Of all the multitude of threats facing the global environment, none are greater than the changes taking place in the very atmosphere of the planet. In the recent years, painstaking scientific work has demonstrated that man-made chemicals are destroying the ozone layer which shields all life from the lethal ultraviolet rays of the sun. Scientists are also now agreed that pollution is warming the world's climate, threatening to bring about changes unparalleled in the history of human civilization, raising sea levels and devastating food production worldwide. In 1988 the world conference on the changing atmosphere reported that these dangers rank second only to nuclear war. The Vienna convention on the protection of the Ozone layer and its Montreal Protocol are the first truly global agreements on the protection of the environment. They are also probably the first ever global risk-management treaties, for they took pre-emptive action to prevent an emerging problem reaching crisis point by agreeing a series of far-reaching and costly controls in advance of the absolute proof of cause and effect that might come too late to avoid irreparable damage.