One such tipping point listed in the Kerry paper was the runaway greenhouse effect, which talks about an increase of water vapor in the air leading to the oceans and water sources to dry up from increased heat and the cycle that would keep going until the earth was waterless and the heat created would cause the effects of an inferno, basically too hot for human life.
Another is the idea that the more snow that develops and spreads across the Earth will cause more heat and sunlight to be reflected back and would increase the amount of ice and snow covering the Earth until it is completely covered and there is no heat getting in to melt the snow and ice. A recent theory kind of shuts down this idea saying that without any water carbon dioxide could not be absorbed and the greenhouse effect would eventually melt the snow and ice.
One thought about a tipping point in the oceans was mentioned in Sanders' article and said basically that changes in temperature and acidity in oceans could cause a tipping point for coral reef ecosystems causing the cycle to change drastically or completely fail.
He also mentions in that article that melting in Antarctica can lead to a rise in sea and ocean temperatures as the increase in heat creates more melting of ice. The more water and less snow and ice would result in more warming, because of more sunlight absorption by water as compared to snow and ice.
Then the Levitan article talks about more of a domino effect stating that the melting in the Arctic could cause a rise in temperature and spread down northern continents creating a domino effect of increased heat started from the Arctic. Although most have said there is no clear evidence to predict that there is a tipping point for sure, they do not want to rule it out and feel that something should be done such as trying to reduce our emissions, to lessen our effects on the greenhouse effect.
The ones that seem to be the most likely to occur in recent years are the two mentioned by Sanders, being that the sea levels could rise, it states by up to 3 feet by 2200, and our heat from emissions needs to be reduced to stop this and coral reef ecosystems. Then, Levitan's domino effect is more of a slow change, but says there could be a point of no return which we simply cannot guess exactly at this point. Finally, the two extremes of the fire and ice world, seem to be not really something that could happen soon, but it does get people to think that ok this in theory could happen so lets not try and push it past a point of reversing.
Reliability: I think all these articles are quite reliable and list many of the same scientists, some being known as leading scientist, others were still well respected. So overall they were good sources.
http://www.scientificamerican.com/article/do-global-tipping-points-exist/
http://newscenter.berkeley.edu/2013/12/03/report-warns-of-climate-change-tipping-points-within-our-lifetime/
https://docs.google.com/file/d/0B5OYZdqOzxSLa3hSdE9GX0FycFE/edit
