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Transcript
Climate Change
Climate Change Background
 The earth has been in a warming trend for the past
few centuries
 Mainly due to the increase in greenhouse gas
emissions
 CO2, CH4, N2O, H2O
Atmosphere will be warmer because the earth
can retain more heat (larger greenhouse effect)
The Greenhouse Effect

Greenhouse gases: definition:
Greenhouse gases are transparent to incoming
___________________________________
solar radiation (short wave) radiation, but absorb
___________________________________
outgoing long-wave radiation.

warm
Greenhouse gases act to __________
the
atmosphere

The most abundant greenhouse gas is water
________
vapor
The Enhanced, or Runaway
Greenhouse Effect

Burning of fossil fuels cause an increase in
greenhouse gas concentrations


Fossil fuels are coal, petroleum, natural gas
Clearing of forests also


increases carbon dioxide concentrations, because
plants remove CO2 from the air
Enhanced greenhouse gases are expected
to lead to a warmer climate.
Greenhouse warming effectiveness

Different gases vary in their ability to act as a greenhouse
warmer.
Strength of warming
Gas
Concentration (ppm)
warming(W/m-2)
Water Vapor
3000
Carbon Dioxide
353
Methane
1.72
Nitrous oxide
0.31
Ozone
0.01-0.1
CFC11
0.00028
CFC12
0.00484
Greenhouse
~100
~50
1.7
1.3
1.3
0.06
0.12
Current CO2: ~380 ppm
Carbon Dioxide Trend from 1950 - 2010
Future projections of CO2
Concentrations
What happens in the future depends on how
much more CO2 we release into the
atmopshere
 Even the low-emission scenarios result in
greatly increased CO2 concentrations by the
year 2100

Max concentration (of scenarios shown): 970 ppm
 Min concentration (of scenarios shown): 550 ppm
 (Compare with current value: 380 ppm)

Future Predictions: Temperature
Notes on Temperature
Projections

Projected Warming: 2000 – 2100 ranges from
~1.4°C to ~5.8°C. (~2.5°F to ~10.5°F)


not all places will warm at the same rate
Curves represent warming produced for
seven independent scenarios
 Each bar on right represent range of warming
produced by models of differing sensitivies for
a specific scenario.
Land areas are projected to warm more than the
oceans with the greatest warming at high latitudes
Annual mean temperature change, 2071 to 2100
relative to 1990: Global Average in 2085 = 3.1oC
Some areas are projected to become wetter, others
drier with an overall increase projected
Annual mean precipitation change: 2071 to 2100 Relative to 1990
Sea Level
Main climate changes


Higher temperatures –

especially on land

Polar Regions
Hydrological cycle more intense


Storms have more “fuel,” so they can be more
powerful, bringing more intense rainfalls
Sea levels rise

Oceans expand with extra heat

Melting of polar ice
Changes in weather events

As Poles warm quickly relative to the
tropics…

The jet stream will weaken and move north
The storm track will move north with it
 Latitude bands 30-40 degrees should get drier
 Rain events begin to replace snow events
 reduction in the # of strong tornadoes in U.S.
 Tornado Alley migrates north
 Atlantic hurricanes will more easily form and
grow to even greater strength

Predictions For the Bay Area
Decreased winter precipiation as jet
stream moves north
 Increased summer precipiation as water
is warmer/more subtropical moisture
 Weaker sea breeze due to warmer
ocean temperatures results in hotter
summers
 Less snowpack in Sierra Nevada,
leading to water shortages
