Claim: CO2 Causes Extreme Weather Even Without Global Warming

Guest essay by Eric Worrall

A new study by Professor Myles Allen, David Karoly and others claims that even if CO2 does not cause significant global warming, we still have to cap CO2 to prevent a “direct CO2 effect” from messing up the weather.

Rising CO2 may increase dangerous weather extremes, whatever happens to global temperatures

Press release issued: 11 June 2018

New research from the University of Oxford and collaborators at several other institutions, including the University of Bristol, provides compelling evidence that meeting the global warming target of 1.5°C may not be enough to limit the damage caused by extreme weather.

The paper, published today in Nature Climate Change, demonstrates that higher atmospheric CO2 concentrations directly increase temperature and rainfall extremes, meaning there could be dangerous changes in these extremes even if the global mean temperature rise remains within 1.5°C. The research highlights the need for climate policy to complement temperature goals with explicit limits on CO2 concentrations.

Much of the focus of climate change mitigation has been on the goal of limiting warming to 1.5°C warming agreed at the 2015 United Nations climate summit in Paris. However, the atmospheric CO2 concentrations required to limit warming to 1.5oC depend on the climate response. Researchers from Oxford and other institutions participating in the HAPPI-MIP project (Half a degree Additional warming, Prognosis and Projected Impacts Model Intercomparison Project) simulated future climate under the range of CO2 concentrations that all might be consistent with 1.5°C of global warming.

In the models, CO2 levels at the higher end of this range were shown to directly increase Northern Hemisphere summer temperature, heat stress, and tropical precipitation extremes. This means that even if a low temperature response helps us to meet the temperature target, there may still be ‘dangerous’ changes in extremes – in other words, severe weather impacts beyond those currently expected at 1.5°C.

The research points up the need to set explicit CO2 concentration goals to limit the adverse effects of high-impact weather extremes. It also supports existing findings that proposed geo-engineering solutions aimed at reducing global warming impacts without reducing CO2 concentrations may not be effective at counteracting changes in extremes.

Hugh Baker, DPhil student at Oxford’s Department of Physics and lead author of the research, said: “Future work is needed to confirm exactly why we see this direct CO2 effect, but current research points to a combination of circulation and cloud cover changes, and an increase in the amount of direct radiation on the Earth’s surface due to simply having more CO2 in the atmosphere.”

Oxford’s Professor Myles Allen adds: “This puts paid to the Pollyanna argument that we should wait and see before reducing emissions in case the global temperature response to rising CO2 turns out to be lower than current models predict. Hugh’s paper shows that the accumulation of CO2 in the atmosphere itself increases the risk of key damaging weather extremes, regardless of the global temperature response. It’s not enough to get lucky.”

Dr Dann Mitchell, a co-author of the paper from the University of Bristol’s School of Geographical Sciences, said: “Geo-engineering techniques that reduce the amount of sunlight hitting the Earth’s surface are increasingly thought of as a way of achieving the Paris Goals because they decrease surface temperature. However, our results show that for extreme climate such as heatwaves, changing the global mean temperature is not enough, you need to reduce CO2 concentrations themselves.”

The research was carried out in collaboration with researchers at the University of Melbourne, ETH Zurich, the University of Bristol and the National Institute for Environmental Studies in Tsukuba, Japan.


The abstract of the study;

Higher CO2 concentrations increase extreme event risk in a 1.5 °C world

Hugh S. Baker, Richard J. Millar, David J. Karoly, Urs Beyerle, Benoit P. Guillod, Dann Mitchell, Hideo Shiogama, Sarah Sparrow, Tim Woollings & Myles R. Allen

The Paris Agreement aims to ‘pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels.’ However, it has been suggested that temperature targets alone are insufficient to limit the risks associated with anthropogenic emissions2,3. Here, using an ensemble of model simulations, we show that atmospheric CO2 increase—an even more predictable consequence of emissions than global temperature increase—has a significant direct impact on Northern Hemisphere summer temperature, heat stress, and tropical precipitation extremes. Hence in an iterative climate mitigation regime aiming solely for a specific temperature goal, an unexpectedly low climate response may have corresponding ‘dangerous’ changes in extreme events. The direct impact of higher CO2 concentrations on climate extremes therefore substantially reduces the upper bound of the carbon budget, and highlights the need to explicitly limit atmospheric CO2 concentration when formulating allowable emissions. Thus, complementing global mean temperature goals with explicit limits on atmospheric CO2 concentrations in future climate policy would limit the adverse effects of high-impact weather extremes.

