L. 8: Projected Regional Changes in Mean States, C. 7-Gleick

Question 1

Climate change observational records

Answer 1

Increase in SST and surface air temperatures; increasing atmospheric water vapor content; changing precipitation patterns–frequency and intensity and extremes, spatial and inter-decadal variability; reduced snow cover; widespread melting of ice (glaciers, sea ice) and decrease in glacier mass balance and reduced water storage; changes in soil moisture (decrease in frozen ground); and shifts in the amplitude/timing of glacier runoff and snowmelt-fed rivers.

Question 2

Interconnections

Answer 2

Climate, freshwater, biophysical and socioeconomic systems are interconnected in complex ways, so a change in any one of these induces changes in others.

Question 3

GCMs

Answer 3

General Circulation Models– climate models developed in 60s to 70s using same equations as in NWP, but long term predictions/ simulations of climate. Use grid structure. Evolved to include: (1) solar radiation, atmosphere, precipitation; (2) clouds, land surface, sea ice sheets; (3) swamp ocean; (4) volcanism, sulfates, ocean currents; (5) carbon cycle, hydrological cycle, deep ocean circulation, aerosols; (5) atmospheric chemistry/ processes, interactive vegetation. Interactions and feedbacks among components, temporal and spatial. Still uncertainty in forcing mechanisms of clouds, aerosols.

Question 4

NWP

Answer 4

Numerical Weather Prediction– models to produce timely, accurate forecasts (< 10 days).

Question 5

IPCC

Answer 5

Compares most robust GCMs (30 in 2013). Temperature predictions pretty clear, but precipitation not.

Question 6

Climate projections

Answer 6

1. Precipitation increases in high latitudes and parts of tropics, decreases in some subtropical and lower mid-latitude regions.
2. By 2050, annual average river runoff and water availability are projected to increase at high latitudes and in some wet tropical areas, and decrease over some dry regions at mid-latitudes and in the dry tropics.
3. Frequency of heavy precipitation events (or proportion of total rainfall from heavy falls) will increase over most areas, increasing the risk of flooding. Increase in land surface in extreme drought. Tendency for drying in continental interiors during summer, especially in sub-tropics, low and mid-latitudes. Trenberth: Rich get richer and poor get poorer; never rains but it pours.
4. Increase/decrease in runoff. Water supplies stored in glaciers and snow cover are projected to decline, reducing water availability during warm and dry periods (through a seasonal shift in streamflow, an increase in the ratio of winter to annual flows, reductions in low flows) in regions supplied by melt water from major mountain ranges (1/6 of global population).
5. Higher water temperatures, and changes in extremes (floods and droughts) will affect water quality. Sea level rise will extend areas of salinization of groundwater and estuaries, decreasing freshwater availability for humans and ecosystems in coastal areas. Water pollution from sediments, nutrients, dissolved organic carbon, pathogens, pesticides, salt, thermal.
6. Area of land subject to increasing water stress due to climate change projected to be more than double that with decreasing water stress. Areas in which runoff is projected to decline face a reduction in the value of the services provided by water resources. Increased annual runoff in some areas will increase total water supply, but may have negative effects: more precipitation variability, flood.
7. Changes in water quantity and quality are expected to affect food availability, stability, access and utilization.

Question 7

Non-climatic drivers affecting freshwater resources

Answer 7

Human activity: agriculture, land use change, construction and management of reservoirs, pollutant emissions, water and wastewater treatment.

Question 8

water use links

Answer 8

Water use is linked to: changes in population, food consumption (type of diet), economic policy (water pricing), technology, lifestyle, society’s views about the value of freshwater ecosystem.

Question 9

Water stressed

Answer 9

Per capita water availability below 1000m3 per year (all uses, domestic/industrial/agricultural).

Question 10

Sectors affected by climate change

Answer 10

Ecosystems and biodiversity
Agriculture and food security, land use, forestry
Human health
Water supply and sanitation
Settlements and infrastructure
Economy: insurance, tourism, industry, transportation

Question 11

Impacts of climate change on water services

Answer 11

1. Temp up – Reduced water availability in basins fed by glaciers that are shrinking.
2. SST up – Reduced dissolved oxygen content, increase in algal blooms
3. Sea level rise – Salinization of coastal aquifers
4. Shift in precipitation patterns – Changes water availability (changes in groundwater recharge, ET)
5. Increase in interannual precipitation variability – harder to control floods and use reservoirs
6. ET up – Reduced water availability, lower groundwater levels, salinization of water resources
7. More frequent and intense extreme events – flooding impact on water quality and infrastructure, increased erosion and pollution of water, droughts affect water availability and quality

Question 12

Peak Water (Gleick)

Answer 12

Water use within renewable peak limits is sustainable.
3 peaks: Peak renewable water; Peak nonrenewable water (like oil); Peak ecological water (balance ecological services with human services provided by water), max combined benefits to society and ecosystems.