International action to cut greenhouse gases is on the way, a leading British expert on the environment believes.
The Larsen B ice shelf collapse: An "instructive disaster"?
Sir Crispin Tickell, a former diplomat and government adviser, says urgent action is needed because climate change is more serious even than terrorism.
Many in the US administration are "in a state of denial", he says, but other US attitudes on climate are changing fast.
In a speech in Cambridge Sir Crispin says he thinks the world will finally act together to confront the threat.
Speaking in the first of a series of lectures entitled Environment On The Edge, he says the Earth is in an unparalleled situation, because several problems are reaching a critical point simultaneously.
The lectures are organised by the United Nations Environment Programme/World Conservation Monitoring Centre, the British Antarctic Survey, and St Edmund's College and New Hall, Cambridge.
Our problems are taking us into "a no-analogue state", Sir Crispin says, and our ability to influence other species "has given us a profound conceit of ourselves".
The six main threats he believes are pushing the environment to the edge are: population increase; land degradation and waste; water pollution and supply; climate change; energy production and use; and the destruction of biodiversity.
He says: "Our use of other species is coupled with an amazing ignorance of how natural systems work, their awe-inspiring interconnectedness, and our total reliance on natural services.
Warning from the past
"Nothing is more difficult than learning to think differently. The problem... goes to the roots of how we run our society. It relates to our value system.
"In addition to the traditional costs of research, process, production and so on, prices should reflect the costs involved in replacing a resource or substituting for it; and the costs of the associated environmental problems.
More roads "are not the answer"
"There have been some 30 urban civilisations before our own. All eventually crashed."
Sir Crispin argues for the creation of a World Environment Organisation "to balance - and be a partner of - the World Trade Organisation".
He says the understandable desire of most poor countries to follow the industrialised world in raising living standards and joining the consumer culture is in many ways impossible.
He says: "Over the last few years stock market indices may have risen, but the world's natural wealth, measured by the health of its ecosystems, fell by no less than 30% between 1970 and 1995."
Sir Crispin identifies the global division between rich and poor as "a prime and growing source of insecurity for all".
Calling for urgent action on climate change, he says: "Sucking up to car drivers or calling for new airports does not suggest that all politicians have yet understood what is at stake."
To bring about change, he says, "we need three things: leadership from above; public pressure from below; and - usually - some instructive disasters to jerk us out of our inertia".