Read more:

Sadly the full study is paywalled, but my guess is what we are seeing is a response to Lord Monckton’s proof that climate sensitivity to CO2 has been massively overcooked.

How do you perpetuate the terror, when you can no longer claim with a straight face that anthropogenic CO2 will cause substantial global warming? I guess we now have our answer – the solution is to claim that even if CO2 does not cause substantial warming, a “direct CO2 effect” will still mess up the weather.


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I should think that there is rainfall, flooding and storm data available to verify or refute the results of the models used for this paper. I know that cyclone data shows no such change. Why did Dr. Allen not test his theory with real data?

Because he didn’t want his theory falsified.


Because they’re saving that exercise to justify the next research grant application.
Don’t you know how climate carpetbagging works?

John Harmsworth

Why should he show you his work when you’re just going to find something (everything?) wrong with it?

This ‘study’ is all models all the way down. That should be enough said.

It would be nice to see a Trump Tweet calling these guys Fraudsters.


Well reality is not the alarmist’s friend, is it?


My eyes are getting sore from all the eye-rolling going on lately.

Bruce Cobb

Well, this is a site for sore eyes.


This one rates a full-body eye roll.

Jacob Frank

New extreme study shows weather going nachos extreme CO2, now with more molecules

Alan Tomalty

The rise of the killer CO2. New study reports that increased CO2 in the atmosphere has now spawned a new breed of CO2 molecule. The researchers are calling it MannCO2, a new breed of molecule that heats up the atmosphere upon a breaking point of 450PPM. The heat created by this new molecule will lead to 5 billion deaths the researchers say. More studies are needed as to exactly how this new breed of CO2 got started. How do the researchers know this?. A new version of a climate model was able to detect it running simulations. 🙂


Again, the models show what we set up the models to do. It proves nothing whatsoever, unless you can prove that the models are right.

BTW, the trend line in the top graph is nonsense. There is no overall trend in that data.

Gerald Machnee

+++++ how many you need.
All I had to see was the word ***models***
Climate pseudo-scientists are proving everything with ***models***
GIGO has not changed.


Right, it looks like temps were steady then there was a shift up a fraction of a degree, and a new steady level. Maybe the Chinese cleaned up their air?


Yeah, I don’t smell the desperation, either. It’s not whether weather is being affected by CO2 raising temps, or not, WE SIMPLY MUST DO SOMETHING!!!

Ian Magness

Surely, surely, this is desperate nonsense? Whatever the blather about “climate change”, it has always really been about how CO2 increases cause higher atmospheric temperatures which, in turn, destabilise the climate, leading to all those “unprecedented” hurricanes, droughts, floods etc (that we are not actually seeing, but hey…). What other catastrophic effects is the superstar CO2 molecule supposed to cause if it cannot even raise temperatures, and how is the physics of this supposed to work given that CO2 is only a trace gas in the atmosphere?
I find this quite extraordinary and, as Eric points out, seems only to have stemmed from the growing conjecture (and indeed evidence) that Charney sensitivity is too low to worry about.


Indeed they must be really getting desperate if they’re pulling this spavined rabbit out of their collective hat!

I didn’t read the whole of the article. I assume they have been messing about with their PlayStations again. You would really think they would have grown out of fantasy toys by now.


Seems like the start of the process by the Cli-Sci community of admission that climate models are running hot and global warming may not be as bad as first thought. However, they recognize that this may affect their future funding so let’s find other unverifiable scare stories to peddle!


It is not heating up but it is still worse than predicted….

Rud Istvan

This study is a logical fail from the gitgo. The use of climate models was justified mathematically to ‘envelope’ the future as a boundary conditions problem, since the modelers are forced to admit long term weather forecasting isn’t possible because of the ‘initial values’ problem in lonlinear dynamic systems (mathematically chaotic). But it directly follows than an ensemble of such climate models cannot simulate future weather or its extremes any better than each individually. See also past posts ‘The trouble with climate models’ and ‘Why Models run hot’.

Jeff Alberts

Even short term weather forecasting is a crap shoot.


This is called a flank attack.

If your main thrust is meeting serious resistance you have to deploy other assets outside the main axis of advance.

Of course, that tactic is massively countered by the productivity benefits of CO2 to the plant and animal kingdom, which can immediately be wheeled out in response.

Ils ne passeront pas!


Hedging their bets for when the collapse of support for Climate change / Global warming arrives.


