Projecting manmade climate change: scenarios to 2050

Reposted from Dr. Judith Curry’s Climate Etc.

Posted on May 19, 2021 by curryja | 

by Judith Curry

Stop using the worst-case scenario for climate change — more realistic scenarios make for better policy. 

The International Energy Agency has just published a document ‘NetZero by 2050: A Roadmap for the Global Energy Sector.‘  This document provides a comprehensive assessment of the challenges of reaching NetZero carbon emissions by 2050, along with clear milestones for meeting this challenge.

The IEA report describes their analysis of the trajectory that our emissions is currently on. Policies that have actually been implemented (STEPS) versus the trajectory that would be achieved if all countries met their current commitments (APC) are shown in the diagram below. The implication of the IEA STEP scenario is that if policies that have already been implemented are maintained, the global carbon dioxide emissions three decades from now will be similar to what they are today. 

How do the IEA emissions scenarios compare with those used by the Intergovernmental Panel on Climate Change (IPCC) in their projections of future climate change?  A brief description of the emissions scenarios used by the IPCC is provided here for reference. 

The Representative Concentration Pathways (RCPs) are a set of four climate scenarios for the end of the 21st century. The RCPs were formulated for use in the 2014 Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report and the CMIP5 climate model simulations, to reflect different potential climate outcomes – RCP2.6, RCP4.5, RCP6.0 and RCP8.5.
The number (e.g. 8.5) reflects the additional radiative forcing (in Watts per square meter) in 2100 from greenhouse gas emissions and other factors, relative to pre-industrial times. To date, radiative forcing relative to pre-industrial levels is ~2.5 Watts per square meter. 

For the forthcoming IPCC Sixth Assessment Report (AR6) and the CMIP6 climate model simulations, Shared Socioeconomic Pathways (SSPs) are formulated from five socio-economic and technological trajectories that reflect pathways that the world could follow in the 21st century. Each pathway has a baseline in which no climate policies are enacted after 2010. Additional SSP scenarios are linked to climate policies to generate different outcomes for the end
 of the 21st century. A subset of SSP scenarios has been selected for the IPCC AR6, with radiative forcing of 1.9, 2.6, 3.4, 4.5, 6.0, 7.0 or 8.5 Watts per square meter in 2100.  While the SSP nomenclature is more recent, the scientific literature and journalists continue to mostly use the RCP nomenclature.

In comparing the IEA scenarios with the IPCC scenarios, we see that the value for 2020 is higher for the IPCC (38 – 42 GtCO2/yr) than for the IEA (34 GtCO2/yr, which is the best available estimate for 2020). The IPCC scenarios – both for CMIP5 and CMIP6 – are higher than the IEA projections for RCP8.5, RCP7.0, RCP6.0 and RCP4.5.  Out to 2050, RCP6.0 and RCP4.5 show similar, nearly flat trends that are comparable to the IEA STEP scenario.  

The most striking aspect of the comparison between the IPCC and IEA scenarios to 2050 is the strong divergence of RCP8.5 from the IEA scenario, with RCP8.5 emissions values more than twice as high as the IEA STEP scenario at 2050.

RCP8.5 was formulated to explore an extreme outcome that is judged by energy analysts to be extremely unlikely. However, RCP8.5 is commonly referred to as the  ‘business as usual’ scenario. Referring to RCP8.5 as ‘business as usual’ implies that it is probable in the absence of stringent emissions mitigation. The IPCC, the U.S. National Climate Assessment and a majority of published papers have centered their analyses on RCP8.5 as a reference scenario against which climate impacts and policies are evaluated.  Further, RCP8.5 is being used by the insurance sector for projecting climate change impacts and also by state and local governments for regional adaptation planning.

Over the past several years, there has been substantial debate over RCP8.5 – whether it is plausible or even possible, and whether it should be used for policy-making purposes. The 8.5 scenarios can only emerge under a very narrow range of circumstances, comprising a severe course change from recent energy use. Both the CMIP5 and CMIP6 8.5 scenarios have drawn criticism particularly regarding assumptions around future coal use, requiring 6.5 times more coal use in 2100 than today – an amount larger than some estimates of recoverable coal reserves.  A recent elicitation of energy experts gives RCP8.5 only a 5% chance of occurring among all of the possible no-policy baseline scenarios; the likelihood of RCP8.5 becomes much lower when recent and future commitments for policy actions are considered. 

In evaluating these scenarios, it is important to recognize that predicting future emissions is inherently uncertain, particularly as the time horizon increases. Poorly understood carbon feedbacks (such as methane emissions from thawing permafrost) could lead to higher forcing levels. However, such speculative feedbacks are unlikely to arise from the relatively modest warming expected between now and 2050. Another source of uncertainty relates to emissions from land use change, which is estimated to account for 5-15% of total emissions. But even with these uncertainties, RCP8.5 is an extremely unlikely, if not impossible, scenario for the 21st century.

We should rightly approach projections far into the future with humility and acknowledge that there is a great deal of uncertainty.  However, for 30-year projections to 2050, which is a key time scale of relevance to the insurance industry and for local adaptation, the range of plausible scenarios can be narrowed from the complete menu of IPCC emissions scenarios. 

Climate impact assessments are being biased in an alarming direction by continued inclusion, and especially sole reliance, on RCP8.5.  For climate change to 2050, RCP4.5 and RCP6.0 are the most likely of the IPCC scenarios, and should be the focus of impact assessments for the insurance sector and for local adaptation planning over the next several decades.



Previous blog posts:

Is RCP8.5 an impossible scenario?

What’s the worst case? Emissions/concentration scenarios

Non-technical articles:

Worst climate scenario probably wind happen, scientists say

Carbon Brief: Explainer: The high-emissions RCP8.5 global warming scenario

Global CO2 emissions are on the brink of a long plateau

Pielke Jr: In 2020 climate science needs to hit the reset button

How billionaires Tom Steyer and Michael Bloomberg corrupted climate science

If climate scenarios are wrong for 2020, can they get 2100 right?

Breakthrough Inst: A 3C world is now ‘business as usual’

Recent journal publications:

Hausfather and Peters: Emissions – the ‘business as usual’ story is misleading

Ritchie and Dowlatabadi: Why do climate change scenarios return to coal?

Pielke and Ritchie: Systemic misuse of scenarios in climate research and assessment

Burgess et al. IPCC baseline scenarios have over-projected CO2 emissions and economic growth

Kriegler et al.: Fossil fueled development (SSP5): An energy and resource intensive scenario for the 21st century

Wang et al.: Implications of fossil fuel supply constraints on climate change projections: A supply-side analysis

Christensen et al.: Uncertainty in forecasts of long-run economic growth

Hausfather and Peters: RCP8.5 is a problematic scenario for near term emissions

Schramm et al. Reply: RCP8.5 is neither problematic nor misleading

Bauer et al.: Shared Socioeconomic Pathways of the Energy Sector – Quantifying the Narratives

Gidden et al.: Global emissions pathways under different socioeconomic scenarios for CMIP6: a dataset of harmonized emissions trajectories through the end of the century

O’Neill et al: The Scenario Model Intercomparison Project

Riahi et al.: RCP8.5 – a scenario of comparatively high greenhouse gas emissions

Riahi et al.: Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas implications: An overview

Ritchie and Dowlatabadi: Defining climate change scenario characteristics with a phase space of cumulative primary energy and carbon intensity8

Van Vuuren et al.: Representative concentration pathways: an overview

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May 19, 2021 2:21 pm

The intent isn’t to project temperatures but to shame and scare countries into submission. If the maximum/minimum scenarios were reported no one would pay attention and the real goal of AGW wouldn’t be realized.

Izaak Walton
Reply to  markl
May 19, 2021 2:43 pm

So we are back to the idea of a global conspiracy of climate scientists who are secretly plotting to take over the world.

Bryan A
Reply to  Izaak Walton
May 19, 2021 2:50 pm

It’s worse case scenario than we thought

Reply to  Izaak Walton
May 19, 2021 2:56 pm

Izaak, Not at all. There are a few Western oligarchs who are profiting, and have experts in manipulation at their beck and call. Many scientists are in part victims, not helpless nor innocent, but victims of deliberate maneuvering to increase profits and dominate business rivals. You don’t need a conspiracy for that. And it has been exposed, repeatedly, here and elsewhere.

I disagree with markl in this sense — he describes a what I think of now as a tactic or a strategic position. It is just one of many that come from the same source. The goal is immense wealth for a few. A return to mercantilism or the days of the robber barons — seemingly with a few of the same family names as the last time around.

But labeling it, what ever it is, as a conspiracy is to diminish it without cause or evidence.

Reply to  dk_
May 19, 2021 3:12 pm

The Billionaires Jeremy Grantham and Christopher Hohn come to mind though I believe that both have made their own fortunes.

Reply to  Martin
May 19, 2021 3:23 pm

There’s a reference with link to a Pielke piece naming Steyer and Bloomberg in Dr. Curries non technical articles above. See WUWT post yesterday CLIMATE LITIGATION BOMBSHELL naming Rockefeller Families Trust with again Bloomberg. Other Pielke articles above, and on WUWT.

Izaak Walton
Reply to  dk_
May 19, 2021 4:23 pm

your scenario is still widely implausible. You appear to be suggesting that a few “western oligarchs” (whoever they might be) somehow decided that the best way to get rich was not to invest in conventional oil and gas and make a quick buck that way (maybe by persuading the USA to invade Iraq and steal their oil) but rather by getting “experts in manipulation” to convince all of the world’s climate scientists, major political parties (apart from the Republican party) all scientific organisations, the UN etc to believe that global warming was a threat and caused by CO2 emissions. Not only that they were apparently prepared to wait decades for this plan to come to fruition.

I am curious to know in what way you think the scientists are victims? Are the western oligarchs forcing them to publish wrong papers, feeding them incorrect data, making them all state that global warming is real and man made? And just how do these western oligarchs manage to manipulate scientists around the world from the USA to China, Russia etc?

Ron Long
Reply to  Izaak Walton
May 19, 2021 6:04 pm

Follow the money, Izaak Walton. The amount of grant money funding scientists who sing the company song is disgusting. The oligarchs mentioned are people who game the system, like Soros and Bloomberg. The scientists who say “wait a minute there is nothing unusual about these climate cycles” don’t get a dime. One hand washes the other and they both get clean, a formula from Roman times, still in effect today.

