We only have a 5 percent chance of avoiding ‘dangerous’ global warming, a study finds

[Note:  This item comes from friend Jock Gill.  DLH]

We only have a 5 percent chance of avoiding ‘dangerous’ global warming, a study finds
By Chris Mooney
Jul 31 2017
https://www.washingtonpost.com/news/energy-environment/wp/2017/07/31/we-only-have-a-5-percent-chance-of-avoiding-dangerous-global-warming-a-study-finds/

In recent years, it has become increasingly common to frame the climate change problem as a kind of countdown — each year we emit more carbon dioxide, narrowing the window for fixing the problem, but not quite closing it yet. After all, something could still change. Emissions could still start to plunge precipitously. Maybe next year.

This outlook has allowed, at least for some, for the preservation of a form of climate optimism in which big changes, someday soon, will still make the difference. Christiana Figureres, the former head of the United Nations’ Framework Convention on Climate Change, recently joined with a group of climate scientists and policy wonks to state there are three years left to get emissions moving sharply downward. If, that is, we’re holding out hope of limiting the warming of the globe to below 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial temperatures, often cited as the threshold where “dangerous” warming begins (although in truth, that’s a matter of interpretation).

This color-coded map displays a progression of changing global surface temperature anomalies from 1880 through 2015. Higher than normal temperatures are shown in red and lower then normal temperatures are shown in blue. (NASA)

Yet a battery of recent studies call into question even that limited optimism. Last week, a group of climate researchers published research suggesting the climate has been warming for longer than we thought due to human influences — in essence, pushing the so-called “preindustrial” baseline for the planet’s warming backwards in time. The logic is clear: If the Earth has already warmed more than we thought due to human activities, then there’s even less remaining carbon dioxide that we can emit and still avoid 2 degrees of warming.

Two new studies published Monday, meanwhile, go further towards advancing this pessimistic view which asserts that there’s little chance of the world will stay within prescribed climate limits.

The first new study calculates the statistical likelihood of various amounts of warming by the year 2100 based on three trends that matter most for how much carbon we put in the air. Those are the global population, countries’ GDP (on a per capita basis), and carbon intensity, or the volume of emissions for a given level of economic activity.

The research finds that the median warming is likely to be 3.2 degrees Celsius, and further concludes that there’s only a 5 percent chance that the world can hold limiting below 2 degrees Celsius and a mere 1 percent chance that it can be limited below 1.5 degrees Celsius (2.7 degrees Fahrenheit). That will come as bad news for vulnerable small island nations in particular, which have held out for a 1.5 degree target, along with other particularly vulnerable nations.

“There is a lot of uncertainty about the future, our analysis does reflect that, but it also does reflect that the more optimistic scenarios that have been used in targets seem quite unlikely to occur,” said statistician Adrian Raftery of the University of Washington, Seattle. Raftery conducted the study, which was just published in Nature Climate Change, alongside colleagues at the University of California, Santa Barbara and Upstart Networks.

Here’s a figure from the study, showing the range of expected temperatures that the study found:

[snip]

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