Mankind is to blame for global warming and there may be nothing we can do to prevent the scale of the catastrophe that awaits us.

We may be able to buy ourselves a little time to adapt to a rapidly changing climate by attempting "safe" forms of geo-engineering.

But large-scale climate engineering – such as schemes to reflect sunlight from the atmosphere or increase uptake of CO2 by the oceans – could prove more dangerous and destabilising to the planet than doing nothing.

That's because today's climate scientists are in a similar position to 19th century doctors – they simply don't know enough about how the planet works. It may be better to let nature take its course and try to adapt to the consequences.

That's the gloomy view of acclaimed Devon-based independent scientist and environmentalist James Lovelock, writing in the latest edition of the Royal Society's Philosophical Transactions journal, out in October, which looks at whether geo-engineering can avert dangerous climate change.

When it comes to the environment, Prof Lovelock holds a unique position.

The 89-year-old Oxford University professor, who is based at St Giles on the Heath on the Devon/Cornwall border, is best known for his Gaia theory, developed in the 1970s while working for NASA and investigating whether there was life on Mars.

The theory proposes that the Earth and its biosphere act as a highly complex single organism that regulates itself and is, in a sense, "alive".

It was instantly embraced by New Age hippies, who adopted Prof Lovelock as a spiritual guru, but derided by the scientific community.

Three decades on, however, the notion of a dynamic, self-regulating Earth underlies virtually all climate science, although scientists prefer to use the term "Earth system science" than Gaia.

In the years since he first propounded Gaia, Prof Lovelock has alienated himself from the environmental community, first by embracing nuclear technology as the only safe, viable energy source, and then by suggesting ethical living is a waste of time because there is nothing we can do to prevent climate change.

Despite such 'betrayals' of the green creed, whatever this maverick scientist says about the planet still matters, which is why his stark warning about the dangers of geo-engineering has made headlines.

"Our ignorance of the Earth system is overwhelming," he says in his article for the Royal Society.

"Before we start geo-engineering, we have to raise the following question: are we sufficiently talented to take on what might become the onerous task of keeping the Earth in permanent homeostasis?"

Prof Lovelock's article is the contrary voice among a collection of scientific papers published in Philosophical Transactions which say political inaction on global warming is so serious that extreme solutions must be considered.

Methods proposed for artificially altering the climate range from using a constellation of trillions of spacecraft as a sun-shade or dust particles in the stratosphere to reflect solar energy, to "seeding" the oceans with iron particles to stimulate algae which absorb CO2.

Another idea is to send sea spray into the air to make clouds whiter so they reflect more sunlight, in a bid to offset the heat trapped by greenhouse gases.

Researchers from Leeds and Manchester universities say the scheme requires just wind- powered vessels and sea water, and could be sufficient to hold the Earth's temperatures constant for decades.

Meanwhile, scientists at Stanford University believe a two per cent reduction in the amount of sunlight warming the Earth is more than enough to offset a doubling of CO2 in the atmosphere, and suggest it would be possible to deflect sunlight from the Arctic – possibly saving the polar bear and the Greenland ice sheet.

Prof Lovelock last year proposed a system of vertical tubes in the ocean to bring cooler, nutrient-rich water to the surface to encourage algal blooms and CO2 uptake.

In his paper for the Royal Society, he suggests biofuels and food could be sourced from the algae, with the waste products buried deep in the ocean to store carbon.

But he warns that massive geo-engineering schemes could create new problems and says there is little we can do to avert a catastrophe for humankind.

Prof Lovelock says: "The planet is likely, massively and cruelly, to cull us, in the same merciless way that we have eliminated so many species by changing their environment into one where survival is difficult.

"Whatever we do is likely to lead to death on a scale that makes all wars, famines and disasters small."

Until four years ago, Prof Lovelock thought global warming was something that the planet's own self-regulating systems would correct for.

He changed his mind after visiting the UK's top climate institute, the Hadley Centre for Climate Change, in 2004 and hearing the latest data about melting ice, shrinking forests and carbon emissions.

It was, he said afterwards, "terrifying". Prof Lovelock became convinced that the planet's ability to correct itself had been destroyed. The whole system was, he decided, "in failure mode" and while the planet would survive, civilisation as we know it would not.

The result of that visit was his book The Revenge of Gaia, published in 2006. Prof Lovelock now believes that by 2020, droughts and other extreme weather will be commonplace, and by 2040, Berlin will be as hot as Baghdad.

The planet is warming far faster than expected, he says, and the computer climate models used by bodies such as the IPCC – the United Nations Panel on Climate Change – are grossly inadequate.

For example, the IPCC believes global warming will cause the Earth's average temperature to rise by 11.5C by 2100, resulting in a maximum sea level rise of 23ins.

However, geological records show that three million years ago, when the temperatures were 5C higher than present levels, the sea rose by more than 80ft.

So, should we abandon all hope? Not so, says Prof Lovelock. Despite his gloomy outlook, he says humankind can adapt to climate change and make the best use of areas of refuge such as Scandinavia and the British Isles, which will be spared the worst of the heat and drought.

"We have to marshall our resources soon and if a safe form of geo-engineering buys us a little time, then we must use it," he says.

"During the global heating of the early Eocene, there appears to have been no great extinction of species and this may have been because life had time to migrate to the cooler regions near the Arctic and Antartic and remain there until the planet cooled."