GEO

Greenhouse Gas/Effect

Sun=shortwave, GHGs transparent to shortwave, energy emitted from Earth= longwave, GHG absorb and remit as heat into atmosphere

Prebiotic atmosphere

4.5-3.8 billion years ago, N2, CO2, H2O, impact degassing released these gases

biotic, pre oxygenated atmosphere

3.8 - 2.5 billion years ago, N2, Ch4, Co2, methane is produced by bacteria

Biotic oxygenated atmosphere

2.5 billion years ago - present, N2, O2, and Ar (from decay of K), O2 produced by algae; CO2 buried in rocks, CH4 short life time in atmosphere

Faint young sun paradox

Early sun had 30% lower luminosity, increased at rate of 1% per 100 million years, should have been ice planet, but GHGs warmed atmosphere

Time scales/ forcings of climate change

tectonic, orbital millennial, centennial

tectonic timescale and forcing

over millions of years, CO2 forcings

orbital forcing and timescale

over 10,000s years, Sun forcings

millennial forcing and timescale

over 1000s years, ocean-ice forcings,

centennial forcing

over 10-100 years, volcanoes and Sun forcings

Carbon Cycle

Exchange between reservoirs, ocean, vegetation, sediment, and atmosphere

long-term carbon cycle

slow exchange from sediments too atmosphere; chemical weathering, ocean mineralization, volcanic degassing

long term carbon cycle summary

weathering takes in CO2, volcanic degassing releases CO2,

Volcanism and climate

negative feedback, warm temps increase chemical weathering, removes CO2, reduces warming

snowball earth

happened when continents moved to low latitudes, increasing chemical weathering, cooling the globe, earth snowballed, leading to no weathering, volcanoes release CO2, snowball melts and releases

History of ice ages

known by changes of 18O/16O ratios in fossil

ice ages cyclic changes

eccentricity - 100,000 years

tilt - 41,000 years

precession - 23,000 years

low tilt, far from sun

cold summer

high tilt, closes to Sun

warm summer

Global warming

GHGs cause too much warming

Natural forcings and climate change

No change in natural forcings

GHGs and climate change

too much warming

aerosols

cooling effect