1. Global Climate Change Overview
Michael D. Mastrandrea, Ph.D.
Woods Institute for the Environment
Stanford University

2. The Key Facts Global climate change is… unequivocal,
almost certainly caused mostly by us,
already causing significant harm
growing rapidly, and
requires global action and local solutions.
Clearly a global problem, but collectively, local actions can have a huge impact

3. Warming is Unequivocal…
2005 was the hottest year on record; tied with 1998 for 2nd hottest; 14 hottest all occurred since 1990
This kind of picture is striking, but implies something:
uniform across the planet, gradual, mainly about temperature.
What’s actually happening is:
nonuniform, rapid, not just about temperature, mostly harmful

4. Average Surface T in 2001-2005 vs 1951-80
…And Not Uniform
Average Surface T in vs
J. Hansen et al., PNAS 103: ( 2006)

5. Shrinking Glaciers Muir Glacier, Alaska August 1941 August 2004
NSIDC/WDC for Glaciology, Boulder, compiler. 2002, updated Online glacier photograph database. Boulder, CO: National Snow and Ice Data Center.

6. Surface melting on Greenland is expanding
1992
2002
2005
Source: ACIA, 2004, CIRES, 2005, Roger Braithwaite, University of Manchester (UK)

7. Changing Patterns of Extreme Events
Major floods per decade,

8. Increasing Wildfire Risk
Western US area burned
Source: Westerling et al. 2006

9. Natural Carbon Cycle

10. Human Impact on the Carbon Cycle
Mention fossil fuels, deforestation/land use, and cement production

11. Carbon Flows (2005) ATMOSPHERE 750 Gt C 379 ppm CO2 OCEANS LAND
emissions from marine systems 100 Gt C per year
ATMOSPHERE
750 Gt C
379 ppm CO2
emissions from terrestrial systems 100 Gt C per year
absorption by marine systems 102 Gt C per year
absorption by terrestrial systems 103 Gt C per year
OCEANS
LAND
human-caused emissions:
9 Gt C per year

12. Increasing CO2 Concentrations

13. IPCC, 2007

14. Increasing CO2 Concentrations
The Greenhouse Effect and Global Warming
Life on earth is possible because the sun’s energy warms the earth and its atmosphere. As this warmth radiates back into space, a portion is absorbed by a delicate balance of heat trapping gases in the atmosphere. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. These gases retain heat somewhat like the glass panels of a greenhouse, and act to elevate temperatures on earth. This “greenhouse effect” is a necessary natural global mechanism. Without it, the earth’s climate would be much colder and more hostile to human life.
What has changed in the last few hundred years is the additional release of carbon dioxide by human activities. Since the beginning of the Industrial Revolution, atmospheric concentrations of carbon dioxide have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. Why are greenhouse gas concentrations increasing? Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide.
IPCC, 2007

15. Ice Core Records

16. Ice Core Records
Source: Hansen, Clim.
Change, 68, 269, 2005.

17. Fingerprint Analysis Black = Observed
Gold = Human and Natural Forcings
Blue = Only Natural Forcings
IPCC, 2007

18. Projected Changes in CA Summer Temperature
Temperature differences emerge by 2050s and are more pronounced by 2090s
2030: 2-5 degrees
2050: 4-6 lower, 4-9 higher
2090: 3-9 lower, 8-18 higher
We found higher summer temps than previously reported, incorporating better physical understanding of the system
Hayhoe annual average: deg F increase by mid-century; deg F warming by end-C
ｷ Substantial increases in both summer and winter temperature, with greater summer warming than has been previously reported.
UCS
UCS

19. Pika Species Shifting and… 1900 >7,800 ft 2004 >9,500 ft
But species do not always have suitable habitat to shift to.
Prime example is species that live on mountain slopes, like the Pika. Species that are sensitive to temperature conditions can only move up the mountainside as conditions get too warm for them lower down.
In the Sierras, Pika were seen at 7,800 feet and above in By 2004, they were not seen below 9,500 feet, and this trend is expected to continue.
The mountains rise as high as 12,000 feet, but the tallus, the rocky hillside that Pika live in, does not reach that high.
The result…
Strong candidate for labeling as a key vulnerability

20. Diminishing Sierra Snowpack
Percentage Remaining, Relative to
Note: Based on HadCM3 model output
Substantial reductions in snowpack, which is 1/2 of CA’s water storage
80% precipitation falls in winter before april, but 3/4 water use is between April and Sept.
Also affects fire risk and other consequences
UCS

21. Mitigation
Adaptation

22. Rapidly Increasing Emissions
2006
2005
Current emissions are tracking above the most intense fossil fuel scenario established by the IPCC SRES (2000), A1FI- A1 Fossil Fuel intensive; and moving away from stabilization scenarios of 450 ppm and 650 ppm.
Raupach et al. 2007, PNAS

23. Regional CO2 Emissions
2004
Growth
Raupach et al., 2007