Climate change danger is real

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I MUST have missed the factual reporting of the latest IPCC report on climate change in last week’s Scotland on Sunday. Gerald Warner’s article also failed to supply the correct details. He’s right that the ability of politicians to edit (but not alter) the science in the report can amount to political massaging. So let’s start with facts that no-one questions. Since pre-­industrial times the CO2 concentration in the atmosphere has increased by 40 per cent. If this trend continues 
it will have doubled by 2050. Climate change deniers have had to accept these increases are almost entirely man-made, so they’ve moved on to even more shaky territory.

Not to let the facts spoil a good argument, Gerald claims that water vapour accounts for 95 per cent of the greenhouse effect and CO2 3.6 per cent. If you want to oversimplify in this way, the actual figures are 50 per cent water vapour, 25 per cent clouds, 20 per cent CO2 and the rest other greenhouse gases. However, since CO2 and water vapour absorb in overlapping parts of the spectrum, and some of the overlap already absorbs 100 per cent of the radiation, this is no way to do reliable arithmetic. His claim that 0.28 per cent of the greenhouse effect is man-made is just plain silly. The greenhouse effect keeps the Earth’s surface about 21C above what it would otherwise be and global warming has added about another 0.9C to this. I make that a 4 per cent increase but what is important is not the percentage but the size of the temperature increase. We’re nearly halfway to a dangerous temperature rise and still increasing our CO2 emissions worldwide.

What about the pause in surface temperature warming over the last 15 years? It looks like a lot of the extra heat has gone into the oceans instead but the IPCC report has correctly used what Gerald calls “hedge-
betting terminology”. It’s funny to complain about a lack of scientific honesty and then grumble when you get it. The science is complicated and our models are far from perfect but they’re the best we have. Should we be worried? Yes, because the effects of CO2 emissions will take centuries to dissipate even if worldwide emissions were already being reduced. Meantime, Gerald might do better to stick to tilting at windmills.

Chris Mullins, Edinburgh