New paper by Nic Lewis and Judith Curry suggests future warming would be a third to nearly half of what the IPCC claims.
A paper just published by the Journal of Climate concludes that high estimates of future global warming from most computer climate simulations are inconsistent with observed warming since 1850. The implication is that future warming will be 30 to 45% lower than suggested by the simulations.
The study estimates climate sensitivity — how much the world will warm when carbon dioxide levels increase* — from changes in observed temperatures and estimates of the warming effect of greenhouse gases and other drivers of climate change, from the mid/late 19th century until 2016.
The paper also addresses previous criticisms of the methodology used, finding that these are unfounded.
Lead author Nicholas Lewis explains,
“Our results imply that, for any future emissions scenario, future warming is likely to be substantially lower than the central computer model-simulated level projected by the IPCC, and highly unlikely to exceed that level.”
He adds,
“Our new sensitivity estimates are slightly lower than those obtained in a predecessor study published several years ago, despite the inclusion of the strong 2015–16 El Niño warming. Importantly, the upper uncertainty bounds of the new estimates are much lower.”
Highlights
- The estimates of effective radiative forcing given in the latest IPCC Assessment Report (AR5) are used, extended up to 2016, with recent revisions to greenhouse gas forcing and post-1990 ozone and aerosol forcing estimates incorporated.
- A median estimate for ECS* of 1.66°C (5–95% uncertainty range: 1.15–2.7°C) is derived using globally-complete temperature data. The comparable estimate for 31 current generation (CMIP5) computer climate simulation models is 3.1°C.
- One of the chief criticisms of the method used is that it does not allow for the possibility of climate sensitivity varying with time after imposition of forcing, as it does in most CMIP5 models. However, the paper shows that when calculated so as to correctly reflect CMIP5 models’ behaviour, this possible effect is immaterial to either the study’s or CMIP5 models’ median ECS estimates.§
- A median estimate for TCR* of 1.33°C (5–95%:1.15–1.9°C) is derived using the same data. The comparable estimate for the 31 CMPI5 models is 1.9°C.
- The estimates of climate sensitivity are remarkably insensitive to the period of analysis chosen (see Figure 1).
Figure 1: Remarkably, estimation of climate sensitivity using the 1927–41 mean gives the same sensitivity estimate as using the 2007–16 mean. Circles show 1872–2016 pentadal-mean changes in net outgoing radiation (cyan pre-1927, blue post-1927) plotted against change in globally-complete surface temperature. The slope of the relationship is inversely proportional to climate sensitivity. Red squares show 15-year means from 1927–41 to 2007–16. Despite the effects of multidecadal internal variability, all the 15-year means lie close to the 1872–2016 pentadal-means regression best-fit line.†
- These median ECS and TCR estimates imply multicentennial or multidecadal future warming under increasing forcing of only 55−70% of the central warming projection using CMIP5 models.
- It has been suggested in various studies that forcing-efficacy effects (principally, cooling aerosol forcing having a stronger than normal effect), variability in sea-surface warming patterns and temperature estimation issues likely lead to climate sensitivity estimates based on warming over the last circa 150 years being biased low. All these issues are examined in detail in the paper, the conclusion being that very minor or no bias was to be expected when using globally-complete temperature data.
Nicholas Lewis and Judith Curry, 2018: The impact of recent forcing and ocean heat uptake data on estimates of climate sensitivity. Journal of Climate, Early Online Release https://doi.org/10.1175/JCLI-D-17-0667.1
Abstract
Energy budget estimates of equilibrium climate sensitivity (ECS) and transient climate response (TCR) are derived based on the best estimates and uncertainty ranges for forcing provided in the IPCC Fifth Assessment Scientific Report (AR5). Recent revisions to greenhouse gas forcing and post-1990 ozone and aerosol forcing estimates are incorporated and the forcing data extended from 2011 to 2016. Reflecting recent evidence against strong aerosol forcing, its AR5 uncertainty lower bound is increased slightly. Using a 1869–1882 base period and a 2007−2016 final period, which are well-matched for volcanic activity and influence from internal variability, medians are derived for ECS of 1.50 K (5−95%: 1.05−2.45 K) and for TCR of 1.20 K (5−95%: 0.9−1.7 K). These estimates both have much lower upper bounds than those from a predecessor study using AR5 data ending in 2011. Using infilled, globally-complete temperature data gives slightly higher estimates; a median of 1.66 K for ECS (5−95%: 1.15−2.7 K) and 1.33 K for TCR (5−95%:1.0−1.90 K). These ECS estimates reflect climate feedbacks over the historical period, assumed time-invariant. Allowing for possible time-varying climate feedbacks increases the median ECS estimate to 1.76 K (5−95%: 1.2−3.1 K), using infilled temperature data. Possible biases from non-unit forcing efficacy, temperature estimation issues and variability in sea-surface temperature change patterns are examined and found to be minor when using globally-complete temperature data. These results imply that high ECS and TCR values derived from a majority of CMIP5 climate models are inconsistent with observed warming during the historical period.
