I should probably start by saying that I am not an expert on what follows. An interested amateur can get to pick up quite a lot of useful information, but some of it may well be wrong. Anyway, here goes:
I did a blog on climate change only a fortnight ago, but make no apologies for returning to the subject so soon - it is the biggest challenge mankind faces, and so far there is no sign of an even halfway-adequate response. If you read that one (and if you didn't, it's still there - just page down a bit) then you will know it was quite apocalyptic about the prospects for the human race in a warming world. I didn't go into too much detail about how the apocalypse would manifest itself, so I think it's time to do that. There are still plenty of people whose attitude is "A mediterranean climate in Britain? Bring it on!".
Leaving aside the strong possibility, mentioned in that other article, that we would end up no warmer - and maybe even colder - on account of the loss of the Gulf Stream, there's more to getting warmer than just hot summer days and no snow in winter. Plants and animals that are happy with the conditions we have now may be unable to survive as conditions change. Rainfall levels will change - they already have, haven't they? Crops won't grow any more. Pity the poor farmer who has to change his whole way of doing things every decade or so - who in this country knows how to grow olive trees?
Actually, trees will have the biggest problem, due to their long life-cycle and to being tied to one spot. A tree species can only 'move north' by having its seeds fall in areas north of the line which used to mark its furthest limit of growth and have them germinate successfully. If global warming gets into runaway mode, the southern border of viability may catch up with the northern border of where the newly-growing trees have got to. And trees, plants and animals all have a problem when their 'northern border' hits the sea.
None of that applies just to the UK, of course. Taking a wider perspective, we also need to look at rainfall patterns. They're going to change, sometimes dramatically, and probably not very predictably. Places that have been used to rainfall will find themselves drought-stricken; places that have been drought-stricken may get rainfall. That last isn't necessarily all good news, as there are no river systems in place to cope with all that water. Topsoil may well be lost in large quantities. The developing world, being mainly in the tropics and being least able to cope with the unexpected, will be hardest hit. There will certainly be mass starvation, which in turn will lead to severe instability, many failed states and hordes of refugees battering at the gates of Europe and other developed countries.
The effects of warming are greater in the polar regions, with the result that much of the world's ice is already melting fast. That is, of course, bad news for sea levels, which are due to rise by amounts which vary according to the commentator from a few millimetres to twenty metres. Goodbye Tuvalu, Vanuatu, assorted island communities and about half of Bangladesh. About a third of humanity lives near a coast and may have to move. At the other end of the height scale, the glaciers in the Andes, the Himalayas and other high mountain ranges are melting too, adding their bit to sea-level rises, but doing something worse too. Many of the great rivers of the world are fed during summer by glacial meltwater. No glaciers and the rivers become seasonal. Parts of Peru are already in difficulties for drinking water. The Amazon basin is fed from the Andes. Pakistan, Bangladesh and large swathes of northern India will dry up and blow away if the Indus, Brahmaputra and Ganges go. See Mark Lynas's excellent book High Tide: News from a Warming World for more on this.
I have already touched on the problems all species will face as their habitats change. As the world warms further, more and more of them will be unable to cope and die out. Every species has its place in a food chain; what do you do when your food supply is extinct? Or when the lake you live in dries up? The more gaps that appear in the food chain, the harder it becomes for the species that survive to hang on. In the previous blog I said that 250 million years ago when the world experienced a sudden 6 degree warming, 90% of the species then existing died out. That probably scared some of you and I apologise, for I got it wrong. The figure was actually 95%. Life itself came perilously close to dying out. Kids, don't try this at home.
Link to the Tyndall Centre for research on and responses to climate change.
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