Chapter One: Greenhouse gases and their effect
HNR 330
Dr. Hengchun Ye
Climate Literacy
USGCRP: U.S. Global Climate Research Program. Established in 1989,
coordinates and integrates the climate change activities of 12 federal
departments and agencies.
Seven Principles:
1. The sun is the primary source of energy for the earth’ s climate system
2. Climate is regulated by complex interactions among components of the
earth’s system
3. Life on earth depends on, is shaped by, and affects climate
4. Climate varies over space and time through both natural and humanmade processes
5. Other understanding of the climate system is improved through
observations, theoretical studies, and modeling
6. Human activities are affecting the climate system
7. Climate change will have consequences for the earth system and human
lives
Four Spheres of the Earth’s System
Weather and Climate
• Weather: is a short term status of the atmosphere at a given time.
• Climate: is a long term average weather pattern in a particular
region and its extremes
Shared Variables:
Temperature, precipitation, humidity, sunshine, cloud types and cover,
wind speed and direction, visibility, etc.
To understand the climate is to understand the “HEAT”-energy balance
In order to have a equilibrium condition and keep the air temperature
constant, all components of energy summed up together=0
NASA scientist James E. Hanson discovered the earth’s energy was no
longer balanced, Global warming issue came to the light.
Atmospheric structure-based on temperature profiles
1. Troposphere
Surface to 18 km (11 mi)
90% mass of atmosphere
Lapse rate: the rate of air
temperature decreases with
elevation
Normal lapse rate – average
cooling at rate of 6.4 C°/km
(3.5 F°/1000 ft)
2. Stratosphere
18 to 50 km (11 to 31 mi)
Inversion: air temperature
increases with elevation
Ozone maximum
3. Mesosphere
50 to 80 km (30 to 50 mi)
4. Thermosphere
Roughly same as heterosphere
80 km (50 mi) outward
Atmosphere Global Circulation Pattern
Causes:
1. hot air rises and cold air
sinks
2. Pressure gradients:
changes in air pressure
over a horizontal distance
3. Coriolis effect
Isobars: lines of equal air pressure
Coriolis Force: an apparent force caused by the
rotation of the earth;
1) deflects to the right (of the movement) in
northern hemisphere.
2) Maximum in the poles and zero in the equater
3) Proportional to the wind speed.
Global Circulation Systems
Surface pressure system:
1. Inter-tropical convergence zone-ITCZ
(equator)
2. Polar High Pressure (poles)
3. Subtropical high pressure (30N/S)
4. Subpolar low-pressure cells (60N/S)
Wind Patterns:
1. Northeast trade wind (between equator and
30N/S)
2. Westerlies (between 30N/S-60N/S)
3. Polar northeasterly (between 60N/S-poles
• Hadley Cell: rises from
equator subsides over
Subtropical High
• Polar Cell: rises at 60
latitudes and subsides
over Poles
• Ferrel Cell: rises at 60
latitude and subsides at
30 latitudes
Rises at low pressure and
subsides at high pressure
Ocean Circulation (Fig 1.4)
Surface Current: 5 major
gyres
North Pacific, south
Pacific, North Atlantic,
south Atlantic, Indian
Ocean
Caused by the surface
wind and Coriolis
effect
Warming of the surface
temperature of the
ocean is 0.6°C during
past 100 years
Earth’s Energy Budget
Albedo: the percentage of
solar radiation reflected
by a surface
Half of the solar radiation
energy is absorbed by
the earth’s surface
Earth gives off energy to
atmosphere by
longwave radiation,
conduction/convection
(sensible heat), and
latent heat.
Latent heat: energy transfer
through water phase
change
Albedo distribution
Greenhouse gases: Carbon Dioxide (CO2), Water
Vapor (H2O), Methane (CH4), Ozone (O3),
Nitrous Oxide (N2O), Chlorofluorocarbons (CFCs).
They consists of less than 1% of total atmosphere.
The current average earth’s air temperature is
14C (57.2c). Without greenhouse gases, the
temperature would be -18C (0°F).
Venus atmosphere is 98% CO2, the surface
temperature is 858°F.
Greenhouse Effect
The longwave radiation
emitted by the earth
is absorbed by
greenhouse gases
and re-emitted back
to the earth’s surface
to keep atmosphere
warm.
More greenhouse gases
in the atmosphere,
more heat
accumulates near the
earth’s surface
Atmospheric composition: N2
(78%), O2 (21%), Ar (0.96%),
CO2 (0.04%), etc.
