What is the right climate?
Why are we defining ‘dangerous climate change’ with respect to the climate of the 18th century, which was the coldest period in the last millennia, with wicked winters? Why not use a reference point of 2000 or 1970? The IPCC doesn’t provide a convincing explanation for the overall warming between 1750 and 1950; according to climate models, human causes contributed only a very small amount to the global warming to during this period (so presumably this overall warming was caused by natural climate variability). Co-opting the period between 1750 and 1950 into the AGW argument muddies the scientific and the policy waters.
It would make much more sense — from a scientific perspective, from the perspective of adaptation and engineering, and in the public communication of climate change — to refer to warming relative to a more recent reference period. Since the emissions reference periods are between 1990 and 2005, this also adds to the argument of citing a more recent reference period for defining ‘dangerous’.
The argument that human caused warming is already ‘dangerous’ — widely made by politicians, the media and some scientists — flies in the face of scientific evidence reported by the IPCC AR5 and SREX. Extreme weather events were worse earlier in the 20th century, and sea level has been rising for millennia, with recent rates of sea level rise comparable to what was observed in the middle 20th century.
It’s almost as though there’s some sort of political agenda at work.
This has always been the foundation of my skepticism regarding ‘Climate Change’ (which is now, apparently, synonymous with Anthropogenic Global Warming) – what is the baseline from which the climate is ‘changing’?
Coupled with my inherent mistrust of computer models (derived from years of analysing them in the financial industry), I just don’t buy into the hysteria. ‘Climate’ is a dynamic system that we clearly don’t fully understand…yet.
Why are we defining ‘dangerous climate change’ with respect to the climate of the 18th century, which was the coldest period in the last millennia, with wicked winters?
Who’s using the 18th century as the bench mark? The earliest start date for AGW I’ve seen was the industrial revolution, it was from then that we started pushing up atmospheric CO2 concentrations.
So Curry’s whole article is a straw man.
OK, going through the whole article she does make some good points.
So what is/should be the baseline, and what is the “right” climate” and why is that the “right” climate, and how can we know that CO2 is a magical control knob that will get us there?
Curry suggests more recent climate – “Or perhaps it was the climate of the 1970’s, before the late 20th century warming” as being more optimal, which I agree with. I’d focus on the rate of change over the next century as a possible problem.
CO2 is undoubtedly a major climate forcing, nothing “magic” about it.
“Undoubtedly” is far too strong a word.
Keeling’s observatory on Mauna Loa shows that the CO2 concentration in the atmosphere has been inexorable increasing from a “pre-industrial” level of 280 ppm to over 400 PPM today.
The CO2 concentration curve, however, shows considerable fluctuation from a steady increase. There is the well-known seasonal oscillation in the CO2 level attributed to Northern Hemisphere land plants. On an annual scale, the biome draws down and then re-releases CO2 at rates (steepness of slope of the Keeling CO2-with-time curve) that dwarf any part of the long-term trend.
In addition to the “annual wiggles” of the Keeling CO2 curve, there are low-amplitude meanders from a steady increase. The slopes of these deviations are much milder than the seasonal oscillation superimposed on the multi-decade trend, but they are not trivial. As CO2 is neither created nor destroyed in the atmosphere, these slopes quantify the net emission of CO2 into the atmosphere.
The variation in net CO2 emission determined from these slopes is large in relation to the assayed CO2 contribution from humans — fossil fuel combustion, cement making, and forest clearance. Although the human emission of CO2 is large, it is unlikely that it fluctuates over a 2:1 or more range on short time scales so something else must be fluctuating to make the Keeling curve behave that way.
It has been noticed that the fluctuation in net atmospheric emission correlates well with global temperature — see http://www.woodfortrees.org/. Atmospheric physicist Murry Salby notoriously has generated a proverbial firestorm by showing according to a linear model of CO2 absorption and emission, these data establish that most if not nearly all the 20th century increase in CO2 that everyone is worried about is the result of the climate indeed warming in the 20th century. Furthermore, it is inferred from this that the warming is indeed real, but the arrow of causation is the warming resulting in increased CO2 rather than the other way around.
When someone like Salby comes around, it provokes a storm of ad hominems, four-letter words, hateful words describing persons with intellectual disability, and very little information on why Dr. Salby even might be wrong. One such diatribe posted as a comment on Dr. Judith Curry’s fine blog, however, contained enough a germ of information in it that I ran with it.
