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Abrupt Climate Change

Page history last edited by David Bright 15 years, 1 month ago

 

ABRUPT CLIMATE CHANGE

 

Abrupt Climate Change is a rather indeterminate expression; we could use alternatives such as dangerous, sudden or runaway climate change, passing the climatic tipping point, etc. Definition may also be rather imprecise, partly because of the difficulty in deciding what timescales we should use. Should we measure speed of change in terms of decades, centuries or millennia? And, in the end, would any of these measures embody any real significance? If our own actions were to plunge mankind into an inescapable progression of violent climatic disasters, timescales would become irrelevant.

 

On balance, public opinion now understands that driving global temperatures upwards risks further accelerating global climatic effects already obvious to us all. Common sense also appreciates that all plant and animal species (including humanity itself) have only limited tolerance to major changes in their environment. Politicians are belatedly coming to accept that uncontrollable climate change, which would threaten the very foundations of human civilization, must be avoided at all costs.

 

Current scientific reports suggest that powerful natural feedback processes are well established in a number of critical geographical areas. Each of these processes is making abrupt climate change more likely. The most prominent are:

 

  • Marine Ice Sheet InstabilityThe current retreat in arctic ice cover is reinforcing rapid melting and rising temperatures at high latitudes. Ice shelves in Antarctica are also becoming affected by the effects of rising sea temperatures.

 

  • Arctic and Boreal Ecosystems  Widespread warming of ancient permafrost and the drying out of northern peatland and bogs risks catastrophic gas release from very large methane and carbon dioxide deposits.

 

  • Methane Hydrate Destabilisation  Significant warming of methane hydrates in shallow arctic waters is already suspected, and this could create further massive releases of methane gas.

 

  • Desertification and Megadroughts  Trends towards hotter, drier conditions in the subtropics, intensive agriculture and widespread destruction of rainforests threaten to expand land areas of reduced or negligible fertility, with serious potential effects on regional weather patterns and the global carbon balance.

 

If all these  processes become firmly established, global average temperatures will inevitably rise well above 2 C (compared with preindustrial levels). Such increases would be extremely dangerous, since abrupt and irreversible climate change would then become highly likely. The adverse consequences for human civilisation of such an event are impossible to predict, but would undoubtedly be severe and widespread.

 

Effective measures to limit carbon emissions worldwide are therefore a key focus for international action. Intergovernmental negotiations now well under way are expected to produce a major new agreement in Copenhagen this autumn.

 

 

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