Atmosphere and Climate Module 8 Atmosphere and Climate 45:211: Environmental Geography

Learning Objectives Explain what is meant by the term “global warming” Know the major greenhouse gases and their main sources Describe the objectives of the Kyoto Agreement Describe examples of climate change impacts Explain the link between CFCs and ozone depletion Describe the objectives of the Montreal Protocol 45:211: Environmental Geography

Atmosphere The layers of air masses surrounding the Earth are collectively referred to as the atmosphere. 45:211: Environmental Geography

How is atmosphere important? The atmosphere controls climate - which keeps us comfortable and safe Ozone depletion and increasing GHGs are a current concern We use it to dispose of wastes within the past century, the composition of the atmosphere has been changed on the scale of human time 45:211: Environmental Geography

Atmospheric Layers Troposphere Where weather is. Where most of the pollutants are. Thickness - 15 km at the equator, and about 8 km over the poles. It is well mixed by air motions which disperse pollutants 45:211: Environmental Geography

Atmospheric Layers Stratosphere Extends from about 20-50 km. The ozone layer. This “good” ozone protects us from solar UV radiation Very thin air with virtually no weather or turbulence. Compared to Troposphere, the volume of water vapor is 1000 x less, and volume of ozone is 1000 x greater. 45:211: Environmental Geography

Ozone: the Good and the Bad 45:211: Environmental Geography

Climate Control and Atmospheric Composition Earth’s surface absorbs incoming solar radiation, and converts it into heat. Some of this heat escapes into space Some is absorbed by greenhouse gases in the atmosphere, warming the air  Heat is radiated back to Earth, warming it by about 33oC This trapping of heat is called the Greenhouse Effect 45:211: Environmental Geography

Greenhouse Effect 45:211: Environmental Geography

Trace Gases Most of Earth’s atmosphere is climatically neutral the important gases are present in trace amounts only 45:211: Environmental Geography

Anthropogenic Climate Change The Greenhouse Effect that warms the surface of the Earth occurs because of a few minor constituents of the atmosphere (GHGs) that absorb IR radiation very efficiently. As a result of human activities, the concentrations of GHGs is increasing. This will lead to a warmer Earth, the amount depending on other climate effects. 45:211: Environmental Geography

Main Greenhouse Gases Carbon Dioxide - fossil fuel burning (80% of emissions), deforestation (20%). Methane - breakdown of organic material by anaerobic bacteria. Nitrous Oxide - biomass burning, breakdown of nitrogen-rich products. Chlorofluorocarbons - refrigerants. 45:211: Environmental Geography

What is Global Warming The term Global Warming is widely used to describe a potentially dramatic rise in the average global temperature as a result of the continuing and accelerating buildup of greenhouse gases in the atmosphere. It is different to the problem of ozone depletion in the Stratosphere, although this also arises from atmospheric pollution 45:211: Environmental Geography

Atmospheric carbon dioxide (CO2):1750 to present Atmospheric Carbon Dioxide (CO2) Concentrations (1750 to present) Preindustrial atmospheric CO2 concentrations were approximately 275 parts per million. Today concentrations are approximately 367 ppmv, an increase of over 30 percent. Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm 45:211: Environmental Geography

The Historical Data 45:211: Environmental Geography

Cumulative Radiative Forcing of GHG Emissions 45:211: Environmental Geography

Temperature Change, 1400-2000 (Northern Hemisphere) 45:211: Environmental Geography

Global climate change ….. We frequently view climate change in terms of a global average - but nobody lives in a global average climate. Location (geography) is important. 45:211: Environmental Geography

… is spatial Climate change is not uniform over the Earth. Magnitude varies with location And with season …. 45:211: Environmental Geography

Canada: Temperature Changes 45:211: Environmental Geography

Possible Effects of A Warmer World Higher temperatures (wider extremes?) Changes in precipitation - wetter and drier Rising sea level (e.g. Fig. 17.16 in text) and melting of ice bodies Changes in food production and ecosystems Longer growing seasons Range of tolerance See Figure 17.18 in text 45:211: Environmental Geography

