<p>It's the first very significant report to make that claim because the claim is unscientific in nature.</p>
<p>As <a href="https://books.google.com/books?id=IOFmZoesMNoC&amp;pg=PA1602&amp;lpg=PA1602&amp;dq=%22The%20scientific%20theorist%20is%20not%20to%20be%20envied.%20For%20Nature,%20or%20more%20precisely%20experiment,%20is%20an%20inexorable%20and%20not%20very%20friendly%20judge%20of%20his%20work.%20It%20never%20says%20%22Yes%22%20to%20a%20theory.%20In%20the%20most%20favorable%20cases%20it%20says%20%22Maybe,%22%20and%20in%20the%20great%20majority%20of%20cases%20simply%20%22No.%22%20If%20an%20experiment%20agrees%20with%20a%20theory%20it%20means%20for%20the%20latter%20%22Maybe,%22%20and%20if%20it%20does%20not%20agree%20it%20means%20%22No.%22%20Probably%20every%20theory%20will%20someday%20experience%20its%20%22No%22%E2%80%94most%20theories,%20soon%20after%20conception.%22&amp;source=bl&amp;ots=sVp_d0NO1L&amp;sig=pIt5kjxteB_51khNld7sdaFqN-8&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwiN79KTg9HXAhUrjFQKHQG7CHcQ6AEIKDAA#v=onepage&amp;q=%22The%20scientific%20theorist%20is%20not%20to%20be%20envied.%20For%20Nature%2C%20or%20more%20precisely%20experiment%2C%20is%20an%20inexorable%20and%20not%20very%20friendly%20judge%20of%20his%20work.%20It%20never%20says%20%22Yes%22%20to%20a%20theory.%20In%20the%20most%20favorable%20cases%20it%20says%20%22Maybe%2C%22%20and%20in%20the%20great%20majority%20of%20cases%20simply%20%22No.%22%20If%20an%20experiment%20agrees%20with%20a%20theory%20it%20means%20for%20the%20latter%20%22Maybe%2C%22%20and%20if%20it%20does%20not%20agree%20it%20means%20%22No.%22%20Probably%20every%20theory%20will%20someday%20experience%20its%20%22No%22%E2%80%94most%20theories%2C%20soon%20after%20conception.%22&amp;f=false" rel="nofollow noreferrer">Albert Einstein once said</a>:</p>
<blockquote>
<p>The scientific theorist is not to be envied. For Nature, or more
precisely experiment, is an inexorable and not very friendly judge of
his work. It never says &quot;Yes&quot; to a theory. In the most favorable cases
it says &quot;Maybe,&quot; and in the great majority of cases simply &quot;No.&quot; If an
experiment agrees with a theory it means for the latter &quot;Maybe,&quot; and
if it does not agree it means &quot;No.&quot; Probably every theory will someday
experience its &quot;No&quot;—most theories, soon after conception.</p>
</blockquote>
<p>Or, more recently, as <a href="https://histsci.fas.harvard.edu/people/liv-grjebine" rel="nofollow noreferrer">Liz Gerjbine</a> writes in <a href="https://www.scientificamerican.com/article/why-doubt-is-essential-to-science/" rel="nofollow noreferrer">Scientific American</a> &quot;[S]cience cannot provide certainties.&quot;</p>
<p>This isn't an attempt to cast doubt on climate change, in fact I think <strong>a better comparison would be saying we're about as certain as we are about gravity</strong>.</p>
<p>So they're the first to publish that statement because a core tenet of science, if not <em>the</em> core tenet, is <em>doubt</em>.</p>
<p>I'm actually quite shocked any serious scientist or group would make the statement &quot;can no longer be scientifically disproved&quot; about anything. Seems more like political grandstanding than genuine science.</p>
<p>The other answers so far do a fine job explaining the slow dissemination and acceptance of scientific findings.</p>

