Potential Causes of Climate Change ENVS 110. orbital parameters.

Potential Causes of Climate Change

ENVS 110

orbital parameters

planetary temperatures

100 1000 10000

Average D istance from Sun (10 6 km )

note logarithm ic scale !

-400

-200

0

200

400

600

Ave

rage

Pla

net

ary

Tem

pera

ture

(°C

)

M ercury

Venus

Earth

M ars

Jup ite r Saturn

U ranus N eptune

eccentricity:the influence of elliptical orbits

http://astroprofspage.com/archives/1024

Note: for the Earth this difference is quite small – about 3%

the seasons

http://avc.comm.nsdlib.org/cgi-bin/wiki.pl?Seasons_In_The_Sun

• changes in the shape of the earth’s orbit

• affects how solarradiation is distributedthroughout the year

http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm

• axial tilt orobliquity

• determines howmuch sunlight reaches the northern and southern hemispheres during summer / winter

• influences the severity of the seasons

Milankovitch (over) simplified

• changes in orbital parameters change the way solar radiation is distributed across the earth

• it changes the absolute amount of solar radiation a little

(due to Kepler’s second law)

• so why don’t the effects just average out?

equator

http://www.planetaryvisions.com/release2007-1/satmap.jpg

Important Greenhouse Gasses

Water vapor H2O 0.1 ppm – 40,000 ppm

Carbon Dioxide CO2 370 ppm

Methane CH4 1.7 ppm

Nitrous Oxide N2O 0.3 ppm

Ozone O3 0.01 ppm (at surface)

Freon – 11 CCl3F 0.00026 ppm

Freon – 12 CCCl2F2 0.0054 ppm

Data from Kump et al., 2004

The Greenhouse Effect

• Atmosphere transparent to visible light

• Atmosphere opaque to long wavelength radiation (infrared)

Change in CO2 Concentrations

Long Term CO2 , CH4 Variability

Source:Vostok ice core recordPetit et al., 2001

http://upload.wikimedia.org/wikipedia/commons/2/28/Sunspot_Numbers.png

1600 1700 1800 1900 2000

Year

1363

1364

1365

1366

1367

mea

n a

nnua

l sol

ar ir

radi

ance

(W

/ m

2 )

data from :Lean, J.. 2004. Solar Irradiance Reconstruction.IG BP PAG ES/W orld Data Center for Paleoclim atology Data Contribution Series # 2004-035.NO AA/NG DC Paleoclim atology Program , Boulder CO , USA.

total solar irradiance 1610 - 2000

The Reverend Robert WalkerSkating on Duddingston Loch

attributed to Henry Raeburn, 1790's

Pieter Brueghel the Younger. Winter Landscape, 1621

little ice age

London Bridge Frost Fair Luke Clenell, 1814

Mount Pinatubo erupts

feedback mechanisms

• initial signal quite small

• need amplifiers– ice albedo feedback– plant cover feedback– cloud feedback– radiation feedback– greenhouse gasses ?