Health Effects of Climate Change THE HEALTH EFFECTS OF CLIMATE CHANGE.
Climate Change – 2: Effects on Freshwater Resources.
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Transcript of Climate Change – 2: Effects on Freshwater Resources.
Climate Change – 2: Effects on Freshwater Resources
Human Activities Affect Freshwater Resources• Both quantity and quality
Emissions of greenhouse gases Climate
Land Use
Food Demand
Population, life style, economy,
technology
Terrestrial part of hydrological cycle
Water Use
Water Resources Management
Observed climate-related trendsPrecipitation Increasing over land north of 30°N over the period 1901–2005.
Decreasing over land between 10°S and 30°N after the 1970s. Increasing intensity of precipitation
Cryosphere Snow
cover Decreasing in most regions, especially in spring
Glaciers Decreasing almost everywhere Permafrost Thawing between 0.02 m/yr (Alaska) and 0.4 m/yr (Tibetan Plateau)
Surface waters
Streamflow Increasing in Eurasian Arctic, significant increases or decreases in some river basins. Earlier spring peak flows and increased winter base flows in Northern America and Eurasia.
ET Increased actual evapotranspiration in some areas Lakes Warming, significant increases or decreases of some lake levels, and
reduction in ice cover Groundwater No evidence for ubiquitous climate-related trend Floods and droughts
Floods No evidence for climate-related trend, but flood damages are increasing Droughts Intensified droughts in some drier regions since the 1970s
Water quality No evidence for climate-related trend Erosion and sediment
No evidence for climate-related trend
Irrigation water demand
No evidence for climate-related trend
Current Vulnerabilities of Freshwater Resources and Their Management
Projected Vulnerabilities of Freshwater Resources
Impacts due to increases in temperature, sea level and precipitation variability
• Seasonal shift in streamflow• Increase in the ratio of winter to annual flows• Reduction in low flows caused by decreased
glacier extent or snow water storage• Sea-level rise will extend areas of salinisation of
groundwater and estuaries, decrease in freshwater availability in coastal areas
• Increased precipitation variability will increase risks of flooding and drought
Semi-arid and arid areas particularly exposed to impacts of climate change on freshwater
• Mediterranean basin, western USA, southern Africa, and north-eastern Brazil) will suffer a decrease in water resources due to climate change
• Groundwater recharge will decrease considerably
• Effects will be exacerbated by the rapid increase in population and water demand (very high confidence)
Water Quality
• Higher water temperatures• Increased precipitation intensity• Longer periods of low flows • Exacerbate water pollution• Impacts on – Ecosystems, – Human health, – Water system reliability – Operating costs
Climate change affects infrastructure as well as water management
• Aggravates impacts of other stresses– population growth, changing economic activity, land-use
change, and urbanisation• Water demand will grow due to population growth and
increased affluence• Large changes in irrigation water demand are likely• Current water management practices are very likely to
be inadequate to reduce the negative impacts of climate change on – water supply reliability, flood risk, health, energy, and
aquatic ecosystems
Driver - Temperature• Will increase by – 2020s ~ 1°C– 2100 ~ 2 - 4°C
• Greatest increases at high northern latitudes and over land
• Increases will be stronger in summer than in winter• Sea-level rise will be between 14 and 44 cm within
this century (does not take ice sheet melting into account)
Driver - Precipitation• Will increase at high latitudes and in the
tropics – e.g., the south-east monsoon region and over the
tropical Pacific• Will decrease in sub-tropics – e.g., over much of North Africa and the northern
Sahara• Variability will increase
Water Stress
• Population at risk of increased water resources stress (A2 scenario):– 2020s 0.5-1.7 billion; – 2050s 1.5-2.0 billion; – 2080s 2.4-3.2 billion
• By the 2050s water stress on global land area is projected to – Decrease on 20-29% and – Increase on 62-76%
Zbigniew W. Kundzewicz, Sept. 2007
Water ScarcityRegion Problem
Africa Increased water shortages due to reduced rainfall leading to large increases in the number of people suffering water scarcity
Asia In some large basins: water availability and agricultural yields are projected to decline
Australia and NZ Ongoing water security problems are very likely to increaseEurope In Southern Europe, negative impacts on water resources,
hydropower potential, agriculture, and wildfire outbreaksLatin America In Andean countries, glacier melt leads to changes in the
seasonal pattern and amount of runoff, hence affecting water resource availability and hydropower
North America
Warming in the western mountains is very likely to cause decreases in snowpack and summer flows, expanding water management challenges for competing uses
Small Islands Current water shortages are due to pressures from population growth, agriculture and tourism. Sea level rise leads to groundwater salinization and any reduction in rainfall will intensify pressures
Zbigniew W. Kundzewicz, Sept. 2007
FloodsRegion Problem
Asia In the Himalaya, glacier melt will lead to increasing numbers and severity of melt-related floods, such as GLOFs (Glacial Lake Outburst Floods), ice and rock avalanches from destabilized slopes and disruption of water resources
Australia and NZ
Higher risks to major infrastructure such as floodplain protection and urban drainage/sewerage
Europe Flash floods are likely to increase in all of Europe, while snowmelt-related floods in Central and Eastern Europe are expected to decline
Latin America In Andean countries, melting glaciers causeflooding and changes in the seasonal pattern and amount of runoff
North America
Projected warming in the western mountains by the mid 21stcentury is very likely to cause increased peak winter flows and flooding.
Zbigniew W. Kundzewicz, Sept. 2007
Water-related Hotspots on Map of Relative Changes in Runoff
Uncertainties
• Increase with the length of the time horizon– Near term (e.g., the 2020s), model uncertainties– Longer time horizons, emissions scenario
• GCMs subject to uncertainties in the modeling process• Climate projections not easy to incorporate into hydrological impact
studies• For the same emissions scenario, different GCMs produce different
geographical patterns of change, particularly with respect to precipitation
• Agreement with respect to projected changes of temperature is much higher than with respect to changes in precipitation
• GCM structure is the largest source of uncertainty, next are the emissions scenarios, and finally hydrological modeling
Some GCM Issues• Most climate change studies consider only changes in precipitation
and temperature• Time series of observed climate values are adjusted with the
computed change in climate variables to obtain scenarios that are consistent with present-day conditions to minimise the error in GCMs
• Mismatch of spatial grid scales between GCMs (typically a few hundred kilometers) and hydrological processes
• Techniques to downscale GCM outputs to finer spatial (and temporal) resolution have been developed– Dynamic downscaling - based on links between the climate at large and at
smaller scales– Statistical downscaling - using empirical relationships between large-scale
atmospheric variables and observed daily local weather variables
Model resolutions as function of spectral truncation2.8o x 2.8o
(200 x 300 km)1.4o x 1.4o
(100 x 150 km)1990’s
2005
2011?
3 x 3 o o
Change in Annual Runoff by 2041 (relative to 1900-70)
Change in Annual Runoff by 2090 (relative to 1980-99)
Adaptation