So what is the projected mechanism of extra atmospheric local heating? Ah I know, it is the “positive feedback” factor again, which no one has yet shown except in computer models which are completely discredited. The PhD student should do some experiments with greenhouses and a supply of CO2 rather than computer models, he would then understand what the words “research and physics” mean, and be able to write a thesis with some value. The result would be that CO2 level has no significant effect on the internal temperature, but then his thesis would be a bit thin wouldn’t it?

While it’s undeniable that Barbara Palvin is absolutely gorgeous, it’s also undeniable that models are an unreliable reflection of what to expect from real life.

Bruce Cobb

Bahaha, I could have predicted this would happen. Wait, I did, yesterday. Warmunists are so very predictable.

Tom Halla

“We still need a carbon tax despite any lack of warming” redux.


CO2 Causes Extreme Weather Even Without Global Warming

Without a doubt — if a cloud w/too much CO2 in it gets shaken up, it can fizz up & blow its top.

Ben Vorlich

Well it would wouldn’t it especially as there is no global warming.


This seems like a fairly safe position.

Since the planet has kicked out dangerous climate extremes even before CO2 rose above 280 ppm, there is no doubt that in the future, no matter what the CO2 levels, we will have 500 year floods and hurricanes and other examples of “extreme weather”.

So shift the test to trying to prevent extreme weather and the climate alarmists have it made!

Might as well call for a year without rain (or a year without drought).

The weather is getting, like, I mean, REALLY Weird, man. (Taking another toke)


The Climatistas are getting desperate. They’re throwing everything they’ve got against the wall to see what sticks.

howard dewhirst

Can anyone explain HOW CO2 damages the climate if there is no temperature increase, as satellite and balloon data consistently show; what does the molecule do? And if the satellite and balloon data are wrong, why keep collecting it?

Tom Abbott

“Can anyone explain HOW CO2 damages the climate if there is no temperature increase”

Good question. The answer wasn’t given in the article, just the claim.


howard dewhirst

It’s all those bloody balloons that are causing the problem.

There are so many of them they fill the atmosphere and compress the CO2 into smaller and smaller spaces.

Burst the balloons, they are the cause of AGW!!!!!

Well, it’s as plausible a hypothesis as this published rubbish.


It causes plants to grow more/faster, which is very bad because those plants produce more oxygen which can then be used to burn more fossil fuels producing more CO2 and causing even more plants to grow. It’s a chain reaction and before you know it the planet will collapse in on itself due to the weight of all those plants and we’ll all die. Where do I get my grant money to study this? I think I’ll start in the Maldives.

A. Scientist

I suspect it has to do with land-sea equivalent potential temperature contrasts which cause changes in circulation under the direct effect of CO2 ( . A change in circulation and atmospheric waves could cause extremes under the centres of the anticyclonic parts of the waves.

Alan Tomalty

A. Scientist said
“I suspect it has to do with land-sea equivalent potential temperature contrasts which cause changes in circulation under the direct effect of CO2 ( . A change in circulation and atmospheric waves could cause extremes under the centres of the anticyclonic parts of the waves.”

Not so fast. I checked the abstract of your link to the study Note below
“Using idealized aquaplanet simulations, we show that the different circulation responses are directly connected to the opposite responses of land–sea thermal contrast to the two forcing components”

Just another garbage study using computer simulations. Pleaseeeeeeeeeeeeeeeeeeeeeee!!!!!

If this is research, there needs to be a required and prominent disclaimer between model manipulation research and objective research based on real observations. But I wouldn’t use the term research for this, period. Bias projection using math?

Pat Frank

You’ve got it Coach. Climate Studies is a liberal art decorated with mathematics. It belongs with the like of post modern critical theory.


With a heavy dose of Marxist thought.


Wait, Marxists think?

Alan Tomalty

What is post modern critical theory?


“that atmospheric CO2 increase—an even more predictable consequence of emissions than global temperature increase—”

they didn’t really just say this…did they?

Pat Frank

Yet another study using climate models that have no predictive value.

All promoted by climate modelers who are not scientists, but rather critical theorists fit only to populate modern departments of Sociology or Cultural Studies. They all assume what should be proved, they merely elaborate a stock narrative, and they ensure that every study is confirmatory.

Tom in Florida

Listen, and understand. Those CO2ists are out there. They can’t be bargained with. They can’t be reasoned with. They don’t feel pity, or remorse, or fear. And they absolutely will not stop, ever, until they are dead.

