The greatest environmental challenge of the new century is global warming. Scientists tell us that the 1990s were the hottest decade of the entire millennium. If we fail to reduce emissions of greenhouse gases, deadly heat waves and droughts will become more frequent, coastal areas will be flooded, economies disrupted. Many people in the United States and around the world still believe we can't cut greenhouse gas pollution without slowing economic growth. In the Industrial Age that may have been true. In the digital economy, it isn't. (2000)

—President Bill Clinton, State of the Union address

This is clearly an issue that we will win on over time because of the evidence. The overwhelming impacts of climate change are becoming more and more visible every day. The problem is: will it be too late? We are a country that emits nearly 25 percent of the world's greenhouse gases. How much damage will have been done before we act?

—Senator John McCain

What is now plain is that the emission of greenhouse gases ... is causing global warming at a rate that began as significant, has become alarming and is simply unsustainable in the long-term. And by long-term I do not mean centuries ahead. I mean within the lifetime of my children certainly; and possibly within my own. And by unsustainable, I do not mean a phenomenon causing problems of adjustment. I mean a challenge so far-reaching in its impact and irreversible in its destructive power, that it alters radically human existence. ... [T]here is no doubt that the time to act is now. (2004)

—Prime Minister Tony Blair