The Paris Climate Accord

"The new deal will not, on its own, solve global warming. At best, scientists who have analyzed it say, it will cut global greenhouse gas emissions by about half enough as is necessary to stave off an increase in atmospheric temperatures of 2 degrees Celsius or 3.6 degrees Fahrenheit."
- Coral Davenport, Nations Approve Landmark Climate Accord in Paris, NYT, Dec. 12, 2015

In a 2016 New York Times article, Julie Davis, Mark Landler, and Coral Davenport describe the Paris climate accord on greenhouse gas emissions as "an aggressive — some say unrealistic — pledge made in Paris to reduce greenhouse gas emissions 80 percent from 2005 levels by 2050." The accompanying video interview contains the following exchange:

Mark Landler: We're told you've thought a lot about how and why civilizations collapse, and we wanted to ask you, do you believe the threat from climate change is dire enough that it could precipitate the collapse of our civilization.
President Obama: Well, I don't know that I can look into a crystal ball and know exactly how this plays out, but what we do know is that historically, when you see severe environmental strains of one sort or another on cultures, on civilizations, on nations, that the byproducts of that are unpredictable and can be very dangerous. And what we know is that if the current projections, the current trend lines on a warming planet continue, it is certainly going to be enormously disruptive worldwide and---just imagine for example monsoon patterns shifting in South Asia, where you've got over a billion people. If you have even a portion of those billion people displaced you now have the sorts of refugee crises and potential conflicts that we haven't seen in our lifetimes. And you're looking at a much more dangerous world, and severe strains on nation states, on communities, on economies.

- Julie Davis, Mark Landler, and Coral Davenport, Obama on Climate Change: The Trends Are ‘Terrifying’, NYT, Sept. 8, 2016

Since an agreement in Cancun in 2010, the official goal of international climate policy has been to limit the warming of the Earth to 2 degrees Celsius, or 3.6 Fahrenheit, above the level that prevailed before the Industrial Revolution. With the rapid warming that has occurred since 1950 as a result of industrial emissions, the planet is already nearly halfway there.

The Paris deal sets a more ambitious target, declaring that the global average temperature rise ought to be kept “well below” 2 degrees Celsius, and that countries should try go further, limiting warming to 1.5 degrees Celsius. ...

The research organization Climate Central found recently that 280 million people live on land that could eventually be submerged by the sea if warming were allowed to reach the higher number. If it were kept to the lower target, that number would be cut by more than half, to 137 million people.

Yet action on global warming has been delayed for so long, and emissions allowed to rise so high, that reaching either target will be exceedingly difficult.

Scientists say that limiting warming to the higher target would require that industrial emissions of greenhouse gases come to an end by roughly 2050, and to stay below the lower target, by about 2030.

But coal-burning power plants are being built today that can be expected to operate well past 2050, and fossil-fuel companies are spending hundreds of billions a year looking for new reserves that cannot be burned if either target is to be met.
- Justin Gillis, Climate Accord Is a Healing Step, if Not a Cure, NYT, Dec. 12, 2015

Dr. Rahmstorf said the rise would eventually reach five feet and far more — the only question was how long it would take. Scientists say the recent climate agreement negotiated in Paris is not remotely ambitious enough to forestall a significant melting of Greenland and Antarctica, though if fully implemented, it may slow the pace somewhat.
- Justin Gillis, Seas Are Rising at Fastest Rate in Last 28 Centuries, NYT, Feb. 22, 2016

A recent analysis by scientists at the Massachusetts Institute of Technology concluded that the promises made in Paris would reduce the concentration of greenhouse gases in the atmosphere at the end of the century to 710 parts per million from 750. That is still far from the 450 p.p.m. ceiling needed to tip the odds in favor of staying under the temperature threshold scientists consider safe.

According to the International Energy Agency, the commitments made in Paris will cap the growth of greenhouse gas emissions between now and 2040 to 13 percent. The 450 p.p.m. target requires them to fall by 43 percent.
- Eduardo Porter, Earth Isn’t Doomed Yet. The Climate Could Survive Trump Policies., Nov. 29, 2016

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