Gaia Theory

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James Lovelock

February 2003

James Lovelock is one of the world's truly extraordinary scientists. For the last 35 years, he has worked independently from home, where he has consistently produced world-class science. His electron capture detector was the first to show us that low levels of pesticides were present throughout the natural world. For this he is credited with inspiring the green movement of the 1960s. He also discovered that CFCs were accumulating in Earth's atmosphere. From this we learnt that we were putting the protective ozone layer in jeopardy. But most important is his revolutionary theory, Gaia. His metaphor that Earth behaves like a living organism couldn't be more profound in its implications for how we live on Earth. In January 2003, Lovelock was made a member of the Order of the Companions of Honour – a fitting tribute to a tireless worker. For Lovelock, this was confirmation that Gaia has made it through the establishment gates. Here, he tells us how his Gaia Theory was conceived.

Astronomers sometimes scare us by reminding that the Sun is due to swell up into a red giant star that will burn Earth to a cinder. This is true but it won't happen until another five billion years have passed. What astronomers rarely mention is that this inflammation is no sudden change but the inevitable end of a long, long fever. Our Sun started to warm up soon after its birth 4.5 billion years ago. So far it has only warmed by about 30% but the rate of warming will steadily increase until the red giant stage marks the end of its active life. A 30% warm up doesn't sound much until you realise that it's equivalent to about a 25ºC rise of temperature for the Earth's surface. Or to put it in more familiar terms, seven times the difference between an ice age and now. If the Sun was delivering a third less heat when life started four billion years ago how on earth was it warm enough for it to flourish? alternatively, if it was warm enough then why are we not now intolerably hot?

One answer to this puzzling question about Earth's temperature, and why it has always been comfortable for life, is that maybe our planet has the capacity to keep its temperature right for life. Just as we keep our core temperature close to 37ºC regardless of whether it is freezing outside or torridly hot. Temperature is not the only property of Earth that somehow or other stays right for life. Have you ever wondered about the air you breathe and why the oxygen is 21%, not 50% or 10%? It so happens that if the oxygen were above 25% fires would be so fierce that few if any trees would survive and if it were below 15% it would be impossible to start a fire. 21% is just right.

Many other properties of Earth, like the cloudiness of the skies and the abundance and quality of rain, are uncannily right for life. So many of them in fact that it's reasonable to ask if all these things can be right by chance?

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