Models show how to limit global temperature rise to 1.5 C

global warming
Credit: CC0 Public Domain

There are several ways to limit global temperature rise to 1.5°C by 2100, and new research led by IIASA researcher Joeri Rogelj shows under what conditions this could happen.

The team's paper, published in Nature Climate Change, is the first to look at how socioeconomic conditions such as inequalities, , and international cooperation might affect the feasibility of achieving these goals, and also considers technological and resource assumptions.

"One of the goals of the Paris Agreement is to limit warming to 1.5°C, but scientific studies mainly looked at the question of limiting warming to 2°C. This study now fills this gap and explores how by the end of the 21st century can be brought in line with 1.5°C of warming. Individual studies have looked at this question in the past, but this study is the first to use a broad and diverse set of models," says Rogelj.

The researchers used six integrated assessment computer models that attempted to model scenarios limiting warming by the end of the century to 1.5°C, under five so-called Shared Socioeconomic Pathways (SSPs). The SSPs, developed previously by IIASA and other key partner organizations, look at different ways the world and society could progress, including one in which the world pursues sustainability, one in which economic and population growth continue much as they have done historically, and another in which the world pursues high economic growth with little emphasis on sustainability.

The computer models could not find a scenario that would limit warming to 1.5°C in all of the SSPs. All of the successful scenarios include a rapid shift away from fossil fuel use toward , lowered energy use, and the removal of CO2. Strong social and economic inequalities, a focus on continued high fossil-fuel use, and poor short-term policies emerged as key barriers to achieving the 1.5°C goal.

"A critical value of the paper is the use of the SSPs, which has helped to systematically explore conditions under which such extreme low targets might become attainable. Our assessment shows particularly the enormous value of pursuing sustainable development for reaching extreme low climate change targets. On the other hand, fragmentation and pronounced inequalities will likely come hand-in-hand with low levels of innovation and productivity, and thus may push the 1.5°C target out of reach," says IIASA Energy Program Director and coauthor Keywan Riahi.

In the successful scenarios, by 2030, greenhouse gas emissions had peaked and begun a decline that continued rapidly over the following two to three decades. Zero net were reached between 2055 and 2075. Energy demand was limited by improving energy efficiency measures. In the SSP where economic and population growth continue as they have done historically, energy demand in 2050, for example, was limited to 10-40 percent above 2010 levels.

Bioenergy and other renewable technologies, such as wind, solar, and hydro, scaled up drastically over the coming decades in successful scenarios, making up at least 60 percent of electricity generation by the middle of the century. This marks a clear shift away from unabated fossil fuel use, without carbon capture and storage. Traditional coal use fell to less than 20 percent of its current levels by 2040 and oil was phased out by 2060. Negative emissions technologies, such as bioenergy with carbon capture and storage (BECCS) and both afforestation and reforestation, are considered as means to additionally remove CO2 from the atmosphere.

The 1.5°C pathways created as part of the study will now be used by the wider climate change research community to run the most complex coupled climate models. This will serve as a starting point for further research, enabling better understanding of the residual impacts at low levels of global warming.

"The study provides decision makers and the public with key information about some of the enabling conditions to achieve such stringent levels of climate protection," says Rogelj.

The researchers stress that more work will be needed. The scenarios can only take into consideration technological and economic feasibility. In the real world, other factors, such as social acceptability and international cooperation, for example, can have a large effect on feasibility. Policy advisors will need to take these into consideration.


