The Greenhouse Effect is a natural control on the Earth's climate. It is caused by the presence of certain gases in the atmosphere, which absorb heat radiated from the Earth's surface, and keep the atmosphere's temperature in a range that can support life as we know it. The main gases involved are water vapour, carbon dioxide and methane. These and some other gases are known as greenhouse gases. Without greenhouse gases the average temperature of the atmosphere would be about 33°C lower.
However, for the last two hundred years or so, levels of carbon dioxide and other greenhouse gases in the atmosphere have increased above natural levels. The table compares levels of carbon dioxide and methane measured in 1850 with those measured in 1990.
| Greenhouse Gas | 1850 level (ppm*) | 1990 level (ppm) | Increase in concentration (%) |
|---|---|---|---|
| Carbon dioxide | 280 | 350 | 25 |
|
Methane |
0.75 | 1.7 | 127 |
| *ppm = parts per million. A level of "280 ppm carbon dioxide" means that of every million molecules of air, 280 are carbon dioxide molecules | |||
Most of this recent increase in carbon dioxide in the atmosphere is due to burning of fossil fuels (petrol, diesel, coal etc) to generate electricity, for transport (cars, buses, trains, planes etc) and other purposes. Abundances of other greenhouse gases have also increased. For example, increases in methane in the atmosphere come from rotting vegetation in rice paddies and land fills, from coal mining and extraction of crude oil and natural gas, and from the digestive processes of grazing animals such as sheep and cattle.
Release of additional greenhouse gases into the atmosphere is undesirable because it may be contributing to the Enhanced Greenhouse Effect. Many scientists (although not all) believe that the Earth's climate may warm up because of increases in the levels of greenhouse gases. If this happens, the effects may be very serious in many parts of the world. These effects may include rising sea levels flooding low lying land, and increased severity and frequency of "unusual" weather events such as cyclones or droughts.
Although the Enhanced Greenhouse Effect is not yet proven to exist, many people believe that it is now time to act to reduce the amounts of greenhouse gases in the atmosphere.
There are two basic ways to do this. One is to establish "sinks" for greenhouse gases. Sinks are means of removing these gases from the atmosphere, and the most effective way is to plant trees. Actively growing trees remove carbon dioxide from the air and "fix" it as wood and leaves.
The second method is to reduce "emissions", or to cut down the amount of greenhouse gases that we release or "emit" to the atmosphere. This usually involves using less energy or energy conservation, so that less fossil fuels are burnt, and less carbon dioxide is produced.
There are many ways in which energy can be saved. Perhaps you can think of ways you and your family can practise energy conservation and help reduce greenhouse gas emissions.
Henty mine obtains its electrical power from the State power grid, supplied via overhead transmission lines. Nearly all the electrical power generated in Tasmania is hydro-electric power, generated by Hydro Tasmania. Hydro-electric power generation does not involve any combustion of fossil fuels such as coal or diesel, but rather the energy is derived from the gravitational potential energy of water stored high in lakes and dams in mountainous regions. This means that Greenhouse gasses are not produced in generating the electric power used at the Henty Mine.
To find out more about hydro generation of electricity visits the Hydro Tasmania web-site.
Lake Henty, an artificial lake formed as part of Hydro Tasmania's Anthony Power Scheme.