* Two standard metrics summarize the sensitivity of global surface temperature to an externally imposed radiative forcing. Equilibrium climate sensitivity (ECS) represents the change in temperature to a doubling of atmospheric CO2 concentration once the deep ocean has reached equilibrium. The transient climate response (TCR), a shorter-term measure over 70 years, represents warming at the time CO2 concentration has doubled when it is increased by 1% a year.
† Changes are relative to the 1850–1884 mean (this period has the same mean volcanic forcing as for 1850–2016). All volcanic forcing has been scaled by 0.55 to adjust for its low efficacy [discussed in the paper]. ΔR (= ΔF − ΔN) is estimated by scaling ΔF, based on ΔF and ΔN values for 2007–16.
§ This finding is in line with that in Mauritsen & Pincus 2017.
PDF copies of a version of the accepted manuscript for the paper and its Supporting Information, along with an article giving information about the paper and its findings, is available on Nicholas Lewis’s personal web-site, here. A blog-post version of the article is available at Judith Curry’s web-blog, here. Nicholas Lewis is the sole or lead author of six previous peer-reviewed papers about climate sensitivity.
Climate Sensitivity (ECS) is a bit of a myth. Mainly because water ignores it and provides the reactive mechanism to ensure the the Earth’s temperature remains within a suitable range to ensure continuity of life. It is remarkable that this has been going on for millions of years and we don’t appear to have noticed it. In rough terms say within about 3% of the optimum whatever that is?.
Mind you water is not very good at keeping us warm; but is very good at making sure we don’t roast. Hence long periods when it is too cold for our liking; interspersed with our current benign circumstances.
Engineers know how this is done; but scientists seem to be ignoring this, hell bent as the are on matters of radiation, when Enthalpy is the crux of the matter, where temperature is an “also ran” in the dealings with how Enthalpy moves around.
One fact which needs to be noted here (amongst many others) and that is that at phase change in water the ECS is a big fat Zero. There being a lot of water up there in the atmosphere and the speed at which it operates is a function of the equilibrium balance prevailing. It is a continuing process there in the clouds.
Don”t expect many will understand what I am talking about.
I think I’ve never heard so loud
The quiet message in a cloud.
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[ water … provides the reactive mechanism to ensure that Earth’s temperature remains within a suitable range to ensure continuity of life ]
Yep …. water explains it all. Increase heat, increases flow of heat to poles, melts ice cap, which shuts down flow of heat to poles, increases heat and evaporation and clouds at equator, decreases solar input, and poles refreeze, resulting in major albedo earth cools, ….. repeat.
CO2 is just an effect, outgassing. Has practically no impact, cause it can’t effect the incoming solar energy.
I hate backward ‘driving’ equations. Let’s call it what it is:
ΔR = 2.269 ΔT and
ΔT = 0.441 ΔR
Because, after all, we are lead to believe that it is the change in outgoing radiation (driven mostly by greenhouse gasses) that drives retained median temperature change, and not vice versa.
Sheesh
GoatGuy
Lewis and Curry’s new median estimate for ECS* of 1.66°C (5–95% uncertainty range: 1.15–2.7°C) is consistent with Chris Monckton’s calculation of ECS=1.2.
It would be a very satisfactory – if somewhat anticlimactic – resolution of the bitter and rancourous climate war to simply coalesce at a physically realistic and observation-consistent lower ECS of this order.
Oh but that would put the rent-seekers and the neo-Marxists out of the climate alarm business. Can’t have that.
Well let’s see how much warming we get this year, because its looking like mother nature has moved the NH into cooling mode for this summer. Why do l say this.?
Because since around 2005 there has been sharp declines in the Eurasian snow extent during May/June.
Last year bucked that trend, this year am expecting that trend to be busted big time.
Also am expecting a cooler northern Atlantic this summer. As there is likely to have been alot heat loss from the ice free waters in the NW Eurasian Arctic during March.
(less) by a third or nearly a half.
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Heh, Klipstein and Bellman beat me to it. Didn’t I learn years ago not to comment until I’d read the whole thread?