Explore further

Thinking outside the box on climate mitigation

More information: Rogelj J, Popp A, Calvin KV, Luderer G, Emmerling J, Gernaat D, Fujimori S, Strefler J, Hasegawa T, Marangoni G, Krey V, Kriegler E, Riahi K, van Vuuren DP, Doelman J, Drouet L, Edmonds J, Fricko O, Harmsen M, Havlík P, Humpenöder F, Stehfest E, and Tavoni M (2018) Scenarios towards limiting global mean temperature increase below 1.5 °C. Nature Climate Change DOI: 10.1038/s41558-018-0091-3
Journal information: Nature Climate Change

Citation: Models show how to limit global temperature rise to 1.5 C (2018, March 5) retrieved 25 June 2019 from https://phys.org/news/2018-03-limit-global-temperature.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
164 shares

Feedback to editors

User comments

Mar 05, 2018
For the uninformed, the "computer models" are based on flawed assumptions and incomplete understanding of complex processes that interact chaotically. The most recent compilation of climate studies by the IPCC, AR5 in 2013, showed the computer models were way off. This graphic shows the difference between dozens of model simulations of global temperature and measured temperatures:

https://www.ipcc....S-14.jpg

The models haven't gotten better since then. Garbage in, garbage out, as they say.

The "1.5°C pathway" is essentially the RCP2.6 scenario where all major countries on earth coordinate together to drastically (and extremely expensively) reduce CO2 emissions. It's a fantasy scenario that will never happen, but interestingly, the actual measured temperatures show that "business as usual" (doing very little) are producing temperatures in the RCP2.6 range (dark blue lines).

Mar 05, 2018
So, aksdad, if I understand correctly? Your contention is in itself created from bad data and sloppy procedures?

That you are claiming that previous errors and lack of reliable data collection invalidate new data from still developing technology, still evolving procedures?

And we should all just sit around, our asses firmly planted upon our thumbs and avoid making any decisions that do not meet your insistence that this is "The Best of All Perfect Worlds"?

Please share with the rest of us the roadmap to that pluperfect fantasyland you inhabit.

So we too can escape the oncoming catastrophe looming over the real world.

Mar 05, 2018
For the uninformed, the "computer models" are based on flawed assumptions and incomplete understanding of complex processes that interact chaotically. The most recent compilation of climate studies by the IPCC, AR5 in 2013, showed the computer models were way off. This graphic shows the difference between dozens of model simulations of global temperature and measured temperatures:

https://www.ipcc....S-14.jpg

The models haven't gotten better since then. Garbage in, garbage out, as they say.).


Thanks, aksdad. That's actually from 8 years ago and shows that observations at that time were within the projection bands. You really do see what you want to see, don't you?

Mar 05, 2018
That you are claiming that previous errors and lack of reliable data collection invalidate new data from still developing technology, still evolving procedures?

Despite "developing technology" and "evolving procedures" in climate modeling, there has been no substantial improvement in accuracy.

As of March, 2017 the models are still way off (see graph on p.5):
https://science.h...0329.pdf

Please share with the rest of us the roadmap to that pluperfect fantasyland you inhabit. So we too can escape the oncoming catastrophe looming over the real world.

This: Don't worry, be happy.
https://www.youtu...iB65scQU

Relax. So far there is zero evidence that there is an "oncoming catastrophe". All the evidence points to warming, sea level rise, etc. well within natural variation. I'll include some links so you can see for yourself.

Mar 05, 2018
That's fantastic. I particularly love where he's averaged out the climate models to create a singular projection line and fails to represent MoEs. I also love that his observation line is cherry picked and fails to include 90% of temperature observations that show that temp increases to 2015 were around 0.4 of a degree higher than represented.

That's some quality work right there. That level of obfuscation takes serious fucking effort.

Mar 05, 2018
That's actually from 8 years ago and shows that observations at that time were within the projection bands.

Stating that measured temperatures were "within the projection bands" requires seeing "what you want to see" doesn't it? Even in 2012, which is 6 years ago, measurements were at the very bottom of the "projection bands". Since 2012 global temperatures remained flat with a bump up from the huge 2017 El Niño which is already receding (note the 1998 temperature bump from that year's big El Niño).

https://www.nsstc...copy.png

So the models are even FURTHER off now. From CMIP5 model runs in 2016 (see p. 5):

https://science.h...0329.pdf

Bottom line? The models are wrong, which is understandable because they are attempting to model a coupled, non-linear chaotic system with limited understanding of the parameters.

