During the past couple of years our understanding of how the world works has seen a change at least as great as when Nicolaus Copernicus placed the sun rather than the Earth at the centre of the solar system.

Just as in Copernicus' time, this change in our 'world view' is only slowly being recognised as it upsets the prevailing paradigm and power base. Although science has known for over 100 years that burning fossil fuels releases large volumes of locked away carbon which could cause changes in our climate systems, it is only in the past could of years, we have realised just how serious this could actually be.

Whether we know it or not, humanity is now conducting a vast experiment with the planets climate, taking us all into uncharted territory. The key to this experiment lies in the vast tracts of rainforest which have remained un-changed for millions of years, at least so we thought. The prevailing belief has always been that the world's rainforests, such as those in the Amazon Basin have long ago reached a steady state. Growth is 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 a rapid rate. This astounding growth rate is clearly a relatively recent phenomenon, as new growth at such a rate could not be sustained for more than a few decades without reaching physical limits.

Carbon dioxide is one of the basic building blocks from which plants are made; it is in effect their food. This new growth is the rainforests response to the 30% increase in global carbon dioxide levels which have occurred since the start of the industrial revolution. This new growth has the effect of removing the carbon released by burning fossil fuel and locking it away as new timber growth. This has the effect of buffering us from the worst effects of our emissions, but in the process we are gradually building up a huge reserve. The 5000 million hectares in the Amazon Basin alone could re-assimilate 3/4 of the carbon emissions from all the cars in the world - but the question is for how long?

The key drawback in locking carbon up in 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 causes could cause droughts and forest fires which could turn the Amazon Basin from rainforest into savannah. This would convert it from being a net carbon sink into a massive carbon source, releasing massive amounts of greenhouse gasses back into the atmosphere, triggering a widespread change in the worlds climate and in particular warming the oceans.

Beneath the oceans there exists vast amounts of an even more vicious greenhouse gas 60 times more powerful than carbon dioxide. Methane formed from the an-aerobic decay of organic materials falling to the seabeds is held in a semi-solid form as a methane hydrate by the ocean's pressure and low temperatures. These methane hydrates are normally safely stored well below the surface kept solid by the high pressures and low temperatures. However as the seas begin to warm, particularly in the shallow polar waters where it is the low temperature which is the crucial factor, the methane can begin to escape into the atmosphere causing climate havoc on a massive scale.

In the light of this new evidence we must change our 'world view' from the traditional model in which the effects of climate change gradually builds up until we feel uncomfortable about the effects, we then gradually clean up our act and things return to normal. In this new model, once we exceed a critical threshold, climate change can run away of its own accord, fundamentally changing the world's climate. Such runaway effects have occurred in the planets distant past, and are known to have occurred remarkably quickly. At the Palaeocene / Eocene boundary global temperatures leaped by 15 degrees. This is higher than anything humans have ever experienced to date. Things will, of course, return to normal, but the last time this happened, it took sixty thousand years!

It may not yet too late, but we must recognise that there is a critical point, beyond which climate changes will continue of their own accord.

From the geological records, we know such runaway climate events have happened before. We can therefore 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. This may prove to be the ultimate irony as transport related emissions are the fastest growing source of greenhouse gasses, driven relentlessly by unchecked globalisation of the world's economies.

We in the over-developed west are consuming far beyond our share of the planet's ability to deal with carbon emissions. We are taking far more than our fair share, yet are encouraging other developing nations to follow in our footsteps. In the light of recent evidence, our current emissions target of a 20% reduction on 1990 levels by 2010 is looking sadly past its sell by date. The Johannesburg earth summit needs to recognise a 60% to 80% reduction in emissions is urgently required. This could then allow the developing nations to get through the carbon intensive stage of building the schools, railways and hospitals they need to stabilise their populations without our global net emission levels crossing that vital critical point.

The barriers to achieving a carbon-controlled economy are not solely technical or economic. We now know how to generate energy from renewable sources, we can even do in a way which can compete on cost with fossil fuels. But before we can make any realistic comparison between renewable sources and fossil fuels or even nuclear energy, we need to make sure we have a level playing field. There are many hidden subsidies and externalised costs which need to be considered before realistic comparisons can be made. This is particularly true for the nuclear industry. However, once these hidden distortions are remove, there is a clear case for a massive renewable energy construction programme, the like of which the world has never known.

Although the continuing technical improvements and increases in economies of scale in carbon controlled generation are clearly key barriers to achieving the 60% targets are likely to be social rather than technical or economic. These will arise in a number of ways. Firstly we must accept that the visual of wind turbines or solar water heating panels is a small price to pay for our comfortable modern lifestyle. Secondly there will be an important array of lifestyle choices that must be optimised to maximise quality of life, yet minimise the associated carbon footprint. Although the earth summits are clearly rank amongst the most important milestones in human history, we cannot simply sit back and wait for the politician to solve the problems for us, we as citizens and consumers have a vital role to play in developing, testing and replicating low impact lifestyles.

Paul Allen 20 / 11 / 02