What are tipping points? They are points in a process or timeline where something happens to create a "point of no return," where there is a loss of control over the eventual outcome. There are several critical tipping points in climate change. These include amount of methane gasing into the atmosphere, atmospheric CO2 levels, ocean temperature, and ocean acidity.
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Methane (CH4, the simplest organic gas, is a far more potent greenhouse gas than carbon dioxide. This is even considering that its half-life in the atmosphere is much shorter than that of CO2 (half-life is the amount of time it takes for half of the gas to be removed from the atmosphere). Over a twenty-year period, methane is 86 times more potent in capturing heat than is carbon dioxide. Over a century, it is 34 times more potent.
There are currently about 4.85 megatonnes of methane in the atmosphere (about 5.4 million tons). This results in a concentration of about 1.75 ppm (parts per million). This may not seem like much, but remember how potent methane is. Currently, 29% of the methane being released into the atmosphere is from natural sources, while 71% is from anthropogenic (human-caused) sources. The current annual emissions of methane into the atmosphere is about 598 megatonnes (about 658 million tons), more than double what it was two centuries ago.
It is estimated that at least 1,400 gigatonnes of methane are locked up in Arctic methane clathrates -- sequestered methane in a somewhat gelid form in the tundra and in the Arctic seabed. That's about 1.5 million million tons of methane -- obviously far more than 5.4 million tons. An estimated 50 gigatonnes (55 billion tons) of this are thought to be at shorter-term risk for release. There is disagreement about the rate of release that may be experienced. The amount of methane in the atmosphere could multiply very quickly to astronomical levels. Alternatively, it may release slowly enough that the recapture of methane from the atmosphere would prevent the most disastrous buildups -- but the results, nonetheless, would still be very serious and damaging to our planetary potential.
If the worst scenario happens, global warming may become completely uncontrollable, and the best the human race can then do is to try to create isolated self-sufficient compounds, while most of the people around the Earth die. This is not a joking matter. In the best scenario, there will be massive die-offs of population due to famine and other factors.
Atmospheric Carbon Dioxide
The amount of carbon dioxide (CO2) in the atmosphere is now over 0.04%, over 40% more than it was several hundred years ago. This is estimated to be the highest level achieved in the past 20 million years. And it's still going up - steeply. It has been estimated that the tipping point for carbon dioxide may be around 0.055%, or about 38% more than it is now.
Currently, more than 34 gigatonnes (about 38 billion tons) of carbon dioxide are being released into the atmosphere annually. This is 50% more than was being released only twenty years ago. And the release rate is growing. Current trends will result in over 0.06% concentration by the year 2100. It is calculated that it will take a full millennium - 1,000 years - for this to ameliorate.
But the results aren't just limited to warming. There are other drastic consequences. The warming causes ocean warming (see below), and the rising atmospheric concentration also causes ocean acidification (see below).
One result is an alteration in plant growth. All plant communities are regulated by ecological delimiters. These may be substrate (a place to grow), temperature, moisture, nutrients, etc. And one of these is the availability of carbon dioxide in the atmosphere. While that level does vary somewhat around the globe, it's still within a fairly restricted range. However, with increased CO2 in the atmosphere, certain plants, generally the most aggressively-growing "weedy" plants, will grow much faster. One study found that one of the plants most benefitting from higher levels was poison ivy!
The oceans disproportionately absorb the heat from global warming. The predictions of rising atmospheric temperatures have fallen short of predictions, and the reason, it turns out, is that all that heat is going into the oceans much more quickly than predicted. This has multiple levels of serious consequences:
The tipping point here is that the oceans will reach a point where they become barren desserts, UNRECOVERABLE ON A HUMAN SCALE.
The pH of the ocean is highly dependent on the composition of our atmosphere. And the more carbon dioxide there is in the atmosphere, the more than becomes dissolved in our oceans, where it largely becomes carbonic acid, thus acidifying the oceans. This is death for much sea life.