Mar 05, 2018
Within the projection bands is within the projection bands. It's not "way off". It literally means that observations were projected.

And if you want to bring in the ENSO cycle then how about you acknowledge that the temperatures seen during the most-recent El Nino had a mean shifted significantly upward from the last El Nino in 1998. You know, the one you're using to pretend that temps aren't increasing despite the fact that 10 of the hottest years on record were this century.

What's the matter? You don't actually have a source that shows how the observations were well outside the projection bands and are therefore "way off"?

Mar 05, 2018
Now to actually comment on this article:

In all the optimism, it could be easy to miss this:

The computer models could not find a scenario that would limit warming to 1.5°C in all of the SSPs. All of the successful scenarios include a rapid shift away from fossil fuel use toward low-carbon energy sources, lowered energy use,

* and the removal of CO2 *

That last one is the kicker. We cannot meet 1.5 degrees without geoengineering. Fucking around with the climate when we don't know what we're doing is what got us into this mess in the first place. The only way we limit to 2 degrees is by shifting to a low-carbon economy right now. And that will never happen.

Mar 05, 2018
I also love that his observation line is cherry picked and fails to include 90% of temperature observations


There's nothing cherry-picked about it. The global temperature data line is from widely-used data sets. See the following, paying close attention to how they match up with Christy's graph of observations between 1980 and 2016.

Berkeley Earth temperature:
http://berkeleyea...arge.png

UAH Satellite:
https://www.nsstc...copy.png

RSS Satellite:
http://images.rem...ies.html

HadCRUT4 (note "Global" temperature in bottom graph):
https://crudata.u...RUT4.png

Still waiting for you to show us your data that refutes 2 different graphs that show the models are wildly inaccurate and getting worse with each passing year.

Mar 05, 2018
Since 2012 global temperatures remained flat with a bump up from the huge 2017 El Niño which is already receding (note the 1998 temperature bump from that year's big El Niño)..


The 2017 report from NOAA notes that temperatures are now about 1 degree for the first time IN THE ABSENCE OF AN EL NINO

https://www.ncdc....l/201713

Mar 05, 2018
Here's NOAA's report from 2015, which is the year mentioned in that graph, and it clearly shows that the average global temperature across land and ocean surface areas for 2015 was 0.90°C (1.62°F) above the 20th century average of 13.9°C (57.0°F), beating the previous record warmth of 2014 by 0.16°C (0.29°F).

https://www.ncdc....l/201513

Here's NASA's report that also shows temperatures at around 1 degree C for that same period

https://svs.gsfc....ata.html

And yet that graph says temp rises are 0.5 degrees? In what universe?

Mar 05, 2018
Within the projection bands is within the projection bands. It's not "way off". It literally means that observations were projected.

Apparently you didn't look at Christy's graph as of the end of 2016.

temperatures seen during the most-recent El Nino had a mean shifted significantly upward from the last El Nino in 1998

Sorry, the El Niño was in 2016. Max global temperatures in 2016, measured by satellite, exceeded the 1998 El Niño by about 0.1° C; a statistical tie. In other words, warming has leveled off over the last 20 years, while the CMIP projections continue to show warming. They are no longer "within the projection bands". Even James Hansen, a vocal proponent of catastrophic climate change, cautioned that the warming hiatus may continue for another decade:

http://www.columb...2017.pdf

Mar 05, 2018
From the NOAA page:

global land and ocean temperature for the month of March 2017 was 1.03°C (1.9°F) above the 20th century average—this marked the first time the monthly temperature departure from average surpassed 1.0°C (1.8°F) in the absence of an El Niño episode in the tropical Pacific Ocean.