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I’ve found that the urge to appear witty usually overcomes cautious patience on a thread, Kim.
That’s MY urge.
EWCD, Explosive Witty Comment Disorder. I’m glad to see other sufferers.
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It’s interesting that Lewis and Curry get lower estimates than I do in my newly published paper, though mine are not too high either.
This is a summary of my peer-reviewed paper “On the influence of solar cycle lengths and carbon dioxide on global temperatures” recently published by the Journal of Atmospheric and Solar-Terrestrial Physics (JASTP), available at https://doi.org/10.1016/j.jastp.2018.01.026 , or in publicly accessible pre-print form at https://github.com/rjbooth88/hello-climate/files/1835197/s-co2-paper-correct.docx .
The paper builds on the work in the 1990’s by Friis-Christensen and Lassen, by adding a CO2 element to their model based on solar cycle lengths (SCLs). By using a linear regression model, statistical significance levels can be measured for these two effects. Using HadCRUT4 as the global temperature series, averaged over 11-year periods starting 4 years before solar cycle maximum, the CO2 variable is hugely significant, as it explains the overall upward trend, while the length of the previous cycle has a 1.3% significance level (more on this below), and this variable explains the wiggles in the graph which is Figure 1 of the paper.
The upshot of the analysis is an estimate of TCR (Transient Climate Response) of 1.93K, and of ECS (Equilibrium Climate Sensitivity) of 2.22K. Under an assumption of continuing increases of CO2 concentration by 2 parts per million each year, the expected HadCRUT4 anomaly in AD2100 is only 1.1K higher than it was during the period 1996-2006.
Allowing for the SCLs does make material (but not vast) differences:
• without them the TCR estimate would be 2.37K instead of 1.93K
• they explain 37% of the observed warming between 1980 and 2001
• without them the residual errors significantly differ from the model assumptions
And now, a few words on the statistics. For “layman” readers the meaning of the 1.3% above is that if there really is no solar effect, then it was an 80 to 1 shot or so against these observations having occurred. Of course, 80 to 1 shots do sometimes happen by chance, but…
For more mathematical readers, it is worth noting that compared with a lot of climate papers the statistics are pretty rigorous, with quoted significance levels rather than mere correlation values, and distributional tests on the residuals – specifically the Durbin-Watson test, which can detect missed low frequency effects as well as true serial correlation. And there are still papers published which use the bounds on DW significance rather than calculating the exact value as per my thesis of 40 years ago. To allow others to benefit from these calculations, ‘R’ code for them may be found in the SI.
I intend to add more to this summary in the near future, but for now the bottom line is:
There is a statistically valid effect from solar cycle variation on global temperature.
These ceteris parabus ( all other factors being equal) studies are all well and good, but there seems to be s lack of awareness by climate researchers of the obvious time limitations on their possible usefulness (centennial scale).
We know with certainty that during periods in the past, temperatures rose rapidly with low unchanging levels of CO2 or fell during rising levels. Ice cores indicate that rising temperatures preceded rising CO2. Had we nice time series for such periods, we would be unlikely to expend time and money worrying about ECS of CO2 and if we did, we would arrive at ECS figures of colossal values both positive and negative!
This means certain non-CO2 drivers of T over longer periods greatly overwhelm the clearly modest effect that CO2 may have when the Big Movers are quiet.
Even with the centennial series, we get 30yr cooling reversals that much of Climate research has spent trying to erase because it’s implications for the mission are too terrible for them to contemplate . Homogenizing is an unfortunate revealing term. You could put the Amazon rain forest through a wood chipper and say we really didn’t change the essentials.
All climate researchers know this fact but put this CO2 stuff out as if it occupies a central place over earth temperature history.
1. Note: the myth of “gatekeeping” contrary findings is busted.
2. Note: Nic and Judith did not have to question known science ( c02 IS a ghg ) to establish a skeptical
position.
3. Note: They didnt have to slur people and accuse them of fraud to establish a skeptical position.
4. Note: they didnt have to rely on the weak argument that warming might be caused by “something else”
5. Note: They established a skeptical position from WITHIN the framework of accepted science.
6. Note: No need to misrepresent the working done on observations.
As I explained years ago the most effective way of challenging the science.. is…
Do science and publish it.
And to be really effective do it within the framework of existing science.
no sun nuttery required. No political attacks required. No claims of fraud or hoax required.
no grade school Monktonesque “we win, you lose” buffonery required.
Now imagine if ALL the skeptical energy were focused on the problem Nic has been talking about.
