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.
