Climate change and especially global warming has become the overriding environmental concern since the 1990s. Most discussions about the environment end up pointing out that, despite all other indicators that may show us doing better and better, we still have to change our current lifestyle dramatically because our way of life is now changing the climate and causing global warming.

In the words of the President's Council on Sustainable Development: “The risk of accelerated climate change in the next century has emerged as one of the most important issues we will face as we seek to achieve our sustainable development goals.” In their 2000 edition, Worldwatch Institute concludes that stabilizing the climate along with stabilizing the population growth are the two “overriding challenges facing our global civilization as the new century begins.” Likewise, UNDP sees global warming as one of the two crises that nudge humanity ever closer to “the outer limits of what earth can stand.” Global warming is, according to former President Clinton, “one of the two or three major issues facing the world over the next 30 years.” Head of the George W. Bush EPA, Christine Todd Whitman, has called global warming “one of the greatest environmental challenges we face, if not the greatest.” And the opening remark on their homepage proclaims that “Greenpeace has identified global climate change as one of the greatest threats to the planet.”