Earth Day April 22 of each year Designed as a day to become aware of and appreciate the Earth’s environment Started in reaction to population growth and overpopulation Proposed by Senator Gaylord Nelson of Wisconsin First Earth Day, April 22, 1970 is considered the beginning of the modern environmental movement Designed to be a teach in day at Universities Protest and rallies against things like oil spills, polluting factories and power plants, raw sewage, toxic dumps, pesticides, freeways, the loss of wilderness, and the extinction of wildlife were held across the nation. In 2000, focus shifted to global warming and clean energy

Global Warming The name given to the increase in the average temperature of the Earth’s near surface temperature and oceans that has occurred since the middle of the 20th century. In the graph to the right, panel a gives the Earth's surface temperature is shown year by year (red bars) and approximately decade by decade (black line, panel b gives the year by year (blue curve) and 50 year average (black curve) variations of the average surface temperature of the Northern Hemisphere for the past 1000 years have been reconstructed from "proxy" data calibrated against thermometer data.

Greenhouse effect Main culprit behind global warming Sunlight enters the atmosphere and warms the Earth (UV, visible, IR) At night, Earth radiates heat energy it gained during the day(mostly at IR wavelengths) Not all of this energy escapes the atmosphere-some of it is absorbed and re-emitted back into the atmosphere, warming the atmosphere and the Earth. Not necessarily a bad thing-without it the Earth would be cold and life (a least as we know it) would not be possible

Venus Hottest planet in the solar system But not the closest to the sun Atmosphere is 96.5% carbon dioxide Venus once had immense amounts of water, but no ozone layer-the UV radiation broke up the water molecules Unfortunate, water absorbs carbon dioxide wand mitigates the greenhouse effect Resulted in an extreme greenhouse effect

Greenhouse effect-What could happen Global temperatures rise until boiling point of water is reached As water boils away, it becomes water vapor in the atmosphere, accelerating the heat rise (called positive feedback). At a few hundred degrees celsius, carbon dioxide would be released from the rocks (sublimation), accelerating the heating again Eventually the Earth would stabilize at surface temperatures similar to Venus (T=860F)

Greenhouse Gasses –in order of importance water vapor carbon dioxide methane nitrous oxide ozone CFCs

Changes in greenhouse gas concentrations Historical variations can be tracked via analysis of ice cores Ice core - a core sample (a cylindrical section of a naturally occurring medium consistent enough to hold a layered structure) from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods. The composition of these ice cores provides a picture of the climate at the time. Record for over 800,000 years Gas Preindustrial Level Current Level Increase since 1750 Carbon dioxide 280 ppm 387ppm 104 ppm Methane 700 ppb 1,745 ppb 1,045 ppb Nitrous oxide 270 ppb 314 ppb 44 ppb CFC-12 0 533 ppt 533 ppt

What do the ice cores tell us? Natural variations occur in the greenhouse gas concentrations

Post industrial revolution

Man made sources of greenhouse gasses Also called Anthropogenic, which designates an effect or object resulting from human activity burning of fossil fuels and deforestation leading to higher carbon dioxide concentrations. Account for one third of total anthropogenic CO2 emissions. livestock enteric fermentation and manure management, paddy rice farming, land use and wetland changes, pipeline losses, and covered vented landfill emissions leading to higher methane atmospheric concentrations. Many of the newer style fully vented septic systems that enhance and target the fermentation process also are sources of atmospheric methane. use of chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and halons in fire suppression systems and manufacturing processes. agricultural activities, including the use of fertilizers, that lead to higher nitrous oxide (N2O) concentrations.

What are we seeing? Since 1860-1900, global surface temperatures have increased by 1.35 F Urban heat island effect only accounts for 0.02 C rise Since 1979 land T have increased twice as fast as ocean Temperatures Temperatures on the lower troposphere have have increased by 0.62 between 1979 and 2000.

Hold on, could it be the sun? No overall increase in solar brightness in over 1000 years Solar cycles do cause small variations in brightness, but not enough to account for what has been seen No its not the sun

Feedback-making the problem worse (or better) Positive feedback-when the warming induces further warming Negative feedback – when the warming induces a cooling

Sources of Feed back Positive Negative Water vapor Clouds Ice albedo Arctic methane release Reduced carbon dioxide absorption in the oceans Negative Lapse rate