There is no doubt, Stephen Mosher is a good person. He cares enough about this topic that he comes back here again trying to help the rest of us despite the fact that he gets called out every time he posts.
Mosher is one the good guys. Trying to make society a better place. He has probably always been this kind of good moral person but also one who has mad skills.
Now, he hasn’t made a lot of headway with us skeptics. Maybe he is wasting his valuable skills trying to make us understand.
You know, maybe his logic and math skills could make a lot of money in the stock market instead, building up a cool retirement fund.
Yeah, riiight Bill. (i can just see mosh collecting tin cans in his retirement)…
He’s piling up the Bitcoins.
The correct answer is
“no one knows what ECS or TCS is”,
and no one may ever know in our lifetimes.
But the wild guessing
( educated guessing? )
will never stop.
I’m happy that the ECS / TCS
estimates by scientists have been
in a downward trend for a long time.
For many years it seemed like
climate “science” was nothing more
than extrapolating the warming
in the 1990s.
I suppose it still is for the corrupt IPCC,
whose published numbers are
apparently carved in stone (since 1979),
3.0 +/- 1.5 degrees C.,
and it seems those IPCC numbers
won’t ever change
even if Chicago and Detroit
were covered by ice again,
like they were 20,000 years ago !
The best we can do for now is
to make an assumption
that ALL warming after 1975
was caused by CO2,
to create a worst case
TCS estimate.
Unfortunately there are no global
surface data — too much infilling
(still true today) and too little
Southern Hemisphere data (before 1940)
… but there is near global
data from weather satellites,
with far less infilling, which
are verified by similar data
from weather balloons.
The era of man made CO2 is after 1940,
but we can live without 1940 to 1975 data,
when cooling was claimed, per surface data.
All of the known post-1940 warming was
after 1975.
Fortunately, we have satellite data
since 1979 — so we can assume ALL
warming since 1979 was caused ONLY
by CO2, and if we so that
worst case TCS would be about 1.
And that means CO2 is harmless,
even in a worst case situation where
we assume only CO2, and nothing else,
caused the warming since 1979.
Once you have that estimate of worst case
TCS, any complicated attempt to create a “better”
TCS estimate is likely to be a waste of time,
especially because there are no accurate global
temperature data before 1979.
Some so-called “scientists”
try to impress people
by estimating TCS or ECS in
in tenths or hundredths of a degree C.
per CO2 doubling = that’s false precision.
The TCS / ECS wild guessing
is not likely to stop
because it serves a purpose:
— Getting attention for scientists
who need to publish to justify
their salary (or their “expertise”).
A smart scientist would say
“I don’t know TCS or ECS,
but it must be low
because there’s no evidence
CO2 is harmful, and much evidence
CO2 is beneficial”,
… but I don’t hear that much,
so I have to assume
there are not that many smart
scientists out there who are adding
anything of value to real climate science
(as opposed to fake climate science,
where government bureaucrats
with science degrees play
computer games all day
and make wrong climate forecasts
… for 30 years so far ! ).
Sometimes the smartest person
in the room is the one who says
“I don’t know”, or
“No one knows
what TCS or ECS is”.
My own climate blog
with over 16,000 page views:
http://www.elOnionBloggle.Blogspot.com
ECS of 1.66 means that the observed warming in the second half of the 20th century was primarily caused by something else. QED
Mosh,
1. One need only be regular reader of Science and Nature to know that Gatekeeping is alive and well.
2. Lewis and Curry, 2018 maintain the possibility of higher bound of ECS to 2.7 K. Political correct and thus acceptable.
3. It is Mann who slurs Curry. The push-back from her peanut gallery defenders is justified, as Mann, Jones, et al are proven Liars by any objective assessment. Even you must know they are liars and hucksters.
4. “something else” is internal dynamical variability of the climate system that even Gavin S. acknowledges the models do not properly capture. No one actually knows what the real warming contribution of CO2 versus internal variability is. The IPCC pulled mostly (or majority) out of their collective ass.
5. Judith was driven out her faculty position and loss of funding by the “accepted framework”. Nuff said.
6. The observations (manipulated by infilling and homogenizations) are a separate topic. What is clear is surface temperature data sets do not adequately account for modern day UHI and loss of rural stations.
And yes, do science (little “s”). It is a method. Not a thing that must be defended like the rent-seeking partisans at the AAAS and Science (big “S” ) would like the public to believe.
