'100 days to Copenhagen. 100 months to get the world onto a declining emissions trajectory. 100 years to determine the destiny of the human species. Such powerful, symbolic numbers. And the way we frame the timescales involved in climate change is indeed hugely significant.  

I have just been looking at Oxfam's latest campaign to raise people's awareness of the relative imminence of climate change in terms of impacts on their own lives, represented through images of a family eating their evening meal under water in full diving gear. Deliberately 'sensational', unapologetically 'emotional'. And it's not a 'Third World' family, but identifiably 'developed world'.  

Is that the right way to do it? Isn't a campaign of that sort 'playing fast and loose with the science'?  Might it not 'drive people even deeper into disempowerment and denial'?

The dilemma for campaigners today is that we're damned if we do (talk it up, press the panic button, try and bring it home to people as powerfully as possible), and damned if we don't – by remaining calm, measured, reflecting all the uncertainties and nuances of the science as it is today.

It's complicated, both personally and professionally. Unbelievably, I still find myself over-reacting to that small (but hugely problematic) brand of climate deniers. On Any Questions? last week (21 August), I had the dubious pleasure of appearing alongside one such journalist–contrarian called James Delingpole.  He weighed in with the usual tosh about the world not getting any warmer, the 'zealotory' of green campaigners, and the uselessness of wind power as part of any appropriate response from Government. I know I should have just stayed aloof, demonstrated the error of his ways in a low-key, reasoned manner, and trusted to the common sense of listeners to sort it out in their own minds. Fat chance! An undignified scrap ensued, during which I also took time-out to weigh into that army of Nimbies who are still out there doing everything in their power to block the deployment of wind power in the UK. Often using an incredible mish-mash of misinformation and scare stories. And I don't suppose that helped very much either.

But exactly what will it take to persuade people that the Royal Society, for instance, really is a better guide on climate change than controversialists like James Delingpole?

So full marks to Oxfam for using all sorts of different tactics. If you don't like their 'water world images', then have a look at their incredibly powerful 'Suffering the Science' report which came out in June.

As far as hundreds of millions of people in some of the world's poorest countries are concerned, the title of that Report really tells it all. Unfortunately, most of the rich world just doesn’t see it, let alone feel it, quite like that.'

Jonathon Porritt is Founder Director of Forum for the Future