From the NATIONAL CENTER FOR ATMOSPHERIC RESEARCH (home of Dr. Kenneth Trenbert) and the “backpedaling on climate, it’s a travesty” department comes this story that sure looks like they realize climate sensitivity is lower than originally thought. Or, maybe it’s because they finally realize they can’t preach for low emissions when their own coal-power-driven supercomputing center in Wyoming has a massive carbon-footprint.
Reconciling Paris Agreement goals for temperature, emissions
New study finds two targets don’t always go hand in hand
BOULDER, Colo. — As society faces the challenge of limiting warming to no more than 2 degrees Celsius, new research finds an apparent contradiction: Achieving that goal doesn’t necessarily require cutting greenhouse gas emissions to zero, as called for in the Paris Agreement. But under certain conditions, even zero emissions might not be enough.
The Paris Agreement, a global effort to respond to the threats of human-caused climate change, stipulates that warming be limited to between 1.5 degrees C (2.7 degrees Fahrenheit) and 2 degrees C (3.6 degrees F). It also stipulates that countries achieve net-zero greenhouse gas emissions in the second half of this century. But the relationship between the two — is the emissions goal sufficient or even necessary to meet the temperature goal? — has not been well understood.
In a new study published in the journal Nature Climate Change, scientists used a computer model to analyze a variety of possible future scenarios to better understand how emissions reductions and temperature targets are connected. The study, published March 26, was led by Katsumasa Tanaka at the National Institute for Environmental Studies in Japan and co-authored by Brian O’Neill at the U.S. National Center for Atmospheric Research.
“What we found is that the two goals do not always go hand in hand,” Tanaka said. “If we meet temperature targets without first overshooting them, we don’t have to reduce greenhouse gas emissions to zero. But if we do reduce emissions to zero, we still might not meet the temperature targets if we don’t reduce emissions quickly enough.”
The team also found that whether temperatures overshoot the target temporarily has a critical impact on the scale of emissions reductions needed.
“If we overshoot the temperature target, we do have to reduce emissions to zero. But that won’t be enough,” Tanaka said. “We’ll have to go further and make emissions significantly negative to bring temperatures back down to the target by the end of the century.”
The research was supported by the Environment Research and Technology Development Fund (2-1702) of the Environmental Restoration and Conservation Agency in Japan and by the U.S. National Science Foundation, NCAR’s sponsor.
Drafted in 2015, the Paris Agreement has been ratified by more than 170 countries. President Donald Trump announced last year the intention to withdraw the United States from the agreement.
Modeling the problem from both sides
For the study, the researchers used a simplified integrated assessment model that takes into account the physical connections between greenhouse gases and global mean temperature in the climate as well as the economic costs of emissions reductions.
“We investigated the consistency between the Paris targets in two ways. First we asked, what happens if you just meet the temperature target in a least-cost way? What would emissions look like?” said O’Neill, an NCAR senior scientist. “Then we said, let’s just meet the emissions goal and see what kind of temperatures you get.”
The team generated 10 different scenarios. They found that Earth’s warming could be stabilized at 1.5 or 2 degrees C — without overshooting the goal — by drastically cutting emissions in the short term.
For example, total greenhouse gas emissions would need to be slashed by about 80 percent by 2033 to hit the 1.5-degree target or by about two-thirds by 2060 to meet the 2-degree target. In both these cases, emissions could then flatten out without ever falling to zero.
Due to the difficulty of making such steep cuts, the scientists also looked at scenarios in which the temperature was allowed to temporarily overshoot the targets, returning to 1.5 or 2 degrees by the end of the century. In the 1.5-degree overshoot scenario, emissions fall to zero by 2070 and then stay negative for the rest of the century. (Negative emissions require activities that draw down carbon dioxide from the atmosphere.) For the 2-degree temporary overshoot scenario, emissions fall to zero in 2085 and also become negative, but for a shorter period of time.
On the flip side, the scientists also looked at scenarios where they set the emissions levels instead of the temperature. In those cases, they analyzed what would happen if emissions were reduced to zero around mid-century (2060) or at the end of the century (2100). In the first case, the global temperature peaked around the 2-degree target and then declined. But in the second case, the temperature rose above 2 degrees around 2043 and stayed there for a century or more.
