Climate: What we know about it, How we know

about it, and What we’re doing to it.]

CO2 and the Greenhouse Effect

CO2 concentrations between 1995 and 1990

CO2 concentrations in ice cores 1000 to 2000 AD

global view:

CO2 concentrations 1000 to 2000 AD.

Note change during industrial revolution!

Global

Antarctica

How the Greenhouse effect works

1. Different frequencies of light act differently

2. Greenhouse Gasses in Earth’s atmosphere trap infrared light (heat)

Same process that makes your car warm on a cold winter day, or heats up a Greenhouse!

Most of the radiant energy from the sun is concentrated in the visible and near-visible parts of the spectrum.

The narrow band of visible light, between 400 and 700 nm, represents 43% of the total radiant energy emitted.

Water, Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Fuorocarbons (CFCs)

What are the major Greenhouse Gasses?

Greenhouse EffectThe rise in temperature that the Earth experiences because certain gases in the atmosphere trap energy from the sun.

Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder.

Because of how they warm our planet, these gases are referred to as greenhouse gases.

Gases include: water vapor, carbon dioxide, nitrous oxide, and methane

Trace greenhouse gases are relatively transparent to incoming visible light from the sun, yet opaque to the energy radiated from the earth.

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Northern Hemisphere Temperature since 1900 A.D.

Northern Hemisphere Temperature since 1400 A.D.

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Temperature

Carbon Dioxide

What does the future hold?

• What is “climate variability”?• What is “interannual climate variability?”• Why is it important?• What can we learn about past climate?• How are our activities impacting climate?

Climate varies on long (millennial) timescales

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_18 (‰)O

Climate varies on short (interannual) timescales

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Why is understanding interannual variability important?

1) It is necessary if we are going to make a reasonable prediction of future climate.

Why is understanding interannual variability important?

2) It provides a framework for understanding variability in other systems.

The Pacific Decadal Oscillation

Sea surface temperatures.

Time for a movie!

The isotope paleothermometer

• The 18O isotope ratio in water is influenced by temperature – both during evaporation of H2O from the ocean and its eventual precipitation on land as rain or snow.

• At high latitudes, there is a very strong, approximately linear relationship between 18O and local temperature.

What is “delta 18 O”?

( )

definitionby 0

1000*1

/

standard

18

standard

sample18

161818

≡

⎟⎠

⎞⎜⎝

⎛−=

=

O

R

RO

OOR O

δ

δThe ratio of 18O/16O in ice is compared to the ratio of 18O/16O in average ocean water.

This comparison is called 18O.

Variations in the 18O of the oxygen in the water molecule, H2O, is used in climate studies

Why does 18O relate to temperature?

↔ lvEQlv OHOHOHOH 182

162

162

182 ++

This equilibrium is temperature dependent

The O18/O16 ratio provides an accurate record of ancient water temperature.

d18Ollllliiiiiqqqqquuuuuiiiiiddddd=====00000

d18Ov~-10‰

d18Ov<<-10‰

d18Osnow

~-40‰

poleward moisture transport

d18Ov~-30‰

d18Orain~0‰ddddd1111188888OOOOOrrrrraaaaaiiiiinnnnn<<<<<<<<<<00000‰‰‰‰‰

adiabatic cooling

Worldwide Ice Core Sites

Mt. Logan, Yukon (Canada)

What can we learn about interannual climate variability from ice cores?

Annual layers in glacier ice

Central England temperature estimates

After Lamb, 1982

“Medieval warm period”

“Little ice age”

Ice core data: trends removed

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anomaly (per mil)r =+ .52

Siple – 1400-1983

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Temperature anomaly

Siple Dome- 1900-1996

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Temperature anomaly

Abrupt Climate Change

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Temperature (C)

End of the “Younger Dryas” took <50 years

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s!)

“Proxy” data(tree rings, ice cores, corals)

Central Greenland temperatures

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Temperature (C)

10-year average temperatures from the GISP2 ice core

Central Greenland 18O

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18 (‰)O

The GISP2 ice core record

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Northern Hemisphere Temperature since 1400 A.D.

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Ice coring sites

Queen Maud Land

Siple Dome

Siple

Spatial covariance of Antarctic temperature with PC1

Antarctic T trends since 1982

AVHRR (infrared) satellite observations

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18O (‰)

Queen Maud Land

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What to do next?

A good example is how Society dealt with the Ozone Hole

1. UV radiation breaks off a chlorine atom from a CFC molecule.

2. The chlorine atom attacks an ozone molecule (03), breaking it apart and destroying the ozone.

3. The result is an ordinary oxygen molecule (0) and a chlorine monoxide molecule (ClO).

4. The chlorine monoxide molecule (ClO) is attacked by a free oxygen atom releasing the chlorine atom and forming an ordinary oxygen molecule (O).

5. The chlorine atom is now free to attack and destroy another ozone molecule (03). One chlorine atom can repeat this destructive cycle thousands of times.