Sub-theme 2. Management of climatic extremes with focus on floods and droughts
As per IPCC (2012) an extreme (weather or climate) event is generally defined as the occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends (‘tails’) of the range of observed values of the variable. Some climate extremes (e.g., droughts, floods) may be the result of an accumulation of weather or climate events that are, individually, not extreme themselves (though their accumulation is extreme). A changing climate leads to changes in the frequency, intensity, spatial extent, duration, and timing of weather and climate extremes, and can result in unprecedented extremes.
There is evidence from observations gathered since 1950 of change in some extremes such as an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, at the global scale, statistically significant increases in the number of heavy precipitation events (floods) in more regions than there have been statistically significant decreases, but there are strong regional and subregional variations in the trends, some regions of the world have experienced a trend to more intense and longer droughts, in particular in southern Europe and West Africa, but in some regions droughts have become less frequent, less intense, or shorter, for example, in central North America and north western Australia, an increase in extreme coastal high water related to increases in mean sea level in the late 20th century etc. Models project substantial warming in temperature extremes by the end of the 21st century as well as likelihood of increase in the frequency of heavy precipitation or the proportion of total rainfall from heavy rainfalls in the 21st century over many areas of the globe, particularly in the high latitudes and tropical regions, and in winter in the northern mid-latitudes. Projected precipitation and temperature changes imply possible changes in floods. Further intensification of droughts are projected in the 21st century in some seasons and areas due to reduced precipitation and/or increased evapotranspiration.
These climate extremes have significant impact on human and ecological systems, which are influenced by changes in climate, vulnerability and exposure, resulting into increased fatalities and economic losses especially in developing countries. Increasing exposure of people and economic assets has been the major cause of long-term increases in economic losses from weather- and climate-related disasters. Extreme events have greater impacts on sectors with closer links to climate, such as water, agriculture and food security, forestry, health, and tourism. Disasters due to climate extremes, in terms of loss of life and property, are most acutely experienced at the local level. These localized impacts can then cascade to have national and international consequences. In order to reduce impact due to these climate extremes it is essential to develop strategies for disaster risk management in the context of climate change which may include coping and adaptation mechanism, informed by and customized to specific local circumstances. Adaptation to climate change and disaster risk management provide a range of complementary approaches for managing the risks of climate extremes and disasters. Effectively applying and combining approaches may benefit from considering the broader challenge of sustainable development. 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. 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 to 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. Integration of local knowledge with additional scientific and technical knowledge can improve disaster risk reduction and climate change adaptation. An iterative process of monitoring, research, evaluation, learning, and innovation can reduce disaster risk and promote adaptive management in the context of climate extremes. Estimates of adaptation costs to climate change exhibit a large range and relate to different assessment periods. For 2030, the estimated global cost ranges from US$ 48 to 171 billion per year (in 2005 US$) with recent estimates for developing countries broadly amounting to the average of this range with annual costs of up to US$ 100 billion.
Keeping above in view one of the sub-themes adopted for WIF2 is 2 ‘Management of climatic extremes with focus on floods and droughts’ to facilitate discussion on various related topics such as adaptation of design and operation criteria for irrigation and drainage schemes in light of climate change impacts; managing impacts of extreme events – floods and droughts; dealing with climate change impacts on food security; regional water management in ASEAN countries and international river basins etc.
1.1 Adaptation of design and operation criteria for irrigation and drainage schemes in light of climate change impacts
1.2 Managing impacts of extreme events – floods and droughts
1.3 Dealing with climate change impacts on food security
1.4 Regional water management in Asean countries and international river basins