Bellwork 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?

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. 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.

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. Electromagnetic Spectrum Image: (SPECS, 1996) Most of the sun’s energy reaches Earth in the form of visible light. Light energy represents just one portion of the electromagnetic spectrum.

Atmospheric Reflection Need to purchase or get alternative 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.

The rest of the incoming solar radiation penetrates the atmosphere and reaches the Earth’s surface. At the surface one of two things occur:

Earth’s Albedo Effect (surface reflection) Some of the light penetrating the atmosphere reflects off of the Earth’s surface and bounces back out into space.

Absorption and Conversion to Heat 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.

Electromagnetic Spectrum Same as slide Image: (SPECS, 1996) 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.

Earth cannot travel back out through the atmosphere as easily. Image: (Our changing climate, United States Global Change Research Program) 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.

A summary of the greenhouse effect Image: (Our changing climate, United States Global Change Research Program)

How does water vapor influence the greenhouse effect?

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

The greater the percentage of water vapor in the atmosphere, Need to purchase or get alternative The greater the percentage of water vapor in the atmosphere, the greater the reflectivity or Albedo Effect of the Earth’s atmosphere.

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 effect and where do they come from?

Chlorinated Fluorocarbons (CFCs) 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: 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 * Rice paddies * Livestock * Landfills Nitrous Oxide * Temperate and tropical soils * Oceans * Fertilizer * Industrial processes Chlorinated Fluorocarbons * None * Liquid coolants * Foam production

Given the different characteristics of each greenhouse gas, which has the greatest overall effect?

The Summative Impact of Various Gases on the Greenhouse Effect (given their unique characteristics) Carbon Dioxide 62.9% CFC’s 12.8% Nitrous Oxide 6.2% Methane 18.2% (Working Group I, 2007)

What are “carbon sinks” and how do they influence the carbon cycle?

The oceans as a carbon sink Our planet would be better named “Water” than “Earth,” since most of its surface is covered by ocean. 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.

Because photosynthesis captures carbon, forests are also a form of carbon sink. Buy photo

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.

anthropogenic sources of carbon dioxide affected How have more recent anthropogenic 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.

anthropogenic source of CO2 changed the carbon cycle? 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.