CC BY-SA 4.0
2022-07-21T12:20:22.833Z
While _theories_ will get a "no", _models_ can keep their "yes, and here are the error bars in this circumstance". Newtonian gravity is still useful for modelling the behaviour of aeroplanes, even if it isn't good enough for GPS satellites and – as a _theory_ – it's been thoroughly debunked for quite some time.
wizzwizz4
CC BY-SA 4.0
2022-07-21T13:51:40.143Z
Gravity is a good comparison really. We know it exists but science still gets fuzzy on the precise details, and the modeling of it gets shaky fast (see: three body problem). Same with climate change. It's one thing to observe that it exists. The quibbling is mostly over the nature of it, the origin, the effects, the timetable, and the fact that the modeling is always inaccurate to a variety of degrees. (We have had global warming but nothing like the models from 20-30 years ago said we were going to have in 20-30 years.)
JamieB
CC BY-SA 4.0
2022-07-21T16:49:30.667Z
@JamieB I had a long parenthetical disclaimer after originally writing the theory of gravity, then decided on this word choice instead. Couldn't agree more with your analysis.
TCooper
CC BY-SA 4.0
2022-07-21T20:28:51.217Z
Scientists tend to be bad at public speaking. When asked something, they say "probably", meaning +90%, yet the "average Joe" will think that's more like 50-60%. "Statistically insignificant" goes from < 0.001% to < 20% in the public eye. "Almost certainly" becomes "this is a lie". Bill Nye, Neil deGrasse Tyson, and others have furthered scientific speaking enormously with their smooth and natural speaking styles, immense intelligences, specific use of terms, and defining the terms they use. They don't just assume "John Doe" understands the scientific terms the same way they do.
computercarguy
CC BY-SA 4.0
2022-07-22T17:13:48.770Z
One of the things that bothered me for decades on this issue has been the failure to make testable predictions with a reasonable defined null hypothesis.  The climate modelers predicted that CO2 forcing would cause temperatures to keep rising, but then when temperatures fell (contrary to predictions) the climate modelers said that too was a result of CO2 forcing.  Given the their initial long run of inaccurate predictions, scientific rigor would suggest that climate modelers should need to produce a good run of accurate predictions before they should be taken seriously.
supercat
CC BY-SA 4.0
2022-07-23T08:05:19.943Z
@supercat: "when temperatures fell". When was that? https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature
Eric Duminil
CC BY-SA 4.0
2022-07-23T08:07:42.683Z
@JamieB: "nothing like the models from 20-30 years ago". "Nothing" seems a bit harsh. https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming/ do you have other sources?
Eric Duminil
CC BY-SA 4.0
2022-07-23T09:19:31.717Z
"Seems more like political grandstanding than genuine science." I cannot blame the IPCC. They wrote 5 reports over 30 years, explaining us very clearly "There's a large concrete wall just ahead of us. We might want to not crash into it". And all they got as an answer was "Braking is bad for the economy", "There's no wall", "The wall has always been here", "How do you know crashing into a wall is bad for us?", "Is the wall 2m or 3m thick?", "How will my car look like, exactly, after it hits the wall?". No wonder the IPCC now writes "CRASH IS IMMINENT. EMERGENCY BRAKE, NOW!!!!"
Eric Duminil
CC BY-SA 4.0
2022-07-23T09:37:49.687Z
Trying to say that climate change science is as mature as gravity science is a nonsense. Gravity theory is testable to umpteen sigmas.
Valorum
CC BY-SA 4.0
2022-07-23T10:25:33.547Z
@supecat can you remove that line "when temperatures fell" - this is a statement that *is* not true and thus misinformation. You are incorrect and using that as argument breaks down any discussion one can have. -- Or you have to show the truth that temperatures fell.
paul23
CC BY-SA 4.0
2022-07-23T16:07:11.363Z
@paul23: Some record low temperatures as well as record high temperatures have been set in many places in the last twenty years, and the response was often to say that the presence of high temperatures in some places would change wind patterns in ways that caused record low temperatures, a notion which while plausible *was not part of climate modelers' predictions*.  A fundamental requirement of a scientific theory is identifying what possible future observations would be consistent with it, and what *what possible future operations would be inconsistent with it*.
supercat
CC BY-SA 4.0
2022-07-23T16:22:01.243Z
@paul23: While there may have been some climate modelers somewhere that were properly employing scientifiic principles, the scientific methodology of those covered by the press was severely lacking.  Further, those who complained about the sloppy "science" were branded as heretics without making any effort to address their legitimate concerns.
supercat
CC BY-SA 4.0
2022-07-23T17:43:12.027Z
@supercat: "Some record low temperatures". You're talking about weather, we're talking about climate. Weather is a chaotic system : adding more energy to it will raise the average temperature, but will also lead to extreme events with more frequency and intensity than before. So record lows, record highs, record droughts, record hurricanes are expected, and have been predicted by climate models for a long time now. The opposite of global warming would be : lower average temperatures, fewer extreme events, "boring", stable winters and summers, with small temperature variations from day to day.