Typical of temperature reports by alarmists, it's cherry-picked and qualified to imply something astonishing, but in fact it's meaningless. It's talking about a 1.03°C variance "in the tropical Pacific Ocean". That's from a temperature data set (satellite) that only extends back to 1979, not the "20th century average". That's like saying the temperatures in Haiti in March 2017 were 1°C above the most recent 30-year average. So? Meanwhile GLOBAL temperatures in March 2017 were about 0.25°C above the 30-year average (not 1.03°C). And the El Niño bump is fading.

https://www.nsstc...copy.png

Mar 05, 2018
"The globe isn't warming, you can see this clearly from NOAA data".
"You mean this NOAA data that shows the globe is warming?"
"NOAA are LIARS and their data CANNOT BE TRUSTED".
"But you just... ergh, I give up".

Mar 05, 2018
Saving the planet and humanity from the apocalyptic eco-disasters always have the same solutions:

Transferring trillions of dollars from western countries (mainly the US) to unelected, unaccountable international elites to disperse as they see fit.

Impoverishing the prols and forcing them to live a 'sustainable' lifestyle (not surprisingly, the uber wealthy and politically connected won't be affected).

And curtailing our freedoms for the 'good of the planet'.

I doesn't matter whether the predictions are overpopulation, destruction of the oceans, global cooling or global warming; it's always the same solutions. It's almost as if the people pushing these dire prophecies are just power hungry wannabe tyrants who despise the prols.


Mar 06, 2018
I have to agree with @Leetennant, Either the science is good and projections are on target, and/or your just making stuff up to hear yourself talk. Regardless of which trendline you pick, the lowest or the highest, all of the trajectories are going up. And just like Al Gore's "Indisputable Truths" argued, CO2 levels are leading the trajectory. Solar input is certainly not going exponential. like CO2 levels and global temperature measurements.

The last I read, Earth is following some of the extremely high trend lines for future planetary warming. The trendlines that read, 6 to 8 degree C by 2100. Your a fool if your not concerned by simulations predicting the high end as new measurements are added to the sims. Personally I look at them, and I go "YIKES!" be it 2C, 3C, 4C, 5C, 6C, 7C, 8C, 9C or 10C. Why? Becaust that is just the beginning.



Mar 06, 2018
For the uninformed, [...]


http://www.dictio...se/irony

Mar 06, 2018
I have an idea. Let us put our futures in the hands of modelers. Absolutely nothing could go wrong with that.

Mar 06, 2018
The deniers, overpaid shills for the Carbon Lobby. Insist on belaboring their agitprop. With deliberate lies and false obfuscations as 'proof' that there is nothing to be concerned about.

Why? Why because they say so! They got their thirty pieces of silver, so all is right with the world.

Mar 06, 2018
1)The deniers, 2)overpaid shills for the 3)Carbon Lobby. Insist on 4)belaboring their agitprop. With 5)deliberate lies and 6)false obfuscations as 'proof' that there is 7)nothing to be concerned about.

Why? Why because they say so! They got their 8)thirty pieces of silver, so 9)all is right with the world.
All right this post is NOTHING BUT slogans.

A definite giveaway.

"... an inner world that is banal, sophomoric, and devoid of the color and detail that generally exists in the inner world of normal people. This goes a long way to explain the inconsistencies and contradictions in their speech."

-The evidence mounts.

Mar 09, 2018
What a lot of chatter as the planet heats. This illustrates perfectly how and why humanity will disappear along the line of extinctions already happening in the thousands annually.
The temperatures talked about are just that, temperatures talked about, no relevance to the real wortld since they were chosen by politicians as a range they have been told we could cope with, but with no idea how that would be achieved.
Emmissions are still rising. It's important to restate that fact, we haven't even this far down the line managed to reduce emmissions' RISE yet, just the RATE of INCREASE is slowed. And since even if wee were able to cancel all emmissions right now, warming would continue for several more centuries, it isn't too difficult to see we won't make it, haven't the necessary determination to make it, and will become extinct by the next century, perhaps at the end of this one if the 'unforeseen' feed-ins continue to add to the mix.
It will be a good thing for the planet.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more