“The timing of when emissions are reduced really matters,” O’Neill said. “We could meet the goal set out in the Paris Agreement of reducing emissions to zero in the second half of the century and still wildly miss the temperature targets in the same agreement if we wait to take action.”
The new study is part of a growing body of research that seeks to better understand and define what it will take to comply with the Paris Agreement. For example, another recent study — led by Tom Wigley, a climate scientist at the University of Adelaide who holds an honorary appointment at NCAR — also looks at the quantity and timing of emissions cuts needed to stabilize global temperature rise at 1.5 or 2 degrees above preindustrial levels. This work focuses in particular on implications for emissions of carbon dioxide, the main component of the broader greenhouse gas emissions category that makes up the Paris emissions target.
O’Neill and Tanaka believe their work might be useful as countries begin to report the progress they’ve made reducing their emissions and adjust their goals. These periods of reporting and readjusting, known as global stocktakes, are formalized as part of the Paris Agreement and occur every five years.
“Our study and others may help provide countries with a clearer understanding of what work needs to be done to meet the goals laid out in the agreement. We believe that the Paris Agreement needs this level of scientific interpretation,” Tanaka said.
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The study:
The Paris Agreement zero-emissions goal is not always consistent with the 1.5 °C and 2 °C temperature targets
Abstract
The Paris Agreement stipulates that global warming be stabilized at well below 2 °C above pre-industrial levels, with aims to further constrain this warming to 1.5 °C. However, it also calls for reducing net anthropogenic greenhouse gas (GHG) emissions to zero during the second half of this century. Here, we use a reduced-form integrated assessment model to examine the consistency between temperature- and emission-based targets. We find that net zero GHG emissions are not necessarily required to remain below 1.5 °C or 2 °C, assuming either target can be achieved without overshoot. With overshoot, however, the emissions goal is consistent with the temperature targets, and substantial negative emissions are associated with reducing warming after it peaks. Temperature targets are put at risk by late achievement of emissions goals and the use of some GHG emission metrics. Refinement of Paris Agreement emissions goals should include a focus on net zero CO2—not GHG—emissions, achieved early in the second half of the century.
https://www.nature.com/articles/s41558-018-0097-x
Mods: typo? First sentence, first paragraph. Is it “Trenbert”? or “Trenberth”. His email address starts with “trenbert@…” but surname is “Trenberth”?
” . . .we still might not meet the temperature targets ”
Their target is bogus, as is the ream of stapled country papers called the Paris Agreement.
They could read about the Texas Sharpshooter, then adjust the target accordingly.
PAPER !
What’s that ?
“On the flip side, the scientists also looked at scenarios where they set the emissions levels instead of the temperature. In those cases, they analyzed what would happen if emissions were reduced to zero around mid-century (2060) or at the end of the century (2100). In the first case, the global temperature peaked around the 2-degree target and then declined. But in the second case, the temperature rose above 2 degrees around 2043 and stayed there for a century or more.”
In order to get to zero emissions by 2100, we would have to reduce current emissions by about 1.22% per year, according to a linear trend, and the “scientists” also believe that would result in a 2-degree temperature rise by 2043, or 25 years from now, or an average rise rate of 0.08 C per year.
Why do these “scientists” think that reducing emissions will result in an average rise rate of 0.08 C per year, when since the 1975 low point (after a period of falling temperatures), temperatures have risen by less than 0.03 C per year on average, during a period of rising CO2 emissions? What would cause such an acceleration (more than doubling) in the temperature rise rate?
So, if CO2 emissions are not reduced from their present levels, and temperatures actually rise less than 2 C by 2043, will these scientists admit they were wrong about their predictions? After all, past models have over-estimated the temperature rise observed so far!
By the way, how do the scientists propose to get to zero emissions? Build nuclear power plants everywhere, and use plug-in electric cars? But if someone in the year 2100 is shivering in a nor’easter and throws another log on their fire, that’s still emitting CO2!
With apologies to ‘HotScot’, I believe the Tanaka-O’Neill paper is a confuséd mess. I would like to see the 2-degree target surpassed and hear the warmist explanations for why the world has become a more fecund and livable place.