Eric Duminil
CC BY-SA 4.0
2022-07-23T18:07:25.940Z
@EricDuminil: Do you think the media's reporting has adequately described predicitons and associated null hypotheses in such a way that predictions would likely fail if observed warming had been purely coincidental?  Do you think that the models have been sufficiently rigorous in compensating for phenomena such as the heat island effect or changes to measurement methodology that any apparent temperature increase could only caused by CO2 and not by other real factors (like heat islands) or imaginary ones (changing methodologies)?
supercat
CC BY-SA 4.0
2022-07-23T18:38:49.010Z
@supercat what is your point, exactly? All the scientists who contributed to IPCC reports are stupid, corrupt, or both? That they only use weather stations if they are close to the exhaust of an air conditioner? How do you explain that large glaciers are disappearing? You don't need to trust anyone for this example, you simply need to watch them shrink from one year to another.
Eric Duminil
CC BY-SA 4.0
2022-07-23T22:17:03.447Z
@EricDuminil: The portion of the research covered by the media is scientifically unsound.  That is likely, at least in part, because the media are prone to view scientifcally-dubious studies that yield dramatic conclusions as more newsworthy than scientific studies which yield more timid conclusions.  I don't know whether the climate modelers did shody work, or wehther scientists did good work but the media only presented an unsound collection of snippets from it, but the overall reporting has been objectively terrible from the standpoint of scientific soundness.
supercat
CC BY-SA 4.0
2022-07-24T14:02:59.663Z
@EricDuminil "I cannot blame the IPCC." Why not? The reason no one has taken their "wall" seriously so far is every time they claim its "right here", its been more like a gentle hill. I personally believe 100% we need to invest in green technologies and make an effort to reduce carbon footprints etc to build a sustainable future that is worth living in. If I consider time scales and the relatively limited amount of actual data collected on the topic, I would never make aggressive, seemingly fear-mongering statements that once again, seem more like political grandstanding than actual science.
TCooper
CC BY-SA 4.0
2022-07-24T14:14:06.283Z
@Valorum I've edited the answer slightly. I think gravity is a near perfect comparison as described prior in the comments. We have a ridiculous amount of evidence it exists but that's about all we have evidence and a *great* understanding of. The rest are theories that we shouldn't dismiss but rather research and test extensively rather than claim "we're going to make the earth void of human life in [always 10-30 years later] if we don't act RIGHT NOW". Hopefully that helps explain the comparison? Open to a better one if you have suggestions?
TCooper
CC BY-SA 4.0
2022-07-24T15:39:51.417Z
@TCooper: I don't know where you live or how old you are. I'm 40, and live in western Europe. I remember seeing large glaciers and lakes as a kid which have now completely disappeared. The last few years have been so dry that the region I live in (in Germany) now looks like southern Spain. There were large wildfires in Brittany this year, in a region known for typically being very rainy. If that's a gentle hill to you, I do not want to know what a wall looks like. Atmosphere+oceans have such a large inertia, if we wait until we notice that we overshot, it will be *way* too late.
Eric Duminil
CC BY-SA 4.0
2022-07-24T15:46:03.303Z
@TCooper: https://xkcd.com/1379/ We're already at +1.2°C, and the effects are highly non linear.
Eric Duminil
CC BY-SA 4.0
2022-07-24T20:10:27.133Z
@EricDuminil - If we go back 10,000 years, your house is a mile under ice.
Valorum
CC BY-SA 4.0
2022-07-27T11:30:48.710Z
https://mobile.twitter.com/JohnBri64148431/status/1551961365744607233/photo/1
Valorum
CC BY-SA 4.0
2022-07-20T20:38:39.183Z
2022-07-24T14:03:32.160Z
2022-07-24T14:03:32.160Z
TCooper
<p>Just because a &quot;small number&quot; of scientists knew about something in the mid 1820s doesn't mean it was initially accepted by other scientists. You also have to consider the means of disseminating information and knowledge then and since. You also have to consider what other attitudes prevailed.</p>
<p>Charles Darwin's Theory of Evolution was vigorously opposed by many eminent people because of religious beliefs. In some places it still is.</p>
<p>Personally, I first became aware of global warming via the mass media many years <em>after</em> I completed my university studies. I was taught other scientific things - there's a lot to learn - and I still think I had a good education.</p>
<p>I became aware of Darwin's Theory of Evolution in high school, but no-one mentioned global warming or the heat retaining potential of carbon dioxide or methane, or whatever else. It wasn't part of the science curriculum, other things were.</p>
<p>People may have been warning about global warming before that, but from what I'm aware of they were few in number, they didn't captivate the attention of the mass media and they were essentially voices in the wilderness. There's a saying &quot;the squeaky wheel gets the oil&quot;, they weren't squeaky enough.</p>