As you may have heard, of the CO2 emitted by human activity, only half is ending up in the atmosphere with the other half going “somewhere else.” Of the well-known “missing half”, half of that is absorbed inorganically, inferred to be dissolved into ocean water with the other half absorbed by photosynthesis. This partition of net CO2 is firmly established by more recent measurements that track total atmospheric oxygen quite accurately.
The half-of-half that is “going somewhere other than dissolved in ocean water” is hypothesized, conjectured, guessed-at as largely going into the land biosphere, but by the IPCC’s admission, this is largely speculation at this point.
Based on the temperature correlation, Salby proposes a model for the “missing 4th of anthropogenic CO2” derived from a mantra “absorption is proportional to (atmospheric CO2) concentration, emission is proportional to temperature.”
What Salby gets wrong is that CO2 dissolving into ocean water is not linear with atmospheric concentration owing to something called the “carbonate buffer system.” The inorganic-solution ocean CO2 reservoir is vast compared to either the atmosphere or the biosphere, but few of the Warmists or anybody else with such certain opinions on both sides of the warming controversy understand it — anyone seen a car on a college campus with the bumper sticker “Honk if you passed P-Chem.”
Inspired by Salby’s mantra and using a model that plant absorption of CO2 is proportional to atmospheric concentration and that CO2 emission from dead vegetation is proportional to temperature (warmer means faster rotting), using a non-linear model of ocean absorption of CO2 taking into account the chemical barrier to ocean water absorption as well as the time lag for ocean mixing with the deep layers, and using global temperature records and assays of human emissions, I come up with a simple model that predicts everything — the Keeling curve of the increase in CO2 from 280 to 400 ppm, the surface and deep ocean-water apparent radiocarbon ages, the multi-decade trends in carbon 13 concentrations, the above mentioned curve of atmospheric O2 depletion, the “bomb-test” curve of atmospheric radiocarbon showing rapid exponential depletion after the 1963 Test Ban Treaty, every last thing . . .
BUT
the year-to-year fluctuation in net CO2 emission as shown in the Keeling curve.
When I “crank up” the CO2 absorption rate of the land plants, which is entirely “made up” and speculative on my part but still plausible given the steepness of the annual wiggles in the broader Keeling curve, and I increase the temperature sensitivity of organic decay to balance this under the mantra “absorption proportional to (CO2) concentration, emission proportional to temperature”, I can now account for all of the above mentioned concentrations and radiocarbon ages AND for the correlation of the wiggles in the Keeling curve with global temperature.
When I do this, nearly half of the increase in CO2 that everyone is worried about is result of a natural process and not humans. In other words, humans have emitted a large amount of CO2, and the atmospheric CO2 has increased by half that amount. But were humans not to have emitted all that CO2, the atmospheric CO2 would have nevertheless increased by a large amount. And were this the case, one could draw the inference that temperature is driving CO2, especially in light of the increase in temperature in the early 20th century before human emissions really ramped up.
There are some Occam’s Razor problems with my analysis. Salby found the correlation between temperature and net CO2 emission to be the same at all time scales at which you compare known temperatures against known CO2 levels. My model uses the physical chemistry of ocean water CO2 absorption to “wash out” this correlation at longer time scales, and that the correlation exists at the multi-decade level is a chance occurrence — kinda like Secretary Clinton winning 6 successive coin tosses — that the 20th century ramp-up in human CO2 emissions was timed right with respect to a natural warming trend.
The other fly in the ointment is the ice core record. Were natural CO2 emissions to be correlated with temperature, you would see similar fluctuations in the CO2 levels derived from 19th century and earlier ice cores. In addition to the temperature-proxy compared against temperature-record Hockey Stick that our esteemed host Rand is all too familiar with, there is a CO2 hockey stick where atmospheric CO2 is rock steady and then zooms up in the 20th century.
For my model to be right that only half the CO2 increase can be blamed on humans, this casts doubt that the ice core CO2 is right, and there are fierce partisans on both sides of the ice core data, but Salby offers evidence in the Fourier transform of the correlation according to a technique taught in undergrad Electrical Engineering classes that the ice core record is smoothed, but the pro ice core people claim that with enough pressure, the bubbles are trapped and this ‘taint so.
As Pope Francis has brought Christian belief into the picture as to why we should take the CO2-Climate Change link seriously, I am channeling Augustine of Hippo in saying “Lord, give the ability to eliminate my carbon footprint . . . but not quite yet!”
