Physics of the Atmosphere Global Warming

The sun Emits Light that radiates through space and warms the Earth

Blackbody Curve The sun emits most of its light as visible light

Absorbed radiation heats up the Earth and it radiates as a blackbody at a lower temperature

Molecules Combination of atoms; most in the atmosphere contain only a few atoms (e.g. CO 2, O 2 ) Molecules are held together by an attractive electrical force. If they get too close to each other, the atoms start to repel. The net result gives something that behaves like a spring

Emission and Absorption of Electromagnetic Radiation by Molecules Emission: Because of the spring-like forces between atoms in a molecule, they can vibrate and vibrating charges emit electromagnetic radiation. For most molecules this radiation is in the infrared part of the electromagnetic spectrum Absorption: If electromagnetic radiation of the right wavelength passes near the molecule, it can “resonate” and the molecule can absorb the radiation. For many molecules, this is also in the infrared part of the electromagnetic spectrum Light

Composition of the Atmosphere Major : N % O % Ar00.934% % Some Trace Gases (in ppm) CO H 2 O20-20,000 Ne12 He5 NO 2 2 CH 4 2 Greenhouse gases

Albedo: Snow and clouds have high albedo; dark earth has low albedo Solar constant: increased by about 30% during the lifetime of Sun

CO 2 Emissions From Fossil Fuel Combustion: 1996 Source: CO 2 Emissions from Fuel Combustion , International Energy Agency, page II.4-5, 1998 Edition Million Tonnes of CO 2

United States Canada Germany Russia United Kingdom Japan South Africa Mexico People's Rep. Of China India Million Tonnes of CO 2 CO 2 Emissions Per Person: 1996

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks: U.S. EPA publication #236-R Carbon Dioxide Hydroflourocarbons (HFCs), perflourocarbons (PFCs), and Sulfur hexaflouride (SF 6 ) Nitrous Oxide Methane

Global Warming is a complicated problem There are many complicated affects that work together e.g. Increased CO 2 causes planet to warm which causes more water vapor to form. Water vapor is also a greenhouse gas which will cause more warming (positive feedback) Increased CO 2 causes planet to warm which causes more water vapor to form. This causes more clouds which increases the amount of sunlight reflected away from the Earth (increases the albedo) which would cause the planet to cool.

Actions of the US on Global Warming Developing countries are not included Cost is too great – wait until science is more precise Warmer temperatures are not necessarily bad Too many uncertainties in science -Climate models have “fudge” factors -Global climate models don’t agree with each other -Evidence for connection of solar cycle and warming -Discrepancies between surface and atmospheric temperature data