Can Paris pledges avert severe climate change?

November 26, 2015, Pacific Northwest National Laboratory
Satellite image of ship tracks, clouds created by the exhaust of ship smokestacks. Image: NASA

More than 190 countries are meeting in Paris next week to create a durable framework for addressing climate change and to implement a process to reduce greenhouse gases over time. A key part of this agreement would be the pledges made by individual countries to reduce their emissions.

A study published in Science today shows that if implemented and followed by measures of equal or greater ambition, the Paris pledges have the potential to reduce the probability of the highest levels of warming, and increase the probability of limiting global warming to 2 degrees Celsius.

In the lead up to the Paris meetings, countries have announced the contributions that they are willing to make to combat global , based on their own national circumstances. These Intended Nationally Determined Contributions, or INDCs, take many different forms and extend through 2025 or 2030.

Examples of these commitments include the United States' vow to reduce in 2025 by 26-28 percent of 2005 levels and China's pledge to peak emissions by 2030 and increase its share of non-fossil fuels in primary energy consumption to around 20 percent. In the study, the scientists tallied up these INDCs and simulated the range of temperature outcomes the resulting emissions would bring in 2100 under different assumptions about possible emissions reductions beyond 2030.

"We wanted to know how the commitments would play out from a risk management perspective," said economist Allen Fawcett of the U.S. Environmental Protection Agency, the lead author of the study. "We analyzed not only what the commitments would achieve over the next ten to fifteen years, but also how they might lay a foundation for the future."

Although many researchers have focused on the importance of the 2 degree limit, Fawcett and colleagues assessed uncertainty in the climate change system from an overall risk management perspective. They analyzed the full range of temperatures the INDCs might attain, and determined the odds for achieving each of those temperatures. To determine odds, they modeled the future climate hundreds of times to find the range of temperatures these various conditions produce.

"It's not just about 2 degrees," said Gokul Iyer, the study's lead scientist at the Joint Global Change Research Institute, a collaboration between the Department of Energy's Pacific Northwest National Laboratory and the University of Maryland. "It is also important to understand what the INDCs imply for the worst levels of climate change."

In the study, the scientists compare the Paris commitments to a world in which countries don't act at all or start reducing greenhouse gas emissions only in 2030.

The team found that if countries do nothing to reduce emissions, the earth has almost no chance of staying under the 2 degree limit, and it is likely that the temperature increase would exceed 4 degrees. They went on to show that the INDCs and the future abatement enabled by Paris introduce a chance of meeting the 2 degree target, and greatly reduce the chance that warming exceeds 4 degrees. The extent to which the odds are improved depends on how much emissions limits are tightened in future pledges after 2030.

"Long-term temperature outcomes critically hinge on emissions reduction efforts beyond 2030," said Iyer. "If countries implement their INDCs through 2030 and ramp up efforts beyond 2030, we'll have a much better chance of avoiding extreme warming and keeping temperature change below 2 degrees Celsius. It's important to know that the INDCs are a stepping stone to what we can do in the future."

To perform the analysis, the team incorporated the INDCs along with assumptions about future emissions reductions into a global, technologically detailed model of the world called the Global Change Assessment Model or GCAM that includes energy, economy, agriculture and other systems. The GCAM model produced numbers for global , which the team then fed into a climate model called Model for the Assessment of Greenhouse-gas Induced Climate Change or MAGICC. Running the simulations for each scenario 600 times resulted in a range of temperatures for the year 2100, which the team converted into probabilities.

Iyer said the next thing to look at was the question of the kinds of policies and institutional frameworks that could pave the way for a robust process that enables emissions reduction efforts to progressively increase over time.

Explore further: Current climate commitments would increase global temperature around 3 C

More information: "Can Paris pledges avert severe climate change?," Science www.sciencemag.org/lookup/doi/ … 1126/science.aad5761

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9 comments

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freeiam
2.3 / 5 (3) Nov 26, 2015
"It's not just about 2 degrees," said Gokul Iyer, the study's lead scientist at the Joint Global Change Research Institute, a collaboration between the Department of Energy's Pacific Northwest National Laboratory and the University of Maryland. "It is also important to understand what the INDCs imply for the least levels of climate change."

