This openDemocracy debate starts from the point that man made climate change is a challenge that requires a political response.

It is about the politics, not the science of climate change. Specifically, it is about the politics in the run up to the July the summit of leaders of the G8 (richest industrialised countries plus Russia), and beyond.

The British government, which is hosting the G8 summit, and goes on to hold the presidency of the EU, the world's largest trading block, in the second half of 2005, says climate change is the most serious long term threat facing humanity.

So what are the British doing? What are their partners doing?

Today oD publishes a call to action by David King, the chief scientific advisor to the UK government in which he argues cimate change presents real and present danger requiring urgent and committed action.

As Sir David notes, there is an influential body of opinion that says climate change is not a problem. Are any of their criticisms justified?

oD also publishes today a comment by a critic who points to what he sees as important evidence, both old and new, that needs to be taken into account. Benny Peiser argues on the basis of evidence and reasoned judgement that is open to scrutiny. Please post your response to his arguments and his evidence in the forum.

In some cases - if not necessarily in this one - the claims of climate sceptics are easily discredited by a short examination of the evidence. In the UK, for example, a scientist and formerly well known TV personality called David Bellamy published a letter in the 16 April edition of New Scientist magazine arguing that worldwide glaciers were actually growing and that, therefore, talk of global warming was nonsense.

Anyone with online access could check the basis of his claims in two or three minutes, as I did on the day his letter was published by going to the web site of the World Glacier Monitoring Service and checking the most recent mass balance data. (I wrote to New Scientist, who kindly acknowledged and published an excellent refutation by Philip Ward. George Monbiot has gone further into the matter in his column in today's Guardian).

It is good to see reason and evidence being used in the forum for this debate too. C Austin, for example, has caught someone out (scroll down here).

The efforts of C Austin and many others will not, of course, stop those who continue to spread lies and attempt to sow confusion. But if no efforts are made we will all be in trouble, and not just because of climate change.

Caspar Henderson