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What is the greenhouse effect?

What is global warming?How are they related?

What is the greenhouse effect?

What is global warming?How are they related?

The Greenhouse Effect:Earth’s Climate Mediator

What is the natural greenhouse effect?

How does it influence our climate?

Without the thermal blanketing of the natural greenhouse effect, Earth’s

climate would be about 33 degrees Celsius

(about 59 degrees Fahrenheit) cooler, too cold for most living organisms to

survive.

The greenhouse effect is the capacity of certain gases in the atmosphere to trap heat emitted from Earth’s surface, thereby insulating and warming

the planet.

As this schematic indicates, the greenhouse effect involves a

number of different responses to sunlight and the energy it represents.

Most of the sun’s energy reaches Earth in the form of visible light.

Light energy represents just one portion of the electromagnetic spectrum.

Electromagnetic Spectrum

Image: (SPECS, 1996)

When the visible light arriving from the sun interacts with our atmosphere, a portion of this light energy is reflected back into space by the atmosphere.

Atmospheric Reflection

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The rest of the incoming solar radiation penetrates the atmosphere and reaches the Earth’s surface.

At the surface one of two things occur:

Some of the light penetrating the

atmosphere reflects off of the Earth’s surface and bounces back out into

space.

Earth’s Albedo Effect(surface reflection)

Some of the light energy reaching the surface is absorbed by Earth’s surface.

In the process, visible light energy is transformed into

heat energy and certain characteristics are altered.

Absorption and Conversion to Heat

As light is absorbed at the Earth’s surface, it can be re-radiated as heat energy. This form of energy, also referred to as infrared,

has a longer wavelength than visible light.

Same as slide

Electromagnetic Spectrum

Image: (SPECS, 1996)

The longer wavelength of the heat radiated back from the surface of the Earth cannot travel back out through the atmosphere as easily.

Some of this energy is trapped by the various gases in the atmosphere.

This is the basis of the greenhouse effect.

Image: (Our changing climate, United States Global Change Research Program)

A summary of the greenhouse effect

Image: (Our changing climate, United States Global Change Research Program)

How does water vaporinfluence the

greenhouse effect?

Water vapor is the most abundant greenhouse gas in the atmosphere. As the temperature of the

atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, and soil). Because the air is warmer, the relative humidity can be higher (the air is able to hold more water when it is warmer), leading to more

water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal (infrared) energy

radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold

more water vapor. This is referred to as a positive feedback loop (Greenhouse gases frequently asked questions,

2010).

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Water vapor has a strong and complex effect as a greenhouse gas.

The greater the percentage of water vapor in the atmosphere,

the greater the reflectivity or Albedo Effect of the Earth’s atmosphere.

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Because the influence of water vapor as a greenhouse gas is complex

and highly responsive to the impact of all other greenhouse gases,

these other greenhouse gases will be looked at separately.

What other gases contribute to the

greenhouse effectand where do they

come from?

There are a great number of influential greenhouse gases in addition to water vapor.

The most influential are:

Carbon Dioxide (CO2)Methane (CH4)Nitrous Oxide (N2O)Chlorinated Fluorocarbons (CFCs)

Each has unique heat-trapping properties as a greenhouse gas.

Sources of various greenhouse gases:

Sources of various greenhouse gases:

Greenhouse Gas

Natural Sources

Anthropogenic

Carbon Dioxide * Cellular respiration and decay * Natural fires* Volcanoes* Warming oceans

* Combustion of fossil fuels* Land use conversion * Cement production

Methane * Animal digestion* Methane hydrates

* Combustion of fossil fuels* Rice paddies* Livestock * Landfills

Nitrous Oxide * Temperate and tropical soils* Oceans

* Combustion of fossil fuels* Fertilizer* Industrial processes

Chlorinated Fluorocarbons

* None * Liquid coolants* Foam production

Given the different characteristics of each

greenhouse gas, which has the

greatest overall effect?

Carbon Dioxide 62.9%

Methane 18.2%

CFC’s 12.8%

Nitrous Oxide 6.2%

The Summative Impact of Various Gases on the Greenhouse Effect

(given their unique characteristics)

(Working Group I, 2007)

What are “carbon sinks” and how do they influence

the carbon cycle?

Earth’s oceans act as a huge carbon sink”holding immense amounts of dissolved CO2.

This huge carbon sink responds to global temperature changes.

As ocean waters cool, they absorb more CO2 from the atmosphere.

As ocean waters warm, they release more CO2 into the atmosphere.

The oceans as a carbon sink

Our planet would be better named “Water” than “Earth,”

since most of its surface is covered by ocean.

Because photosynthesis

captures carbon, forests are also a form

of carbon sink.

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Geologically, huge amounts of carbon dioxide can be captured in limestone. This is another important,

though slow-to-respond, carbon sink.

Throughout our planet’s history, natural processes have kept CO2 and global temperature in close correlation.

How have more recentanthropogenic sources of carbon dioxide affected

the cycling of carbon dioxide?

Carbon dioxide is released into the atmosphere when things are burned.

Today’s industrial societies rely heavily on the burning of different types of fuels.

How have these recent anthropogenic source of CO2

changed the carbon cycle?

Since our shift to an industrial

way of life, carbon dioxide concentrations

in the atmosphere have been

rising.

This simple graph of the Mauna Loa Carbon Dioxide Record documents a 0.53%, or two parts per million per year, increase in atmospheric carbon dioxide since 1958. This gas alone is responsible for 63% of the warming attributable to all greenhouse

gases according to NOAA's Earth System Research Lab.

REVIEW:

CO2 has a major role as a greenhouse gas.

There are both natural and anthropogenic sources of CO2.

CO2 cycles between the Earth and the atmosphere.

The concentration of CO2 in the atmosphere is going up.

The Earth is currently experiencing a warming trend.