45:211: Environmental Geography

Ecozones 45:211: Environmental Geography

Rising Seas: The Future One of the most striking consequences of global warming will be the associated rise in global mean sea level. 45:211: Environmental Geography

Change in Arctic Ocean: Summer Ice Cover 45:211: Environmental Geography

Permafrost in Canada Present 2xCO2 45:211: Environmental Geography

Good or Bad? Whether global warming is “good” or “bad” is a matter of perspective (and self-interest) There will be “winners” and “losers” This is not a scientific issue but social and economic 45:211: Environmental Geography

Slowing Global Warming Reduce emissions - the quickest, cheapest, most effective way to reduce emissions is to use energy more efficiently. Slow population growth - if we cut per capita greenhouse gas emissions in half, but double the population - we do not help the problem. 45:211: Environmental Geography

Cumulative carbon emissions, 1950-1996 In terms of historical contributions to the atmospheric buildup of emissions, the industrialized countries like the US have contributed roughly 80 percent of the carbon dioxide buildup in the atmosphere to date. On a country-by-country basis, the comparisons between the rich and poor countries are even more stark. Since 1950, the US has emitted a cumulative total of roughly 50 billion tons of carbon, while China (4.5 times more populous) and India (3.5 times more populous) have emitted only 15 and 4 billion tons respectively. Data Source: Marland et al, 1999. Carbon Dioxide Information Analysis Center. 45:211: Environmental Geography Data Source: Marland et al, 1999. Carbon Dioxide Information Analysis Center.

How much will the Kyoto Protocol reduce emissions? How Much will the Kyoto Protocol Reduce Global Emissions? According to global carbon emission projections, even with the implementation of the Kyoto Protocol, emission levels in 2010 are still expected to be more than 30 percent higher than 1990 levels, largely due to increases from rapidly growing developing countries that are not bound by emission limitations under the Kyoto Protocol. Data Sources: United States Department of Energy, Energy Information Administration, International Energy Outlook, 1998 and 1999. Data Sources: United States Department of Energy, Energy Information Administration, International Energy Outlook, 1998 and 1999. 45:211: Environmental Geography

Ozone Depletion Ozone is formed in the Stratosphere when high-energy solar ultraviolet radiation splits molecular oxygen (O2) into atomic oxygen (O+O). The atomic oxygen may then combine with another oxygen molecule to form triatomic oxygen (O3, ozone).  45:211: Environmental Geography

Problem: In the 1970s, it was discovered that CFCs were reducing the concentration of ozone in the stratosphere. CFCs take 10-20 years to diffuse up into the stratosphere, but they are long-lived.  45:211: Environmental Geography

In the stratosphere, UV radiation breaks down CFC molecules, releasing atomic chlorine. A free chlorine atom reacts with an ozone molecule, converting it from O3 to O2. Cl + O3 = ClO + O2 Unstable Cl + O Cl + O3 = ClO + O2 45:211: Environmental Geography

Consequences of Ozone Loss More UV radiation will reach Earth’s surface. More/worse sunburns - leading to increased rates of skin cancers Suppression of immune system Lower crop yields 45:211: Environmental Geography

Montreal Protocol (1987) Reduce production of CFCs and phase out their use by 2000 82 nations have signed the agreement U.S. stopped production of CFCs in 1996. As a result of these efforts, the levels of CFCs in the atmosphere will stabilize and should decline in the future. But CFCs will remain in the atmosphere for several decades (residence time) 45:211: Environmental Geography

Summary Global warming is due to increased levels of greenhouse gases. Impacts of climate change are varied and may be viewed as positive and negative. Kyoto Treaty calls for emissions reductions. CFC’s are thought to lead to the destruction of the ozone layer. Increase of UV radiation poses a health risk. Their use is being curtailed through the Montreal Protocol. 45:211: Environmental Geography