Izaak Walton
Reply to  Ron Long
May 19, 2021 6:33 pm

The amount of grant money allocated to climate science is small compared to overall government spending. The USA spends considerably more on nuclear weapons research for example so if scientists really wanted to get rich they would be looking for new ways to kill people. Secondly almost none of the grant money goes to the scientists who receive it. That money mostly goes on paying post-docs and lab assistants plus University overheads.

Teddy Lee
Reply to  Izaak Walton
May 20, 2021 1:19 am

False premise Izaak.
Every research program includes a reference to “climate”.That is the great grant scam.

Reply to  Izaak Walton
May 20, 2021 2:48 am

The money allocated to climate science compared to govt spending has no relevence. Over 35 years climate science/alarmism related funding has probably gone from millions to billions to 100s of billions if UN climate funding is included. This is a massive industry for pro AGW climate scientists. Motivation for money would have to be a major factor. Funding for scientists with a contrary view is almost non existant. Some data on this would be interesting.

Reply to  Izaak Walton
May 20, 2021 5:36 am

We’re talking Climate Scientists here. They’re the ones that are still not sure about what this scientific method is all about and make up their own statistics on the fly.

Reply to  Ron Long
May 19, 2021 8:24 pm

“The scientists who say wait a minute there is nothing unusual about these climate cycles” don’t get a dime.”
Umm because they are usually amateurs who are clueless or motivated by the fear of losing money. Show me a climate scientist who denies the current accepted position (that we are warming and it is indeed at least partly due to the burning of fossil fuels) and I’ll show you one who is a conservative concerned more with their political position than the science.

Reply to  Simon
May 19, 2021 9:10 pm

You haven’t even looked at a temperature graph or are completely credulous of people who shout “climate emergency” all the time. Thete is no way any sane person would give a rat’s ass about 1.5°C over the past 100+ years, and that’s without even taking into consideration that the ‘pre-industrial’ benchmark coincided with the end of the Little Ice Age. Based on agricultural info, we’re not even back up to the temperature range of the Medieval Period, much less the Roman or Minoan Period. You just have to put in ear plugs to muffle the propagandists and look at the facts

Reply to  PCman999
May 19, 2021 10:24 pm

Looked at plenty of graphs thank you. And plenty of sane people do care about such a sudden increase. The rest of what you have written is pure nonsense so we will leave it there.

Bill Toland
Reply to  Simon
May 19, 2021 10:49 pm

What part of what PCman has written is “pure nonsense”? What he is saying is the scientific consensus.

Reply to  Bill Toland
May 19, 2021 11:26 pm

There is no such consensus that the medieval warm period was as warm as today. And it almost certainly wasn’t global.

Bill Toland
Reply to  Simon
May 19, 2021 11:46 pm

Proxy reconstructions of Earth’s temperature are worthless and pointless. The physical evidence that today’s temperature is colder than it has been for most of the last 10000 years is utterly overwhelming. Sea level was higher during the Medieval Warm Period and the Holocene Climate Optimum. Trees grew at higher latitudes and altitudes during both these periods. The current level of Arctic sea ice is greater than it has been for most of the last 10000 years. What the Vikings did in Greenland during the Medieval Warm Period is simply not possible today.

Reply to  Bill Toland
May 20, 2021 12:14 am

Bill. You are entitled to your imaginings, but the current consensus is not what you wrote. Maybe a few conspiracy theorists would agree with you, but that’s about it I’m afraid.

Bill Toland
Reply to  Simon
May 20, 2021 12:25 am

Simon, everything I have written is a matter of scientific record. Perhaps you should start to read the actual science rather than regurgitating discredited nonsense from climate alarmists.

Bill Toland
Reply to  Simon
May 20, 2021 12:30 am
Reply to  Bill Toland
May 20, 2021 12:39 am

OK that’s funny. Seriously you should be on the stage. Never has, or ever will, the website “no tricks zone” ever be considered representative of the scientific consensus on climate change. It is a site that presents ideas that are contrary to current thinking. Many ideas are crazy, most complete nonsense.
You have made my day though….

Bill Toland
Reply to  Simon
May 20, 2021 12:42 am

So you are saying that all of the scientific papers referred to in the article are fabrications? Perhaps you should notify the climate scientists who wrote these papers that they are wrong and explain exactly why they are wrong.

Reply to  Bill Toland
May 20, 2021 12:59 am

That site cherry picks more than most denying sites. It’s famous for it. Sure some of the quotes would be from papers, but they only quote what backs their argument.

Carlo, Monte
Reply to  Simon
May 20, 2021 6:10 am

The Simon Clown Show gets renewed for another season.

Bill Toland
Reply to  Simon
May 20, 2021 12:39 am

Sea level was higher during the Medieval Warm Period.

Reply to  Bill Toland
May 20, 2021 12:57 am

Oh boy. Go to reputable sites not ones that produce crayon graphs. This is what NASA has to say…
From about 3,000 years ago to about 100 years ago, sea levels naturally rose and declined slightly, with little change in the overall trend. Over the past 100 years, global temperatures have risen about 1 degree C (1.8 degrees F), with sea level response to that warming totaling about 160 to 210 mm (with about half of that amount occurring since 1993), or about 6 to 8 inches. And the current rate of sea level rise is unprecedented over the past several millennia.”

Bill Toland
Reply to  Simon
May 20, 2021 1:03 am

Simon, what you have posted doesn’t contradict anything that I have said. Perhaps you should read my posts more carefully. The physical evidence that today’s temperature is colder than it has been for most of the last 10000 years is utterly overwhelming. Nothing that you can say can change that scientific fact.

Reply to  Bill Toland
May 20, 2021 1:22 am

Simon, what you have posted doesn’t contradict anything that I have said.”
Yes it does. It says “From about 3,000 years ago to about 100 years ago, sea levels naturally rose and declined slightly, with little change in the overall trend.” So not much change.
Then “Over the past 100 years, global temperatures have risen about 1 degree C (1.8 degrees F), with sea level response to that warming totaling about 160 to 210 mm (with about half of that amount occurring since 1993), or about 6 to 8 inches. And the current rate of sea level rise is unprecedented over the past several millennia.”
So in the last hundred years we have seen a steep rise, one not seen in past millennia. That means it was not higher during the MWP.

And your statement “The physical evidence that today’s temperature is colder than it has been for most of the last 10000 years is utterly overwhelming.”is not only not the “consensus” it is nonsense. Find me a peer reviewed paper that says that. You will be looking a long time. OK some nutter denying blogs might say it, but they don’t represent the science.

Bill Toland
Reply to  Simon
May 20, 2021 1:32 am

“So in the last hundred years we have seen a steep rise, one not seen in past millennia. That means it was not higher during the MWP”.
Do I really need to point out how absurd that statement is?

Bill Toland
Reply to  Bill Toland
May 20, 2021 2:09 am

Simon, I will try to give you an example that you can understand why your statement is absurd.
A company floats on the stock market at 80p. Over the next few years the price oscillates in the range 80p to 100p. Suddenly the company announces that its accountant Simon has been cooking the books and the share price falls to 30p. Simon is sacked and a new honest accountant called Bill is appointed. On this news, the share price recovers to 60p. The rise from 30p to 60p is steep and unprecedented but the share price is still below the previous trading range. Do you understand now?

Reply to  Bill Toland
May 20, 2021 12:41 pm

Except your analogy has nothing to do with the past sea level in relation to today.
Yawn …. here we have the Smithsonian saying the same thing. Not much change for the last 2000 years then a steep rise

But over the past century, the average height of the sea has risen more consistently—less than a centimeter every year, but those small additions add up. Today, sea level is 5 to 8 inches (13-20 centimeters) higher on average than it was in 1900. That’s a pretty big change: for the previous 2,000 years, sea level hadn’t changed much at all. The rate of sea level rise has also increased over time. Between 1900 and 1990 studies show that sea level rose between 1.2 millimeters and 1.7 millimeters per year on average. By 2000, that rate had increased to about 3.2 millimeters per year and the rate in 2016 is estimated at 3.4 millimeters per year. Sea level is expected to rise even more quickly by the end of the century.”
comment image

Reply to  Simon
May 20, 2021 1:27 pm

Simon, you’re wrong.
And “consensus” is the worst argument you can make. Try sticking to facts. Read Koonin’s book and learn something.

Reply to  DrEd
May 20, 2021 2:26 pm

Did you even read what you sent?
The results showed that for China as a whole, the longest warm period during the last 2000 years occurred in the 10th–13th centuries,”
Longest not highest. Clearly 2000 is the highest point on their graph. And that doesn’t take in the warming since 2000.

So… this is one part of the world, and does not change what I said and that is, it is not the consensus of the scientific community that the MWP was warmer than today. And that was Bill Toland’s false, untrue, wrong, point.

Travis T. Jones
Reply to  Simon
May 20, 2021 2:56 pm

Uh oh.
Simon has invoked “ the science”.
Begone all you non-believers!

Reply to  Travis T. Jones
May 20, 2021 5:20 pm

Hey mate if you want to believe in voodoo and low quality opinion pieces be my guest.

Bill Toland
Reply to  Simon
May 21, 2021 9:22 am

Simon, youv’e just described your own position perfectly.

John VC
Reply to  Bill Toland
May 20, 2021 9:08 am

Bill, and others–best to not feed the trolls.

Bill Toland
Reply to  John VC
May 20, 2021 9:16 am

What I am concerned about is people who visit wuwt occasionally read Simon’s posts and believe them if they are not refuted. I know Simon is an idiot but some people who have not read the scientific literature might not.

Reply to  Bill Toland
May 20, 2021 12:43 pm

Simon is an idiot”
Ad hominem… I win.

Reply to  Simon
May 20, 2021 7:45 pm

not when its a statement of fact…

Reply to  Bill Toland
May 20, 2021 7:55 pm

What I am concerned about is people who visit wuwt occasionally read Simon’s posts and believe them if they are not refuted. “
There is very little chance that the residents here are going to accept what I write. I don’t do it for them, I do it for the people who visit with an open mind.

