Now is the time: we must find a global response to this most global of problems.

• Author: Ki-moon, Ban
• Position: Environmental problems and solutions

The lines were drawn as the industrialized nations of the Group of Eight gathered in Heiligendamm, Germany on 6 June 2007. The forces mustered to fight global warming were divided into competing camps.

Germany and the United Kingdom sought urgent talks on a new climate change treaty, to go into effect when the Kyoto Protocol expires in 2012. They spoke of stiff measures to curb carbon emissions and limit the rise in global temperatures to 2° Celsius over the coming four decades. The United States, offering an initiative of its own, opposed what it considers to be arbitrary targets and timetables.

As I travelled to Heiligendamm that day, my chief concern was to ensure that all these different and potentially conflicting initiatives come together in a multilateral process within the United Nations framework. And that is precisely what was achieved at the summit. The eight Governments agreed that the United Nations climate process is the appropriate forum for negotiating future global action, accepted their responsibility to act on emission reductions and eventual cuts, and called for closure by 2009 on a global agreement, under the United Nations Framework Convention on Climate Change, to ensure that there is no gap between future approaches to climate change and the expiry of the Kyoto Protocol in 2012.

With this breakthrough, the Group of Eight recognized that certain basic facts are beyond dispute. First, the science is clear. The earth's warming is unequivocal; we humans are its principal cause. Every day brings new evidence, whether it is the latest report on retreating glaciers or the recent discovery that the Antarctic Ocean can no longer absorb carbon dioxide (C[O.sub.2]). Think of that: the world's largest carbon trap, filled to capacity.

Second, the time for action is now. The cost of not acting, most economists agree, will exceed the cost of acting early, probably by several orders of magnitude. The damage Hurricane Katrina inflicted on New Orleans may or may not have something to do with global warming, but it is a useful caution nonetheless on the financial and social perils of delay. It is equally evident that we can no longer afford to endlessly parse our options. Global greenhouse gas emissions have to start to come down. Carbon-trading is but one weapon in our arsenal, even if it does range among the most effective policy solutions. New technologies, energy conservation, forestry projects and renewable fuels, as well as...