Greenhouse Effect & Global Warming
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Greenhouse Effect & Global Warming
Some Evidence The global air temperature at the Earth's surface has increased about 0.5oC during the past century
Earth’s Temperature Sun Solar Energy
The Greenhouse
Greenhouses are used to
grow plants, especially in
the winter.
The glass panels of the
greenhouse let in light but
keep heat from escaping.
This causes the
greenhouse to heat up,
like the inside of a car
parked in sunlight, and
keeps the plants warm
enough to live in the
winter.Greenhouse
Glass, the material
that greenhouse is
made of, 1) transmit
short-wavelength
visible light, 2)
absorbs and
redirects the longer
wavelengths of
energy. These two
aspects make the
greenhouse warmer
than outside air
temperature.Greenhouse effect of the atmosphere
• Light from the sun includes the
entire visible region and smaller
portions of the adjacent UV and
infrared regions.
• Sunlight penetrates the atmosphere
and warms the earth’s surface.
• Longer wavelength infrared
radiation is radiated from the earth’s
surface.
The gases in the
atmosphere that act • A considerable amount of the
like glass in a outgoing IR radiation is absorbed by
greenhouse are called gases in the atmosphere and
greenhouse gases. reradiated back to earth.Natural Greenhouse effect The natural greenhouse effect causes the mean temperature of the Earth's surface to be about 33oC warmer than it would be if natural greenhouse gases were not present.
Enhanced greenhouse effect When concentrations of greenhouse gases increase, more infrared radiation is returned toward the earth and the surface temperature rises.
What makes a gas greenhouse gas?
Able to absorb infrared light
• Must have molecular vibration(s)
• The molecular vibrations must be non-
symmetric, i.e. infrared active
– Homonuclear diatomic molecules only have
symmetric vibrations. That’s why N2, O2 are
not greenhouse gases.What are the major greenhouse gases? • H2O • CO2 • CH4 • N2O • O3 • CFCs
Carbon Dioxide
Are human beings causing increases in greenhouse gases?
CO2
Concentrations
at Mauna Loa,
Hawaii
The average atmospheric CO2 concentrations observed at Muana Loa,
Hawaii increased approximately 40 ppmv between 1958 and 1995.Methane Rate of increase: 0.9% annually Atmospheric methane has increased steadily to present day levels; this increase is highly correlated with human population growth and with related activities, including agricultural practices.
Nitrous oxide (N2O) Rate of increase 0.25%/year Use of fertilizer increases both nitrification and denitrification increase N2O production
CFC-11
Is the earth getting warmer?
Temperature over the past one century The global air temperature at the Earth's surface has increased about 0.5oC during the past century
Temperature over the past 1000 years
Carbon Dioxide
Sources and sinks of CO2
• Sources
– Natural: respiration of vegetation and soil detritus
– Man-made: Fossil fuel combustion, deforestation
• Sinks:
slow exchange of carbon between surface waters
and deep layers of ocean.
(Seawater is alkaline while CO2 is acidic The
oceans are a vast reservoir of CO2).Worldwide Carbon Emissions
8
Carbon (109 metric tons)
Total
7 Liquid fuel
6 Solid fuel
Gas fuel
5
4
3
2
1
0
1750 1800 1850 1900 1950 2000
YearFuture Carbon Dioxide Levels
• Increasing CO2 emissions, especially in
China and developing countries
• Likely to double within 150 years:
Increased coal usage
Increased natural gas usage
Decreased petroleum usage (increased
cost and decreasing supply)Status of CO2
Pre-industrial Amount: 280 ppm
Present Amount: 382 ppm
Maximum Allowable ≤ 450 ppm
Rate of Change: +2 ppm/year
(and growing)Kyoto Protocol • Adopted in 1997 • Cut CO2 emissions by 5% from 1990 levels for 2008-2012 • Symbolic only, since cuts will not significantly impact global warming
CO2 Concentration Vs. Temperature
SST (°C) Tropical Pacific
370
CO2 (ppm) Antarctica
320 31
30
270 29
28
220 27
26
170
600000 400000 200000 025
Time (YBP)More Important Data
6
5
4
3
2
1
0
World USA OECD Asia
Per Capita Carbon EmissionsGreenhouse Effect & Global Warming
• The “greenhouse effect” & global
warming are not the same thing.
– Global warming refers to a rise in the
temperature of the surface of the earth
• An increase in the concentration of
greenhouse gases leads to an
increase in the the magnitude of the
greenhouse effect. (Called enhanced
greenhouse effect)
– This results in global warmingConsequences of global warming • Sea level rise – Beach erosion – Coastal wetland loss – Loss of low-lying territories • Water resources change – Precipitation pattern shift – Increases instances of heavy precipitation • Effects on agriculture – Changes in the length of growing season – Growth of undesirable plant species
Consequences of global warming (Continued)
• Effects on air quality
– Increase in reaction rates and concentrations of certain
atmospheric species increase in O3 in urban areas
• Impacts on human health
– Changes in patterns of sickness and death.
– Respiratory problems affected by air quality change
• Biodiversity
– Some species may grow too quick and overshoot their
reproductive period (e.g. reef corals)
• Change in the pattern of ocean currentPossible Solutions to Global
WarmingMitigation of Global Warming • Conservation Reduce energy needs Recycling • Alternate energy sources Nuclear Wind Geothermal Hydroelectric Solar
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