Bryan A
Reply to  Simon
May 20, 2021 3:59 pm

160 MMs … 16 CMs = 6.5″
210 MMs … 21 CMs = 8.5″
So over the last 100 years seas have risen 6-1/2″ to 8-1/2″…we’re doooomed

Reply to  Simon
May 20, 2021 8:29 am


In one sentence, you prove your stupidity. Clearly, you imagine that Consensus is the Truth.

Reply to  TonyN
May 20, 2021 8:46 am

Clearly, you imagine that Consensus is the Truth.

argumentum ad populum

Reply to  TonyG
May 20, 2021 2:30 pm

Read above…

Reply to  TonyN
May 20, 2021 2:30 pm

I may be stupid but clearly I am cleverer than you. I was merely pointing out the Bill Toland claiming the current consensus was that the MWP was warmer than today and that that, was in fact disastrously and obviously wrong. He seems to be the one who thinks consensus is on his side and so values it.

Reply to  Simon
May 20, 2021 6:29 pm

Bill Toland claiming the current consensus was that the MWP was warmer than today and that that, was in fact disastrously and obviously wrong”

Dear Simon,
Please list all the papers you can find which suggest the MWP was cooler than today.

Reply to  Mike
May 20, 2021 7:35 pm

At the end of the wiki page is a string of them. Enjoy.

Reply to  Simon
May 21, 2021 7:35 pm

In 2013 a study from three US universities publicized in Science magazine showed that the water temperature in the Pacific Ocean was 0.9 degrees warmer during Medieval Warmth Period than during the little ice age and 0.65 degrees warmer than the decades before the study”

Lloyd D. Keigwin’s 1996 study of radiocarbon-dated box core data from marine sediments in the Sargasso Sea found that its sea surface temperature was approximately 1 °C (1.8 °F) cooler approximately 400 years ago (the Little Ice Age) and 1700 years ago and approximately 1 °C warmer 1000 years ago (the Medieval Warm Period).[21]

The Medieval Climate Anomaly (MCA) is a well-recognized climate perturbation in many parts of the world, with a core period of 1000–1200 CE.”

Adhikari and Kumon (2001), investigating sediments in Lake Nakatsuna in central Japan, found a warm period from 900 to 1200 that corresponded to the Medieval Warm Period and three cool phases, two of which could be related to the Little Ice Age.[45] Another research in northeastern Japan shows that there is one warm and humid interval, from 750 to 1200, and two cold and dry intervals, from 1 to 750 and from 1200 to now.[46] Ge et al. studied temperatures in China during the past 2000 years and found high uncertainty prior to the 16th century but good consistency over the last 500 years highlighted by the two cold periods, 1620s–1710s and 1800s–1860s, and the warming during the 20th century. They also found that the warming during the 10–14th centuries in some regions might be comparable in magnitude to the warming of the last few decades of the 20th century, which was unprecedented within the past 500 years.[47]

A 1979 study from the University of Waikato found,”Temperatures derived from an 18O/16O profile through a stalagmite found in a New Zealand cave (40.67°S, 172.43°E) suggested the Medieval Warm Period to have occurred between AD c. 1050 and c. 1400 and to have been 0.75 °C warmer than the Current Warm Period.”[49] More evidence in New Zealand is from an 1100-year tree-ring record.[50]

I guess Mann ”findings override those of these scientists…

Ababneh, L.
Abbott, M.B.
Abrantes, F.
Aceves, H.L.
Addyman, P.V.
Adhikari, D.P.
Agnihotri, R.
Ai, L.
Airo, A.
Alden, H.A.
Alenius, T.
Alessio, S.
Alexander, C.
Almeida-Lenero, L.
Almogi-Labin, A.
Alvarez-Iglesias, P.
An, Z.S.
Andersen, K.K.
Anderson, D.E.
Anderson, D.M.
Anderson, J.B.
Anderson, R.S.
Anderson, S.P.
Andersson, C.
Andrade, A.
Andreev, A.A.
Andrews, J.T.
Andrén, E.
Andrén, T.
Anselmetti, F.S.
Antognini, M.
Aono, Y.
Appleby, P.
Aravena, J.-C.
Arnaud, F.
Arsenelault, D.
Astor, Y.
Austin, W.E.N.
Axford, Y.
Ayalon, A.
Ayenew, T.
Badura, M.
Bahk, J.J.
Bakker, J.
Balascio, N.L.
Balsam, W.
Baltzer, A.
Bao, Y.
Baofu, N.
Baolin, H.
Bar-Matthews, M.
Barber, K.E.
Barclay, D.J.
Barnola, J.-M.
Baroni, C.
Barron, J.A.
Bartels-Jónsdóttir, H.
Bartholdy, J.
Bartholin, T.S.
Battarbee, R.W.
Baumgartner, T.R.
Beaty, R.M.
Becagli, S.
Beer, J.
Behling, H.
Beilman, D.W.
Bell, R.E.
Belmonte, A.
Belt, S.T.
Benito, G.
Bennike, O.
Bennion, H.
Bentaleb, I.
Berge, J.
Bernabeu, A.M.
Bernard, S.
Bernasconi, S.
Berstad, I.M.
Bertin, X.
Bertler, N.A.N.
Bertrand, S.
Besonen, M.R.
Betancourt, J.L.
Bezada, M.
Bhattacharyya, A.
Bhushan, R.
Bickert, T.
Billeaud, I.
Bird, B.W.
Birks, H.J.B.
Birks, S.J.
Bischoff, J.L.
Bjorck, S.
Bjune, A.E.
Blaauw, M.
Black, D.E.
Blanco, N.
Blazauskas, N.
Bodri, L.
Boettger, T.
Booth, R.K.
Borromei, A.
Borsato, A.
Bouaouina, F.
Box, J.E.
Bracco, R.
Bracht, B.
Bradley, R.S.
Brauer, A.
Bräuning, A.
Brenner, M.
Briffa, K.R.
Brook, G.A.
Brooks, S.J.
Brown, T.A.
Brutsch, S.
Bryson, R.A.
Brubaker, L.B.
Budeus, G.
Bukry, D.
Bunbury, J.
Bunn, A.G.
Burnett, A.W.
Burns, S.J.
Buster, N.A.
Byrne, A.R.
Büntgen, U.
Cage, A.G.
Cai, Q.F.
Cai, Y.
Calanchi, N.
Calkin, P.E.
Calvert, S.E.
Came, R.E.
Campbell, C.
Campbell, I.D.
Canals, M.
Cane, M.A.
Cannariato, K.G.
Cao, Q.-Y.
Carbotte, S.M.
Carson, E.C.
Carter, L.
Carter, T.
Castellano, E.
Castineira, C.
Catalan, J.
Causey, D.
Cazelles, B.
Cermák, V.
Chacornac-Rault, M.
Chambers, F.M.
Chang, X.L.
Chaudhary, V.
Chauhan, M.S.
Chaumillon, E.
Chen, D.L.
Chen, F.H.
Chen, JianHui
Chen, Jiaqi.
Chen, Jun.
Chen, L.
Chen, S.-H.
Chen, T.
Chen, Z.
Cheng, G.
Cheng, H.
Cheng, W.
Chepstow-Lusty, A.
Chipman, M.L.
Chivas, A.R.
Chou, M.
Christiansen, C.
Christie, D.A.
Chu, G.
Chuang, P.-P.
Cini Castagnoli, G.
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Reply to  Simon
May 21, 2021 7:44 pm

You well know that the NH MWP is only disputed by moronic climatism zombies so what about the SH?

South Africa

Sea surface temperatures (SSTs) were derived from Mg/Ca ratios of Globigerinoides ruber foraminifers that were extracted from gravity core GeoB 9501-5 that was recovered off southern Mauritania at 16°50’N, 16°44’W from a water depth of 323 m during Meteor cruise M65/1 – described by Mulitza (2006) – using the calibration for the 250-350 µm fraction of G. ruber (pink) from Anand et al. (2003) to produce a 1700-year summer-fall SST history. Between AD 850 and AD 1150, Kuhnert and Mulitza identify a period of warmth that they equate with the Medieval Warm Period, the peak 50-year mean SST of which was 1.1°C greater than the corresponding 50-year mean SST at the end of the record, which had been trending upward over the prior half-century.

Maybe you can argue with the stalagmites? They are known to lie from time to time!

”Maximum annual air temperatures in the vicinity of Cold Air Cave (24°1’S, 29°11’E) in the Makapansgat Valley of South Africa were inferred from a relationship between color variations in banded growth-layer laminations of a well-dated stalagmite and the air temperature of a surrounding 49-station climatological network developed over the period 1981-1995, as well as a quasi-decadal-resolution record of oxygen and carbon stable isotopes (MWP: AD 800-1100): Peak warmth of the Medieval Warm Period was as much as 2.5°C warmer than the Current Warm Period (AD 1961-1990 mean).

South America…

The authors derived sea surface temperatures from alkenones extracted from a high-resolution marine sediment core retrieved off the coast of Peru (12.05°S, 77.66°W), spanning the past 20,000 years and ending in the 1960s. From their Figure 11, adapted below, it can be seen that the warmest temperatures of this 20,000 year period (~23.2°C) occurred during the late Medieval time (AD 800-1250). Taking this value, 23.2°C, and comparing it with the modern monthly long-term means in sea surface temperature, which the authors characterize as between 15°C and 22°C, we estimate the peak warmth of the Medieval Warm Period for this region was about 1.2°C above that of the Current Warm Period.”

Reply to  Simon
May 20, 2021 1:49 am

Pine cone research 😉

Reply to  Simon
May 20, 2021 8:50 am

Except the Medieval Warm Period was global in extent. Red is a study that found warm conditions, blue found cool conditions. The other colors are for wet or dry. Notice how studies that found warm conditions overwhelming outnumber the studies that found cool conditions across the entire globe.

The fact that a small number of studies found cooling is no different than the variability of temperature trends now – almost all locations across the US have shown the same or FEWER number of unusually hot days over the period from 1948 to 2020.

Simple Simon, you’ve been schooled on this before so you know better and are just lying. Why?