Honest liberty



I was with you all the way up to Professor Myles Allen, David Karoly and others


From the Happi-MIP web link above this :
Following the Paris Agreement, we aim to quantify the impacts on weather-related risks corresponding to 1.5oC and 2oC of warming relative to pre-industrial conditions. We provide a set of bias corrected climate model output to be used in impact models. Our super-ensemble allows the quantification of relative risks of high-impact, low-probability events under present-day and 1.5oC and 2oC worlds, conditioned on a specific instance of internal climate variability, maximizing signal-to-noise.

What are relevant impacts that could be studied under a super-ensemble experiment?
Again an experiment in a controlled computer environment is supposed to be physics?
The problem here is not new – even the CERN CLOUD experiment mixed in a model “experiment” and even Svensmark took a while to spot it. He did an actual Forbush CME real experiment on aerosol growth.
Henrik Svensmark NEWS On Cosmic Rays, Clouds and Climaet,

Just waiting for someone to to publish an “experiment” on a super-ensemble of big-bangs!

“… using an ensemble of model simulations …”

Ensembles! They’re perfect for those times when one Tinkertoy™ model just refuses to give you the answer you want!



Everyone knows that when average together 20 wrong answers, you get the right answer.


Willis Eschenbach

Tinkerbell models more like. It’s all magic.

I so love how they stole terminology from physics and use it so wrongly. NOT.

Alan Tomalty

Battisti actually called a special model he coded for a study of his “our toy model”

this is just another scam to perpetuate the old scam – if the old scam {global warming) does not work out as planned…

However, an empirical experiment carried out by me shows that there is no effect from more CO2, nothing really,

and the world is already cooling.



Brilliant experiment, thank you for that. It’s a shame more climate alarmist supporters don’t take the time to do this sort of thing to actually test what they are being preached.

Now I’m not a God fearing man, but something does intrigue me. Around the time the planet was at 180 ppm atmospheric CO2, a mere 30 ppm from the extinction of all meaningful plant life, humankind popped up, seemingly from nowhere.

Man discovered fire and how to control it, then discovered fossil fuels, then technology. All the time atmospheric CO2 increased, I have no idea if we were the caused of the increase, somehow I doubt it, but I find it almost miraculous that during mankind’s tenure, plant life is flourishing and, surprise, surprise, that’s the only empirical evidence we have that CO2 is affecting the planet in any way.

Thank you for your diligence and impartiality Henry.

Hot scot

In the interglacial periods temperatures were occasionally than they are at present , resulting in the melting of the ice sheets (mostly Antacrtica/Greenland), and a sea level higher than today. Around the Cape here (South Africa) you can see the places when the water was in fact 30 meters higher than today and the Cape peninsula was transformed into a string of islands.

Of course we cannot blame man for this …….., can we? For the past 10000 years (Holocene) sea levels have remained more or less constant and this is the period when man showed up on earth…..
Funny, that you should mention it: we are carbon made and everything we eat depends on getting CO2.


“Future work is needed to confirm exactly why we see this direct CO2 effect”

Send Money


Right, the old ‘2 C isn’t going to be reached, let’s make 1.5 C scary’ tactic.

Sad really. I wonder if they realise what a bunch of utterly desperate fools they look like? Probably not. Psychopaths have notoriously thick skin.

Henry Galt

Evidence. – “You keep using that word. I do not think it means what you think it means.”

These idiots are insulting and ignorant. They should be ashamed.


“Using an ensemble of model simulations” – what could possibly go wrong?

DW Rice

The lead chart splices UAH and HadCRUT4 – lower troposphere (TLT) and surface – with an IPCC 1990 prediction of supposedly 3.3C/dec. AFAIK the IPCC doesn’t cite a model that splices TLT with surface; so the model forecast is either surface or TLT, not a combination of both. Since it’s citing the 1990 IPCC report, it must be surface, as the TLT record wasn’t even published in 1990 (neither was HadCRUT4, but let’s just stick with ‘surface’ anyway).

Secondly, the IPCC 1990 report stated that surface warming was predicted to be 3 C/century, but with an uncertainty range of 2°C to 5°C per century. It’s important to note that they are talking about the average rate of rise *starting 2001 and spanning to 2100*; also to state the uncertainties. This forecast was conceived about 30 years ago, after all.

Subsequent IPCC reports, starting 2007, lowered this best estimate rate from 3 to 2 C per century. HadCRUT4’s current best estimate range since 2001 is just fractionally below and well within the uncertainty range of that value. The other main surface data sets show warming that rounds to 0.2 C/dec since 2001.