I’m with you…..jump this thing up 2 degrees and get it over with….then, when nothing happens…maybe they will shut up
….on a positive note….the way they are adjusting temps it might happen sooner than they think
It doesn’t make sense as a scientific report because it is not a scientific report. It is political. What they are trying to do is spur action now while they still have some momentum left. Public interest is waning. Hence: “we got to act now, if we act later it will be too late.” to paraphrase all they are saying.
Yeah, it’s the latest iteration of, “Soon it will be too late, but we can save the planet if we just ACT NOW.” More rushing to codify the BS into law so nobody can undo the (REAL) catastrophe even after the pseudo-science they have used as the excuse for the “agenda” was a bunch of nonsense.
Meanwhile, the loudest blather comes from the nations whose emissions are rising, “Paris” be damned, and the nation who refuses to support the delusion is the only one with falling emissions. They can stick the Paris agreement and every other one like it where the sun doesn’t shine, it was just a money grab like the whole damn scheme.
…was SHOWN TO BE a bunch of nonsense…(typo)
Well certainly looks to me they just adjusted their simplified model to give them the exact snswer they already ordained.
In 20 years my CO2 emissions will be zero. Happy to do my part!
Think of the trees.
“Conserving our oil and gas reserves isn’t a terrible idea, anyway”
Indeed. There will be more of the stuff left in the ground for future generations to benefit from. And while they do so, they’ll maybe ponder how it was that their ancestors were fooled into leaving it there.
When one’s main fails, rather than admit to being wrong, one finds a convenient 2nd, or 3rd, … argument. It’s called lying to oneself.
If leaving it in the ground means the children/grandchildren end up being poorer, then we have done them no favors.
DaveS,
if we should ever solve the problem of controlled thermonuclear fusion, the hydrocarbons left in the ground will be practically worthless. With cheap energy of the electric kind, it will be possible to make designer molecules for things like plastics and lubricants without needing fossil hydrocarbons. Your remark is a bit like saying “Why did those of the neolithic period leave behind so much flint?” While good flint was highly prized by those living prior to the age of metallurgy, today it probably finds its greatest use in bolo-tie jewelry..
1.5C measured from When? This has been obfuscated a few times. This ‘science’ seems to require flexible targets, effects and add-ons to keep it running. After arguing against The Pause for a decade and a half, they modelled it and homogenized it and “discovered” it would have to exceed 17 yrs before the “theory” was compromised, which it was. So, on the eve of his retirement, Karl Karlized (one of my several contributions to the terminology) not only temperature but the whole Pause – it had become an intractable problem for the Team.
The IPCCs position prior to all this was the CO2 problem began only after 1950. However, the length of the Pause was closing in on a tie with the duration of the alarming warming. Worse, most of the CO2 rise since 1950 occurred during The Pause!
What to do? Well the trashing of Michael Mann’s hockey stick, and reinstating the LIA gave an out. “Let’s let 1950s temperature ‘float’ at an ever changing uncertain level to be determined in the far distant future (recall Mark Steyn observation in the Senate hearing “How can one be so certain what the temp is in 2100 when we don’t even know what the temp will be in 1950!”), and let’s make use of the reinstated LIA. We’ll move the beginning of the CO2 problem back 100 years giving us a bigger temperature rise and reducing the effect of The Pause.
Moreover, with Climate Sensitivity’ declining with each study, and forecast warming too hot by 200%, a much smaller CO2 warming is in the offing. What to do? ” I got It! instead of 3-5C of warming from 1950 being the end of the world, let’s make it, what, 2C from the end of the LIA for Armageddon. Heck, we’re halfway there”. This was in the middle of the Pause when it had been agreed to not notice it exists. With its embarrassing extension before Karlization, and after T observations stubbornly fell out the bottom of the projected envelope, 2C was beginning to look like an indigestable lump, so they bit the bullet and chopped another half a degree off the death by fire. This is all a left handed forecast that we can meet by doing nothing!
Late to the party here, but I know what the frequency is, and it ain’t Kenneth. It’s Kevin, but I can understand, as he mostly goes by “Travesty Trenberth”.
It is bizarre to me that knowing how the models have missed they wouldn’t have serious caveats in their statements. Given the lack of predictive ability of their models all statements as precise as we need to get emissions cut by 80% by this specific year and overshooting will produce this much temperature and we know the damage is so great that this will happen as a result so ….
JUST WORTHLESS GARBAGE. EVERYONE MUST KNOW IT AND YET THEY STILL SAY IT.