Christian apologist C. S. Lewis allowed there to be lesser gods who were the object of pagan worship, who were real but Christians were admonished to no longer give homage. Maybe those lesser gods have the sort of strange sense of humor ascribed to such beings and are given license to confound and confuse humans — Salby believing a correlational model and not talking to physical chemists about ocean absorption, Mr. Romney’s polling data that he had Ohio, everything believed to certainty by the entire Warmist community — so we don’t become prideful and so sure of ourselves?
Rand, thanks for indulging this long post, but “CO2” and “undoubtedly” in the same sentence were “fighting words” even according to the Roberts Court.
Something for your perusal, Paul.
https://judithcurry.com/2016/01/24/undersea-volcanoes-may-be-impacting-long-term-climate-change/#comment-761028
This is exactly what I am referring to, and commenter “Bartemis” is one of the leading “evangalists” regarding the correlation between net CO2 emissions and global temperature.
The Warmist line is on the correlation between temperature and total atmospheric CO2 — as CO2 has increased, so has global temperature, and indeed global temperature has gone up — in fits and starts with Pauses in between as atmospheric CO2 concentration has risen steadily.
What “Bartemis”, Salby and others are talking about is the too-strong-to-dismiss correlation between global temperature and the slope of the CO2 curve — not the CO2 curve but its slope. Owing to the atmosphere itself not creating nor destroying CO2 (unlike the case for ozone or methane), that slope is in direct proportion to “net emission” of CO2 — the balance between all sources, human or natural, and all (largely natural) sinks outside the atmosphere.
This correlation between temperature and net CO2 emission is strong over a broad range of time scales. If you take correlation to mean causation (I’m speaking to you, Warmists), this means that almost all of the increase in CO2 in the atmosphere is the consequence of whatever mechanism causes large swings in net emission with year-to-year temperature changes. Humans are not driving those swings because the amount of SUV driving, concrete pouring, forest chopping, and leaving the lights on doesn’t fluctuate anywhere near that much.
What I am saying is that for once, Warmists are (partially) right that (a good fraction) of the increase in total atmospheric CO2 is human-caused (I am saying about half). The Warmist community is right about Salby being wrong (that the increase in atmospheric CO2 has little to do with humans) — stopped clock, two correct readings each day. They are right, however, for reasons that most people Warmist or not, do not understand and probably wouldn’t understand. How many of them took the dreaded “P-Chem” in college?
I spent a goodly amount of time in 2015 teaching myself enough P-Chem to be dangerous after reading commenter “M” posting August 29, 2011 on Dr. Judith Curry’s blog. I really wanted to know if there was any rational counter-argument to Salby’s assertion that the ocean would swallow up all of the human CO2 in the absence of a natural source of the increase in atmospheric CO2. “M” takes the exasperated “you have intellectual deficits for not understanding my reasoning” line, but I invested considerable energy to overcome my natural level of intellectual disability in not having P-Chem under my belt.
“M”‘s comments as they are not adequate to dismiss Salby and others regarding the human contribution to the increase in atmospheric CO2, but they contain leads to the references of scientific papers to get a “handle” on the question. There are two mechanisms to invoke to account for any increase in atmospheric CO2 not being swallowed up into the vast inorganic-solution ocean reservoir.
One mechanism is the “Revelle buffer” — the P-Chem part where the ocean absorption of a delta CO2 from the atmosphere follows the 10th power — a highly nonlinear function that is the consequence of a chain of chemical reactions in ocean water, but I take the word of those who have passed P-Chem on this one and use my engineering-major math and computer skills to take it from there.
Revelle and Suess (1957) (yes, the Revelle Buffer dude), however, thought that the ocean CO2 reservoir was so vast that even taking the Revelle buffer into account (something “M” described people not knowing about as having intellectual shortcomings), that the increase in CO2 in the air had to have a strong natural component.
To the Revelle Buffer mechanism I added a time constant for the mixing of the surface and deep ocean reservoirs. Many (including “M”) regarding deep ocean mixing as having a multi-hundred year time constant that it cannot participate in meaningful sequestration of the human CO2 “pulse”, but that too is wrong for reasons that I can explain as an Electrical Engineer with resistor-capacitor circuit time constants.
