Two degrees of warming does not guarantee instantaneous, total extinction of the human race.
http://www.pbs.org/newshour/bb/why-2-degrees-celsius-is-climate-changes-magic-number/
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While there’s some uncertainty about how much of a problem two degrees of additional warming will be and how we will be able to adapt to it, scientists say we will likely see longer droughts and more intense heat waves, which could cause big disruptions to the world’s food supply.
At two degrees, sea levels could rise several feet, which would flood many coastal communities in the U.S. and potentially cause large migrations of people from countries like Bangladesh and India and Vietnam.
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Most scientists believe that, even if every country followed through 100 percent on their voluntary pledges, there’s already enough CO2 in the atmosphere to warm the planet by two degrees.
Scientists and world leaders in Paris hope that, even if this threshold is breached, nations will not just follow through on their pledges, but will agree to dial back emissions even more in the future.
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http://data.huffingtonpost.com/2015/11/two-degrees-will-change-the-world
2 Degrees Will Change The World
More Floods, More Drought Inevitable. How Bad Do We Want It To Get?
By Alissa Scheller
MONDAY, NOV. 30, 2015, 8:30 AM EDT
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https://www.nrdc.org/onearth/argument-degree
An Argument of Degree
An IPCC author assails the two-degree target as scientifically bankrupt and geographically biased.
March 27, 2015 Brian Palmer
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The two-degree target has a strange history. In 1975, Yale economist William Nordhaus speculated that a global mean temperature increase of two or three degrees would be unprecedented in the “last several hundred thousand years.” Nordhaus was not proposing those figures as potential policy targets, nor did he suggest that they represented any kind of threshold for disaster.
In 1990, however, the predecessor to the IPCC published forecasts suggesting that, were the temperature to cross the two-degree Rubicon, “grave damage to ecosystems” and “nonlinear responses” would follow. Although many researchers questioned the use of a single number to indicate the moment of catastrophe, the notion became popular. Malcolm Gladwell’s hit book The Tipping Point, in particular, primed public interest in the idea of trend inflections. Policymakers, scientists, and many politicians soon coalesced around the two-degree target. It was part of the Copenhagen Accord and statements from the G8, and it has formed the basis of most global negotiations.
There are a few major objections to the two-degree target. First, it’s somewhat arbitrary. The climate is a complex system. To the extent that we accept the notion of tipping points, there are likely to be several rather than one. Two degrees is, in the view of many, a handy rallying cry rather than a scientific threshold. A widely cited paper on the history of the target compared it to a speed limit—it may not be a scientifically optimal number, but it serves as a useful focal point. The paper concludes: “The two-degree target emerged nearly by chance…Policy makers have treated it as a scientific result, scientists as a political issue.” (Incidentally, the paper was part of an endorsement of the target. That’s how lukewarm its support is among climatologists.)
Others say the target is simply too high. That’s the point Tschakert made today in Climate Change Responses She cites evidence that most of the world’s coral reefs would perish and sea levels would rise more than three feet after a two-degree increase. Moreover, the temperature rises associated with anthropogenic climate change are not uniform across the globe. As Archbishop Desmond Tutu argued at the 2009 Copenhagen climate conference, a two-degree global mean temperature rise might result in Africa’s temperature rising as much as 3.5 degrees—a potentially disastrous change.
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