Why is it important to distinguish between anthropogenic greenhouse effect and natural greenhouse effect?

Answer 1

There is a natural greenhouse effect which is necessary to keep the earth warm enough for life. The earth has had a natural greenhouse effect for millions of years.

Anthropogenic greenhouse effect means caused by human activity. When we seriously started burning fossil fuels about 150 years ago to warm our houses, produce electricity and power transport the temperature of the world has been slowly increasing. Most climate scientists believe it is almost too late to stop the world warming by 4 or 5 degrees Celsius, which will bring about catastrophic change to the planet.

Answer 2

A man-made greenhouse gas is one that would not have been emitted but for man. It's this concept that underlies the perspective that human activity has led to increased global surface temperatures. Examples include burning fossil fuels (such as coal and natural gas) for electricity and burning petroleum for our cars. Deforestation also releases gases stored in the earth (and removes the natural CO2-capturing effect plants have), but effects of this activity are arguably minimal by comparison.

Man-made greenhouse gases may, in some circumstances, be better termed "man-emitted greenhouse gases."

As for naturally-emitted GHGs, it may be helpful to take a look at just what greenhouse gases are. The primary 6 GHGs are carbon dioxide (what we exhale), methane (naturally occurs in flatulence!), nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexaflouride. Some, such as methane, are more concentrated than others, such as CO2, and have the potential to cause more harm (sometimes called "GWP," or "global warming potential"), but because CO2 is emitted in far greater amounts, its effects outweigh the effects of the other gases, despite their greater intensities.

Some examples of naturally-emitted GHGs may include water vapor, volcanic eruptions, and even releases of methane pockets that have been stored in seabeds.

It is generally agreed that energy generation is the leading source of man-emitted GHGs. For example, burning coal emits CO2, and the use of natural gas results in methane emissions.

For more detailed (and readable) information, check out the Annual Energy Review, put out by the Department of Energy, at http://www.eia.doe.gov/emeu/aer/contents.html

And a study by the IPCC, a U.S.-based and widely renown research group:

...and http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf

Hope that helps!

Answer 3

The anthropogenic greenhouse effect is the combined heating of the atmosphere due to human activities.

these activities include but are not limited to:

• Deforestation
• Burning fuels (wood and fossil fuels - oil, gas, coal...)
• Release of gasses into the atmosphere (Chlorinated fluorocarbons, ozone, water vapor at high altitudes (jet trails)...)
• Release of particles (smoke, ash, dust, ...)
• Altering the albedo (reflectiveness of the surface) by huge monocultures (farming, plowing, building cities...)

Answer 4

The important greenhouse gases, water vapour, carbon dioxide, methane and ozone are naturally occurring, but can also be added to the atmosphere by human activities.

Natural sources of carbon dioxide do not add to the the atmospheric concentration, and the atmospheric concentration has remained in the range of 260 to 280 parts per million (ppm) for hundreds of thousands of years, with animals breathing out carbon dioxide and plants absorbing it from the atmosphere again, producing food which animals eat. Anthropogenic sources include fossil fuels, such as coal, oil and natural gas, which have sequestered carbon underground for millions of years. By burning fossil fuels for industry, production of electricity and for transport, we are actually adding to the level of carbon dioxide in the atmosphere, thereby creating an enhanced greenhouse effect. Cement manufacture releases carbon dioxide which was also sequestered in mineral form. The other major source of additional greenhouse gases is deforestation. Forests hold large stores of carbon for thousands of years, so by removing trees without allowing new ones to grow and absorb as much carbon as the previous trees, we add to the level of atmospheric carbon dioxide.

Methane is produced naturally from the digestive systems of ruminants and from anaerobic decomposition, and anthropogenically by industry and as a byproduct of coal mining. Because of increasing human populations, we now maintain large herds of ruminants such as sheep and cattle, thereby adding considerably to methane emissions. Scientists have found ways to alter the diets of cattle so as to markedly reduce their production of methane, but these techniques are not in widespread use.

The one greenhouse gas that humans can not add directly to the atmosphere is water vapour, since any excess would precipitate within days, maintaining a global equilibrium. However, water vapour is indirectly implicated in global warming. As average global temperatures rise in response to increasing levels of carbon dioxide and methane, the atmosphere takes up more water vapour. This in turn adds a little more to the greenhouse effect and therefore to global warming, providing an example of positive feedback.

So, the essential difference is that anthropogenic sources increase the atmospheric concentration of greenhouse gases and create an enhanced greenhouse effect.

Answer 5

Superficial and Inconsequential.