Met 10 - De Anza College
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Transcript Met 10 - De Anza College
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