CC BY-SA 4.0
2022-07-20T21:10:08.750Z
"but no-one mentioned global warming or the heat retaining potential of carbon dioxide or methane" - greenhouse gasses were part of my high school curriculum in the 70s - water vapor, then methane, then CO2.
Don Branson
CC BY-SA 4.0
2022-07-20T22:09:14.700Z
[*Planet Earth*](https://en.wikipedia.org/wiki/Planet_Earth_(1986_TV_series)), aired on PBS in 1984. I've watched it *at least* once a year for the last ~30y. It's so jammed packed with information I'm still learning things from it. Via that series, I *knew* all these things before HS, but it's still an ongoing process to understand all their affects on our world.
Mazura
CC BY-SA 4.0
2022-07-20T22:09:28.900Z
Titles of some of the episodes: "The Living Machine" (the Biosphere), "The Climate Puzzle" (the effect of on biosphere), "Gifts from the Earth" (our effects), "The Fate of the Earth" (and *the end*.) ... Then there's the original *Cosmos*, but that's hellbent on worrying about nuclear war.
Mazura
CC BY-SA 4.0
2022-07-21T17:30:49.983Z
@Mazura Oh yeah, Sagan was _very_ vocal about it, and there was his famous and memorable address to the US congress in 1985.
Luaan
CC BY-SA 4.0
2022-07-21T20:16:09.630Z
The "squeaky wheel" often gets mischaracterized or gets seriously derogatory stereotyped. "Hippies", "tree huggers", and other counter culture terms were often made synonymous with drug use, violent behavior, craziness, or other negative aspects of life. Women were a big part of this "squeaky wheel", and have been (and still are) ostracized and ignored simply because of their gender. "Those who knew better" simply couldn't be bothered with caring about the "distant future of 40+ years", since they spent all of their time "bringing home the bacon". There's still a lot of that happening, too.
computercarguy
CC BY-SA 4.0
2022-07-23T02:26:01.813Z
PBS doesn't captivate the attention of the masses, is the problem. If everyone had religiously watched [*The Mechanical Universe*](https://www.youtube.com/watch?v=XtMmeAjQTXc&list=PL8_xPU5epJddRABXqJ5h5G0dk-XGtA5cZ) we wouldn't have this flat Earth non-sense and there'd be a lot more engineers. - What I haven't seen in about 20y is anyone who works for an energy company being in a documentary.... Fastest way to get fired from Exxon? Do an interview about climate change.
Mazura
CC BY-SA 4.0
2022-07-20T13:15:06.617Z
2022-07-20T13:15:06.617Z
Fred
<p>Svante Arhennius' crude calculations published in 1896 of the likely global temperature changes from halving and doubling CO2 (based on prior work by Tyndall, Foote and Fourier) were considered speculative - amongst other speculations about climate - and were not taken seriously at the time or for a long time after. In part because the prevailing view was nothing humans could do could change the climate but also, in science terms, through incorrect understandings around &quot;saturation&quot; of Infrared absorption and ocean uptake (drawdown?) of CO2.</p>
<p>The re-emission of IR from greenhouse gas molecules within the atmosphere was not fully accounted for, leading to the incorrect conclusion that with enough CO2 to catch 100% of IR on the way to space adding more would make no difference.</p>
<p>With respect to ocean uptake of CO2, the <a href="https://en.wikipedia.org/wiki/Revelle_factor" rel="nofollow noreferrer">Revelle Factor</a> - resistance of the ocean surface layer to taking in CO2 - was not known until 1957; it was assumed rapid ocean uptake would prevent CO2 concentrations rising significantly in the atmosphere.</p>
<p>By the early 1970's most factors that are now deemed capable of causing &quot;inadvertent climate modification&quot; were known - including that aerosols from fossil fuel burning had a reflective effect that reduced solar intensity, ie a cooling influence - but not it's relative strength over time compared to enhanced greenhouse effect. The relative strengths of all the known factors and the impacts of interactions and feedbacks within the global climate system were not known with sufficient precision for it to be possible to be sure, even into the 1970's.</p>
<p>From &quot;Understanding Climatic Change: a Program for Action&quot; - US National Academy of Sciences, 1975 -</p>
<blockquote>
<p>&quot;Unfortunately, we do not have a good quantitative understanding of
our climate machine and what determines its course. Without this
fundamental understanding, it does not seem possible to predict
climate — neither in its short-term variations nor in its larger
long-term changes.&quot;</p>
</blockquote>
<p>The &quot;Program for Action&quot; was intended to achieve that better &quot;quantitative understanding&quot; and by the 1980's had done so well enough for then still current &quot;little ice age&quot; fears to be put to rest. Unfortunately the reason why - warming was expected to dominate - was not so reassuring as was hoped.</p>
<p>A lot of debate and dispute has followed but every high level science based report and study from the world's leading science and climate science institutions since then (about 4 decades so far) has consistently concluded that we have global warming and can expect more so long as we keep burning fossil fuels and adding CO2 (and methane) to the atmosphere.</p>