When I model both the Revelle Buffer and the deep ocean mixing, I find that the Warmist assertion (attributed to Callendar — look him up on Wikipedia) that almost all the increase in atmospheric CO2 is from humans is indeed right and Salby is completely wrong — that is, if you don’t take into account the temperature-rate of net emission correlation.
When you take the correlation between temperature and net emission and the Revelle Buffer and deep ocean mixing into account, the Warmists are half right, Salby is half right, and you can explain, at least to “first order” everything from the rapid extinction of radiocarbon in the air after the 1963 cessation of atom bomb testing to all of the CO2 and gas isotope time histories known.
But you are left with this curious were the fossils Created to give the appearance of Evolution argument. The 20th century CO2 emissions had to be timed just right with respect to a natural warming trend to fool Salby and others to think the causes-and-effects driving the correlations are uniform across time scales when they are not. This puts Warmists of all stripes (including me, a partial Warmist) in the Creationist camp and puts Salby the correlationist in the Darwinist camp.
Bartemis is I. There were too many Barts around at Dr. Curry’s site, and I had to adopt something more distinguishable there. WordPress forced me to adopt it at other venues as well.
I had doubts about the attribution of the rise in CO2 from the start. The narrative just didn’t jibe. We supposedly had very little variation in CO2 for centuries, then all of a sudden, our emissions pushed everything off balance. However, the previous tight control of CO2 indicates what should be a fairly high bandwidth regulation – otherwise, there should have been an effective random walk in CO2 over the long timeline associated with the low bandwidth of a system that would be so sensitive to human inputs. You simply cannot have high bandwidth for natural forcing, and low bandwidth for anthropogenic forcing. They must be treated equally.
When I happened on the incredibly tight relationship between the rate of change of CO2 and temperature, it was game over for me. This was the smoking gun, the proof that humans have negligible impact on atmospheric CO2.
Why? Because, human inputs have been experiencing a more-or-less linear rise in their rate of emissions as well. To fit them in, in any significant measure, you would have to reduce the scaling factor in that plot for the natural, temperature driven input. There is room to do it, because those data are rather variable. If I used a 12 month filter instead of 24 months, the peaks would be higher, and I could scale them down by perhaps about half, and then human emissions could account for about half, as well. But, it is klugey, and the simplest explanation continued to be that it is virtually all natural.
Then, I got a look at the higher accuracy satellite data here. This is not as long term, but it fits much better, without so much variability. A 12 month average to take out the annual variation shows a very tight relationship with temperature. There really is very little room here at all for significant human forcing.
The upshot being that Occam’s razor was correct using the surface data. The simplest explanation is that temperature accounts for essentially the entire ball of wax, and the impact of human inputs is negligible.
I’ve had a lot of people argue with me on this, using all kinds of rationalizations to deny the obvious. One recurrent theme is the so-called “mass balance” argument, which argues that, since the observed rise is less than the cumulative sum of emissions, we must be responsible. This is an incredibly jejune argument, and the people making it have the IQ of navel lint. However, they are invincibly ignorant, and you cannot reason with them.
Another recurrent criticism is that people just cannot see a mechanism for how this could come about. My current thinking is along the lines of the link I sent previously. Most of our production probably ends up in the ocean. But, the temperature induced imbalance between CO2 concentration of upwelling and downwelling waters simply accumulates at the surface, forcing the atmospheric concentration to a level dictated by concentration in the surface oceans, resulting directly into the observed relationship of dCO2/dt = k*(T – T0).
I am looking forward to La Nina’s revenge for the recent El Nino. I am expecting temperatures to fall off a cliff, then resume the natural combination of the trend + approximately 60 year oscillation that has been evident since the end of the LIA, and for which we are in no way responsible. Temperature cannot be terrifically sensitive to CO2, because the integral relationship above plus high positive sensitivity to CO2 would create a positive feedback system, which would have hit a limiting regime of high temperature and high atmospheric CO2 eons ago. I think the Earth’s temperature is basically regulated by the water cycle, and CO2 is simply a bit player.
So it was you, as “Bartemis”, who tangled with Ferdinand Englebeen, one of Anthony Watts’ regular guest bloggers? Anthony seems to tolerate or even encourage a wide range of opinions, but who is Ferdinand anyway, a keeper of anthropogenic-warming skepticism who aims to “purge the movement” of those who are too far out (cough, Salby, cough)? And does he ever come up for air (Ferdinand, that is, not Murry)?