Reply to  meab
May 20, 2021 2:34 pm

“Simple Simon”

Ad hom I win. And you are right. I have had people try to convince me here of the fiction the MWP was warmer than today. But there simply is no credible, reliable evidence to support that. There is some evidence some parts of the planet may have been as warm as today. But not that it was warmer globally. Sorry, but that is the state of thinking as it stands.

Bill Toland
Reply to  Simon
May 20, 2021 3:16 pm

“I have had people try to convince me here of the fiction the MWP was warmer than today. But there simply is no credible, reliable evidence to support that”.
Is this meant to be a joke? There are many studies showing that treelines were higher during the Medieval Warm Period.
You are obviously a fan of the Hockey Stick which is the most discredited scientific artefact since Piltdown Man. I am not aware of a single credible scientist who still supports that construction. I have personally asked some climate scientists if they believe in the Hockey Stick and they have all said no or they have refused to answer. Even climate alarmists have disowned it. Except for you, Simon.

Reply to  Bill Toland
May 20, 2021 5:25 pm

Mann has his faults but his work is by en large a lot better than most. But you don’t need to believe Mann. There are so many studies that are peer reviewed that call BS on your fairy tale stuff. Google “was the MWP warmer than today?” Then do a search of the sites that use peer reviewed papers. Then read those. I think you will find I am right.

Carlo, Monte
Reply to  Simon
May 20, 2021 5:54 pm

Mann has his faults but his work is by en large a lot better than most.

Hahahahahahahahahahahahahah! Good one thanks.

Reply to  Carlo, Monte
May 20, 2021 7:36 pm

Just because you struggle to understand his work does not mean he is wrong.

Carlo, Monte
Reply to  Simon
May 20, 2021 8:58 pm

“A Disgrace To The Profession,” — referring to Mickey Mann

Just because you are a liar pushing the wokerati agenda does not mean I struggle.

Bill Toland
Reply to  Simon
May 21, 2021 7:41 am

Simon, the problem is that we understand Michael Mann’s work all too well.

Reply to  Simon
May 20, 2021 6:35 pm

Google “was the MWP warmer than today?” Then do a search of the sites that use peer reviewed papers. Then read those. I think you will find I am right.”

Dear Simon
Instead of asking other people to walk the maze of Google to find out you are wrong, please (since you’ve already done it) provide links to those papers which which will lead us to find that you are right.

Bill Toland
Reply to  Simon
May 20, 2021 10:18 pm

Simon, I notice that you have not explained how treelines were higher in the MWP if the MWP was not warmer than today.

Reply to  Bill Toland
May 20, 2021 5:27 pm

“I am not aware of a single credible scientist who still supports that construction.”You have not read this then.

Reply to  Bill Toland
May 20, 2021 5:40 pm

And I’m not surprised you CS friends had no interest in the hockey stick. It’s only on sites like this people bring it up. It is sooooo old now and been superseded so many times, it really is not worth mentioning.

Bill Toland
Reply to  Simon
May 21, 2021 3:05 am

Simon, it is good to know that even you have abandoned the Hockey Stick. Your exposure to people who understand science on this website is starting to work on you. This is step 1 on your road to accept the science. Like all adherents of religious cults, I know this will be a long journey for you. But you should persevere and eventually you will see the light of logic and reason.

Reply to  Simon
May 20, 2021 6:32 pm

I have had people try to convince me here of the fiction the MWP was warmer than today. But there simply is no credible, reliable evidence to support that”

Dear Simon,
Please list all the papers you can find which show credible and reliable evidence which refutes the MWP being warmer than today.

Reply to  Mike
May 20, 2021 7:30 pm

Start with Berkley earth. You can use google. There are squillions.

Reply to  Simon
May 20, 2021 10:26 pm

You’re obviously just lying. Berkeley Earth determined that about 1/3 of all temperature stations globally show a declining temperature trend over many decades, so where precisely does Berkeley Earth conclude that the MWP was cooler than today?

Here’s the U.S. map. Red is a warming trend, blue is cooling.

comment image

Reply to  Simon
May 20, 2021 10:21 pm

You LOSE. Why? You couldn’t refute the claim that you were just lying when you said the MWP was not global. You couldn’t even try. I never said that the MWP was warmer than today globally, but it was about as warm. Why can’t it be said that it was warmer globally? Nothing to do with whether or not the MWP was actually warmer globally – it’s just that proxy data isn’t that accurate. Proxy data also isn’t good enough to say that the MWP was cooler than today either. Claim that proxy data is good enough and you’re lying again. Sorry, but your state of thinking isn’t what the scientific evidence shows, Simple Simon.

Reply to  Simon
May 21, 2021 7:47 pm

 I have had people try to convince me here of the fiction the MWP was warmer than today. But there simply is no credible, reliable evidence to support that.”

Wrong. You mean there is no credible reliable evidence to support that it was colder than today.

Carlo, Monte
Reply to  Simon
May 20, 2021 6:08 am

Where is the hockey stick?

Reply to  Ron Long
May 20, 2021 4:10 am

I agree re following the money.
No one ever wants ‘Wars’ but it just happens to be a fact that a few people make a shed load of money from major conflicts. I see a similarity to CAGW. I always ask why only ‘one’ side of the argument only ever turns up to discuss/debate the issues and only one side tells us that they won’t sit down with Deniers! Surely that must ring alarm bells to anyone involved in science.
BTW, I firmly believe in Climate Change but nothing I have read or seen will convince me that me, or my family, only have days left on this Earth (if we don’t spend Trillions of $ fixing ‘the problem’ they have identified). I may be the Village Idiot but not even they can convince me I am wrong!

Reply to  JoHo
May 20, 2021 7:50 pm

BTW, I firmly believe in Climate Change but nothing I have read or seen will convince me that me, or my family, only have days left on this Earth”
But that’s the thing. No one is saying that. If you read the IPCC reports they have never said human life on the planet is doomed.

4 Eyes
Reply to  Izaak Walton
May 19, 2021 6:55 pm

All of the world’s climate scientists are not convinced! Maybe in your mind a climate scientist is someone who is convinced otherwise they can’t possibly be a climate scientist. Stop playing with words.

Reply to  dk_
May 19, 2021 4:39 pm

The so called robber barons never were.
They got wealthy by providing products that people wanted at prices people were willing to pay.

Izaak Walton
Reply to  MarkW
May 19, 2021 6:06 pm

plus being able to get government troops to fire upon workers striking for better wages always helps improve profits.

Reply to  Izaak Walton
May 19, 2021 7:39 pm

But that was when the climate wasn’t out of control. You know, the good old days we all want to return to.

Reply to  Izaak Walton
May 19, 2021 9:23 pm

Read the real history izzy! That isn’t why the Presidents/governors declared emergencies and called in troops.

Reply to  MarkW
May 20, 2021 11:05 am

MarkW, We disagree on history, but I’ll stipulate your view.
I am convinced that the money and power, starting with Rockefeller and Bloomberg, but no doubt many others, are after domination today’s energy industry. To do this, they are engaged in political corruption, lawfare, corruption of academia, and manipulation of media. The largest block of influence over all of those is the green movement, under the oxymoronic name of climate justice.
While there seems to be no end of evidence for it, the most convincing bit to me is that this scenario is exactly the opposite spin of the narrative that the climate activist movement has been saying about the oil industry, current and past (even quite liberal) governments in what is thought of in the West, and anyone who opposes them. Simon and Izaak read off the green shill’s credo every appearance here, and probably elsewere.
While annoying, I’m not even half convinced that they are aware, or even have awareness, that they are being duped. But I do feel justified in pointing out, in one case repeatedly over the past 24 hours, that they are both simply here to argue incessantly from the climate activist canon. They won’t change or back down, they aren’t arguing points that they believe in or even understand, but just shift to another nonsense point if put on the spot. Arguing past a certain point always just results in invective, here, but while in small ways is in itself propaganda also helps the greens develop propaganda and disinformation tactics that can be used elsewhere.
People may argue like this for entertainment, others for mental disorder, others because of ideology, and some because they are paid. They don’t even need to be people, the same tools that can make an automated chat product support can replace 90% of what these characters post here. Simple programming, made to seem to be argumentative in text, goes back to the 1980’s.
I’ll pass on arguing about interpreting 19th-20th century history. The threat that matters in front of you. Here and now.

Reply to  Izaak Walton
May 19, 2021 3:57 pm

So we are sticking with the idea that 97% of the experts are being overwhelmed by the 3% dumb scientists that are in the pockets of the greedy corporations as Exxon choreographs all the opposition to a reduced standard of living?

Reply to  Izaak Walton
May 19, 2021 4:37 pm

The evidence that the goal of many of the leaders of the so called climate change community is the imposition of socialism has been presented to you many times.
Like griff, you seem incapable of seeing anything that you don’t agree with.

That there is no science behind the scare has also been amply demonstrated.

Reply to  Izaak Walton
May 19, 2021 4:39 pm

Well what else can one deduce when the political narrative is driven by just a few scientists whose crap gets recycled and amplified by “if it bleeds it leads” media, and when the hyperbole gets ratcheted up from global warming to climate change to climate emergency even though the temps have levelled off compared to the 1970’s-1990s rise? And compared to higher temperatures recorded in the paleo record. Where’s the crisis??? I’m sure future generations will back and think what a bunch of idiots that despoiled the land with useless wind and solar garbage when we’re supposed to be taking care of the planet.

Reply to  Izaak Walton
May 19, 2021 7:20 pm

Yes, You have to hide the decline in order to protect “The Cause”.
Yes, You have to use “Mike’s nature trick” to get the results you want.
Yes, you have to armtwist reviewers and editors to only publish what you want.
Yes, You have to adjust past temperatures endlessly because measurements made with ships buckets, thermometers, radiosondes, thermocouples, thermistors and satellites don’t agree with our models and theories.

And finally, Yes, because we have to extract your cash from your wallet in order to reduce global average temperature (whatever that is) 0.2 degrees C by 2100.

But think of the children. We are doing it all for them.