CC BY-SA 4.0
2022-08-09T00:33:21.953Z
2022-08-09T01:38:47.247Z
2022-08-09T01:38:47.247Z
Ken Fabian
<p><a href="https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-chapter9-1.pdf" rel="noreferrer">Chapter 9</a> of the Fourth Assessment Report gives a comprehensive overview of the difficulties involved in 'detection and attribution'. It is worth reading in detail - it gives a much better idea of the complexity and residual uncertainties of the conclusions than the newspaper headlines do.</p>
<p>There are two basic problems: first, the natural background level of variation of the climate on longer timescales (decades and centuries) is not precisely known, since we don't have accurate global measurements for very long, so it is very hard to tell whether any given observed change in the weather is natural or artificial. There is geological evidence of large and sudden changes of climate in the past, long before humans industrialised, and we don't know how they all work or how big they can get.</p>
<p>The second problem is that while the opacity of CO2 to infrared has been known about for a long time, this is only part of the story. There are a large number of <em>feedback mechanisms</em> that can magnify or reduce the effect of CO2, and these are often poorly understood. For example, warming due to CO2 is thought to cause more water vapour to evaporate, and water is also a powerful greenhouse gas - a positive feedback. But water vapour also reduces the lapse rate in the atmosphere (the rate at which temperature drops with height), which is a negative feedback. The biggest uncertainty is the effect on clouds. Current climate models have the effect of multiplying the effect of CO2 alone by about 3; around two thirds of the projected effect are thus due to other causes. But the error bars on that estimate are huge, and there is an ongoing scientific debate about whether the empirical measurements agree.</p>
<p>From p688 of the linked report:</p>
<blockquote>
<p><strong>Both detection and attribution require knowledge of the
internal climate variability on the time scales considered,
usually decades or longer</strong>. The residual variability that remains
in instrumental observations after the estimated effects of
external forcing have been removed is sometimes used to
estimate internal variability. However, <strong>these estimates are
uncertain</strong> because the instrumental record is too short to give
a well-constrained estimate of internal variability, and because
of uncertainties in the forcings and the estimated responses.</p>
</blockquote>
<p>From p669:</p>
<blockquote>
<p>The approaches used in detection and attribution research
described above <strong>cannot fully account for all uncertainties</strong>,
and thus ultimately <strong>expert judgement is required</strong> to give a
calibrated assessment of whether a specific cause is responsible
for a given climate change. The assessment approach used in
this chapter is to consider results from multiple studies using a
variety of observational data sets, models, forcings and analysis
techniques. The assessment based on these results typically
takes into account the <strong>number of studies, the extent to which
there is consensus among studies on the significance of detection
results, the extent to which there is consensus on the consistency
between the observed change and the change expected from
forcing, the degree of consistency with other types of evidence,
the extent to which known uncertainties are accounted for
in and between studies, and whether there might be other
physically plausible explanations for the given climate change</strong>.</p>
</blockquote>
<p>As an aside, while Fourier did publish some predictions on the effect of CO2 on temperature, the mechanism he described <em>does not apply in a convective atmosphere</em>. The correct mechanism was actually identified during the study of the atmosphere of stars in the 1940s, and was applied to planetary atmospheres by <a href="https://climate-dynamics.org/wp-content/uploads/2016/06/manabe64a.pdf" rel="noreferrer">Manabe and Strickler</a> in the early 1960s.</p>
<p>When gases are compressed, they warm up, and when gases are allowed to expand, they cool. So as the atmosphere circulates convectively, rising air cools and descending air warms. This sets a particular temperature gradient in the atmosphere, called the <em>adiabatic lapse rate</em>. Temperature gradients much larger than this cannot normally be maintained, as convection starts up and transports heat vertically to cancel out the excess. Moist air has a lower adiabatic lapse rate than dry air, about 6.5 C/km on average.</p>
<p>To a very close approximation, all the energy from the sun that arrives on Earth is subsequently radiated as infrared to outer space - the black body temperature needed to radiate this much energy is about -20 C. However, when the atmosphere is opaque to infrared, it radiates not from the ground, but from the first 10 km of the atmosphere. The average altitude of emission to space is about 5 km. So it is the air at this altitude settles at -20 C. And because of the adiabatic lapse rate, the surface is roughly 6.5*5 = 32.5 C warmer (i.e. about +13 C.) This is the greenhouse effect in a convective atmosphere. (In an atmosphere without convection, using Fourier's mechanism, the surface temperture would be about 60 C.) More CO2 and water vapour raises the average altitude of infrared emission to space, thus raising the surface temperature. But more water vapour reduces the vertical temperature gradient, <em>reducing</em> the surface temperature rise and at the same time <em>increasing</em> the temperature of the upper troposphere 10 km up. If you look at figure 9.1 panels (c) and (f) on p675 of the IPCC Report linked, which show where the models say the warming will be seen, you will see this as a big red blob in the middle of the picture. This is the 'fingerprint' of water vapour feedback.</p>
<p>Please note - everything I say here comes from the AR4 IPCC Report or the mainstream climate literature.</p>

