Greenhouse Effect and Global Warming

Greenhouse Effect

• Key FactorsEarth-Sun Temperature

DifferencesGreenhouse Gas Concentrations

• The atmosphere is transparent to incoming solar radiation (short wave, high energy), outgoing terrestrial radiation (longer waves, lower energy) is absorbed by GHGs. (also relates to Black body radiation)

→WIEN’S LAW !!!

Energy Balance

Greenhouse Gases

• Carbon dioxide – CO2

• Methane – CH4

• Nitrous oxide – N2O• Freons – CFCs (totally

anthropogenic)What makes it a GHG???

• Water vapor – H2O

GHG Concentration Changes Years 1000-2000

Global Warming• An increase in global temperatures

due to increases in the concentrations of greenhouse gases

• Increased CO2 concentrations exerts largest radiative forcing (i.e., explains bulk of temperature increase)

• NOT CAUSED BY STRATOSPHERIC OZONE DEPLETION

GHG Sources

• Combustion of fossil fuels • Deforestation (loss of sink)

– Slash and burn techniques release CO2

– Fewer trees, less photosynthesis• Fertilizers• CFCs• Methane

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) concentrations (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

Mauna Loa (1958-present)

Siple Station (1750-)

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

Variations in the Earth’s surface temperature

Impacts

• Rise in sea level– Thermal expansion of the oceans– Melting ice caps and glaciers

• Climatic shifts• Shifts in agriculture• Increase in disease• Declines in biodiversity• Coral bleaching

Reducing GH Emissions

Solutions

Global Agreements

• IPCC – Intergovernmental Panel on Climate Change 1988 UNEP

• Rio de Janeiro 1992• Kyoto Protocol 1997

– Ratified Nov. 2006– U.S. and Australia have not signed the treaty

U.S. Position

Bush Sr. (1988 – 1992)

Clinton (1992 – 2000)

Bush Jr. (2000 – 2008)

Obama (2008 - )