COLUMN-Climate change: what we do and don't know-Gerard Wynn - Reuters Africa

(The author is a Reuters market analyst. The views expressed are his own.)

By Gerard Wynn

LONDON Jan 30 (Reuters) - The public profile of climate change has slipped as a global economic downturn presses, but that could usefully spur new efforts to narrow the uncertainty that remains over the risks posed by global warming.

The need for clarity has grown for renewable energy in the wake of new fossil fuel and especially shale gas finds which threaten to undermine the energy security case for low-carbon alternatives.

Manmade greenhouse gas emissions are probably responsible for a definite global warming in the past three decades, a tinkering with the world's climate which seems dangerous and demands a response.

But even that basic assertion is qualified, and that's just the start: climate science deals in uncertainties which include the amount of future warming, regional impacts and so-called tipping points.

Complicating the message, not all the world is warming, and where it is, this may have a beneficial effect in the short term especially in cooler areas.

That leaves space for sceptics. Some 16 scientists doubted any urgency writing in the Wall Street Journal last week, on the basis that the Earth hadn't warmed relentlessly since 1998, a very hot year in the long-term record.

Following is a review of the latest science, of what we do and don't know, drawn from visits to Britain's two main research centres and conversations with scientists and sceptics.   Continued...