CC BY-SA 4.0
2022-07-23T09:54:14.170Z
This answer should be the accepted answer
Peter A
CC BY-SA 4.0
2022-07-24T14:30:03.010Z
@PeterA I think this is a fantastic answer providing great insights and I upvoted myself. Although I think at a certain point it becomes more an explanation of the current state of climate science than directly answering the question. I think it more so says "yeah... they shouldn't be claiming anything with certainty because x,y,z" more than "Here's *why* this report makes a claim of certainty". Either way, has my +1 and I'm glad I got to read it in response to the question.
TCooper
CC BY-SA 4.0
2022-07-20T23:20:40.403Z
2022-07-20T23:27:56.520Z
2022-07-20T23:27:56.520Z
Nullius in Verba
<p>I just read the IPCC's Fourth Assessment Report and noticed that this is the first (or first very significant) report to state that climate change exists and can no longer be scientifically disproved. However, humankind has known since 1824, since the discovery of Jean-Baptiste Joseph Fourier, that greenhouse gases are changing the atmosphere. So I ask myself, why did it take so long to gain knowledge and what were the major theories that speak against human-made climate change?</p>

CC BY-SA 4.0
2022-07-20T09:04:04.323Z
I believe the difference is that since 1824 anthropogenic global warming had been _predicted_, but in IPCC AR4 it had for the first time been _measured_ beyond doubt.
gerrit
CC BY-SA 4.0
2022-07-20T21:50:11.437Z
'Why *has* climate change *still* not been proven beyond doubt?' - 'this is the first very significant report to state' ... that's kinda rude to everyone else's work for the last 200y. - "Why did it take so long to gain knowledge and what were the major theories that speak against man-made climate change?" [Money](https://politics.stackexchange.com/a/9550/8460), [Money](https://politics.stackexchange.com/a/1213/8460), and [Money](https://earthscience.stackexchange.com/a/24060/654)
Mazura
CC BY-SA 4.0
2022-07-21T01:43:39.380Z
The discovery of greenhouse effect as such has nothing to do with the theory of climate change. The latter concerns the _dynamics_ of it, due to the _change_ of the atmosphere composition. The effect itself is not dangerous per se, in fact, it provides hospitable conditions for us on Earth.
Zeus
CC BY-SA 4.0
2022-07-21T06:45:53.107Z
[This](https://en.wikipedia.org/wiki/Cry_Wolf): people just cried wolf without proving there is a wolf, for too long. So over time, they lost credit and other people stopped believing them. That's how I see it, at least.
Shadow Wizard
CC BY-SA 4.0
2022-07-21T12:05:30.167Z
If you boil a pot of water with ice cube in it, it takes quite a while before the water gets noticably warmer because the ice melts first.
Thorbjørn Ravn Andersen
CC BY-SA 4.0
2022-07-21T23:39:51.800Z
The AR Report is the first report to restate a convention agreed by politicians.
user2617804
CC BY-SA 4.0
2022-07-22T06:47:07.857Z
Because in the 1970s the same scientists were warning us about global cooling?
Valorum
CC BY-SA 4.0
2022-07-22T15:20:57.060Z
For many people the question is not whether the climate is changing, but whether this change is primarily caused by human activity (particularly the use of fossil fuels) and whether we should take action to mitigate it.
Barmar
CC BY-SA 4.0
2022-07-22T15:26:26.580Z
@Valorum That's a widespread myth based on media distortions that did not reflect the scientific consensus at the time. Climatologists in the 1970s were interested in the *long-term* potential for ice ages, but even then the imminent threat of anthropogenic global warming was considered much more important: https://journals.ametsoc.org/view/journals/bams/89/9/2008bams2370_1.xml
David
CC BY-SA 4.0
2022-07-23T05:42:28.753Z
Maybe because people go around saying things like "climate change exists and can reportedly no longer be scientifically disproved"? No one ever disagreed that climate change exists. Pretty much everyone other than YEC agreed that there used to be an ice age, and there isn't one now, which means that the climate has changed. Maybe you mean anthropogenic climate change, but then you'd need even more precision. Are you talking about historical climate change? Future predicted? Significant vs. any measurable change? Etc.
Acccumulation
CC BY-SA 4.0
2022-07-23T10:20:33.830Z
What is "beyond doubt"? Science never has "doubt" it just is always to be falsified and thus change the common understanding. But in the scientific community the common understanding has already since the 80s that climate change was happening like it is. That doesn't mean the scientific community will try to convince people to not falsify it, it *promotes* people trying to do that. That is not however "doubt", it just means you hear a lot about research.
paul23
CC BY-SA 4.0
2022-10-11T13:08:13.020Z
You should not edit a question just to make it go back to the front page, you should edit it only to make significant changes.
Jean-Marie Prival
CC BY-SA 4.0
2022-11-08T17:25:54.847Z
@Weiss, what changes do you keep making to the question?  I can't see any difference...
JeopardyTempest
<climate-change><earth-history>
Why had climate change not been proven beyond doubt for so long?
Weiss
# Why had climate change not been proven beyond doubt for so long?

(Asked by: username_0 on 2022-07-20)

I just read the IPCC's Fourth Assessment Report and noticed that this is the first (or first very significant) report to state that climate change exists and can no longer be scientifically disproved. However, humankind has known since 1824, since the discovery of Jean-Baptiste Joseph Fourier, that greenhouse gases are changing the atmosphere. So I ask myself, why did it take so long to gain knowledge and what were the major theories that speak against human-made climate change?

**Tags:** climate-change, earth-history

> **Comments:**
> **username_1**: I believe the difference is that since 1824 anthropogenic global warming had been _predicted_, but in IPCC AR4 it had for the first time been _measured_ beyond doubt.  
> **username_2**: 'Why *has* climate change *still* not been proven beyond doubt?' - 'this is the first very significant report to state' ... that's kinda rude to everyone else's work for the last 200y. - "Why did it take so long to gain knowledge and what were the major theories that speak against man-made climate change?" [Money](https://politics.stackexchange.com/a/9550/8460), [Money](https://politics.stackexchange.com/a/1213/8460), and [Money](https://earthscience.stackexchange.com/a/24060/654)  
> **username_3**: The discovery of greenhouse effect as such has nothing to do with the theory of climate change. The latter concerns the _dynamics_ of it, due to the _change_ of the atmosphere composition. The effect itself is not dangerous per se, in fact, it provides hospitable conditions for us on Earth.  
> **username_4**: [This](https://en.wikipedia.org/wiki/Cry_Wolf): people just cried wolf without proving there is a wolf, for too long. So over time, they lost credit and other people stopped believing them. That's how I see it, at least.  
> **username_5**: If you boil a pot of water with ice cube in it, it takes quite a while before the water gets noticably warmer because the ice melts first.  
> **username_6**: The AR Report is the first report to restate a convention agreed by politicians.  
> **username_7**: Because in the 1970s the same scientists were warning us about global cooling?  
> **username_8**: For many people the question is not whether the climate is changing, but whether this change is primarily caused by human activity (particularly the use of fossil fuels) and whether we should take action to mitigate it.  
> **username_9**: @username_7 That's a widespread myth based on media distortions that did not reflect the scientific consensus at the time. Climatologists in the 1970s were interested in the *long-term* potential for ice ages, but even then the imminent threat of anthropogenic global warming was considered much more important: https://journals.ametsoc.org/view/journals/bams/89/9/2008bams2370_1.xml  
> **username_10**: Maybe because people go around saying things like "climate change exists and can reportedly no longer be scientifically disproved"? No one ever disagreed that climate change exists. Pretty much everyone other than YEC agreed that there used to be an ice age, and there isn't one now, which means that the climate has changed. Maybe you mean anthropogenic climate change, but then you'd need even more precision. Are you talking about historical climate change? Future predicted? Significant vs. any measurable change? Etc.  
> **username_11**: What is "beyond doubt"? Science never has "doubt" it just is always to be falsified and thus change the common understanding. But in the scientific community the common understanding has already since the 80s that climate change was happening like it is. That doesn't mean the scientific community will try to convince people to not falsify it, it *promotes* people trying to do that. That is not however "doubt", it just means you hear a lot about research.  
> **username_12**: You should not edit a question just to make it go back to the front page, you should edit it only to make significant changes.  
> **username_13**: @username_0, what changes do you keep making to the question?  I can't see any difference...  

