Atmospheric Chemistry Atmospheric Chemistry

Objectives Know the components of the atmosphere. Discuss the different forms of electromagnetic radiation emitted by the sun. Understand how solar radiation interacts with the atmosphere.

Components of the Atmosphere 1% Ar varies H2O <1% CO2 <1% CH4 <1% ozone, O3 (block UV) “greenhouse gases” trap heat

Solar Radiation Sunlight is mostly: ultraviolet, UV visible light, VL infrared, IR UV

Absorption of UV and IR Ozone absorbs UV CO2 and H2O absorb IR

Energy Budget IR heats air; emits to space as IR IR VL UV IR heats air; emits to space as IR VL reflects back to space; or heats surface and IR emits to space ozone converts UV to IR, emits to space energy in = energy out global temperature stays fairly constant

Objectives Understand how CO2 affects global temperature. Be familiar with opinion polls regarding global warming. Understand how ice core samples show a relationship between CO2 and temperature. Be familiar with modern data regarding changing atmospheric conditions. Know which countries/regions produce the greatest quantities of CO2.

Global Warming fossil fuels: coal, oil, natural gas fossil fuel + O2 → H2O + CO2 greenhouse effect: gases such as CO2 or CH4 act like a blanket, maintaining a higher average temperature global warming: more greenhouse gases result in a warming effect (like adding more blankets) global dimming: more clouds (from heating and smog) result in a cooling effect warming > cooling 97% of climatologists say humans play a role in global warming. U of Illinois-Chicago Survey

Scientist Survey

Public Opinion

Ice Core Data source: IPCC Trapped air in ice cores reveal CO2 levels. Low levels of oxygen-18 in ice = lower temperatures. CO2 and temperature are closely related.

Ice core samples taken from two locations 650 km apart show data is credible

Increasing CO2 Levels CO2 levels up from 315 to 390 ppm (up 24%) 1 kg of gasoline makes 3 kg of CO2 CO2 levels up from 315 to 390 ppm (up 24%) US Dept of Energy

Temperature Change avg. global temperatures up 0.8o C Goddard Institute for Space Studies (NASA) avg. global temperatures up 0.8o C most warming in polar regions

Who makes greenhouse gases? The US and China produce about 1/2 of all human-caused CO2 emissions.

Predicting Future Global Climate Change

Objectives Understand that computers can be used to predict future climates. Be familiar with potential future climatic conditions predicted by computer models. Be familiar with environmental changes that are currently occurring in polar regions.

Computer Models Computer models for climate changes are pretty accurate. 1950 2000

CO2 Scenarios Various CO2 possibilities are used to make predictions about the future. (IPCC report)

Temperature Changes Temperatures rise 2oC – 4oC (source: IPCC)

Sea-Level Changes Sea-levels rise 30 cm – 50 cm (source IPCC)

Melting Ice Sheets Trapped air in ice cores Greenland’s ice is melting four times faster than it was in 2002; about 65 mi3/yr (Science, 2009). Sea levels now expected to rise 32 cm by 2050 (Geophysical Research Letters) video1 video2 NASA, 2007

Arctic Perennial Ice The summer arctic ice cap is now about ½ as large as historical average. Less ice results in less reflection, more absorption, and increased warming. NASA, 2007

Objectives Understand the impact of melting ice sheets. Be familiar with the thermohaline cycle and its influence on climate.

Long-term Sea Level Rise Melting the entire West Antarctic Ice Sheet or the Greenland Ice Sheet would each raise sea-levels by about 20 feet (for each). But this will take 1000s of years at current rates.

Thermo-Haline Cycle Ocean currents transfer heat from the equator to the poles. Melting ice caps may stop this cycle and cool off climate in Europe. Ice age patterns may be related to this process.

Global Dimming Air pollution particles produce more cloud cover. More clouds trap heat → warming effect But less sunlight hits surface → cooling effect Air pollution has reduced the amount of global warming!