I am also coming around to seeing the CO2 ice core readings as the “hill” on which the CO2-increase-is-anthropogenic lives or dies (Callendar’s Hypothesis — Revelle and Suess (1957) mention him, but there is a recent Wikipedia entry on him too).
Ferdinand is simply not giving up any ground: once the “firn” closes, the gas bubbles in the ice cannot move, and will argue that point until people are tired of posting replies. But Salby points out that the temperature–ice core CO2 correlation has a phase difference in relation to the correlation between temperature and net CO2 emission in the atmospheric records indicative diffusion and is muttering under his breath eppur si muove?
Yeah, I think the ice cores estimates are bogus. There’s nothing to validate them against, and if my time in the lab has taught me anything, it is that just because you expect something to happen is no reason that it will. Open loop speculation without verification is just not very reliable. Nature has a tendency to slip through any loophole it can find.
There are things to validate them against – stomata records, for example. They just don’t jibe. And, since they do not agree, reasons are found to disbelieve them, and elevate the ice core records, which agree with the narrative.
The whole damned thing is a circular exercise. They believe the ice cores because it agrees with the narrative. And, the narrative is true because of the ice cores.
Except, as I mentioned, the demand for simultaneous high and low bandwidth is incoherent.
PS: Ferdinand is just some retired process controls guy who has made a hobby of studying up on the narrative. He’s not very math-oriented, though, and he doesn’t understand a lot of control theory. But, he is really nice and cool-headed, I will say that for him. I think he is Dutch.
Alf,
Tell us when you think the Industrial revolution began.
This pretty much the baseline for it.
“The Industrial Revolution was the transition to new manufacturing processes in the period from about 1760 to sometime between 1820 and 1840. This transition included going from hand production methods to machines, new chemical manufacturing and iron production processes, improved efficiency of water power, the increasing use of steam power, the development of machine tools and the rise of the factory system. Textiles were the dominant industry of the Industrial Revolution in terms of employment, value of output and capital invested; the textile industry was also the first to use modern production methods.”
https://en.wikipedia.org/wiki/Industrial_Revolution
CO2 is undoubtedly a major climate forcing
Since there’s nothing magic about it, perhaps you can state exactly what it is about the climate that is being forced by it.
CO2 absorbs IR radiation.
In doing so it slows the rate at which heat can travel from the Earths surface to the top of the atmosphere from where it can escape to space.
No scientists on either side of the debate disagrees with this physics.
No one here does, either. That doesn’t make it “major” in the context of other factors.
What other factors? Other GH gases, aerosols, cloud changes and the Sun are other major forcings, CO2 certainly ranks high in that group, do you have other, yet to be discovered forcings up your sleeve?
CO2 certainly ranks high in that group
Certainly. High up. Very high up. And… somehow… something’s getting “forced”. And that’s bad. Very bad. I mean, how can something being “forced” be anything other than bad??
Got it. Thank-you.
Feedback, tides, and normal response modes.
Feedback effects, due to changing wind patterns and clouds, as well as biological activity and probably others, are very poorly understood and characterized.
Lunar and Solar tidal forcing produces significant effects on ocean mixing which, IMO, have not been sufficiently studied.
And, the Earth’s climate has modes of oscillation, just like a bell has tones. These are extremely long term, and store and release energy over timelines of centuries.
I need none.
Ocean currents, both in atmospheric temperature and atmospheric CO2 changes.
“In doing so it slows the rate at which heat can travel from the Earths surface to the top of the atmosphere from where it can escape to space.”
Is radiation the only means by which heat can travel from the surface to the top of the atmosphere from where it can escape to space?
Radiation isn’t even a leading mechanism for heat transfer from the surface to upper atmosphere. Convection and evaporo-transpiration are far larger movers of heat. In addition, assigning IR absorption by CO2 a major role neglects that water vapor already saturates the wavelengths CO2 is active at.
Exactly. Lots of paths for the heat to bypass the filter of IR absorbing gases once convection kicks in. Projected heating of the surface comes from assuming a specific balance of competing influences, and then going out and finding evidence which would tend to be consistent with that balance. And, that is where confirmation bias kicks in to give a patina of legitimacy to the assumptions.
