The term 'greenhouse effect' is a description of the natural way the atmosphere works to regulate the Earth's surface temperature. Below are a series of diagrams which show how the greenhouse effect works.

In the greenhouse, sun rays pass through the glass and some heat (infra-red radiation) is absorbed by the ground. However, most of heat is radiated away from the ground. As the heat hits the glass, most passes through, while some is reflected back by the glass. This increases the temperature inside the greenhouse and makes it possible for plants which like warm climates to grow.

The diagram below shows the natural greenhouse effect. Like the greenhouse, the suns rays shine down on the Earth and while some energy is absorbed by the ground, most of heat is radiated back into the atmosphere.

The greenhouse gasses which form naturally in the atmosphere reflect some of the heat back, making the Earth warm enough for plants and animals to live.

Our atmosphere works differently to that of the glass in a greenhouse, however the results are similar and that is why the term greenhouse effect is used.

The diagram below shows what would happen if we had no natural greenhouse gasses in the atmosphere. There is nothing to stop the infra-red radiation continuing out into space.

Without the natural greenhouse effect the temperature on the Earth would be similar to the moon (-18°C or 0 F) which has a very thin atmosphere.

There are a number of gases in the atmosphere which absorb infra-red radiation leaving the Earth which causes the greenhouse effect.

The main greenhouse gases:

• Carbon Dioxide
• Methane
• Nitrous Oxide
• Ozone
• Water Vapour

There are also a number of other gases which are produced by industry, however these are made in very low amounts in comparison to Carbon Dioxide.

The most important greenhouse gas is Carbon Dioxide because it accounts for about 60% of the enhancement of the greenhouse effect. ₍₁₎

Carbon Dioxide occurs naturally mainly from volcanic out-gassing, the burning of plants and trees and when living organisms breathe.

However, since the industrial revolution in the 1800’s, humans have contributed greatly to the level of Carbon Dioxide in the atmosphere.

People have been increasing the level of Carbon Dioxide in the atmosphere because of:-

• Power generation in coal fired power plants
• Transportation, the use of carbon-based fuels in cars, buses, trucks & planes
• Industrial processes such as steel manufacture

Prior to the industrial revolution the level of Carbon Dioxide in the atmosphere was about 280 ppmv (parts per million by volume)₍₂₎. In 2006 it was recorded that the level of Carbon Dioxide in the atmosphere was 380 ppmv.

The increase of Carbon Dioxide in the atmosphere is much more than would normally happen in natural circumstances. This is called the enhanced greenhouse effect.

On the left is the natural greenhouse effect and on the right is a build-up of Carbon Dioxide in the atmosphere, creating a thicker ‘blanket’ around the planet. As the infra-red radiation is kept in by greenhouse gases, the temperature increases.

These diagrams are simplified in order to make the explanation easy. There are a number of other factors that are involved in greenhouse effect, for more detail click here.

When the average surface temperature of the Earth increases, this is referred to as global warming.₍₃₎ Since the late 1800's, the global average temperature has increased about 0.4 to 0.7 degrees Celcius.₍₄₎

There has been a large amount of research into global warming by scientists from around the world.

This research will be quoted in order to answers a number of questions about global warming. These reports represent the most internationally respected and thorough research available today.

The following three reports will be quoted:-

"The Economics of Climate Change"

Dated: 2006
For: The UK government Treasury

Click on this link to download the Stern Review

"Climate Change 2007: The Physical Science Basis - Summary for Policymakers"

Dated: April 2007
For: United Nations

Click on this link to download the IPCC 4th Assessment Report

"Climate Change Impacts on Australia and the Benefits of Early Action to Reduce Global Greenhouse Gas Emissions"

Dated: February 2006
For: The Australian Business Roundtable on Climate Change

Click on this link to download the CSIRO Report

"An overwhelming body of scientific evidence now clearly indicates that climate change is a serious and urgent issue. The Earth’s climate is rapidly changing, mainly as a result of increases in greenhouse gases caused by human activities."

There is a "very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming."

"The global atmospheric concentration of Carbon Dioxide has increased from a pre-industrial value of about 280 ppm to 379 ppm3 in 2005." "The primary source of the increased atmospheric concentration of Carbon Dioxide since the pre-industrial period results from fossil fuel use, with land use change providing another significant but smaller contribution."

"Australia is one of the many global regions experiencing significant climate change as a result of global emissions of greenhouse gases (GHGs) from human activities."

"Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level."

"Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature9 (since 1850)."

"The total temperature increase from 1850 to 2005 is 0.76 C".

"The average surface air temperature of Australia increased by 0.7°C over the past century – warming that has been accompanied by marked declines in regional precipitation, particularly along the east and west coasts of the continent. These seemingly small changes have already had widespread consequences for Australia."

"The scientific evidence on the causes and future paths of climate change is strengthening all the time. In particular, scientists are now able to attach probabilities to the temperature outcomes and impacts on the natural environment associated with different levels of stabilisation of greenhouse gases in the atmosphere. Scientists also now understand much more about the potential for dynamic feedbacks that have, in previous times of climate change, strongly amplified the underlying physical processes."

The following diagram shows a number of countries and their levels of Carbon Dioxide emissions per capita.

It also shows that the most developed countries in the world are also the ones who are contributing the most to the problem of global warming. The countries that can afford to do the most should be leading the way in fixing the problem. However, the United States and Australia still have not agreed to the Kyoto Protocol.

Of all the developed countries in the world, only two have not ratified the Kyoto Protocol, Australia and the United States.

"The majority of emissions have come from rich countries in the past. North America and Europe have produced around 70% of the CO2 from energy production since 1850, while developing countries account for less than one quarter of cumulative emissions."

"The scientific evidence is now overwhelming: climate change presents very serious global risks, and it demands an urgent global response."

"Climate change threatens the basic elements of life for people around the world - access to water, food production, health, and use of land and the environment."

"CSIRO research has confirmed that Australia is particularly vulnerable to climate change. The impacts on the economy are projected to be significant and widespread."