Reply to  Izaak Walton
May 19, 2021 9:00 pm

Secretly? They’re doing it openly, questioning democracy because it’s getting in the way of ‘climate action’ and praising China for how it’s so organized (and of course it’s huge and skyrocketing emissions never get mentioned). No need for conspiracy if left wing universities turn out left wing academics who hate industry and oil companies especially. Brain washed about Big Oil as though it was a 100 years ago and Rockefeller was still around. They don’t seem mind about Big Social Media filtering our online news and comments. And throw into the mix that essentially left wing governments control the science budgets that left wing academics hand out to other left wing academics – I surprised that any genuine science, damn the politics, can get done.

Reply to  Izaak Walton
May 19, 2021 9:15 pm

climate scientists who are secretly plotting”

Typical izaak fake red herring.

There is nothing secret about the climate alarmists pushing marxist goals using marxist methods.

Joseph Zorzin
Reply to  Izaak Walton
May 20, 2021 3:43 am

It’s good for their funding.

Reply to  Izaak Walton
May 20, 2021 4:20 am

Not sure Izaak, was Trump Russia colluuuusion a conspiracy 😉

That conspiracy always cracks me up with laughter

Carlo, Monte
Reply to  Derg
May 20, 2021 5:52 pm

Rachel Madcow was deadly serious about it for years upon years.

Reply to  Izaak Walton
May 20, 2021 7:41 pm

More a most convenient lie, that became a bandwagon that nearly everyone found it convenient to jump on. It is now totally out of control.

Reply to  Izaak Walton
May 21, 2021 10:33 pm

So we are back to the idea of a global conspiracy of climate scientists who are secretly plotting to take over the world.

They’re not plotting to take over the world. Simply to get more money.

Carlo, Monte
May 19, 2021 2:27 pm

Global avg T =/= climate

CO2 is not the control knob

Where is the hockey stick?

Gregory Woods
May 19, 2021 2:30 pm

Projecting manmade climate change: scenarios to 2050

My unexpert opinion: Naaaadaaaaa!

May 19, 2021 2:37 pm

Do not let them own the conversation.

CO2 is not a problem.

May 19, 2021 2:39 pm

” Referring to RCP8.5 as ‘business as usual’ implies that it is probable in the absence of stringent emissions mitigation.”

No, it describes what will happen if you ignore the problem, and continue with “business as usual”. The other scenarios describe what happens with various degrees of stringency of emissions mitigation.

It is totally necessary that someone calculates the consequences of doing nothing. Scenarios are designed to cover a range of possibilities, and that is one. It is the default.

Carlo, Monte
Reply to  Nick Stokes
May 19, 2021 2:53 pm

The “calculations” are nonsensical pseudoscience.

Reply to  Carlo, Monte
May 19, 2021 5:51 pm

100%. Repeat bullsh*t enough and people will believe it.
It’s amazing how a projection using a model is considered scientific fact. It’s just part of a process, the validity of which can only be verified through direct observation. So far….pfft…

Climate believer
Reply to  Carlo, Monte
May 20, 2021 12:14 am

I don’t know if nonsensical pseudoscience does it justice, it is utter fantasy.

RCP 8.5 has CO²ppm at ~1370 by the year 2100.

So we have to get to 1370ppm from 415ppm in 80 years, that’s +12ppm per year!

Taking the period 2010-2020, CO² went from ~388ppm to ~415ppm, that’s +27ppm in 10 years.

BAU, we don’t do anything different from the last 10 years, that’s 8x27ppm.

415+216 = 631ppm in 2100…. where does the other 739ppm come from?

You would have to add an extra ~9ppm per year! That has never happened.

Please point out the error in my back of the envelope calculations.

Carlo, Monte
Reply to  Climate believer
May 20, 2021 6:15 am

The climate “models” are the modern day equivalents of soothsaying with goat entrails; predictions have been 100% wrong.

Reply to  Carlo, Monte
May 20, 2021 10:11 pm

There’s a saying that models are almost always wrong, but often useful.

Joseph Zorzin
Reply to  Carlo, Monte
May 20, 2021 3:53 am

Right, there can’t be calculations- only predictions and/or prophecies.

Rud Istvan
Reply to  Nick Stokes
May 19, 2021 3:05 pm

The problem with RCP8.5 is that it was sold as, and you Nick bought it as, BAU. It isn’t even close. I studied the issue carefully when writing Blowing Smoke. My results are infused into several of its ‘climate science’ section essays. Best as I could determine from the explicitly stated BAUs of SRES for AR3 and AR4 (yup, there are either two or three depending on how SRES is read), equivalent AR5 ‘BAU’ is about midway between RCP4.5 and RCP6. See my comment below explaining why this IPCC obfuscation was deliberate.

Tom Abbott
Reply to  Nick Stokes
May 19, 2021 3:26 pm

“No, it describes what will happen if you ignore the problem, and continue with “business as usual”. The other scenarios describe what happens with various degrees of stringency of emissions mitigation.

It is totally necessary that someone calculates the consequences of doing nothing. Scenarios are designed to cover a range of possibilities, and that is one. It is the default.”

I copied this comment, meaning to add “Exactly” as my comment and then I looked and saw it was Nick I was agreeing with. Now you don’t see that very often! 🙂

Nick is right. The RCP8.5 scenairio is one where nothing is done to mitigate CO2 production. In other words, the world proceeds as if there is not problem with CO2, and continues to build numerous coal-fired powerplants.

Btw, this below is OT but I’m sure it is of interest to many here. It should be of interest to all the governments currently having problems with the Wuhan virus:

Ivermectin crushes Delhi cases

By Justus R. Hope, MD May 18, 2021 Updated 23 hrs ago

Rich Davis
Reply to  Tom Abbott
May 19, 2021 3:48 pm

Just as rare that I would disagree with you Tom, as that you would agree with Nick. RCP8.5 is borderline impossible. Refer to the first link in the references section at the end of the head post.

Reply to  Rich Davis
May 19, 2021 4:45 pm

I’m going to have to disagree with Rich. RCP8.5 is not borderline impossible. It is absolutely impossible.

Reply to  Tom Abbott
May 19, 2021 4:44 pm

The problem is that even though the difference between what was done, and the so called doing nothing scenario is too small to measure reliably, yet the amount of CO2 that was actually emitted was way, way below what the 8.5 scenario predicted.

It’s pure nonsense, but since it’s useful nonsense, it is the preferred scenario of those who’s only goal is frightening people into giving up their freedoms.

Reply to  Tom Abbott
May 20, 2021 1:36 pm

You can’t do simple arithmetic either.

Rich Davis
Reply to  Nick Stokes
May 19, 2021 3:30 pm

come on Nick, you know very well that it is a worst-case scenario (and dubious at that). Certainly not “business as usual”. You could earn some credibility by admitting that at least.

Reply to  Rich Davis
May 19, 2021 3:53 pm

Yes, it is certainly the worst case of the scenarios offered. There is always a best and a worst, of any finite number. If you removed 8.5, then 6.0 would be the worst case. People talk freely here of it being called BAU, without saying who called it that or what exactly they said. I would interpret BAU as take no action. Some may see it as take only the actions currently planned. But keeping up current plans is not the worst case; back-sliding is certainly possible.

Reply to  Nick Stokes
May 19, 2021 4:11 pm

If you removed 8.5, then 6.0 would be the worst case.

No, no and no. Wrong again.
RCP 8.5 was designed to be the practical/theoretical “Worst Case”, that could plausibly be constructed.
Many, including J. Curry, have criticized RCP 8.5 as either impossible, practically impossible, or so stilted with all assumptions made to be worst case, that it is not credible.

To characterize it as the “do nothing” RCP, is to wholly misrepresent it.
But I think Nick Stokes knows all of this.

Rud Istvan
Reply to  Nick Stokes
May 19, 2021 4:15 pm

Nick, you remind me of Mann in the Congressional hearing with Judith, where he said ‘ I have never called any one a denier, and she responded, ‘You just did about me in your written submission for this hearing’. YOU yourself just did, above. Now that is a BIG short term memory problem, or proof of warmunist prevarication. You can explain which it is. I call an in writing Nick checkmate.

Reply to  Nick Stokes
May 19, 2021 4:48 pm

8.5 uses an assumption of population growth that is not possible.
It also assumes that there will be absolutely no improvement in economic efficiency. Once again, beyond absurd.

8.5 is simply an impossible scenario, and only someone who is more interested in obfuscation than education would use it. Which would explain why it is Nick’s favorite scenario.

Reply to  MarkW
May 19, 2021 7:22 pm

I think the responsibility of modellers is to calculate the range of scenarios that people might want to know about. It is the responsibility of users to use them responsibly for their purpose. Policy makers should look at the cost-benefit of trying to attain each, and act accordingly. And they wouldn’t choose 8.5. Judith mentioned insurance companies, but they are necessarily interested in worst case scenarios; that is what they insure against. And so on.

Reply to  Nick Stokes
May 19, 2021 8:00 pm

According to you blatant lying is justified under the guise of modelling, and is up to the interested parties how to use it.

Rory Forbes
Reply to  Lrp
May 19, 2021 8:56 pm

That’s the basis upon which all Leftist government is formed.

Reply to  Nick Stokes
May 19, 2021 9:54 pm

I think the responsibility of modellers is to calculate the range of scenarios”

Model programmers working for a living in the real world would be fired for submitting pure fiction and claiming it is any kind of plausible.

Bosses want real probabilities and the exact ranges of those probabilities along with exactly why one range is different from every other ranges.

That said, all bosses know that models are only today’s possibilities. Today’s reality generally invalidate tomorrow’s possibilities.

10 years? 20 years? All are fraudulent models with alarmist claims by their operators are far more fraudulent.

Hades, I can’t trust the weather models more than 8 days out.

Reply to  ATheoK
May 20, 2021 2:00 am


I live in the upper Midwest; try 2 days at best

Reply to  Derg
May 20, 2021 4:38 am

You are correct, Derg, when considering NWS official weather predictions in toto. NWS rarely gets the entire forecast cloae.

Allow me to rephrase my previous comment a bit.
As a grower of plants, I primarily look at two portions of weather predictions; temperature and precipitation.

Here in Virginia, temperature predictions are generally ballpark correct for 5-7 days.
I always pay attention to Joe Bastardi weather forecasts and reasons along with any hints on WeatherBell.
Bastardi and the WeatherBell team’s predictions are more accurate further in advance than the National Weather Service.

