Geneva, September 2008
Climate Change and Disaster Risk Reduction
Weather, climate and climate change
Defining climate change For most people, the expression “climate change” means the alteration of the world’s climate that we humans are causing, through fossil fuel burning, clearing forests and other practices that increase the concentration of greenhouse gases (GHG)1 in the atmosphere. This is in line with the official definition by the United Nations Framework Convention on Climate Change (UNFCCC) that climate change is the change that can be attributed “directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”.2 However, scientists often use the term for any change in the climate, whether arising naturally or from human causes. In particular, the Intergovernmental Panel on Climate Change (IPCC) defines “climate change” as “a change in the state of the climate that can be identified ... by changes in the mean and / or the variability of its properties, and that persists for an extended period, typically decades or longer”.3 Each of these two definitions is relevant and important to keep in mind. 1 Greenhouse gases (GHGs) “are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, the atmosphere itself, and by clouds.” The primary greenhouse gases include H2O, CO2, N2O, CH4 and O3. IPCC Fourth Assessment Report, Working Group I, Glossary of Terms: http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Annexes.pdf. 2 UNFCCC Article 1, Definitions: http://unfccc.int/essential_background/convention/background/ items/1349.php. 3 IPCC Fourth Assessment Report, Working Group I, Glossary of Terms: http://ipcc-wg1.ucar.edu/wg1/ Report/AR4WG1_Print_Annexes.pdf.
Climate change and disaster risk reduction are closely linked. More extreme weather events in future are likely to increase the number and scale of disasters, while at the same time, the existing methods and tools of disaster risk reduction provide powerful capacities for adaptation to climate change. This Briefing Note, prepared by the secretariat of the United Nations International Strategy for Disaster Reduction Secretariat (UNISDR), outlines the nature and significance of climate change for disaster risk, as well as the main perspectives and approaches of disaster risk reduction and how they can support adaptation strategies. It is aimed at experts and practitioners as well as non-specialists such as teachers and students, journalists and the interested public.
Briefing Note 01 ─ Climate Change and Disaster Risk Reduction Weather and climate Weather is the set of meteorological conditions – wind, rain, snow, sunshine, temperature, etc. – at a particular time and place. By contrast, the term “climate” describes the overall long-term characteristics of the weather experienced at a place. For example, Singapore, in the tropics, has a hot wet climate, while continental Mongolia always has cold winters. The ecosystems, agriculture, livelihoods and settlements of a region are very dependent on its climate. The climate therefore can be thought of as a long-term summary of weather conditions, taking account of the average conditions as well as the variability of these conditions. The fluctuations that occur from year to year, and the statistics of extreme conditions such as severe storms or unusually hot seasons, are part of the climatic variability. Some slowly changing climatic phenomena can last for whole seasons or even years; the best known of these is the El Niño phenomenon.4 Since the atmosphere connects all weather systems and all climates, it is sometimes useful to describe the atmosphere, oceans and Earth surface as the “global...
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