From the 1999 Reith lectures, by Anthony Giddens

Original: see

This quote comes from the 1999 Reith lecture, by Anthony Giddens, where he is primarily talking about risk.

Or consider where we stand with world climate change. Most scientists well versed in the field believe that global warming is occurring and that measures should be taken against it. Yet only about 25 or so years ago, orthodox scientific opinion was that the world was in a phase of global cooling. Much the same evidence that was deployed to support the hypothesis of global cooling is now brought into play to bolster that of global warming - heat waves, cold spells, unusual types of weather. Is global warming occurring, and does it have human origins? Probably - but we won't, and can't, be completely sure until it is too late.

He provides no references (well, its only a lecture) so detailed analysis is difficult.