As far as precipitation, your 2 day caveat is spot on.
Even then what NWS predicts in the morning for tomorrow often changes by evening.

The National Weather Service’s short term forecasts are more general (vague) yet fare better than the NWS local forecasts.

During March through early May, NWS fared very poorly on temperature forecasts in my local area. There were many nights I took precautions against overnight frosts when NWS was predicting overnight lows as being in the 40°F – 50°F.

Several times NWS switched overnight temperature overcasts from mild to frost warnings after 5PM.

All thanks to NWS weather models running warm because of alleged CO₂ warming and feedbacks.

Ryan Maue also has good forecasts, opinions and things of interest about America’s weather.

Ryan retweeted a tweet concerning Baltimore’s airport located official temperature station and their thorough ruination of the temperature stations surrounding environment.

Reply to  Nick Stokes
May 20, 2021 4:30 am

Old Stokesy said “Policy makers should look at the cost-benefit of trying to attain each, and act accordingly.”

Careful the likely cost-benefit would be do nothing if a few polar bears and reefs die so be it., most of the humans will adapt. The bleeding heart lefties will cry that it’s unfair on some people and nature but life isn’t fair 🙂

Carlo, Monte
Reply to  Nick Stokes
May 20, 2021 6:19 am

Name just one “scenario” that has proven correct.

Reply to  Nick Stokes
May 24, 2021 4:26 am

I think the responsibility of modellers is to calculate the range of scenarios that people might want to know about.

It is the responsibility of modellers to inform users of the probability of the scenarios they model actually occurring. There is nearly zero chance (far less than one percent) that the amount of coal assumed to be burned to produce the emissions in RCP 8.5 will actually occur in the 21st century.

Any honest modeller would make the public aware off that fact. And if the IPCC were honest, they would make the public aware of that fact.

Rich Davis
Reply to  Nick Stokes
May 19, 2021 5:22 pm

Ok you really demonstrated your knack for sophistry on that response Nick. As you well know, it is not a question of the worst case in a set of arbitrary scenarios. It is supposed to be the worst feasible outcome in the real world. It fails at being any such thing.

The scenario does not describe “doing nothing different”, nor even mere backsliding. It represents 6.5x the present use of coal. Perhaps close to the exhaustion of economically extractable fossil fuels.

How could that be described as BAU? It is what we probably couldn’t achieve even if we suddenly decided that we need to raise CO2 levels as high as possible as quickly as possible.

Sad to see that you can’t embrace the least degree of intellectual honesty.

Reply to  Rich Davis
May 19, 2021 9:42 pm

With that comment you refer to, Nick has exposed himself as a full blown alarmist pushing the worst case, no matter how impossible.

Reply to  Nick Stokes
May 19, 2021 4:00 pm

So how are the actual current emissions lining up with R8.5…seems temperatures are lower than that trend despite more CO2 than the prediction used. Ie even that model bunked it.

Rud Istvan
Reply to  Macha
May 19, 2021 4:22 pm

Macha, a gentle logical rebuke. Your question confounds two separately important problems.
1.Here, how do the IPCC emission scenarios line up with each other and reality.
2.Separately, how do those model inputs line up with model outputs?

Reply to  Nick Stokes
May 19, 2021 4:48 pm

But RCP8.5 is not BaU – it’s a coal orgy. Emissions in the US went down with a real business as usual scenario where utilities switched to cheaper and more efficient natural gas.

Reply to  PCman999
May 19, 2021 4:51 pm

Ironically, if the rest of the world would have or could have done the same instead of wasting resources on Rube-Goldberg-esque wind-solar-biomass-storage-peaking plants, their emissions and electric bills will be a lot lower and orangutans would not be missing half the forests in Borneo.

Reply to  PCman999
May 20, 2021 2:02 am

Why do we want to switch?

Isn’t CO2 beneficial?

Reply to  Nick Stokes
May 19, 2021 7:48 pm

There is no :”default” rcp 8,5 scenario, you just made it up.

Yeah lets make up 5,000 modeling scenarios, maybe one will be the right one in 20-80 years from now. Surely that is better than just 4-5 scenarios, that bulls eye science YOU eagerly follow sure impresses you and no one else here.

There is no climate problem to ignore, you didn’t even try to answer Willis’s post and Where is the climate emergency?

Where is this emergency, Nick?

You are getting worse at this Nick…… stick to REPRODUCIBLE science research instead.

Rory Forbes
Reply to  Sunsettommy
May 19, 2021 9:13 pm

stick to REPRODUCIBLE science research instead

Is there some other kind of science you can direct me to? Maybe Mr. Stokes knows of a type of science not requiring reproducibility.

Reply to  Nick Stokes
May 19, 2021 7:57 pm


Gerald Machnee
Reply to  Nick Stokes
May 19, 2021 8:10 pm

RE:*** No, it describes what will happen if you ignore the problem, and continue with “business as usual”.***
Nick, what is the problem?
I see the problem as cooling about to hits us. Your buddies will blame it on “warming”.

Paul Johnson
Reply to  Nick Stokes
May 19, 2021 9:25 pm

If RCP 8.5 represents a “business as usual” scenario, why is it given only a 5% probability of occuring?

Reply to  Paul Johnson
May 19, 2021 11:58 pm

Because someone thinks there is a 95% chance that we’ll do something about it. That doesn’t remove the need to know what would happen if we don’t.

Reply to  Nick Stokes
May 20, 2021 2:05 am

After the pandemic where the world started to crawl did C02 increase?

Are you advocating the world return to the horse and buggy?

Reply to  Nick Stokes
May 20, 2021 4:32 am

Whoever predicted the 95% was a climate scientist and optimist I rate the chance at about a snowballs chance in hell.

Paul Johnson
Reply to  Nick Stokes
May 20, 2021 6:58 am

If RCP 8.5 is the promise anything, do nothing response, shouldn’t it be called the “China as usual” scenario?

paul courtney
Reply to  Nick Stokes
May 20, 2021 3:23 am

Mr. Stokes: Didn’t you recently criticize the use of the tag “business as usual”, saying Hansen only used the phrase “once”? Now, it’s legitimate, neigh “totally necessary”, to show it on the chart and discuss it as such? See why it’s so hard to keep up with CliSci, we never know when it’s ok to call a spade a spade.

Tom Abbott
Reply to  paul courtney
May 20, 2021 4:06 am

“business as usual”

This is another case of imprecise language being used in alarmist climate change science.

This climate science subject has enough ambiguity as it is, and using language such as “business as usual” or “carbon”, out of context, just confuses the issues more.

Climate Alarmists thrive on confusion. They must, because they generate so much of it.

Reply to  Nick Stokes
May 20, 2021 4:24 am

If you wanted to calculate the consequences of doing nothing … you certainly wouldn’t ask a climate scientist most if not all of them are tech, physics and economic illiterate.

Bruce Friesen
Reply to  Nick Stokes
May 20, 2021 11:39 am


Data points at the ends of the probability spectrum are needed for good science, agree with you there. RCP 8.5 provides a data point outside the core range, with the benefit of providing a bit of an anchor for the results curves for various studies, rather than having those curve waggly around excessively. Good science.

But not a good basis for public policy risk assessment.

More important, RCP 8.5 is not ‘business as usual’ or my preferred ‘society as usual.’ Trends in key metrics are well known – trend in energy per unit of GDP, trend in carbon emissions per unit of energy, trend in global population, trend in GDP per person globally. The assumptions for RCP 8.5 are not reflective of any of those key trends. It is not ‘business as usual’. You may argue those trends are already influenced by ‘climate change action’. My response to that argument is to use those trends with whatever end-date resolves that aspect for you. Still not business as usual.

Cheers, Bruce

Reply to  Nick Stokes
May 20, 2021 1:34 pm

Nonsense. You can’t do simple arithmetic.

Reply to  Nick Stokes
May 24, 2021 4:14 am

No, it describes what will happen if you ignore the problem, and continue with “business as usual”.

No, it describes what scientists without scruples can convince the ignorant public to believe could happen.

Rud Istvan
May 19, 2021 2:45 pm

Three observations:

  1. IEA should stay in its energy lane. In that lane, they have done some good empirical work, and some really bad projection work based on it. For examples, see essay IEA Fictions in ebook Blowing Smoke.
  2. Judith is provably for sure right about RCP8.5. It is nonsense, yet represented as ‘business as usual’ (BAU) and thus used to anchor many alarmist papers. That borders on one of three definitions of scientific misconduct: misrepresentation of data/assumptions.
  3. AR3 and AR4 used SRES scenarios. Steve McIntyre was not kind to IPCC AR4 when he compared the AR3/AR4 predictions from the same scenarios. (See essay Hiding the Hiatus in ebook Blowing Smoke for details.) AR5 used RCPs. AR6 will use SSPs. The only logical explanation for now continually changing such basic goal line stuff is to prevent clean backwards comparisons, which would continue to show how off IPCC projections have been since AR3. Having been schooled by McIntyre over a decade ago, the IPCC scoundrels are deliberately obfuscating yet again.
Carlo, Monte
Reply to  Rud Istvan
May 19, 2021 2:54 pm

Nick Stokes thinks RCP8.5 is right on the money.

Reply to  Rud Istvan
May 19, 2021 3:00 pm

Rud, Dr. Curry is also trying very hard to be empathetic and constructive. Skills that I can respect but rather obviously don’t have. We’ve got to remember this if we go to tactics that flip Alinsky on the screaming idiots used as cannon fodder in this conflict.

Rud Istvan
Reply to  dk_
May 19, 2021 3:20 pm

Although we have never met personally, I got to know Judith very well during our sometimes intense and many interactions from 2011 thru when she left Georgia Tech (and from a few further Climate Etc posts after). I agree with you about her, and I was decidedly also in her modus operandi camp until very recently.
I changed my mind after thinking about the impact Koonin’s new book Unsettled might (not) have on people like Kerry and AOC, and on interactions with the likes of senior editors at prestigious journals (specifically McNutt concerning the Marcott 2013 scientific misconduct she published). Posted that mindset change and the reasons for it here a bit ago.

