Climate-Greenhouse Effect
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.
? A considerable amount of the
outgoing IR radiation is absorbed by
gases in the atmosphere and
reradiated back to earth.
The gases in the
atmosphere that act
like glass in a
greenhouse are called
greenhouse gases.
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)
– This excludes monoatomic gases as greenhouse
gases,(That is why argon,the third most abundant
atmospheric constituents is transparent to infrared
irradiation)
? 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
? SF6
Absorption of terrestrial radiation by H2O and CO2
Atmospheric window,8000-12000nm
What determines the contribution of a
greenhouse gas to global warming?
? Concentrations
– H2O and CO2 are the two biggest contributors to
the atmospheric warming because of their higher
concentrations,
? Lifetime
– The longer-live a gas is,the higher the
contribution,e.g,N2O contribution > CH4
? Effectiveness as an infrared absorber
– For example,CFC-11 and CFC-12
CFC-11 and CFC-12
are effective
infrared absorber
The absorption spectra
of CFC-11 and CFC-12
coincides with the
atmospheric window
Comparison of different greenhouse gases
CO2 CH4 CFC-11 CFC-12 N2O
Concentration
Preindustrial (<1800)
Current
ppm
280
370
ppm
0.8
1.74
ppt
0
268
ppt
0
484
ppb
288
314
Atmospheric lifetime
(yr) 50-100 10 45 130 114
Per molecule of
radiative forcing
relative to CO2
1 23 4,000 15,800 296
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,
The small fluctuations in the curve are seasonal variations due
primarily to the withdrawal and production of carbon dioxide by
terrestrial life,Notice that minimum values occur during the northern
hemisphere summers (when global photosynthetic activity is greatest)
and maximum values occur six months later.
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).
Methane
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.
Rate of increase,0.9% annually
Sources and sinks of methane
? Sources
– Natural,end-product of the metabolism from an
anaerobic bacteria,methanogen.
Natural wetlands,enteric fermentation (wild
animals),termites,biomass burning,ocean/fresh
water
– Man-made,rice paddies,gas drilling and
transmission,landfills,coal mining,biomass
burning,enteric fermentation (domestic animals)
? Sink,OH+ CH4? CH3,+ H2O
Nitrous oxide (N2O)
Rate of increase 0.25%/year
Use of fertilizer increases both nitrification and
denitrification ?increase N2O production
Sources and sinks of N2O
? Sources:
– denitrification process for energy
production by anaerobic bacteria.
– Nitrification process (NH4+? NO3-)
– Fertilizer use
– Biomass burning
– Combustion
– Unknown sources
? Sink,Photolysis in the stratosphere
natural
Man-made
CFC-11
Sources and sinks of CFCs
? Sources
– No natural sources
– Synthetic chemicals
? Sink,Photolysis in the stratosphere.
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
Consequences 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
– New burdens on water capture,storage and
distribution system to be expected,
? 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
– More droughts?widespread forest fire? worsen air quality
– Change in how pollutants are dispersed.
? 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)
– Forest could be devastated if the rate of climate change
outpaced the rate at which forest species could migrate.
? Change in the pattern of ocean current
Is the temperature rise due to human activities?
Or is it part of the natural variation?
When greenhouse gases,
aerosols,and changes in
solar irradiance are used
as inputs into general
circulation models,
predicted temperatures
are very close to those
observed,
When greenhouse
gases are the only
input,predicted
temperature are
higher than those
observed.
The state of climate change science
? The Earth’s natural greenhouse effect is
required to support life on earth.
? Aerosol particles are important in formation of
clouds.
? Human activities are contributing to increases
in greenhouse gases and aerosol loading.
? The Earth’s surface has warmed during the last
century and is projected to continue warming.
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.
? A considerable amount of the
outgoing IR radiation is absorbed by
gases in the atmosphere and
reradiated back to earth.
The gases in the
atmosphere that act
like glass in a
greenhouse are called
greenhouse gases.
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)
– This excludes monoatomic gases as greenhouse
gases,(That is why argon,the third most abundant
atmospheric constituents is transparent to infrared
irradiation)
? 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
? SF6
Absorption of terrestrial radiation by H2O and CO2
Atmospheric window,8000-12000nm
What determines the contribution of a
greenhouse gas to global warming?
? Concentrations
– H2O and CO2 are the two biggest contributors to
the atmospheric warming because of their higher
concentrations,
? Lifetime
– The longer-live a gas is,the higher the
contribution,e.g,N2O contribution > CH4
? Effectiveness as an infrared absorber
– For example,CFC-11 and CFC-12
CFC-11 and CFC-12
are effective
infrared absorber
The absorption spectra
of CFC-11 and CFC-12
coincides with the
atmospheric window
Comparison of different greenhouse gases
CO2 CH4 CFC-11 CFC-12 N2O
Concentration
Preindustrial (<1800)
Current
ppm
280
370
ppm
0.8
1.74
ppt
0
268
ppt
0
484
ppb
288
314
Atmospheric lifetime
(yr) 50-100 10 45 130 114
Per molecule of
radiative forcing
relative to CO2
1 23 4,000 15,800 296
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,
The small fluctuations in the curve are seasonal variations due
primarily to the withdrawal and production of carbon dioxide by
terrestrial life,Notice that minimum values occur during the northern
hemisphere summers (when global photosynthetic activity is greatest)
and maximum values occur six months later.
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).
Methane
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.
Rate of increase,0.9% annually
Sources and sinks of methane
? Sources
– Natural,end-product of the metabolism from an
anaerobic bacteria,methanogen.
Natural wetlands,enteric fermentation (wild
animals),termites,biomass burning,ocean/fresh
water
– Man-made,rice paddies,gas drilling and
transmission,landfills,coal mining,biomass
burning,enteric fermentation (domestic animals)
? Sink,OH+ CH4? CH3,+ H2O
Nitrous oxide (N2O)
Rate of increase 0.25%/year
Use of fertilizer increases both nitrification and
denitrification ?increase N2O production
Sources and sinks of N2O
? Sources:
– denitrification process for energy
production by anaerobic bacteria.
– Nitrification process (NH4+? NO3-)
– Fertilizer use
– Biomass burning
– Combustion
– Unknown sources
? Sink,Photolysis in the stratosphere
natural
Man-made
CFC-11
Sources and sinks of CFCs
? Sources
– No natural sources
– Synthetic chemicals
? Sink,Photolysis in the stratosphere.
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
Consequences 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
– New burdens on water capture,storage and
distribution system to be expected,
? 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
– More droughts?widespread forest fire? worsen air quality
– Change in how pollutants are dispersed.
? 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)
– Forest could be devastated if the rate of climate change
outpaced the rate at which forest species could migrate.
? Change in the pattern of ocean current
Is the temperature rise due to human activities?
Or is it part of the natural variation?
When greenhouse gases,
aerosols,and changes in
solar irradiance are used
as inputs into general
circulation models,
predicted temperatures
are very close to those
observed,
When greenhouse
gases are the only
input,predicted
temperature are
higher than those
observed.
The state of climate change science
? The Earth’s natural greenhouse effect is
required to support life on earth.
? Aerosol particles are important in formation of
clouds.
? Human activities are contributing to increases
in greenhouse gases and aerosol loading.
? The Earth’s surface has warmed during the last
century and is projected to continue warming.
