Earth likely to warm more than 2 degrees this century

July 31, 2017
Global carbon emission projections through the year 2100, per year (left) and cumulative (right). Dotted lines show the four 'scenarios' from the latest IPCC climate report. The shaded area is the new statistically-driven approach, where the darker area is the 90 percent confidence interval, and lighter shading is the 95 percent confidence range. Credit: Adrian Raftery/University of Washington

Warming of the planet by 2 degrees Celsius is often seen as a "tipping point" that people should try to avoid by limiting greenhouse gas emissions.But the Earth is very likely to exceed that change, according to new University of Washington research. A study using statistical tools shows only a 5 percent chance that Earth will warm 2 degrees or less by the end of this century. It shows a mere 1 percent chance that warming could be at or below 1.5 degrees, the target set by the 2016 Paris Agreement.

"Our analysis shows that the goal of 2 degrees is very much a best-case scenario," said lead author Adrian Raftery, a UW professor of statistics and sociology. "It is achievable, but only with major, sustained effort on all fronts over the next 80 years."

The new, statistically-based projections, published July 31 in Nature Climate Change, show a 90 percent chance that temperatures will increase this century by 2.0 to 4.9 C.

"Our analysis is compatible with previous estimates, but it finds that the most optimistic projections are unlikely to happen," Raftery said. "We're closer to the margin than we think."

The most recent report from the Intergovernmental Panel on Climate Change included future warming rates based on four scenarios for future carbon emissions. The scenarios ranged from "business-as-usual" emissions from growing economies, to serious worldwide efforts to transition away from .

"The IPCC was clear that these scenarios were not forecasts," Raftery said. "The big problem with scenarios is that you don't know how likely they are, and whether they span the full range of possibilities or are just a few examples. Scientifically, this type of storytelling approach was not fully satisfying."

The new paper focuses instead on three quantities that underpin the scenarios for future emissions: total , gross domestic product per person and the amount of carbon emitted for each dollar of economic activity, known as carbon intensity.

Using statistical projections for each of these three quantities based on 50 years of past data in countries around the world, the study finds a median value of 3.2 C (5.8 F) warming by 2100, and a 90 percent chance that warming this century will fall between 2.0 to 4.9 C (3.6 to 8.8 F).

"Countries argued for the 1.5 C target because of the severe impacts on their livelihoods that would result from exceeding that threshold. Indeed, damages from heat extremes, drought, extreme weather and sea level rise will be much more severe if 2 C or higher temperature rise is allowed," said co-author Dargan Frierson, a UW associate professor of atmospheric sciences. "Our results show that an abrupt change of course is needed to achieve these goals."

Raftery previously worked on United Nations projections for future world population. His 2014 study used Bayesian statistics, a common tool used in modern statistics, to show that world population is unlikely to stabilize this century. The planet likely will reach 11 billion people by 2100.

In the new study, Raftery expected to find that higher populations would increase the projections for global warming. Instead, he was surprised to learn that population has a fairly small impact. That is because most of the population increase will be in Africa, which uses few fossil fuels.

What matters more for future warming is the carbon intensity, the amount of carbon emissions produced for each dollar of economic activity. That value has dropped in recent decades as countries boost efficiency and enact standards to reduce . How quickly that value drops in future decades will be crucial for determining future warming.

The study finds a wide range of possible values of intensity over future decades, depending on technological progress and countries' commitments to implementing changes.

"Overall, the goals expressed in the Paris Agreement are ambitious but realistic," Raftery said. "The bad news is they are unlikely to be enough to achieve the target of keeping warming at or below 1.5 degrees."

Explore further: Allowable 'carbon budget' most likely overestimated

More information: Less Than 2ºC Warming by 2100 Unlikely, Nature Climate Change (2017). DOI: 10.1038/nclimate3352

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12 comments

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sirdumpalot
1 / 5 (6) Jul 31, 2017
We certainly underestimate the expected effect we will have this century, but we also underestimate the effectiveness of tech to fix this.
BackBurner
1 / 5 (5) Jul 31, 2017
"The shaded area is the new statistically-driven approach, where the darker area is the 90 percent confidence interval, and lighter shading is the 95 percent confidence range."

And of course, the 98% confidence interval was too large to fit on the planet.

