Carbon dioxide, or CO2, is one of the gases that contributes to climate change. There are other greenhouse gases including methane, nitrous oxide and CFCs, and these are often expressed in ‘CO2-equivalents’ for ease of explanation. If you’re carbon neutral it means that you’ve managed to balance the amount of CO2 you produce, against the amount that you’ve ‘saved’ or ‘offset’. So your net production of CO2 is zero.
In practice it means that your CO2 emissions have been measured and reductions have been made; with your remaining emissions balanced against investment in renewable energy or other activities which absorb CO2or prevent the additional production of CO2 emissions and consequently reduce the amount in the atmosphere.
Find out more about being carbon neutral.
Offsetting involves buying ‘carbon credits' - investing in projects that are reducing CO2 emissions around the world, such as renewable energy. This investment (buying carbon credits) funds the start-up and running of emission-saving projects.
Independent teams of scientists have analysed more than a century's temperature records and have found that the average air temperature at the Earth's surface over the past century has risen by nearly 0.74°C +/- 0.18°C (source: Defra ).
The first five years of the twenty-first century, along with 1998, have been the hottest on record - and quite possibly warmer than any others in the past millennium (source: The Rough Guide to Saving Energy).
As well as seeing the temperature changes, scientist have found other signs, such as thinning Arctic sea ice, melting glaciers and changes in plant and animal life. Such factors confirm that the Earth is warming up.
For more information download the IPCC's Fourth Report Synthesis (Nov 2007).
A degree or so of warming may not sound like much, but the impact is great. Plus, the rise has been steeper in certain locations, including the Arctic.
Consistent increases in temperature will lead to a rise in serious weather events, including droughts, floods and hurricanes. It will also affect food production, human health and the variety of plant and animal life (biodiversity).
Humans have changed the Earth's climate by adding enormous amounts of carbon dioxide and other greenhouse gases to the atmosphere over the past 150 years. The main source of these additional greenhouse gases are the combustion of fossil fuels, deforestation and decay of biomass, agriculture and waste.
Greenhouse gases absorb heat radiated by the Earth and release only part of this heat into space; they retain the rest, resulting in a warmer atmosphere.
Over the course of 4.5 billion years, the Earth’s atmosphere has gone through many temperature swings. These swings are the result of everything from volcanic eruptions to changes in solar output and variations in the Earth’s orbit.
So how can we be sure that the current warming isn’t ‘natural’? Well, that very question has been tackled by the Intergovernmental Panel on Climate Change (IPCC (opens in a new window) a team of more than 2,500 scientists.
Back in 1995 the IPCC announced: ‘The balance of evidence suggests a discernible human influence on global climate.’
By 2001 the evidence had strengthened: ‘There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities.’
Early in 2007 the IPCC reiterated: ‘Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns.’
(Source: IPCC Working Group I Report ‘The Physical Science Basis’: Summary for Policymakers)
One way scientists support these claims is to look at the changes taking place and compare them with what you would expect from non-greenhouse causes.
All humans, as well as plants and animals, will be affected in one way or another by climate change, but the effect will vary depending on where they are - some places will experience drought, while others may flood.
Some scientists predict a rise of around 40 cm in the sea level by 2100 as a result of warming oceans and melting ice caps and glaciers. This will also reduce white-ice cover which reflects heat back into the atmosphere. Such changes to our oceans will cause many coastlines to change, forcing people to move. Some islands will be completely covered, and there will be an increase in the frequency of hurricanes and coastal storms.
Where droughts occur there will be less water for drinking and irrigation. And the rising sea level will increase the amount of salt that will contaminate ground water in coastal areas.
It is likely that the worst affected areas for drought will be the Middle East, Australia, the Indian subcontinent and Northern Africa. Less water and increases in temperature will also lead to changes in crop cycles and/or crop yields (for example cereals) in Africa, Australia, India and the Middle East.
Warming temperatures will also help the spread of airborne diseases, like malaria and dengue fever. Low lying developing nations will be at the greatest risk of these diseases.
The rise in temperatures and decrease in rainfall could mean that the rainforests, which absorb CO2, may shrink even more rapidly than they are currently, meaning thousands of the Earth's species risk extinction.
The Kyoto Protocol is an agreement (sponsored by the United Nations) between countries to reduce their greenhouse gas emissions. The treaty was finalised in Kyoto, Japan, in 1997, but it didn't become international law until late 2004. By December 2007, 174 states that includes most of the industrialised world had ratified the treaty. Australia the last to sign but the significant exception is the US.
Under Kyoto, industrialised nations have pledged to cut their yearly emissions of carbon by varying amounts, averaging 5.2% by 2012, as compared with 1990. That equates to a 29% cut. However, the protocol didn't become international law until more than halfway through the 1990-2012 period, by that point, emissions had risen substantially in many countries.
The effects of climate change aren't linear, so the worry is that at some stage a ‘tipping point' could make global warming uncontrollable.
Since there are a range of different triggers, there is no single temperature agreed upon as a tipping point for the Earth as a whole. However, one goal adopted by the European Union, as well as many environmental groups, is to limit the global temperature rise to no more than 2°C (3.6°F) higher than pre-industrial levels.
No. Even though we can't stop the effects of greenhouse gas emissions, by acting now we can avoid major changes in the Earth's temperature. The scientific consensus is that greenhouse gas emissions need to decline over the next 10-20 years in order to make a difference. Worryingly, they are still rising.
Carbon dioxide is the main culprit of climate change. Every reduction in CO2 emissions will help to slow the rise in the Earth's temperatures. Every action, like using energy-saving light bulbs and renewable energy, will help to improve the health of our environment and of our future.
Only in the very long run - the human influence on the greenhouse effect could last the better part of this millennium. So, assuming that it takes a century or more for humanity to burn through our remaining fossil fuels, it will take hundreds more years for those greenhouse gases to be absorbed by the Earth's oceans, vegetation and soils as part of the natural carbon cycle.
As individuals we can each make changes to the way we live, to reduce the greenhouse gas emissions that we’re personally responsible for.
Visit What Can I Do? for tips on how you can do this.
(Source: ‘The Rough Guide to Saving Energy and Reducing Your Carbon Footprint, in association with Sky’ (opens in a new window))