Five Global Warming "Tipping Points"

This National Geographic article looks at 5 localities that are likely to change when we reach a tipping point relevant to that system, where crossing it would cause serious changes in some of Earth's system processes with knock-on effects on others. 

http://news.nationalgeographic.com/news/2009/03/photogalleries/tipping-points-climate-change/index.html 

Firstly, the Amazon Basin, where climate shifts may lead to less rainfall,huge loss of species diversity which would damage the forest's regulation of air quality, fresh water cycle, and atmospheric circulation.

Secondly, disruption on the Atlantic Meridional overturning circulation, preventing warm water from moving north and having a dramatic impact on ocean and terrestrial ecosystems, as well as affecting global climatic circulation.

Thirdly, a warming of 4 degrees C would cause massive melting of the Greenland ice sheet. An ice-free Greenland would cause up to 6 to 7 meters of sea-level rise, threatening up to 300 million people, as well as ecosystems, with harmful floods.

Fourth, some have suggested that the El Nino periodic shift in condition of the ocean and atmosphere in the tropical Pacific may become an almost permanent state, causing severe drought in Southeast Asia and the Amazon Basin and increased floods and changes in the marine food web along the South American Pacific coast.

Fifth, melting Antarctic ice could raise raise the world's sea level by up to 6 to 7 meters. The melting ice may reveal islands under the ice that are currently buried. Already fast moving ice streams have released large amounts of freshwater into surrounding oceans.

Pointing to the big picture.

Tasked with keeping a blog for 3 months for my 3rd year module in Global Environmental Change at UCL, I came home with a world of ideas. I told my boyfriend that I'd decided to write about climate tipping points. 

That's great, he said…what are “tipping points”? 

At this I paused, gave a vague description with a few strange analogies about burning your toast, and silently vowed to find a some good articles that would categorically sum up tipping points, for me and for my audience. 

Now, this proved much more difficult than expected. Although I knew about tipping points in Earth’s climate system, I had never considered that they existed elsewhere. As it turns out, ANYTHING that is in the slightest bit dynamic has a so called “tipping point”: fashion, make-up, the economy, sport, there’s even a Tipping Points game show in which contestants play with a giant arcade-style coin pusher (yes I watched it . . . it’s nail-biting). What shocked me most was that climate tipping points didn't dominate the primitive Google search, despite potentially being one of the most daunting and difficult factors in global climate change past, present and future.

TIPPING POINTS are thresholds beyond which dramatic changes in conditions with considerable and largely unpredictable consequences occur. It only takes a small change to make a huge difference; Lenton says “A climate ‘tipping point’ occurs when a small change in forcing triggers a strongly nonlinear response . . . qualitatively changing its future state”. They've happened before, pushing the Earth in and out of Ice Ages, but these have all been natural, caused by solar variability and a chain of events, such as melting permafrost and icesheets. This time, the Anthropocene threatens a new era of climate change, comparable with previous global mass extinctions. The editorial from Nature Climate Change Vol. 1 says “An early warning of Earth tipping points will bring us closer to staving off abrupt climate change, but a societal tipping point is needed to achieve sustainability”. 

Tipping points MUST be considered by policy makers, scientists and the general public worldwide in order for the issue to be addressed and acted upon.

Image from xkcd.com, source of data for image Dyke, A. et al, 2002. "The Laurentide and Innuitian Ice Sheets During the Last Glacial Maximum"