By Alex Kirby
BBC News Online environment correspondent
The world has barely begun to recognise the danger of setting off rapid and irreversible changes in some crucial natural systems, a scientist says.
Antarctic ice shelf: One of the Earth's critical locations
Professor John Schellnhuber says the most important environmental issues for humans are among the least understood.
He told a briefing in Sweden that the Asian monsoon was one of the "tipping points" that could change very quickly.
He said a better understanding of the risks was as important as the programme to prevent collisions with asteroids.
Professor Schellnhuber is research director of the UK's Tyndall Centre for Climate Change Research.
He was speaking at the EuroScience Forum in Stockholm, at a briefing by the International Geosphere-Biosphere Programme entitled Beyond Global Warming: Where On Earth Are We Going?
Professor Schellnhuber said 12 "hotspots" had been identified so far, areas which acted like massive regulators of the Earth's environment.
If these critical regions were subjected to stress, they could trigger large-scale, rapid changes across the entire planet. But not enough was known about them to be able to predict when the limits of tolerance were reached.
"We have so far completely underestimated the importance of these locations," he said.
"What we do know is that going beyond critical thresholds in these regions could have dramatic consequences for humans and other life forms."
One example of a hotspot was the North Atlantic current, the ocean circulation pattern responsible for bringing warmer air to northern Europe, the collapse of which could lead to a very large regional climate shift.
Others were the West Antarctic ice sheet, the Sahara desert, and the forests of the Amazon basin. Yet another hotspot, Professor Schellnhuber said, was the Asian monsoon system.
He told BBC News Online: "Modelling has shown that if air pollution and land use change, this could alter the albedo, the reflectivity, of the land.
"This in turn could weaken or even suppress the monsoon, and there is evidence that several times in the last few years it has in fact been weaker.
Changes to the monsoon could affect millions of people
"We're investing too much in things like improving the accuracy of our weather forecasts, while the really vital elements in the Earth's system are the unstable phenomena like the monsoon.
"We should have a much better understanding of these tipping points, and we have to do everything we can to stop short of triggering these instabilities.
"That means we have to know where they are, and they've been off the radar screen for far too long.
"Scientists have begun to realise that change could be sudden, not gradual - in some cases it could happen within a few decades."
Professor Schellnhuber urged a coordinated global effort to improve understanding and monitoring of Earth's "Achilles' heels".
He said: "Such an effort is every bit as important as Nasa's valuable asteroid-spotting programme designed to protect the planet from collisions.
"If we can afford to gaze up at the sky looking for asteroids, we should be able to watch our own planet with as much care."