I particularly enjoyed the idea this was a "new statistically-driven" approach. New. Yeah. Sure. It's new to you maybe.
antigoracle
1 / 5 (7) Jul 31, 2017
This will require a lot of cooking of the data, by the AGW Cult.
Captain Stumpy
4.2 / 5 (5) Jul 31, 2017
sigh
New. Yeah. Sure. It's new to you maybe.
1- it's a new method
it's not about statistics being new (but you knew that already: it's your strawman you built)

2- the method is far better than blatantly advocating the end of NOAA or NASA just because someone doesn't like the data that demonstrates AGW that is also validated by other nations not related or even friendly

3- is there a relevant argument besides your inability to catch the subtle nuances of the english language when descriptive labels are used to colour an article in an effort to make it more readable to the layman?
tblakely1357
1 / 5 (5) Aug 01, 2017
I thought we were supposed to already be beyond the 'tipping point' by now. Keep moving those goalposts.
TrollBane
5 / 5 (3) Aug 01, 2017
"I thought we were supposed to already be beyond the 'tipping point' by now. Keep moving those goalposts."

That says more about what you thought (or want to imply others said) than what anyone credible ever stated. Just another instance of the much-used straw man.
Guy_Underbridge
not rated yet Aug 01, 2017
We certainly underestimate the expected effect we will have this century, but we also underestimate the effectiveness of tech to fix this

Well why don't you poop out the tech to fix this, and become the richest man on earth in the process? Otherwise, you might think of moving north.
Benni
1 / 5 (3) Aug 01, 2017
The orbit of the Earth around the sun isn't circular, but rather it iselliptical with the Earth being closer at some points and further away at others. The elliptical orbit isn't on a one dimensional plane, as the sun is also moving through the universe.

The Earth NEVER passes through the same point in space twice. Space itself is not a constant temperature everywhere, so as the sun moves through space, with the Earth corkscrewing around it, thus there are many factors affecting our temperature that scientists can not accurately measure them.
Captain Stumpy
3 / 5 (2) Aug 01, 2017
thus there are many factors affecting our temperature that scientists can not accurately measure them
@complete idiot benji
besides your epic failure with basic math in the past, let alone your inability to prove you have any other mathematical skill in any way, despite your copious fallacious claims to the contrary...

scientists also don't have the time, capabilities and resources to name every specific individual bacteria in the flora of your mouth, let alone your entire (ample) gut, so that they can point to specific bacterial "bad seeds" gone awry to arrest, detain and rehabilitate or eradicate them, but that doesn't mean they can't ever know what they do, how they act or overall the statistical likelihood that you will have gingivitis or some other similar decay in your mouth
RealityCheck
3 / 5 (4) Aug 02, 2017
@antigoracle, @tblakely1357, @Benni.

@antigoracle:
This will require a lot of cooking of the data, by the AGW Cult.

and @tblakely1357:
I thought we were supposed to already be beyond the 'tipping point' by now. Keep moving those goalposts.


As I've been pointing out for some time, here in/around OZ continent, the climate change TREND was already on track to become disastrous if we do not curb CO2 emissions. Now comes the most recent data/conclusion from the very conservative BOM here in OZ, recognizing the looming dangers which year-on-year record-breaking heat etc are already bringing:

http://www.abc.ne.../8762266

http://www.abc.ne.../8762560

@Benni:
The orbit of the Earth around the sun isn't circular,..
Even if that's so, why make it worse by adding more CO2 which keeps in any extra solar heat, Benni? :)
eccemarco
5 / 5 (1) Aug 02, 2017
@Benni: I have heard that fake story a million times. And the IPCC compiles scientific consensus over hundreds of peer-reviewed articles that have taken into account solar radiation AND still reach the conclusion that our own warming is what's driving the current climatic changes. Hence: Anthropogenic Global Warming.
But if you want to go on and research a PhD on the different temperatures in space as the Earth corkscrews around the Sun, maybe you can find something revolutionary that will finally teach something new to these climate scientists. You go and start, I sit and wait here.
TheGhostofOtto1923
1 / 5 (1) Aug 02, 2017
I think we have the culpret

"Former Vice President Al Gore's 10,070-square-foot estate near Nashville, Tennessee, expended more than 21 times more energy than the average U.S. household over the past year, according to a new report.

""With an average consumption of 22.9 kWh per square foot over the past year, Gore's home classifies as an 'energy hog' under standards developed by Energy Vanguard — a company specializing in energy efficiency methods," the report said."

-You has all been swindled-

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