David Attenborough wrote a powerful piece on global warming exclusively for Radio Times ahead of world leaders meeting to debate the issue in Durban. Now Jonathan Porritt and Nigel Lawson take sides for and against Attenborough's points.
While a clique of armchair pundits continues to peddle scepticism and ill-informed prejudice, scientists observing real-time phenomena around the world point to one inescapable conclusion: the climate is changing faster than anyone imagined possible even a few years ago.
When a personal testimony comes from David Attenborough, its impact is enormous. Only when he felt the evidence was robust did he declare his opinion (a few years ago) that the climate was changing, and it was changing because of man-made emissions of greenhouse gases. I hope his words will help dispel some of the doubts as to the urgency with which we must address accelerating climate change.
And there's still so much to be done - on energy efficiency, investment in renewables, research into storage technologies and so on.
One simple truth is that population growth is a multiplier of every one of today's converging sustainability pressures, including climate change. We roughly know how much CO2 and other greenhouse gases we can afford to put into the atmosphere and still avoid runaway climate change. Managing that "quantum" depends both on the number of people and emissions per person.
Every country needs a population strategy, including the US and the UK - the only OECD countries still to have growing populations.
I'm sure that David (as a fellow patron of Population Matters) would be advocating huge new investments in family planning programmes in key countries to help slow population growth.
Jonathon Porritt CBE is a Founder Director of Forum for the Future
Sir David Attenborough is one of our finest journalists and a great expert on animal life. Unfortunately, however, when it comes to global warming he seems to prefer sensation to objectivity.
Had he wished to be objective, he would have pointed out that, while satellite observations confirm that the extent of Arctic sea ice has been declining over the past 30 years, those satellite observations show that, overall, Antarctic sea ice has been expanding over the same period.
Had he wished to be objective, he would have pointed out that the polar bear population has not been falling, but rising.
Had he wished to be objective, he would have mentioned that recent research findings show that the increased evaporation from the Arctic Ocean, as a result of warming, will cause there to be more cloud cover, thus counteracting the adverse effect he is so concerned about.
Had he wished to be objective, he would have noted that, while there was indeed a modest increase in mean global temperature (of about half a degree Centigrade) during the last quarter of the 20th century, so far this century both the UK Met Office and the World Meteorological Office confirm that there has been no further global warming at all.
What will happen in the future is inevitably unclear. But two things are clear. First, that Sir David's alarmism is sheer speculation. Second, that if there is a resumption of warming, the only rational course is to adapt to it, rather than to try (happily a lost cause) to persuade the world to impoverish itself by moving from relatively cheap carbon-based energy to much more expensive non-carbon energy.
Lord Lawson, former Chancellor of the Exchequer, is a member of the Global Warming Policy Foundation
Read David Attenborough's personal plea for the world to take on global warming
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