Reply to  Rud Istvan
May 19, 2021 3:48 pm

Rud, I’m with you on mindset and approach, and probably likely targets. I don’t want to foul Dr. Curry’s lane. If she’s talking sense to a pol or administrator in power, I don’t want to mess that up. She’s diplomatically providing a basis for an intelligent stance against the hysterics. There’s no need for friendly fire incidents here, leave that for the other side (as they seem to be doing, well, by themselves).
I am not talking about our buddy Nick here. Weapons free.

Reply to  Rud Istvan
May 20, 2021 3:44 am

Entirely agree with you about the Marcott 2013 shenanigans. I asked the BBC to take the plot down from their website, pointing out even the author had concurred on ClimateAudit that you cannot compare 300 yr resolution data with modern data.

They replied “its in a peer reviewed journal”.

Stupid as a box of rocks.

Reply to  Rud Istvan
May 19, 2021 3:16 pm


Never wrestle with a pig. You get muddy and the pig wins.

Don’t argue the toss with them, CO2 is a non problem.

If you engage on their “facts” you’ve already lost.

Don’t look for the pea. Recognise the game.



Rud Istvan
Reply to  AleaJactaEst
May 19, 2021 4:02 pm

AJE, Agree! You might enjoy essay Shell Games in my ebook Blowing Smoke. The title was a deliberate double entendre (sea shells and shell games) explained in the closing paragraphs. The body of the essay identified the coral and oyster ‘peas’ being palmed by supposed climate scientists. Two explicit and irrefutable cases of clear cut climate scientific mIsconduct, then widely publicized by MSM. (In the Shell Games cases, by a four year supposed investigative reporting series by the Seattle Times.

Chris Hanley
May 19, 2021 2:51 pm

The ‘Representative Concentration Pathways’ (RCPs) themselves are a distraction IMO, the mischief is when the ‘scenarios’ are converted to actual temperature projections.
comment image

Reply to  Chris Hanley
May 20, 2021 3:49 am

Agree, but further to that the real key is Lomborg’s demonstration of how much difference it makes to temperature in 2100 if everyone agrees to (and nobody cheats) on the Paris Treaty.

The answer of course is a temperature difference so small that it could not be measured.

That’s the critical point. If you take hugely expensive actions but could not even measure whether it had made a difference after 80 years why are you doing it? (Rhetorical!).

Rich Davis
Reply to  ThinkingScientist
May 20, 2021 5:06 am

One way to make Paris effective is if the world population is reduced to 100 million (say 99.8 million land-bound peasants and 200k elite). There would be centuries of fossil fuel left, millennia if the servants have to return to a medieval lifestyle and reserve modern energy for the elite only.

But of course nobody is thinking of trying that. Right?

J Mac
May 19, 2021 3:18 pm

The surprising revelation from this is the continued enormous waste of time, energy and money falsely maligning CO2, the foundation food for all plant life on Planet Earth. And by extension, all animal life as well.

The plants are hungry – Feed ’em!

Richard M
Reply to  J Mac
May 20, 2021 7:32 am

It takes energy to feed those plants. It also helps to have a little more water. Oh yeah, that is exactly what doubling CO2 provides. All of the 3.7 watts/m2 of energy provided by doubling CO2 is exactly what is needed to fuel the corresponding growth of the biosphere. Isn’t it amazing that nature provides such a nice balance.

May 19, 2021 3:56 pm

Personally, I hope so….future coal use, … 6.5 times more coal use in 2100 than today….
More people would be healthier and at a higher standard of living.

Reply to  Macha
May 20, 2021 4:35 am

It will be less in the democracies more in non and the one guarantee is higher than now.

Peter W
May 19, 2021 3:57 pm

If you look at the temperature curves from the past 20,000 years of the Milankovitch cycles, it is obvious that we are heading for the next BIG ice age. The amount of CO2 in the atmosphere is irrelevant to earth’s temperature.

In view of what the next ice age will do to our ability to raise food, the best thing we can do is burn more coal in order to add more CO2 to the atmosphere and thereby increase plant growth. I rather suspect that the Chinese have figured this out, and that is why they are busy building more coal-burning power plants.

Richard M
Reply to  Peter W
May 20, 2021 7:37 am

I suspect the only thing needed to prevent the next ice age is to keep Hudson Bay at its current temperature. Of course, since the solar energy is doing down that means energy has to come from something else. Possibly a network of submerged geothermal devices or satellite focused solar enhancement.

M Courtney
May 19, 2021 4:10 pm

RCP8.5 was never a Business As Usual scenario.
It required three things to happen:

1) That fossil fuel use would grow far more than economic growth in the West for the latter half of the 20th century demonstrated. E.g. That China would have exponential economic growth forever.
2) That energy productivity increases would not happen. If they did then assumption 1 may actually be possible.. for a while.
3) That climate change caused by these CO2 emissions will have no impact on economic growth or CO2 emissions. E.g. AGW is not worth worrying about.

Points 1 and 2 contradict each other.
Point 3 is probably untrue. And certainly untrue that no-one would suspect it was untrue and reduce emissions.

Only charlatans and the self-deceived treat RCP8.5 as a Business As Usual scenario.

Reply to  M Courtney
May 20, 2021 4:36 am

You mean Nick 🙂

M Courtney
Reply to  LdB
May 20, 2021 5:30 am

I was not being personal. My three points are not aimed at any individual. They stand on their own merits or not, regardless of partisanship.

Gary Pearse
Reply to  M Courtney
May 20, 2021 10:56 am

MC: Although ‘8.5’ was as you say, point #1) is unexpexpectedly now irreversibly in play. The growth of CO2 will occur because of rapid GDP growth outside of of the West, based largely on coal. It is happening on such a scale that you can’t find an inflection in the global curve that marks efforts at reductions by the west.

Judith was right about the ‘near impossible’ 8.5 scenario several years ago before this paradigm change. I hope she isn’t getting too comfortable being in the mid spectrum of reasonable sceptic. That her whole article is a basically IPCC friendly one ‘sort-of’ means what is happening with the vigorous pursuit of prosperity through coal power by 5 billion people passes under her radar! This is a testament to how the MSM can hide such giant information, even from a thoughtful climate scientist. John Kerry and Joe Biden, in unintentional remarks even show that they get this!

May 19, 2021 5:27 pm

All I want to know is which RCP tracks with reality in terms of the atmospheric CO2 concentration.

Mark BLR
Reply to  Tom
May 20, 2021 7:27 am

Note that the “MLO-prime” line plots the annual averages of the Mauna Loa CO2 (monthly) dataset from September (of year N-1) to August, which provides a “best match” to the IPCC’s “Historical Data” values for both CMIP5 (/ AR5 / RCPs, 1959 to 2005) and CMIP6 (/ AR6 / SSPs, 1959 to 2014).

Mark BLR
Reply to  Mark BLR
May 20, 2021 7:35 am

PS : For context.

Note the scales on both the X and Y axes.

Walter Sobchak
May 19, 2021 5:51 pm

I’m kind of amazed that they didn’t come up with an RCP of 11.

May 19, 2021 5:52 pm

I’m predicting the average climate temperature will be somewhere between a Lut Desert high and a Siberian low. Narrowing it down further is likely best accomplished by blindly throwing darts at a temperature chart with these two extremes.

Geoff Sherrington
May 19, 2021 6:05 pm

Reactions to the Covid-19 pandemic were estimated to lower global CO2 emissions by at least 8% for much of the year 2020.
The effects of this presumed emission reduction are not detectable in observations of CO2 in air such as those from Mauna Loa. Some researchers have given reasons why they should not be detectable. But they are not detectable.
However, it follows logically (if those reasons are correct) that one would see no CO2 change if emissions were increased by a similar 8% estimate.
Does it follow that a failure to detect an emissions increase of 8% applies as well to increases of 16%, 24% … etc., whatever value you choose?
This whole topic of CO2 causes global warming and the scenarios chosen to describe this are a mess in which hard scientific thought, logic and observation is largely missing. Geoff S

Reply to  Geoff Sherrington
May 19, 2021 9:40 pm

Speaking of those CO2 emission graphs – in the spring and summer the huge burst of life in the north drags down CO2 levels almost to what they were the year before, about 2ppm higher. Since even NASA is saying that the Earth has greened by 15-20% over the past few decades, and I would expect similar increases in plankton levels (especially if we help things a bit with ocean fertilization) – I would think that we are very close to reaching CO2 equalibrium. The expected cooler temperatures from the AMO phase change will help with that to, as the oceans won’t outgass co2 as much.

Richard M
Reply to  Geoff Sherrington
May 20, 2021 7:45 am

Now add in the formation of La Nina in 2020 which generally leads to cooler oceans which would increase CO2 absorption as well. The global SSTs tracked this cooling while CO2 levels did not. A real scientific analysis of the situation would probably falsify human CO2 emissions as the primary source of atmospheric increases.

So what is increasing CO2 levels? I suspect a combination of natural ocean salinity increases and human pollution of the oceans. Pure water has the highest absorption rate of CO2 so anything that is added to water will change the balance between the atmosphere and the oceans.

Gary Pearse
Reply to  Geoff Sherrington
May 20, 2021 11:03 am

Geoff, no, the lack of change during 2020 means that a drop in partial pressure of CO2 from human activity results in more ocean outgassing to restore, in part, much of the decrease.

May 19, 2021 6:34 pm

IEA is just jumping on the bandwagon
Birol is trying to show he is a leader
real truth is he just lost all credibility
sad for the industry body spokesman to show such ignorance
Renewables give local electrical instantaneous energy
hydrocarbons give world wide transportable and storable energy

tell an Indian or Vietnamese farmer he has to return to using a donkey or human energy to plough his field and see how much his crop drops

Mass starvation and wars will come
but Birol can hide in his Swiss getaway and blame everybody else

Jim Gorman
May 19, 2021 6:35 pm

I may be all wet here, but using this scenario will make it easier to show how the models do not forecast properly. It will be at the top of the temperature increase projections and probably far off the actuals. Much easier to make fun of.

