The Top Five Climate-Changing Gases Since the industrial revolution, humans have been changing the atmosphere. Agricultural, industrial, and other activities have increased the concentrations of heat-trapping “greenhouse” gases such as carbon dioxide, methane, nitrous oxide, low-level “tropospheric” ozone, and halogenated carbon compounds. These gases now affect the climate. Heat-Trapping Gas Radiative Forcing (W/m 2 ) Carbon dioxide (CO 2 ) +1.66 Methane (CH 4 ) +0.48 Low-level ozone (O 3 ) +0.35 Halogenated carbons +0.34 Nitrous oxide (N 2 O) +0.16 The Top Five Climate-Changing Gases Created by Novem Auyeung for the Boston Area Climate Experiment. This poster was designed during the class “Climate Change: Mechanisms and Biological Impacts,” at the University of Massachusetts Boston, Fall 2006. What is radiative forcing? • A measure of how strongly the human-caused emissions of a gas are affecting the global average temperature. • It is measured in watts per square meter or W/m 2 . • Positive forcings cause warming, and negative forcings cause cooling. • Because humans don't directly affect water vapor concentrations, this abundant greenhouse gas is not contributing to climate change. Low-level ozone (O 3 ) Methane (CH 4 ) Because we release so much of it, carbon dioxide is, by far, the most important greenhouse gas. It has a number of human sources, but the major ones are fossil fuel burning power plants (shown above) and deforestation. Low-level or “tropospheric” ozone can be produced from chemical reactions between car exhaust pollutants such as carbon monoxide (CO) and nitrogen oxides (NO x ). Unlike "the ozone layer", tropospheric ozone is found close to the earth’s surface, and is harmful to health. Besides rice fields, another major source of methane is ruminants (hoofed animals with multiple stomachs like cattle, shown above, and sheep). Methane is released during digestion and from their manure. A large proportion of human- produced nitrous oxide comes from agricultural soils that use large amounts of nitrogen-based fertilizers (shown above), and from cattle waste in feedlots. Halogenated carbons are carbon compounds with halogen atoms (fluorine, chlorine, etc.) like chlorofluorocarbons (CFCs) or carbon tetrachloride (CCl 4 ). These halogenated compounds are used in refrigerators and car air conditioners. The “Keeling Curve” shows that the concentration of CO 2 in air has increased since 1958. Human sources cause the long-term increase. The smaller annual cycles are caused by seasonal patterns of plant growth in the Northern Hemisphere. Atmospheric CO 2 has risen ~35% in 150 years, and is now rising faster than ever. Reference : Intergovernmental Panel on Climate Change. 2007. IPCC Fourth Assessment Report. Nitrous oxide (N 2 O) Halogenated carbons Carbon dioxide (CO 2 ) Concentration of Atmospheric Carbon Dioxide at Mauna Loa, Hawaii © www.freightlinersfarm.org.uk © www.aafeders.com © www.biblelife.org © gardkarlsen.com © Novem Auyeung

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Page 1: The Top Five Climate-Changing Gases

The Top Five Climate-Changing GasesSince the industrial revolution, humans have been changing the

atmosphere. Agricultural, industrial, and other activities have increased the concentrations of heat-trapping “greenhouse” gases such as carbon dioxide, methane, nitrous oxide, low-level “tropospheric” ozone, and halogenated carbon compounds. These gases now affect the climate.

Heat-Trapping Gas Radiative Forcing (W/m2)

Carbon dioxide (CO2) +1.66

Methane (CH4) +0.48

Low-level ozone (O3) +0.35

Halogenated carbons +0.34

Nitrous oxide (N2O) +0.16

The Top Five Climate-Changing Gases

Created by Novem Auyeung for the Boston Area Climate Experiment.

This poster was designed during the class “Climate Change: Mechanisms and Biological Impacts,” at the University of Massachusetts Boston, Fall 2006.

What is radiative forcing?• A measure of how strongly the human-caused emissions of a gas are affecting the global average temperature.

• It is measured in watts per square meter or W/m2.

• Positive forcings cause warming, and negative forcings cause cooling.

• Because humans don't directly affect water vapor concentrations, this abundant greenhouse gas is not contributing to climate change.

Low-level ozone (O3)

Methane (CH4)

Because we release so much of it, carbon dioxide is, by far, the most important greenhouse gas. It has a number of human sources, but the major ones are fossil fuel burning power plants (shown above) and deforestation.

Low-level or “tropospheric” ozone can be produced from chemical reactions between car exhaust pollutants such as carbon monoxide (CO) and nitrogen oxides (NOx). Unlike "the ozone layer", tropospheric ozone is found close to the earth’s surface, and is harmful to health.

Besides rice fields, another major source of methane is ruminants (hoofed animals with multiple stomachs like cattle, shown above, and sheep). Methane is released during digestion and from their manure.

A large proportion of human-produced nitrous oxide comes from agricultural soils that use large amounts of nitrogen-based fertilizers (shown above), and from cattle waste in feedlots.

Halogenated carbons are carbon compounds with halogen atoms (fluorine, chlorine, etc.) like chlorofluorocarbons (CFCs) or carbon tetrachloride (CCl4). These halogenated compounds are used in refrigerators and car air conditioners.

The “Keeling Curve” shows that the concentration of CO2 in air has increased since 1958. Human sources cause the long-term increase. The smaller annual cycles are caused by seasonal patterns of plant growth in the Northern Hemisphere. Atmospheric CO2 has risen ~35% in 150 years, and is now rising faster than ever.

Reference:

Intergovernmental Panel on Climate Change. 2007. IPCC Fourth Assessment Report.

Nitrous oxide (N2O) Halogenated carbons

Carbon dioxide (CO2) Concentration of Atmospheric Carbon Dioxide at Mauna Loa, Hawaii