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Friday, October 14, 2005

Abrupt climate change

According to Nature magazine's in focus on Climate Change:

"A change in global climate has been described as the greatest current threat to humanity. The fierce debate over how we should meet that threat is constantly stoked by researchers' efforts to understand more about how our climate works, and how exactly we are altering it. Here looks at the changing political and scientific climate in this emotive arena."

Recent research articles in Nature point to a growing consensus among climatologists, using many different data sources including satellite data, weather balloons and climate models. Not only is there agreement that global climate change is real, but independent estimates of the rate of global warming based on these different data sources and methods are starting to agree as well, with rates from 0.09-0.2 degrees Celcius per decade.

More alarming is the possibility of abrupt climate change. This can occur when initial global warming creates the opportunity for positive feedback loops, where more warming triggers new events that create more warming or more greenhouse gases. Three examples of such feedback loops that are occuring are:
  • The shrinking polar ice in the arctic is exposing more dark open ocean, which absorbs much more sunlight then the reflective ice it is replacing. This increase absorption causes further rises in ocean temperatures and thus further decline of the polar ice caps. This process is likely to increase the rate at which the polar ice caps are melting, causing still greater rises in temperature and sea levels worldwide.

  • Increasingly hot and dry summers have in recent years caused widespread forest fires in the USA, Australia and this year in Portugal and Spain. These forest fires release a lot of carbon dioxide into the atmosphere, thus accelerating global warming, and causing still hotter and drier summers in the future.

  • Increasingly hot and dry summers, even without fires, have also caused many agricultural crops in Europe to wilt, dry out and sometimes die completely. During this process a huge amount of carbon is released as CO2 into the atmosphere. It has been calculated that in this year alone, as much carbon was released by dry crops in Europe, as was stored by crops in the last 4 years.

These kinds of positive feedback loops could lead to a runaway process whereby even if we cease all human-caused production of greenhouse gases we would still experience the end-game of global climate change -- whatever that may be. Certainly it is likely to involved the complete disappearance of the arctic polar ice and a large increase in worldwide ocean levels. As well we should expect more powerful hurricanes, more forest fires and huge changes in the fauna and flora planet-wide, including the range and distributions of many species.

If the runaway process scenario is correct, than these changes could all occur very abruptly. Even if is not the case, we should expect this century to be the last nice one for humankind for a long time. Taking this scenario together with the fact of diminishing global oil supplies, and you have a recipe for economic paralysis and disaster if the status quo continues. The only good thing is that we know about all of this in advance. Thanks to solid scientific research that is growing more certain and dependable by the day. We are in a position now that we have enough information to act. So lets face this challenge while we are still in good nick! Lets start acting now!


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