Global Climate Cycles, Global Warming and Anthropogenic Greenhouse Effect
Important considerations regarding global warming and the anthropogenic greenhouse effect Cyclical Processes – The earths environmental conditions have been evolving through geologic time. They tend to be cyclical over both long and short periods of time and have changed character greatly and abruptly. Chaos is an operating factor Positive Feedback vs Negative Feedback
Brief History of Earth 4.5 b.y. ago earth formed from a cloud of dust and gas that circled proto-sun as a disc. Luminosity of sun was about 30% less than present in early history, yet earth was as warm then as now. Atmosphere had high content of CO 2
RRed Giant WWhite Dwarf BBlack Dwarf
There have been multiple periods of major continental glaciation.
Continental Glaciation Approx. Time of GlaciationDuration 2300 m.y.200 m.y. 900 m.y.50 m.y. 750 m.y.50 m.y. 600 m.y20 m.y. 450 m.y.25 m.y. 300 m.y.50 m.y. nowabout 10 m.y.so far
Continental Glaciation in North America and Europe began about 1.6 m.y. ago (Pleistocene or ice ages). Glacial and interglacial periods cycle with a period of about 100,000 years. Interglacial periods are about 10,000 years in duration
First modern humans appeared about 200,000 years ago. Peak of last glaciation occurred about 20,000 years ago. Sea level was 400 feet lower Long Island was not an Island then
Shoreline 18,000 b.p
Interglacial period began about 10,000 years ago. We are presently in an interglacial period. Agriculture started about 10,000 years ago.
Past is key to the future
What will Long Island or the earth be like in: 12 hours? 6 months? 100 years? 50,000 years? 2 b.y.? 5 b.y.? 7 b.y.?
What Controls Earth’s Surface Temperature?
10,000 o F 60 o F 0 o F if no Greenhouse Effect C/CarbonCycle.html
Real-time measurements and historical records of climate (back to 1800’s; some earlier)
ToCToC SGlobal Surface temperature
GGlobal Surface Temperature Scientific American, March 2005 p. 35
CClimate Northern Hemisphere Moberg et al, 2005 Nature v 433, p
Record from position of glaciers
Rhone Glacier (Present)
Lithograph from 1850’s
EEurope during “Little Ice Age”
Climate Northern Hemisphere Moberg et al, 2005 Nature v 433, p
VViking settlements during “Medieval Warm Period”
20,000-40,000 year cycles
100,000 year cycles
GGreenhouse Gases
Anthropogenic Greenhouse Gases Carbon Dioxide 60% Burning of Fossil Fuels Deforestation Methane15% Coal Mines Termites Wetlands (beavers) Rice Patties Cattle Subpolar Soil and Wetlands Methane hydrate
Methane Hydrate Immense Carbon reservoir Twice as large as all known fossil fuels Methane is 10 times more effective a greenhouse gas as carbon dioxide Occurs on sea floor at depths greater than about 2,000 feet In polar sediments
Global Carbon Budget
Methane Hydrate
Locations where methane hydrate has been discovered
Mean global temperature has increased since mid-1800’s Has CO 2 ? Can we see correlations earlier? Glacier Ice.
Projected Changes in Global Climate (Short-term)
RRuddiman, 2005, Sci Am. March
Ruddiman, 2005, Sci Am. March
Consequences of Greenhouse Warming Increase in warming least in tropics greatest toward poles.
Consequences of Greenhouse Warming Wandering weather patterns Increased precipitation Less rain in summer in U.S. midwest Intensity and numbers of storms will increase Ocean currents may be modified
Consequences of Greenhouse Warming Expansion of Oceans on heating Melting of glaciers Sea level rise of 1 to 3 feet by 2100 More severe storms Result will be coastal flooding
Consequences of Greenhouse Warming Natural Habitats will be destroyed –Forests dying –Wild animals unable to migrate development isolation Areas with tropical diseases expand
Agriculture may be helped or hurt depending on area and ability of farmers to react fast enough Water for irrigation and human use may be inadequate for populations in drier areas
General Strategies Waiting strategy Compromise increased energy conservation more reliance on renewable energy reduce deforestation
The End