Whether we know it or not, humanity is now conducting a vast experiment with the planet's climate, taking us all into uncharted territory. The key to this experiment lies in the vast tracts of rainforest that have remained unchanged for millions of years, or at least so we thought. The prevailing belief has always been that the world's rainforests, such as those in the Amazon Basin, long ago reached a steady state: growth balanced by decay, so at any one time, the carbon being locked up equals the carbon being released. Recent research using sonic anemometers and gas analysers has shown this to be far from the truth. The rainforests in the Amazon Basin are in fact growing at an astounding rate.

Carbon sinks

Carbon dioxide is one of the basic building blocks from which plants are made; it is in effect their food. The rainforest's increase in growth rate is its response to the 30 per cent increase in global carbon dioxide levels that has occurred since the start of the industrial revolution. This new growth has had the effect of buffering us from the worst effects of our carbon emissions, but in the process we are gradually building up a huge carbon reserve. The 5000 million hectares of forest in the Amazon Basin alone are sequestering carbon equivalent to three-quarters of the emissions from all the cars in the world - but the question is for how long?

The key drawback in locking carbon up in new timber growth is that the process is easily reversible. Many climate models predict that the changes in climate caused by carbon dioxide and other greenhouse gases in the atmosphere could cause droughts and forest fires that would turn the Amazon Basin from rainforest into savannah. This would convert the area from being a net carbon sink into a net carbon source, releasing massive amounts of greenhouse gases back into the atmosphere and triggering a widespread change in the world's climate.

A new model of climate change

Scientists are now being forced to reject their view of climate change as a problem that gradually builds up until we clean up our act, so returning things to 'normal'. In the new model, once we exceed a critical threshold, the planet's ecosystems may begin to amplify rather than buffer climate change, leading to havoc on a global scale. We can be fairly certain it will not be the end of life on Earth, perhaps it may even not be the end for humanity, but our Western free-market economy with its emphasis on globalised distribution systems is likely to be the first casualty.

In the light of recent evidence, our current emissions target of a 20 per cent reduction on 1990 levels by 2010 is looking sadly past its sell by date. The Johannesburg earth summit needs to recognise that a 60 to 80 per cent reduction in emissions is urgently required. This might then allow the developing nations to get through the carbon intensive stage of building the schools, railways and hospitals they urgently need to stabilise their populations without global net emission levels passing the critical runaway point.

Why wait for the Earth Summit?

Achieving a 60 per cent reduction in the carbon emissions from your own domestic situation is not as difficult as you might at first think, and there are a growing number of 'Carbon Calculator' websites that can do the numbers for you easily and efficiently. Here are some ideas to get you well on the wayá

• Make yours an energy saving house Investing in energy efficiency can make massive reductions in your emissions, deliver better returns than many savings accounts, and add to the value of your home. See the energy conservation for your home features in this issue.
• Switch to a green tariff It is now possible (and economic) to buy electricity for all appliances from a renewable source, directly through the national grid.
See the 'Questions and Answers' section in this issue.
• Heat green Space and water heating consumes by far the largest share of a home's energy bill. Consider using solar water heating, passive solar design plus primary fuels such as wood or gas. Also see the 'Heat Pumps' feature in this issue.
• Shop Local Transport related emissions are the fastest growing source of greenhouse gases, relentlessly forced upwards by unchecked globalisation of the world's economies. Shopping local significantly reduces emissions, supports local producers, keeps money in the local economy, and delivers fresher food that needs less packaging and additives.
• Keep your feet on the ground Global air traffic is the fastest growing source of carbon emissions and is set to double by 2015 and triple by 2050. Just one long haul flight from the UK to the US can produce as much carbon dioxide as a motorist driving in the UK for a whole year! There are more attractive holiday destinations in the UK and Western Europe than you could see in a lifetime. Many local people know Majorca better than they know Machynlleth!

Doing the numbersá

Once you try a few of the 'Carbon Calculator' websites, you will find that they don't always give the same answer. They all do the addition well enough, it is the initial assumptions and the 'weightings' given to the different inputs which causes their answers to diverge. Clearly 'Carbon Calculators' are an important area for independent research, free from commercial bias. We hope to tackle this further in a future Clean Slate article - we would welcome your findings!

Carbon Calculator websites include:
www.carboncalculator.org
www.ecologyfund.com/registry/ecology/res_bestfoot.html
www.bestfootforward.com/footprintlife.htm
www.changingclimate.org/index.asp