…sun nuttery…
This coming from a man who calls svalgaard his go to guy on solar. Hey Mosh, are you aware that your go to guy doesn’t think that the oceans are warming? (you’re gonna look pretty stupid standing next to that guy on climate change judgement day)…
Here’s a little sun nuttery for Sloppy Steve:
(it’s called data, mosh, not sun nuttery)…
Note: Mr. Mosher Wanders in the Weeds and comes up with banalities. He can’t even build straw men well.
What the hell happened to the Chinese Bitcoin mining equipment venture?
I think we can just accept that people who care about Mother Earth, the animals, and global warming are good people. I mean they are the best of people.
We note they are very good people and care about the Earth we are leaving to our grandchildren and future generations. The people that care about this are just really good people.
They are so good that they should volunteer and doing other good things which have more immediate impact.
Focussing so much of their valuable attention on this very complicated theory about the quantum impacts of the diatomic molecule of CO2 in a gaseous atmosphere is not worth as much as volunteering and donating. They are very good people and they could put this virtue into things that have more impact than the complicated qauntum science theory of CO2.
Along similar lines all the innumerable morons and other physics illiterates among the so called “skeptics” could certainly do a better thing than post their idiotic babble here and elsewhere.
Ouch!
It doesn’t take a doctorate in physics to note that reality does not follow “physics-based” models.
Leave the future to richer, more technologically advanced people. By contrast, we are benighted rock-banging troglodytes. No matter our good intentions.
Really good people create really big problems.
I believe that the idea that adding CO2 to the atmosphere causes warming is hard coded in which totally begs the question as to whether CO2 causes warming and how bad will that warming be. These simulations are no more than a sophisticated form of make believe. There is no real evidence that CO2 has any effect on climate and plenty of scientific rational to support the idea that the climate sensitivity of CO2 os zero.
“plenty of scientific rationale to support the idea that the climate sensitivity of CO2 is zero”.
But there aren’t many peer reviewed papers which support that statement. The physics of greenhouse gases shows that without water and CO2 the Earth would be a lot (~30K) colder. It is just possible that the interaction of the major GHG water with the minor GHG CO2 totally annihilates the latter. But AFAIK no-one has proved this. Therefore the (wicked) question remains “how much effect does CO2 have?”.
My paper cited above assumes that the HadCRUT4 temperature record is uncontaminated by UHI and that there is no “natural rebound” from the LIA, both of which, despite what Mosher says, are dubious assumptions. I shall be happy to see papers that establish bounds on both of those two things, and then I’ll be able to refine my model and climate sensitivity which, for now, remains pleasantly lukewarm.
R. J. Booth
If you look at the surface temperature data
since 1900, there is nothing different
or unusual in the second half of the 20th century,
when compared to the first half of the 20th century.
That’s means there is no evidence
in the average temperature compilations
that manmade CO2 (after 1940)
did anything to the average temperature that
could not have had natural causes.
But … if you believe the lab experiments
showing that CO2 is a “greenhouse gas”,
then it should cause some warming,
but if it does, there is no way to
distinguish between the natural warming trend
in the first half of the 20th century,
not caused by CO2, and the similar warming trend
in the second half of the 20th century.
So the temperature evidence,
and I know the data are low quality,
tell us TCS must be so low that we can’t distinguish
between one half century with little man made CO2
and the later half of the same century
with lots of man made CO2.
Conclusion:
CO2 is at worst harmless,
concerning night time warming,
and at best very beneficial
concerning greening our planet
The only way to get high ECS estimates is to play with historical aerosol amounts. Until the IPCC or CMIP organizations demand consistent estimates of historical aerosol forcings, models are bunk.
There is a big problem with this. If it’s true that sensitivities are lower than being used in the models then how can people be frightened into going along with the GW/CC agenda?
There is no need to fool everyone. Just give a few what they want and they will scare the rest.
Isaac Newton produced almost as much religious writing as went into his Principia. One of the human indelible human traits he noted in his religious notes was the inveterate human fondness for superstition. The ancient Egyptian although lacking the “shoulders of giants to stand on,” like Newton, had a strikingly advanced science, including knowledge that the Sun was a star and that the planets, including Earth, orbited it. They surmised that all other stars had planetary systems, too. The Egyptian educated and priestly classes also had a very abstract religion consonant with their scientific understanding. For commoners, however, the priestly elite provided a multitude of pagan animal gods and relics to worship. In the introductory chapter of his “Heaven and Earth,”
Ian Plimer called AGW an urban atheistic religion very like a fundamentalism. No doubt it satisfies the need in some people for a superstitious pagan belief, but it also seems to attract people capable of a fanatical devotion bordering occasionally on the psychotic. I imagine any of the skeptical website hosts could exhibit several volumes of hate from their email.