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 CO2

RRed Giant

WWhite DwarfBBlack Dwarf

• There have been multiple periods of major continental glaciation.

Continental Glaciation

Approx. Time  of Glaciation Duration

2300 m.y. 200 m.y.900 m.y. 50 m.y.750 m.y. 50 m.y.600 m.y 20 m.y.450 m.y. 25 m.y.300 m.y. 50 m.y.now about 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?

•

10,000o F

60o F0o F if no Greenhouse Effect

www.ultranet.com/~jkimball/BiologyPages/ C/CarbonCycle.html

Real-time measurements and historical records of climate

(back to 1800’s; some earlier)

ToC

SGlobal Surface temperature

GGlobal Surface TemperatureScientific American, March 2005 p. 35

CClimate Northern HemisphereMoberg et al, 2005 Nature v 433, p. 613-617

Record from position of glaciers

Rhone Glacier (Present)

Rhone Glacier (Present)

Lithograph from 1850’s

Climate Northern HemisphereMoberg et al, 2005 Nature v 433, p. 613-617

20,000-40,000 year cycles

100,000 year cycles

GGreenhouse Gases

Anthropogenic Greenhouse Gases

• Carbon Dioxide 60%• Burning of Fossil Fuels• Deforestation• Methane 15%• 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 hydratehas been discovered

•Mean global temperature has increased since mid-1800’s

•Has CO2 ?

•Can we see correlations earlier? Glacier Ice.

Projected Changes in Global Climate (Short-term)

Ruddiman, 2005, Sci Am. March

Ruddiman, 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