And what are those numbers?
Strange that focus on worst case.
baudrunner
1 / 5 (3) Nov 26, 2015
I doubt it.

They would have us believe that a volcano, super notwithstanding, could initiate an ice age that lasts for ten thousand and more years. And at regular intervals of twenty-six to twenty-seven thousand years.

Krakatoa's effect on the area was such that the light of day did not return there for three days.

A volcano a thousand times as strong would maintain darkness over most of that portion of the hemisphere for no more than a few weeks. One a thousand times stronger than even that one would maintain a darkness over its hemisphere for a maybe a few more weeks than that, and all of the rest of the world would also see evidence of it on their sidewalks. Cold happens, heat is trapped, rains come. Not much more after a few years. No event like that makes all life extinct. We are evidence of that.

We are in a warming phase of a precession-induced ice-age cycle. The glass is half full IMO, but the air is bad in places.
baudrunner
2 / 5 (4) Nov 26, 2015
The explosion of Mount Tambora is the largest ever recorded by humans, ranking a 7 (or "super-colossal") on the Volcanic Explosivity Index, the second-highest rating in the index. The volcano, which is still active, is one of the tallest peaks in the Indonesian archipelago.

The eruption reached its peak in April 1815, when it exploded so loudly that it was heard on Sumatra Island, more than 1,200 miles (1,930 km) away. The death toll from the eruption was estimated at 71,000 people, and clouds of heavy ash descended on many far-away islands.


http://www.livesc...ory.html

That was 1815. And it's getting warmer, mmm, I like it.

runrig
5 / 5 (6) Nov 26, 2015


We are in a warming phase of a precession-induced ice-age cycle.


Really?
Mr Milankovitch would disagree.....
We're actually in a cooling phase 11ky after the Holocene climatic optimum, err, which followed the last IA.

https://www.cabri...orth.jpg

KBK
2.1 / 5 (7) Nov 26, 2015
Interesting that they have an 'attack' issue in Paris .....and then shortly after..while the area is essentially under martial law, so no reporting, no gatherings, no protests..for a huge meeting of world leaders and their representatives... that are there to make a LEGALLY BINDING agreement that BYPASSES all national systems of sovereignty.

Read that again...... legally binding agreements that bypass all systems of national sovereignty, ie a world government wedge, infiltration.... and loophole.

A legally binding world government attack whip, and it only cost 129 lives to distract from it's initiation.

Funny dat, eh?

How did this one sneak by?

While all those people are distracted?
marcush
4.3 / 5 (6) Nov 27, 2015
Yep the worlds climate scientists are working with Isis to bring on a socialist world government. You guys are a bunch of Wackos.
gkam
1.5 / 5 (8) Nov 28, 2015
marcush, Our conservatives are at it again, this time in Colorado Springs, but the mental construct is there: Destroy what you fear. The problem is, conservatives are SCARED. They are scared of paying taxes, they are scared of another race marrying their children, they are scared of others getting help from the government, they are scared of Muslims, they are scared of others "sinning", and they are terrified of the god they invented in their little minds.

Now, they assume all who have other ideas are in a conspiracy. Well it is true: It is a Conspiracy of Reality. The Real World is conspiring to disabuse these goobers of their silly ideas and paralyzing fears.
TheGhostofOtto1923
3 / 5 (2) Nov 30, 2015
marcush, Our conservatives are at it again... they are scared of another race marrying their children, they are scared of others getting help from the government, they are scared of Muslims, they are scared of others "sinning", and they are terrified of the god they invented in their little minds
-So how come its so obvious that youre the stinking bigot here?

"Those of us who have had experiences with psychopaths know that the language of the psychopath is two-dimensional. They are, as someone once said, as "deep as a thimble.""
leetennant
3.7 / 5 (3) Nov 30, 2015
Yep the worlds climate scientists are working with Isis to bring on a socialist world government. You guys are a bunch of Wackos.


Well, they already had a conspracy involving every government, every climate scientist and every scientific organisation across the entire world for the LAST 200 YEARS so adding ISIS to it wasn't really that hard.

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