History of CO2 content
measured in ice cores (Fig
1.10)
ppb: parts per million. They are
measured using fossil air
trapped in ice in Antarctic.
Remote sensing
observation of
CO2 (Fig 1.11)
Sources: burning
fossil fuel, solid
waste,
deforestation,
industrial
agricultural,
cement
production
The Atmospheric Infrared Sounder (AIRS) is able to pinpoint the influence of specific
carbon dioxide sources.
Large amount in 40-50°S:
1. A coal liquefaction in south Africa-a largest single source of CO2 on the earth
2. A Cluster of power generating plants in eastern Austria
Modern greenhouse gas records
(Fig 1.12)
CO2 measure at Mauna Loa
Observatory in Hawaii; has
season oscillations.
Methane: (decreased in 1990s due
to former Soviet Union collapse
and drought)
Natural: wetland, seawater, soil;
ocean sediments; permafrost
thawing.
Anthropogenic (60%):
deforestation, mining and
burning fossil fuels, processing
human waste, cultivating rice
paddies, manure production,
landfill emissions, cattle farms
CFCs have declined since the
Montreal Protocol in 1987
Climate feedbacks
•
Positive feedback: amplified effect. Example: climate warms, more permafrost
thaw, further increase CH4 emission, climate warms further, etc.
• Negative feedback: suppressed effect.
Ozone: good in stratosphere; bad in troposphere.
O3 in stratosphere block UV radiation
O3 in troposphere create smog, a type of air pollution.
Sources: indirect production of emission of CO, N2O, SO2, and hydrocarbons from
burning biomass and fossil fuels. (last a few weeks to month)
N2O
Natural source: activity of microbes in swamps, soil, rainforests, and ocean
surface, thawing permafrost.
Anthropogenic: fertilizer, industrial production of nylon and nitric acid, burning of
fossil fuels, and solid waste.
CFCS: unnatural gas produced by industrial processes including air conditioning,
aerosol sprays, manufacture of plastics and polystyrene. Very stable and long
life time (75-150 years).
• Ozone Hole: CFCs
react with and
destroy O3 in
stratosphere (Fig
1.14)
• Montreal Protocol on
1987 signed by 27
nations; United
states ceased
production of CFCS in
1995.
• Ozone hole show
signs of recover over
the Antarctic.
Dobson unit: one Dobson unit is the number of O3 molecules that would be required
to create a layer of pure ozone 0.01mm thick at a temperature of 0C and a pressure of
1 atmosphere (air temperature at the sea level)
Water vapor
2% of atmosphere.
Hydrological cycle: consists of five major
processes of condensation,
precipitation, infiltration, run off, and
evapotranspiration (evaporation plus
transpiration).
Human has no direct impact except for
local scale: irrigation, reservoir
building, changes in surface features,
etc.
Increasing air temperature has a positive
feedback in water vapor (6%-7.5%
per degree of C).
Could potential double the increases in air
temperature caused by CO2 alone
If the world warms 2-3C, the water cycle
could accelerate 16-24%
Aerosols
Fine solid particles or liquid
droplets suspended in the
atmosphere
Scatter or absorb sunlight
SO4 from burning coal, woods,
dung, and petroleum. 1950s1970s industrial growth,
caused cooling of global
temperature.
Volcanic eruption: Mount
Pinatubo in Philippines erupted
in June 1991, cooled the planet
early 1C, offsetting the
greenhouse effect for more
than one year.
Black soot: burning fuels made of biomass
(wood, coal, animal dung, diesel, vegetable oil
etc). Causes warming in high latitude regions
where snow and ice present
NASA’s Terra Satellite
Radiative forcing:
Positive: increases air temperature
Negative: decreases air temperature
Radiative Balance: incoming solar radiation=outgoing earth radiation;
Despite low solar activity between 2005-2010, earth continued to absorb
more energy than it returned to space as heat.
Methane absorbs 21 times more heat per molecule than CO2
N2O absorbs 270 times more; CFCs is 30,000 times more than CO2.
Human behavior related to radiative forcing
Mitigating Global warming requires managing carbon
Carbon in the atmosphere,
in the water, and in the crust
Carbon stored in the crust:
1. Limestone (CaCO3)
2. Buried as organic matter
Organic material in
ecosystems, such as the
simple carbohydrate
glucose (C6H12O6),
found in plants and
animals.
Sink: reduce carbon
Source: produce carbon