Emissions of greehhouse gasses
Climate forcing factors
=
Factors causing climate to change
Temperature
• Direct temperature measurements span 140 years
• Global temperature has increased about 1 deg C
Greenhouse gases
Earth
Sun
Atmosphere
Some infrared radiation is absorbed by greenhouse gases warming Earth and lower atmosphere
Some solar radiation is reflected by atmosphere
More radiation is absorbed by Earth and
warms it
Infrared radiation (heat) is released from the
Earth
Greenhouse gasesGreenhouse warming potential (GWP) -- takes into
account the ability of a gas to absorb infrared radiation, and the lifetime of the gas in the atmosphere
Gas [conc] GWPcarbon dioxide (CO2) 360 ppm 1
methane (CH4) 1745 ppb 23
nitrous oxide (N2O) 314 ppb 296CFC-11 268 ppt 4600
CFC-13 4 ppt 14000
water (H2O)
A diversion to the stratosphere…
These gases affect the ozone layer in the stratosphere (GOOD OZONE)
BUT
this is not related to their effect as a greenhouse gas in the troposphere (BAD OZONE)
CFC’s:
Stratosphere
Troposphere
Earth
0 to 10 km
10 to 45 km
A diversion to the stratosphere…
Good ozone
Bad ozone
Ozone
• Good ozone shields the earth from UV radiation
Ozone
• Good ozone shields the earth from UV radiation
• Bad ozone = smog; affects animal and plant health
Ozone
• Good ozone shields the earth from UV radiation
• Bad ozone = smog; affects animal and plant health
Neither are climate forcing factors!
Back to greenhouse gasses and climate forcing…
Greenhouse gases
Carbon dioxide is the largest single contributor to climate forcing
Carbon dioxide contributes about half of total climate forcing from greenhouse gases
Measurements of past atmosphere come from bubbles trapped in ice cores
Past temperature recorded in oxygen isotopes; 4-12 deg C variation between ice ages
These records show a correlation between greenhouse gas concentrations and temperature
Greenhouse gases and temperature
Current temperature increase a sharp change from past 1000 years
Climate might otherwise be cooling,but this is speculation
Greenhouse gases
Greenhouse gas sources
Methane Tg/yr
Animals 80Termites 40Rice Paddies 110Wetlands 115Fuels 180
Total 525
Yellow text = anthropogenic source
Nitrous Oxide Tg/yr
Biomass burning 2Land use (agriculture) 1.4Denitrification (soil) 5.7Denitrification (ocean) 2
Total 11.1
Greenhouse gas sources
Yellow text = anthropogenic source
Greenhouse gas sources
Carbon Dioxide Pg/yr
Fossil Fuel 6.3Land clearing 1.7Ecosystem respiration 120Ocean efflux 105
Yellow text = anthropogenic source
The global carbon balance(in Pg C year-1):
From: IPCC 1995
5.5
1 Pg = 1015 grams
Fossil fuels + deforest. = atmosphere + oceans + ???
Eff + Edf = atm + ocean + other
+ 1.8+ 1.6 = 3.3 + 2.0
Predicting climate
Climate predictions
• General circulation models (GCM) are used to predict future climate
• Driven by physical processes that involve transfers of energy and water
• Used with different greenhouse gas ‘scenarios’ to predict climate in a future atmosphere
GCM predictions
• Models are tested against climate records from the past
• Model predictions are compared with other similar GCM predictions
• GCM temperature predictions are typically quite accurate
GCM predictions
• Global climate predicted to warm 1.5 - 6 deg C by 2050 if CO2 increases at current rate.
• High latitudes & and land surfaces warm most.
• Washington DC now has 30 days over 90 deg F. Will have 85 days over 90 deg F.
Gainesville is not predicted to change very much.
Why?
GCM predictions
• GCM precipitation predictions are more variable and considered less accurate
GCM predictions
• Changes in precipitation are more variable globally
• Wet tropics may become wetter
Arid zones may become drier
GCM predictions
Wamer temperatures = more energy
More energy = larger storms
How will climate warming affect life in FL?
Sea level change in FL
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