Greenhouse Effect

Magdalena AnguelovaMagdalena AnguelovaPh.D. Student Advisor: Ph.D. Student Advisor: Prof. Ferris WebsterProf. Ferris Webster

What is a Greenhouse

Effect?

What is a Greenhouse

Effect?5 min.5 min.

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Our Solar System

The Living Planet

Of all planets in our Solar system,

The natural greenhouse effect

caused by the Earth’s atmosphere.

The natural greenhouse effect

caused by the Earth’s atmosphere.

only Earth has life as we know it.

The The reason?reason?

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The Sun The Sun is the major

source of light and warmth that life on Earth needs.

The sun has a temperature of 6000 oC.

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The Solar Spectrum

At such a high temperature the solar emission peaks in the visible range.

Electromagnetic spectrumMedicine Broadcastin

g

The visible range

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Electromagnetic spectrum

The Earth Spectrum

Earth emits in the far infrared (IR) range.

The average surface temperature of Earth is 15 oC (59 oF).

Thus...Thus...

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Greenhouse Effect From the solar radiation at the top of the atmosphere

A, Only a part reaches the Earth surface B.

Earth absorbs part of B and warms.

Then Earth emits that heat as IR radiation C .

Atmospheric gases trap some of this IR radiation D,

and re-emit it back to Earth.

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Greenhouse Effect

This is the natural greenhouse effect. The natural greenhouse effect keeps the Earth’s surface about 33 oC (61 oF) warmer than it would

be without the greenhouse effect.

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The atmosphere is

thin as an onion skin.

The Atmosphere

Without the atmosphere, the IR radiation emitted by Earth would escape to the space.

Earth would Earth would be be

a frozen a frozen planet, planet,

just like Mars.just like Mars.

The natural greenhouse effect is due to the presence of the atmosphere.

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The Greenhouse Gases Atmospheric gases trapping the IR

radiation are naturally occurring.

These are:

» Water vapor (H2O);

» Carbon dioxide (CO2);

» Methane (CH4);

» Nitrous oxide (N2O).

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Carbon Dioxide (CO2)

Sources:» Metabolic reactions

in plants and animals;

» Respiration.

Sinks:

» Ocean;» Land vegetation.

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Methane (CH4)

Powerful greenhouse gas:» Absorbs IR radiation 20 times

more effectively than CO2;

» But CH4 concentration is much less than CO2.

Sources -- biological processes in: » Herbivorous animals;» Wetlands and

swamps.

Sinks:» Chemical

reactions in the atmosphere;

» Ocean.

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Nitrous Oxide (N2O)

Involved in:» Greenhouse effect;» Ozone depletion.

Sources: » Bacterial processes in the

ocean;» Termites;

Sinks: chemical reaction with oxygen in the stratosphere.

» Soil.

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Water vapor (H2O)

Of all natural greenhouse gases H2O is:

» The most abundant;

» The most important in creating the natural greenhouse effect.

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Natural Concentrations

Naturally CO2, CH4, and N2O are in trace amounts compared to water vapor.

In a long run their amounts in the Earth's atmosphere remain relatively stable.

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Climate Variability

A few degree warmer than today.

90 % of Earth’s history the climate has been warm,

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CO2 Variations

During climate swings, CO2 concentration changed too.

» Decreased during glacial periods;

» Increased in warm times.

Ice cores show that CO2:

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Atmospheric CO2 from ice cores

CO2 in the Past

Changes no more than Changes no more than 4 %.4 %.

Natural!Natural!

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Pristine Earth…

The Concern

...until about a century ago,

when concentrations of CO2, CH4, and N2O began to increase due to:» Industrialization, » Demand for energy, » Rising population, » Human settlement.

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Atmospheric CO2 from ice cores

CO2 in the Last Century

Changes about 20 %.Changes about 20 %.

Man-induced!Man-induced!

Changes no more than Changes no more than 4 %.4 %.

Natural!Natural!

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Enhanced Greenhouse Effect

Human activities lead to build-up of CO2, CH4, and N2O in excess of their natural amounts.

This may enhanceenhance the natural greenhouse effect.

The consequences may be dramatic.

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Today

COCO22 increase is responsible for 71% increase is responsible for 71% of the enhanced greenhouse effect.of the enhanced greenhouse effect.

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The EndThe End

Today