The physics you cite is well known and non-controversial. The computer climate models cited by alarmists, however, do not attribute much of the alleged warming to come to rising CO2 levels. Most of the future effects are predicated on a significant rise in average atmospheric humidity that is supposed to be “forced” by the rising CO2. Problem is, this doesn’t seem to be happening. The CO2, by itself, may account for a fractional degree of warming over the next century or so, but that hardly constitutes the sort of “crisis” the Left is alleging in what is merely their latest pretext to take over everything and everyone on the planet.
At the wavelengths absorbed by CO2, what percentage currently is absorbed? Because the only additional light that new CO2 could absorb would be light at that frequency band which is not currently being captured. If 100% of the incident light is already being absorbed, then new CO2 won’t change anything.
The correct reference point for the Earth’s climate for the last million years or so is very cold with a mile of ice covering the location of Chicago (perhaps not such a terrible idea :-)). We had dangerous global warming and sea level rise about 20,000 years ago which had finished about 8000 years ago (Holocene Climate Optimum – wonder why it is called that?) and it has been cooling since on average.
“And, the Earth’s climate has modes of oscillation, just like a bell has tones. These are extremely long term, and store and release energy over timelines of centuries”.
Completely agree, Bart. The oscillation periods may not even be well defined. Think of a large complex mechanical system of springs and double pendulums, masses, pulleys etc. Hit it with a large input (equivalent to end of last ice age). Good luck trying to figure out what any particular part is going to do next.
Actually, every scientist with expertise in atmospheric physics will tell you this is not quite the case.
Furthermore, generalizations about heat transport and the state of the Earth’s atmosphere have to be qualified with “largely” and “mostly” because the Earth’s atmosphere is much more chaotic than the uniformity of the atmosphere on Venus or the steady-state of the convection zones on Jupiter. Every modern textbook on weather starts with these convection zones called Hadley cells, but I once asked some people who would know, why you don’t see them in a satellite picture of the Earth. I was told they are hard to see because unlike Jupiter that is stabilized by a high spin rate, the Earth’s atmospheric flow is “on the edge of chaos” as in Chaos Theory in dynamical systems.
The lower atmosphere is mostly opaque to IR radiation — that is why NASA has that jet with the square cut out of the side for an IR telescope to look out. Heat transfer in the atmosphere is also largely through convection until you get to a height with enough IR transparency, low enough gas density, and dry and stable enough layers for it to be predominantly radiative.
What CO2 does is raise slightly the altitude at which radiation takes over. The temperature of this high layer (on average, it is at the start of oxygen-starvation for humans at the start of the air traffic “flight levels”) is fixed by the Earth’s albedo and radiative equilibrium.
Working downwards from that layer, the surface of the Earth is warmer by the “adiabatic lapse rate”, which is to say, by compression heating (and cooling) from air circulating convectively between ground and the radiative layer.
Like everything to do with weather it is a little bit more complicated as you have a dry adiabatic lapse rate and a different wet lapse rate taking into account the latent heat of phase change of water vapor (cloud formation with altitude).
So the warming of the surface of the Earth relative to the temperature of radiative equilibrium is the result of compression heating, the same effect as with a bicycle air pump or with compression ignition in a Diesel engine and nothing to do with how a greenhouse works. By the way, what causes a reentering spacecraft or meteorite to heat up? It is not atmospheric friction, or only indirectly inasmuch as fluid shear affects the shock wave pattern accomplishing the heating through compression — the engineers working on the aerospace “thermal thicket” problem learned about compression heating early on.
Salby explains the convective and radiative levels of the atmosphere in his atmospheric science textbook held in high regard before crossing to the Dark Side, and the evil Lindzen explains the increase in radiative height acting on the lapse rate (convective heating plus latent heat of H2O phase change) as the source of CO2 forcing.
So the “greenhouse effect” is as scientifically wrong as “friction causes meteorites to burn up as meteors”, but yes, even a Dark Side acolyte as Professor Lindzen will tell you that increased CO2, all other effects being equal (relative humidity, cloud cover, atmospheric circulation patterns, ocean currents, plant photosynthesis and decay of dead things, charged-particle nucleation of high altitude clouds, which are pointedly not equal), such increased CO2 will cause a slight change in surface temperature.
The Catastrophic Warming Hypothesis that we have to impoverish us all to stay within some warming target is based on acceptance, no, make that belief in feedback mechanisms largely involving water vapor that amplify the small contribution of CO2 to warming. Lindzen is famously disrespected because he claims the positive feedbacks are a crock.