---

## 4 answers

### Answer by username_24 on 2022-07-20. Score: 17 | Accepted answer

[Chapter 9](https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-chapter9-1.pdf) of the Fourth Assessment Report gives a comprehensive overview of the difficulties involved in 'detection and attribution'. It is worth reading in detail - it gives a much better idea of the complexity and residual uncertainties of the conclusions than the newspaper headlines do.

There are two basic problems: first, the natural background level of variation of the climate on longer timescales (decades and centuries) is not precisely known, since we don't have accurate global measurements for very long, so it is very hard to tell whether any given observed change in the weather is natural or artificial. There is geological evidence of large and sudden changes of climate in the past, long before humans industrialised, and we don't know how they all work or how big they can get.

The second problem is that while the opacity of CO2 to infrared has been known about for a long time, this is only part of the story. There are a large number of *feedback mechanisms* that can magnify or reduce the effect of CO2, and these are often poorly understood. For example, warming due to CO2 is thought to cause more water vapour to evaporate, and water is also a powerful greenhouse gas - a positive feedback. But water vapour also reduces the lapse rate in the atmosphere (the rate at which temperature drops with height), which is a negative feedback. The biggest uncertainty is the effect on clouds. Current climate models have the effect of multiplying the effect of CO2 alone by about 3; around two thirds of the projected effect are thus due to other causes. But the error bars on that estimate are huge, and there is an ongoing scientific debate about whether the empirical measurements agree.

From p688 of the linked report:

> **Both detection and attribution require knowledge of the
> internal climate variability on the time scales considered,
> usually decades or longer**. The residual variability that remains
> in instrumental observations after the estimated effects of
> external forcing have been removed is sometimes used to
> estimate internal variability. However, **these estimates are
> uncertain** because the instrumental record is too short to give
> a well-constrained estimate of internal variability, and because
> of uncertainties in the forcings and the estimated responses.

From p669:

> The approaches used in detection and attribution research
> described above **cannot fully account for all uncertainties**,
> and thus ultimately **expert judgement is required** to give a
> calibrated assessment of whether a specific cause is responsible
> for a given climate change. The assessment approach used in
> this chapter is to consider results from multiple studies using a
> variety of observational data sets, models, forcings and analysis
> techniques. The assessment based on these results typically
> takes into account the **number of studies, the extent to which
> there is consensus among studies on the significance of detection
> results, the extent to which there is consensus on the consistency
> between the observed change and the change expected from
> forcing, the degree of consistency with other types of evidence,
> the extent to which known uncertainties are accounted for
> in and between studies, and whether there might be other
> physically plausible explanations for the given climate change**.

As an aside, while Fourier did publish some predictions on the effect of CO2 on temperature, the mechanism he described *does not apply in a convective atmosphere*. The correct mechanism was actually identified during the study of the atmosphere of stars in the 1940s, and was applied to planetary atmospheres by [Manabe and Strickler](https://climate-dynamics.org/wp-content/uploads/2016/06/manabe64a.pdf) in the early 1960s.

When gases are compressed, they warm up, and when gases are allowed to expand, they cool. So as the atmosphere circulates convectively, rising air cools and descending air warms. This sets a particular temperature gradient in the atmosphere, called the *adiabatic lapse rate*. Temperature gradients much larger than this cannot normally be maintained, as convection starts up and transports heat vertically to cancel out the excess. Moist air has a lower adiabatic lapse rate than dry air, about 6.5 C/km on average.

To a very close approximation, all the energy from the sun that arrives on Earth is subsequently radiated as infrared to outer space - the black body temperature needed to radiate this much energy is about -20 C. However, when the atmosphere is opaque to infrared, it radiates not from the ground, but from the first 10 km of the atmosphere. The average altitude of emission to space is about 5 km. So it is the air at this altitude settles at -20 C. And because of the adiabatic lapse rate, the surface is roughly 6.5\*5 = 32.5 C warmer (i.e. about +13 C.) This is the greenhouse effect in a convective atmosphere. (In an atmosphere without convection, using Fourier's mechanism, the surface temperture would be about 60 C.) More CO2 and water vapour raises the average altitude of infrared emission to space, thus raising the surface temperature. But more water vapour reduces the vertical temperature gradient, *reducing* the surface temperature rise and at the same time *increasing* the temperature of the upper troposphere 10 km up. If you look at figure 9.1 panels (c) and (f) on p675 of the IPCC Report linked, which show where the models say the warming will be seen, you will see this as a big red blob in the middle of the picture. This is the 'fingerprint' of water vapour feedback.

Please note - everything I say here comes from the AR4 IPCC Report or the mainstream climate literature.

> **Comments:**
> **username_25**: This answer should be the accepted answer  
> **username_14**: @username_25 I think this is a fantastic answer providing great insights and I upvoted myself. Although I think at a certain point it becomes more an explanation of the current state of climate science than directly answering the question. I think it more so says "yeah... they shouldn't be claiming anything with certainty because x,y,z" more than "Here's *why* this report makes a claim of certainty". Either way, has my +1 and I'm glad I got to read it in response to the question.  

---

### Answer by username_14 on 2022-07-20. Score: 23

It's the first very significant report to make that claim because the claim is unscientific in nature.

