Post on 18-Dec-2015
transcript
Climate Change and the Water supply: What Will it Mean for San Diego?
David W. Pierce
Tim P. Barnett
Climate Research Division
Scripps Institution of Oceanography
30 April 2008
What climate forecasts mean
What climate forecasts mean
Evidence for warming
Global surface temperature
Last 1200 years
IPCC 2007, Fig. 6.10
Glacier change: Patagonia
Evidence for warming:
Measured air temperature (including aloft)
Measured ocean temperature (including subsurface)
Atmosphere is more humid
Reduction in glaciers, snowpack, and permafrost
Behavior of plants and animals
“Proxy indicators”: Borehole temperatures, tree rings, corals
Is it caused by humans?
How climate change works
How climate change works
First described by the 3rd Nobel Prize winner in chemistry, over 100 years ago!
Greenhouse gases keep the planet about 60oF warmer
CO2 increasing since 1957
Charles Keeling, SIO
Carbon emissions by source
Courtesy P. Mote
Natural vs. Human Influences
IPCC 2001, Summary Fig. 4
Natural vs. Human Influences
IPCC 2001, Summary Fig. 4
Natural vs. Human Influences
IPCC 2001, Summary Fig. 4
Combination of factors
Meehl et al., J. Climate, 2004, as redrawn by globalwarmingart.com
Solar Volcanoes
Greenhouse gases Ozone
Sulphate aerosols Total
IPCC, 2007
Observed cooling in the stratosphere
IPCC 2007, Figs. 3.17 and 3.18
Is the warming caused by humans?
Greenhouse gasses warm the planet, and atmospheric concentrations are increasing
The gasses released by human activity can account for the increased concentration
Explains increased air temperature (including aloft)
Explains increased ocean temperature (including subsurface)
Natural factors (sun, volcanoes) can account for medieval warm period, little ice age, and 1940’s, but do not match warming since the 1950s.
What does this mean for our water supply?
http://www.publicaffairs.water.ca.gov/maps/
http://www.publicaffairs.water.ca.gov/maps/
"California's water system might have been invented by a Soviet bureaucrat on an LSD trip." --Peter Passell, New York Times (2/27/1991)
http://www.publicaffairs.water.ca.gov/maps/
Reduced snowpack
Peterson, B. / U.S. Fish and Wildlife Service
Runoff Reduction by 2050 (%)
After Milly et al., Nature, 2005
10-30%
Colorado River drainage
Water supply for:
• 27 million people• 3.5 million acres of farmland
Users in:
• 7 states• 2 countries
Colorado river use…
“Upper” = Wyoming, Colorado, Utah and New Mexico“Lower” = Nevada, Arizona, California
Barnett and Pierce, J. Water Resources Research, 2008
Colorado river use…
“Upper” = Wyoming, Colorado, Utah and New Mexico“Lower” = Nevada, Arizona, California
Barnett and Pierce, J. Water Resources Research, 2008
Persistent drought
San Diego imports ~80% of its water
60% of that comes from Colorado River; 40% from Northern California
Hoerling and Eischeid, Southwest Hydrology, 2007
Persistent drought
San Diego imports ~80% of its water
60% of that comes from Colorado River; 40% from Northern California
Hoerling and Eischeid, Southwest Hydrology, 2007
So what is the response?
1. New desalination plant; 56,000 acre-feet/year
So what is the response?
1. New desalination plant; 56,000 acre-feet/year
2. Southern California farmers get a 1/3 cut in water
So what is the response?
1. New desalination plant; 56,000 acre-feet/year
2. Southern California farmers get a 1/3 cut in water
3. Residential and commercial water savings programs being ramped up again
Summary
First realized over 100 years ago CO2 warms the Earth
Since then, CO2 has been steadily accumulating due to human activity
Model predicted changes over the historical era agree with surface thermometers, ocean measurements, measured streamflow, satellites, snowpack, and balloons
We live in an arid region and are vulnerable to warming! Decrease in CA snowpack; less water available in summer; persistent
drought conditions; reduced San Diego water supply
More, earlier, longer heat waves
More wildfires
Sea level rise affects our coasts
Effects on hydropower supplies
Less time for salmon to reproduce