May 19, 2021 8:58 pm

Why don’t these people use words and terms meaningful to the concerned reader. Watts per square meter is meaningless and remains meaningless until converted to temperature scales we are accustomed to. Celsius or Fahrenheit. If you want to be taken seriously speak so you can be understood. I realize there are words, terms and phrases that are customarily used in the sciences and other disciplines. Unless you can boil them down to make what you are trying to express understandable you don’t know what you are talking about.

May 19, 2021 9:12 pm

As usual the luke-warmers like Mrs Curry are wrong. Humans have NOT made any significant global warming or manmade climate change .
It’s just a guilt trip for the gullible, designed and implemented by the UN idiots czars, and their paid for antiscience apparatchiks and model ŵankers.

Richard M
Reply to  tom0mason
May 20, 2021 7:50 am

The lukewarmers are assuming the same energy balance as the catastrophists only without all the positive feedback. They then attack anyone else as being anti-science. But what about those who also accept the same physics but show that the energy flows and not as either the lukewarmers or their alarmist’ counterparts have claimed? As far as I can tell they are ignored.

The whole issue of feedback disappears once the proper energy flow is understood.

May 19, 2021 9:12 pm

More dishonest IEA numbers.

versus the trajectory that would be achieved if all countries met their current commitments (APC) are shown in the diagram below”

Dubious starting emissions.

I read recently that the USA’s CO₂ emissions have declined to approximately 2005’s CO₂’s emissions. Yet, IEA starts the USA at much higher levels.

Then there is their alleged future growth.
Only the USA and China have significant CO₂ emissions growth. In spite of that the USA is the only country to significantly reduce CO₂ emissions by switching to a more efficient fuel.

IEA confirmation bias from beginning through their future imperfect charts.

The good news is that America gets to claim their reductions from the past four years officially and thoroughly destroy IEA’s baked in bias.

Gary Pearse
May 19, 2021 9:19 pm

“Stop using the worst-case scenario for climate change — more realistic scenarios make for better policy.”

It used to be that the “8.5” emmisions scenario was virtually impossible to consider. Now, with 5 billion people well into the race for posterity using mainly coal power and zero chance of turning them off given their staggering success over a mere decade (double digit GDP growth in several Asian countries, and Africa, just getting started, rising above 3%)

Hundreds of new coal powered plants are coming off the drawing boards and with prosperity, as night follows day, come autos, airconditioning, travel, modern homes and countrywide infrastructure.

Put 8.5 back on the program Judith! Only dont continue to be trapped in the IPCC gulag buying into planetary disaster it’s supposed to mean. We will be ushering in instead Garden of Eden Earth (тм), (I coined the term back when NASA first published on the “Greening” years ago here on WUWT and only recently have I noticed some others tentatively using the term). It coincides with peak population settling in not far from where we are now, and finally prosperity, abundance and peace at last. Oh, and дТ in 2100, another 1°C or so if were lucky enough to not be cooler.

Gary Pearse
Reply to  Gary Pearse
May 19, 2021 9:20 pm

Oops prosperity, posterity!

David DeCaro
May 20, 2021 2:54 am

It may or may not be true that Manhattan was bought by the Dutch for 24 bucks. What is true is that the Dutch were great mapmakers.

We know with some precision how big Manhattan Island was in 1624 and we know with great precision how big it is now. It’s bigger. Quite a bit bigger.

Now, Manhattan is a low-lying estuary riverine island of the exact sort that should get a lot smaller when sea level rises. Sea level has risen about 32 inches since the Dutch first mapped it, no dispute about it and yet Manhattan is now larger.

There was never any Federally funded, centrally planned program to save this island from rising tides and yet it seems to have done just fine.

Bruce Cobb
May 20, 2021 4:10 am

The elephant in the room of course, is that none of the RCP’s are based on provable, real-world science. It is pseudoscience, and fraudulent. The IPCC is an organization based on the Biggest Lie in human history, and their only mission is to perpetuate that lie.

Steve Z
May 20, 2021 8:47 am

From the second graph in Judith Curry’s article, the RCP 8.5 scenario assumes that CO2 emissions would reach about 130 GT/yr in the year 2080, as compared to 2020’s 34 GT/yr, or being multiplied by 3.8 in 60 years. How would that be even possible, if global CO2 emissions actually declined from 37.1 to 34 GT/yr from 2018 to 2020?

The article also states that radiative forcing “to date” is estimated at 2.5 W/m2, but somehow the CMIP6-RCP6.0 scenario, which assumes nearly constant emissions through 2080, would result in 6.0 W/m2 of forcing, or 2.4 times that of today. Why would maintaining today’s emission rate more than double the radiative forcing?

The CO2 concentration at Mauna Loa is currently increasing at a rate of about 1.8 ppm/yr, so that continuing that rate through 2080 would result in an increase of 108 ppm, reaching about 520 ppm in 2080. If the IPCC believes that the forcing function is proportional to the natural logarithm of CO2 concentration (the Arrhenius Equation), then by 2080 the forcing function would be 2.5 * ln(520) / ln(410) = 2.6 W/m2, not 6.0 W/m2 ! Increasing the relatively small forcing function by 4% over 60 years would have a negligible effect on global temperatures.

The same graph shows another scenario CMIP-RCP2.6, where CO2 emissions magically decrease to zero by 2080, and somehow go negative thereafter. But supposedly that results in keeping the radiative forcing nearly constant at 2.5 to 2.6 W/m2. How is that possible?

A mass balance over the atmosphere shows that, if all human CO2 emissions remained in the atmosphere, 8 GT of CO2 emissions would increase the concentration by 1 ppm, so that the 34 GT/yr of CO2 emissions in 2020 would result in a concentration increase of 34/8 = 4.25 ppm/yr. Since the actual concentration at Mauna Loa is increasing at a rate of 1.8 ppm/yr, this means that only about 42% of CO2 emissions remain in the atmosphere, and 58% are removed by natural processes, including photosynthesis.

If we somehow reduced human CO2 emissions to zero by 2080 (CMIP-RCP2.6 scenario), those natural processes would continue to remove CO2, and the CO2 concentration in the air would decrease by 2080, which would obviously result in less radiative forcing in 2080 than now. How does the IPCC figure that zero emissions results in nearly constant radiative forcing?

It seems like the IPCC is calculating future radiative forcing by assuming that all human CO2 emissions remain in the atmosphere forever, and neglect the CO2 removal rate by natural processes, which in the real world is currently over 50% of the current human emission rate. This removal rate could actually increase in the future, since higher CO2 concentrations tend to speed up plant growth rates, which would increase the CO2 removal rate by photosynthesis.

If we neglected CO2 removal by natural processes, continuing at the current emission rate would add 4.25 ppm/yr to the atmosphere, or another 255 ppm by 2080, for a total concentration of about 665 ppm. Using the Arrhenius equation, that should result in a forcing of 2.5 * ln(665) / ln(410) = 2.7 W/m2 by the year 2080, not the 6.0 W/m2 for the CMIP6-RCP6.0 scenario. Even if the forcing function is assumed to be linear, the radiative forcing in 2080 would be 2.5 * 665 / 410 = 4.05 W/m2.

So, in addition to neglecting the removal of CO2 from the atmosphere by natural processes (shown in the CMIP-RCP2.6 scenario), the IPCC is adding in another positive feedback (amplification) to the forcing function. What is the source of this positive feedback, and does it represent physical reality?

Or are all these scenarios theoretical garbage based on a non-physical CO2 perpetual feedback machine?

Mark BLR
Reply to  Steve Z
May 20, 2021 10:43 am

It seems like the IPCC is calculating future radiative forcing by assuming that all human CO2 emissions remain in the atmosphere forever

Not quite.

This is covered in the “Supplementary Material” file to Chapter 8 of AR5 (which can be downloaded from a link ~40% down this webpage), especially “Figure 8.SM.4” (on page 8SM-16).

50% of an initial “pulse” of CO2 added to the atmosphere is (supposed to be …) removed after roughly 30 years, but a full 30% will still remain 500 years later.

Everything after that is “basic calculus” (integration).
[ Now, which of these buttons adds a HTML “sarcasm” tag again ? … ]

Mark BLR
Reply to  Steve Z
May 20, 2021 11:05 am

But supposedly that results in keeping the radiative forcing nearly constant at 2.5 to 2.6 W/m2. How is that possible?

For the “RCP x.y” scenarios used in CMIP5 for the AR5 report, and the “SSPn-x.y” ones used in CMIP6 for AR6 (due in July or August this year ?), the “x.y” suffix refers to the radiative forcing for that “pathway” as it passes through the year 2100.

A decade ago what is now known as “RCP 2.6” was often called “RCP3-PD” instead, meaning “peaking at 3W/m2, then falling though 2.6 W/m2 in 2100 (and continuing to slowly fall until 2500)”.

Unlike (global mean surface) temperature “projections” by the various climate models, the following chain of calculations had relatively narrow “error ranges” for all links in the chain :
CO2 (/ GHG) emissions (= inputs to full-blown 3D AOGCM models)
–> Atmospheric CO2 levels (= inputs to “models of intermediate complexity”)
–> Radiative forcing (= inputs to “simple” climate models).

Tables of values for all three of the “input” options used by CMIP5 can be downloaded from the PIK (Potsdam Institute) just over a third of the way down this webpage.

May 20, 2021 8:59 am

I think the RCP concept is just an exercise in obfuscation. What really matters is what is the projected concentration of CO2 (and other trace GHG’s). The models are undoubtedly using concentrations as inputs either directly or indirectly, so why not simply show us what the GHG concentrations are going forward. It is then simple to compare the actual concentration trend with the projections, so an average bloke has some idea what they’re talking about, and some clue as to whether the models are any good or not. People are arguing that RCP8.5 is not realistic; I say, show me the implied or actual CO2 concentration of the RCP, and how it differs from reality.

Mark BLR
Reply to  Tom
May 20, 2021 9:59 am

I say, show me the implied or actual CO2 concentration of the RCP, and how it differs from reality.

See my response “above” to the same request you made yesterday.

If my graphs don’t answer the question in your head (as opposed to “what you typed on the computer” …), please explain exactly what data you would like to see graphed and I’ll see if I already have it on my local hard disk (as was the case above) or not.

Reply to  Mark BLR
May 20, 2021 10:36 am

That was it, thanks.

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