We’re entering the final sprint toward one of the most consequential rounds of climate change negotiations in history, which will take place in Paris this December. Those talks have the goal of devising an international agreement that will limit global warming to below 2 degrees Celsius, or 3.6 degrees Fahrenheit, above preindustrial levels by 2100.
Study after study has already found that this goal is going to be extremely difficult for the world to reach, in light of recent emissions trajectories that have put the world on track for at least double that amount of warming, or possibly more.
During this time period, scientists, think tanks, politicians and even Pope Francis are weighing in to spur on climate negotiators. This week, a prominent climate scientist, James Hansen, entered the fray with a study aimed at getting policymakers’ attention by saying that the 2 degree Celsius target is dangerously reckless, and that we should be aiming for limiting warming to 1.5 degrees Celsius or below.
The study was not peer reviewed, but it has attracted a fair bit of attention anyway, in part because Hansen is known as the godfather of global warming, having first warned Congress of its existence during the sweltering summer of 1988. He was the longtime leader of NASA’s Goddard Institute of Space Studies (GISS) in New York, and now teaches at Columbia University. In the paper, which was published in the open access journal Atmospheric Chemistry and Physics, Hansen is joined by 16 colleagues, some of whom are experts in the Greenland and Antarctic ice sheets.
The argument Hansen and his colleagues make is abrupt melting of the West Antarctic Ice Sheet and Greenland portend a period of rapid sea level rise that could flood coastal cities around the world. And he doesn’t predict this will happen in two centuries from now; rather, as soon as several decades.
His conclusions are frightening, and in some ways compelling — but they are not widely shared in the climate science community.
The study relies on computer modeling to come to this conclusion and others, as well as recent data and observations of the last time period when the Earth was about as warm as it is now, an epoch known as the Eemian period.
During that interglacial period, the study states, global average sea level was up to 30 feet higher than it is now, despite a climate that was just about 1 degree Celsius, or 1.8 degrees Fahrenheit, milder than today.
The study argues that ice sheets in contact with the ocean, including the many West Antarctic glaciers that end in floating ice shelves, “are vulnerable to non-linear disintegration” due to a combination of atmospheric warming and major shifts in ocean circulation that would result from a surge in freshwater flowing into the ocean in the North Atlantic (from Greenland), and Southern Ocean (from Antarctica).
Essentially, the study proposes that climate feedbacks could work completely and totally against us, as warm water becomes trapped on top of a layer of colder Antarctic waters due to a near total shutdown in the global ocean conveyor belt, which circulates ocean heat from the coast of Antarctica to Newfoundland. Studies have already shown that part of this conveyor belt is slowing down, but a full stop is controversial in the scientific community.
The study calls the 2-degree Celsius target “highly dangerous,” rather than a safe guardrail.
“The message for policymakers is that we have a global crisis that calls for international cooperation to reduce emissions as rapidly as practical,” the study states, before endorsing a rising carbon fee as a policy solution.
Here’s the most frightening paragraph from the study, and possibly the reason why it has prompted alarming headlines from some publications:
We conclude that continued high emissions will make multi-meter sea level rise practically unavoidable and likely to occur this century. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilization. This image of our planet with accelerating meltwater includes growing climate chaos and storminess, as meltwater causes cooling around Antarctica and in the North Atlantic while the tropics and subtropics continue to warm. Rising seas and more powerful storms together are especially threatening, providing strong incentive to phase down CO2 emissions rapidly.
Press link for more: Andrew Freedman | mashable.com