It is very likely that there has been an overall decrease in the number of cold days and nights, and an over-all increase in the number of warm days and nights at the global scale, that is, for most land areas with sufficient data. It is likely that these changes have also occurred at the continental scale in North America, Europe, and Australia. There is also medium confidence in a warming trend in daily temperature extremes in much of Asia. There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely that more of these regions have experienced increases rather than decreases, although there are strong regional and sub-regional variations in these trends. Overall, there is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases.

Some Losses Difficult to Value

Global weather and climate related disaster losses reported over the last few decades reflect mainly monetized direct damages to assets, and are unequally distributed. Estimates of annual losses have ranged since 1980 from a few billion US dollars to above $200 billion dollars in 2010, with the highest value for 2005, the year of Hurricane Katrina. Loss estimates are lower bound estimates because many impacts, such as loss of human lives, cultural heritage, and ecosystem services are difficult to value and monetize, and thus are poorly reflected in estimates of losses. Impacts on the informal or undocumented economy as well as indirect economic effects can be very important in some areas and sectors, but are generally not counted in reported estimates of losses. For this reason, economic including insured disaster losses associated with weather, climate, and geophysical events are higher in developed countries. Fatality rates and economic losses expressed as a proportion of GDP are higher in developing countries. During the period from 1970 to 2008, over 95 per cent of deaths from natural disasters occurred in developing countries. Middle income countries with rapidly expanding asset bases have borne the largest burden. During the period from 2001 to 2006, losses amounted to about 1 per cent of GDP for middle income countries, while this ratio has been about 0.3 per cent of GDP for low income countries and less than 0.1 per cent of GDP for high income countries, based on limited evidence. In small exposed countries, particularly small island developing states, losses expressed as a percentage of GDP have been particularly high, exceeding 1 per cent in many cases and 8 per cent in the most extreme cases, averaged over both disaster and non-disaster years for the period from 1970 to 2010.

More Warm Spells, More Rain

Models project substantial warming in temperature extremes by the end of the twenty-first century. It is very likely that the length, frequency, and/or intensity of warm spells or heat waves will increase over most land areas. Based on specific emissions scenarios, a 1 in 20 year hottest day is likely to become a 1 in 2 year event by the end of the twenty-first century in most regions, except in the high latitudes of the northern hemisphere, where it is likely to become a1 in 5 year event. The 1 in 20 year extreme daily maximum temperature (that is, a value that was exceeded on average only once during the period from 1981 to 2000) will likely increase by about 1 degree Celsius to 3 degree Celsius by the mid twenty-first century and by about 2 degree Celsius to 5 degree Celsius by the late twenty-first century depending on the region and emissions scenario. It is also likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy falls will increase in the twenty-first century over many areas of the globe. Based on a range of emissions scenarios, a 1 in 20 year annual maximum daily precipitation amount is likely to become a 1 in 5 to a 1 in 15 year event by the end of the twenty-first century in many regions, and in most regions the higher emissions scenarios used by the IPCC led to a stronger projected decrease in return period. Additionally, it is very likely that mean sea level rise will contribute to upward trends in extreme coastal high water levels in the future.

Disaster Risk Management

Adaptation to climate change and disaster risk management provides a range of complementary approaches for managing the risks of climate extremes and disasters. Measures that provide benefits under current climate and a range of future climate change scenarios, called low-regrets measures, are available starting points for addressing projected trends in exposure, vulnerability, and climate extremes. Many of these low-regrets strategies produce co-benefits, help address other development goals, such as improvements in livelihoods, human well-being, and biodiversity conservation, as well as to help minimize the scope for maladaptation. Potential low-regrets measures include early warning systems, risk communication between decision makers and local citizens; sustainable land management, including land use planning; and ecosystem management and restoration. Other low-regrets measures include improvements in health surveillance, water supply, sanitation, and irrigation and drainage systems; climate proofing of infrastructure; development and enforcement of building codes; and better education and awareness.

The SREX also provides an assessment of specific case studies, which include the heat waves in Europe of 2003 and 2006, the cyclones in Myanmar and Bangladesh, the heavy rainfall in Mumbai in 2005, and several others. These case studies are particularly useful because they provide insights into inadequacies that were observed during these events as well as appropriate measures which, for instance, were much more in evidence during the European heat wave of 2006 as opposed to the one in 2003. Appropriate preparedness for minimizing the risks of future extreme events and disasters would involve improvements in governance systems, establishment of early warning systems, and creating proper awareness and knowledge of likely climate change impacts and measures by which these could be dealt with for protection of life and property. However, it needs to be emphasized, as the AR4 had clearly stated, "that neither adaptation nor mitigation alone can avoid all climate change impacts", however, they "can complement each other and together can significantly reduce the risks of climate change". In fact, many impacts can be reduced, delayed, or avoided by mitigation. Over the next two to three decades mitigation efforts and investments will have a large impact on opportunities to achieve lower stabilization levels.

In conformity with this, the SREX has concluded that limits to resilience are faced when thresholds or tipping points associated with social and/or natural systems are exceeded, posing severe challenges for adaptation. Hence, while at the local level adaptation measures could help in dealing with the risks of extreme events and disasters as a consequence of climate change, at the global level mitigation measures would be an essential part of risk management.