45:211: environmental geography module 8 atmosphere and climate

45:211: Environmental Geography

Module 8

Atmosphere and Climate


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


Atmosphere

• The layers of air masses surrounding the Earth are collectively referred to as the atmosphere.


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


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


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.


Ozone: the Good and the Bad


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


Greenhouse Effect


Trace Gases

• Most of Earth’s atmosphere is climatically neutral– the important

gases are present in trace amounts only


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.


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.


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


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

Atmospheric carbon dioxide (CO2):1750 to present

270

280

290

300

310

320

330

340

350

360

370

1750 1800 1850 1900 1950 2000

part

s pe

r m

illio

n vo

lum

e

Siple Station (1750-1970)

Mauna Loa (1958-present)


The Historical Data


Cumulative Radiative Forcing of GHG Emissions


Temperature Change, 1400-2000 (Northern Hemisphere)


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.


… is spatialClimate change is not uniform over the Earth.

Magnitude varies with location

And with season ….


Canada: Temperature Changes


• 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

Possible Effects of A Warmer World


Ecozones


Rising Seas: The Future

• One of the most striking consequences of global warming will be the associated rise in global mean sea level.


Change in Arctic Ocean: Summer Ice Cover


Permafrost in Canada

2xCO2

Present


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


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 Data Source: Marland et al, 1999. Carbon Dioxide Information Analysis Center.

Cumulative carbon emissions, 1950-1996

7,415

8,504

11,651

15,715

4,235

4,054

2,331

1,361

966

50,795

1,557

2,080

2,118

0 10,000 20,000 30,000 40,000 50,000 60,000

United States

Indonesia

Korea, Rep.

Brazil

Australia

Mexico

South Africa

Canada

India

United Kingdom

Japan

Germany

China

Million tons of carbon


Data Sources: United States Department of Energy, Energy Information Administration, International Energy Outlook, 1998 and 1999.

How much will the Kyoto Protocol reduce emissions?

8.0

5.8

7.6

6.4

0

2

4

6

8

1990 1995 2000 2005 2010

Bill

ion t

ons

of ca

rbon

Business-as-usual

Kyoto Protocol scenario


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).


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.


• 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

Cl + O

Cl + O3 = ClO + O2

Unstable


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


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)


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 module 8 atmosphere and climate

Documents

environmental geography

climate slide

environmental geography

bad slide

atmosphere ghgs

earths atmosphere

atmosphere important

atmosphere controls