In summary, the lead chart splices together surface and TLT data sets and compares them to an obsolete prediction that only ever referred to surface data anyway. We are less than 1/5th of the way through the predicted period and, within the range of uncertainties, the obsolete prediction is still valid. If we take the up to date prediction, then 2 out of 3 surface data sets already show agreement with it.

Alan Tomalty

The only temperature data set that we skeptics trust is the UAH satellite set.

John Hardy

As an Englishman I find this embarrassing from one of our per-eminent universities. As a graduate of the Other place it rather confirms my view that Oxford should stick to English, classics and history.

Smart Rock

Sorry John, the Other Place is no better. They have Peter Wadham (“the Arctic will be ice-free in 2016”). I went there too, back in the 1960s, when it was an unmatched scientific institution.

Gordon Dressler

So, is this just the “tip of the iceberg” (pardon me) of a future 97% consensus of CAGW apologists lining up to break the CO2-global warming link?

Darn that 2001-present warming hiatus, and the 1940-1975 one before that!

Lance Wallace

You can cry wolf too often.


Utter garbage.

When you see things like this being published, you realise instantly that the Warmistas can see that the ‘Global Warming Threat’ is in danger of being disproved and overturned and they realise that it is time to open up new routes for threat and fear to pile on the general population. Right now, they are firing up their computers and models to search for more possible dangers that can be plausibly ascribed to CO2.

Peter O'Brien

This paper is so obviously a stitch up it cries out for a rebuttal. Lets hope someone is up for it. Karoly has form.


So thats the story now?? Cuz u know its getn colder soon….truth be told its the warming that comes first-then the co2 lag and then the north pole melts and shuts down the N.Atlantic conveyor and the earth changes back to cold-possibly a glacial cycle…your co2 plays a tiny role…MAN doesnt have the power to affect the cimate-weather perhaps-but not climate. All there is now is excuses..

Andy Pattullo

Perhaps we need a new form of discipline in scientific discussion and publication. This story would be referred to not as research, or empiric science but rather speculation and prediction. All modeling and prognostication would fall into this category and the consuming public would be advised to treat the material with the same caution they would apply to a smelly wet brown deposit on the living room carpet when the family pet is left alone too long.
Science would refer to research where real observations and measurements support the conclusions, where all the methods and analytics techniques as well as original data are published and where others are allowed the privilege of reproducing the same findings independently.

Derek Colman

My mother had a good theory back in the 1970s when the globe was getting cooler and scientists predicted a new ice age. She explained that all those rockets launched into space were punching holes in the atmosphere and letting the heat out. i’m sure she would have made a great climate scientist.


Nothing to see here. It’s a well-known human brain breakdown. The inverse proportional reaction, of the failure of Co2 to quantitatively increase the non-equalized temperature variant of the global atmosphere, is the very damaging downflow of denser, ionized anti-matter within the atmosphere which causes the separation of predetermined BS from falsified conclusions within a shallow scientific brain. In this case, the outward expression of this condition is called: Co2 failure syndrome. Unfortunately, these (so-called) scientists will probably never recover. So Sad…


Great point!
Plus 10


I hope you don’t mind that I reposted this comment over at clisci blog.
Your post gives a nice example of how credible more and more of what passes for “climate science” actually is.


So it’s even worse than we thought. OMFG.

Phil Cartier

Using the CMURES validated model shows that global temperature increases up up to 3degC may break down the hurricane generation process by reducing latitudinal temperature profiles. The same model shows that increasing C02 may dampen the lapse rate in the lower atmosphere, reducing the severity but increasing the frequency of thunderstorms and tornadoes.

CMURES- Completey Madeup Research Model, which has been validated by numerous peer-reviewed scientific papers.

Jeff Alberts

So, how did this get past peer review?

I can’t believe I just asked that question.

Alan Tomalty

You mean pal review?

Ian Macdonald

I wonder where they got that graph from, that shows NO cooling after the 2016 El Nino. I know of no dataset like that. Suspect there’s been a spot of adjustment going on there.


Perhaps I’m missing something but this statement:

Hugh Baker, DPhil student at Oxford’s Department of Physics and lead author of the research, said: “Future work is needed to confirm exactly why we see this direct CO2 effect, but current research points to a combination of circulation and cloud cover changes, and an increase in the amount of direct radiation on the Earth’s surface due to simply having more CO2 in the atmosphere.”

“this direct CO2 effect” (on ‘extreme weather’) is based upon CO2-driven model predictions, not real data?


Apparently so. The destruction of the human mind seems to be the chief outcome of belief in the climate consensus.