Here are some of the possible triggers of global warming. At what point they might occur, scientists are not sure.
1) Melting of the Greenland icecap: causing rising sea, more free water (dark, so it absorbs heat), less ice (white, so it reflects heat), in the Arctic Ocean, thereby accelerating heating: this is in process & accelerating
2) Melting of West Antarctic ice sheet, which has already begun and is considered unstoppable, which is predicted to cause the oceans to rise 14 feet
3) Melting of the rest of Antarctica, which probably won’t start until a long time after the 1st 2 are well underway, but will be far more catastrophic
4) Burning of peat bogs (such as in Canada, Alaska, Siberia & Indonesia), which puts lots of methane as well as carbon dioxide in the air and depletes our most effective carbon sink ecosystem.
5) Thawing of permafrost, which is beginning in some places, and can have catastrophic results because it contains so much carbon, including methane.
6) Methane explosion from deep into the earth: this phenomenon is rather new, and scientists know little about its full potential, but it could be huge.
7) Large deposits of methane hydrates underneath the ocean bed that could escape into the atmosphere as the ocean warms. Since these deposits are enormous, this could have a major impact on global warming & ocean acidification, and apparently this may be beginning, too *
8) An ocean that becomes so saturated with carbon dioxide, which it seems to be nearing, that it no longer can be a carbon sink whereby atmospheric carbon dioxide can be absorbed, thus no longer providing a modifying effect on carbon accumulation in the atmosphere, thus increasing the rate at which carbon dioxide accumulates in the atmosphere. Carbon dioxide increase is accompanied by oxygen decrease, and low-oxygen or “dead zones” in oceans have greatly expanded in recent years
These are all on top of human activities today that have long been increasing pollution, carbon emissions & warming, such as industrialization, deforestation & livestock raising, that are still going on & for the most part are increasing. When confronting someone who asserts that we have plenty of time to take action, we should be ready to point out these triggers that will accelerate global warming in a way that will be difficult if not impossible for humans to control or contain. The first 2 have already begun, and they may trigger some of the others, which in turn are likely to cause feedback (warming, carbon accumulations) that will speed up ones that have already started and set off new processes, etc. Another thing to keep in mind is that what we put in the air stays there for decades, which means the increase in carbon dioxide today is a result of what we did last century, and what we emit today will stay with us for most of the rest of this century, another reason why waiting around is not an option.
A certain amount of global warming is tolerable but beyond a certain point, particularly if any of these triggers are set off, we’re in deep trouble. Maybe we could tolerate one or two of the milder ones, but beyond that I don’t think we can. Temperatures are likely to go far beyond the 2 degrees scientists have said we can take. And the time frame for us rising several degrees could be just a few years. It may already be too late now to avoid these tipping points, because we’ve been too slow to act, but if there’s any chance of stopping it, we should do all that we can now to avoid it.
* Peat has a high carbon content and can burn under low moisture conditions. Once ignited by the presence of a heat source (e.g., a wildfire penetrating the subsurface), it smolders. These smoldering fires can burn undetected for very long periods of time (months, years, and even centuries) propagating in a creeping fashion through the underground peat layer. Peat fires are emerging as a global threat with significant economic, social, and ecological impacts. Recent burning of peat bogs in Indonesia, with their large and deep growths containing more than 50 billion tons of carbon, has contributed to increases in world carbon dioxide levels. Peat deposits in Southeast Asia could be destroyed by 2040.[40][41]
It is estimated that in 1997, peat and forest fires in Indonesia released between 0.81 and 2.57 Gt of carbon; equivalent to 13–40 percent of the amount released by global fossil fuel burning, and greater than the carbon uptake of the world's biosphere. These fires may be responsible for the acceleration in the increase in carbon dioxide levels since 1998.[42][43] More than 100 peat fires in Kalimantan and East Sumatra have continued to burn since 1997. Each year, the peat fires in Kalimantan and East Sumatra ignite new forest fires above the ground.
In North America, peat fires can occur during severe droughts throughout their occurrence, from boreal forests in Canada to swamps and fens in the subtropical southern Florida Everglades.[44] Once a fire has burnt through the area, hollows in the peat are burnt out, and hummocks are desiccated but can contribute to Sphagnum recolonization.[45]
In the summer of 2010, an unusually high heat wave of up to 40 °C (104 °F) ignited large deposits of peat in Central Russia, burning thousands of houses and covering the capital of Moscow with a toxic smoke blanket. The situation remained critical until the end of August 2010 (Wikipedia)
* http://www.dailykos.com/...
* http://www.ibtimes.co.uk/...
** http://www.dailykos.com/...
* http://worldoceanreview.com/...
(For some reason, the asterisks don't reproduce properly to the text)