In order to understand the human impact on climate change today, a very important concept to know is:


This is important because most human activities affect climate change by enhancing this effect:
  • When the sun's light energy hits the Earth, approximately 70 percent of the energy stays on the planet, absorbed by land, oceans, and molecules within the atmosphere. The rest immediately is reflected back into space by clouds, snow, and other reflective surfaces.
  • The Earth's oceans and land masses eventually radiate heat energy back out. Some of this heat makes it into space. The rest of it ends up getting absorbed when it hits the molecules of gases in the atmosphere, such as carbon dioxide, methane gas and water vapor.
  • In turn, these gases release the energy they have absorbed (also in the form of heat). This creates a warming effect in the atmoshphere, keeping the earth warm.
  • These gases are known as greenhouse gasses. They exist naturally, and the way they absorb and emit heat has kept the eart at a hospitable temperature since life began.
  • Certain human activities have increased the amounts of these gases in the atmosphere (explained below).


In the past, the gases that contribute to global warming have been exclusively provided by nature, but humans have caused a tremendous surge in the output of these gases, in addition to creating our own gases which cause the same damage.

Man contributes to following gases:
  • Carbon dioxide
  • Methane
  • Nitrous oxide
  • HFCs
  • PFCs
  • SF6

…by doing the following things:
  • breeding of excessive amounts of livestock
  • excessive use of automobiles
  • excessive use of factories
  • excessive use of large ships (i.e. oil-tankers, ocean liners, cruise ships)
  • excessive us of tanks (wars)
  • excessive us of airplanes (both peace and warcraft)
  • excessive burning of fossils (i.e coal/oil)
  • use of synthetically produced aerosols

-->for a US-specific breakdown of man’s impact
--> for a nice diagram of the gases, and their contribution to the greenhouse effect
--> for a table of the current atmospheric concentrations of the gases

Quick Facts

  • Deforestation is another possible cause of the global warming. However, there are still some debates of whether the deforestation will get worsened or get better from scientists to scientists.
  • 21% of earth's surface is covered with forest (indigeneous)
  • 27,429 sq. km of the forest in Amazon jungle has been removed in 2004.
  • There is a strong correlation between deforestation and economic growth of the nations.

Causes of deforestation
  • Conversion of forest to farmland due to the need of farmers to feed themselves. (For plantation)
  • Commercial logging (Happening in both developed and developing countries)
  • (Usually in developing countries) Uncontrolled logging for the building material
  • For cattle raising
  • Big governmental projects (dams, etc.)
  • Man-made or non-man made fire in the forest
  • Exploitation of underground resources (oil, coal, gas, etc.)

Evidence suggesting that deforestation will decrease in future
  • FAO (**Food and Agriculture Organization** of the United Nations) has reported that 22 of 50 nations which have the most forest in the world have their size of forest increased for last 15 years.
  • **Proceedings of the National Academy of Sciences** (PNAS) in the U.S. reported that the total size of forest will increase by 10% in 2050.
  • A report from the University of Helsinki suggested that the world economic growth led to the decreased deforestation, since more industrial jobs created by economic growth led to the decreased farmers' need of arable land created by burning the forest.

On the other hand, there are also some contradicting evidences, too.
  • An FAO report has also suggested that developed countries' excessive importing of timber resources from developing countries worsened the deforestation problem.
  • A report from the University of Helsinki concluded that the deforestation problem depends heavily on the future of farmers in developing countries, and suggested that if the living standards of those farmers increase, the threat of deforestation will decrease.

Useful websites for deforestations - Discusses causes of deforestation Gives general outline of the deforestation Gives detailed data about deforestation in Amazon jungle A greenpeace website addressing the issue of deforestation