As [Albert Einstein once said](https://books.google.com/books?id=IOFmZoesMNoC&pg=PA1602&lpg=PA1602&dq=%22The%20scientific%20theorist%20is%20not%20to%20be%20envied.%20For%20Nature,%20or%20more%20precisely%20experiment,%20is%20an%20inexorable%20and%20not%20very%20friendly%20judge%20of%20his%20work.%20It%20never%20says%20%22Yes%22%20to%20a%20theory.%20In%20the%20most%20favorable%20cases%20it%20says%20%22Maybe,%22%20and%20in%20the%20great%20majority%20of%20cases%20simply%20%22No.%22%20If%20an%20experiment%20agrees%20with%20a%20theory%20it%20means%20for%20the%20latter%20%22Maybe,%22%20and%20if%20it%20does%20not%20agree%20it%20means%20%22No.%22%20Probably%20every%20theory%20will%20someday%20experience%20its%20%22No%22%E2%80%94most%20theories,%20soon%20after%20conception.%22&source=bl&ots=sVp_d0NO1L&sig=pIt5kjxteB_51khNld7sdaFqN-8&hl=en&sa=X&ved=0ahUKEwiN79KTg9HXAhUrjFQKHQG7CHcQ6AEIKDAA#v=onepage&q=%22The%20scientific%20theorist%20is%20not%20to%20be%20envied.%20For%20Nature%2C%20or%20more%20precisely%20experiment%2C%20is%20an%20inexorable%20and%20not%20very%20friendly%20judge%20of%20his%20work.%20It%20never%20says%20%22Yes%22%20to%20a%20theory.%20In%20the%20most%20favorable%20cases%20it%20says%20%22Maybe%2C%22%20and%20in%20the%20great%20majority%20of%20cases%20simply%20%22No.%22%20If%20an%20experiment%20agrees%20with%20a%20theory%20it%20means%20for%20the%20latter%20%22Maybe%2C%22%20and%20if%20it%20does%20not%20agree%20it%20means%20%22No.%22%20Probably%20every%20theory%20will%20someday%20experience%20its%20%22No%22%E2%80%94most%20theories%2C%20soon%20after%20conception.%22&f=false):

> The scientific theorist is not to be envied. For Nature, or more
> precisely experiment, is an inexorable and not very friendly judge of
> his work. It never says "Yes" to a theory. In the most favorable cases
> it says "Maybe," and in the great majority of cases simply "No." If an
> experiment agrees with a theory it means for the latter "Maybe," and
> if it does not agree it means "No." Probably every theory will someday
> experience its "No"—most theories, soon after conception.

Or, more recently, as [Liz Gerjbine](https://histsci.fas.harvard.edu/people/liv-grjebine) writes in [Scientific American](https://www.scientificamerican.com/article/why-doubt-is-essential-to-science/) "[S]cience cannot provide certainties."

This isn't an attempt to cast doubt on climate change, in fact I think **a better comparison would be saying we're about as certain as we are about gravity**.

So they're the first to publish that statement because a core tenet of science, if not *the* core tenet, is *doubt*.

I'm actually quite shocked any serious scientist or group would make the statement "can no longer be scientifically disproved" about anything. Seems more like political grandstanding than genuine science.

The other answers so far do a fine job explaining the slow dissemination and acceptance of scientific findings.

> **Comments:**
> **username_15**: While _theories_ will get a "no", _models_ can keep their "yes, and here are the error bars in this circumstance". Newtonian gravity is still useful for modelling the behaviour of aeroplanes, even if it isn't good enough for GPS satellites and – as a _theory_ – it's been thoroughly debunked for quite some time.  
> **username_16**: Gravity is a good comparison really. We know it exists but science still gets fuzzy on the precise details, and the modeling of it gets shaky fast (see: three body problem). Same with climate change. It's one thing to observe that it exists. The quibbling is mostly over the nature of it, the origin, the effects, the timetable, and the fact that the modeling is always inaccurate to a variety of degrees. (We have had global warming but nothing like the models from 20-30 years ago said we were going to have in 20-30 years.)  
> **username_14**: @username_16 I had a long parenthetical disclaimer after originally writing the theory of gravity, then decided on this word choice instead. Couldn't agree more with your analysis.  
> **username_17**: Scientists tend to be bad at public speaking. When asked something, they say "probably", meaning +90%, yet the "average Joe" will think that's more like 50-60%. "Statistically insignificant" goes from < 0.001% to < 20% in the public eye. "Almost certainly" becomes "this is a lie". Bill Nye, Neil deGrasse Tyson, and others have furthered scientific speaking enormously with their smooth and natural speaking styles, immense intelligences, specific use of terms, and defining the terms they use. They don't just assume "John Doe" understands the scientific terms the same way they do.  
> **username_18**: One of the things that bothered me for decades on this issue has been the failure to make testable predictions with a reasonable defined null hypothesis.  The climate modelers predicted that CO2 forcing would cause temperatures to keep rising, but then when temperatures fell (contrary to predictions) the climate modelers said that too was a result of CO2 forcing.  Given the their initial long run of inaccurate predictions, scientific rigor would suggest that climate modelers should need to produce a good run of accurate predictions before they should be taken seriously.  
> **username_19**: @username_18: "when temperatures fell". When was that? https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature  
> **username_19**: @username_16: "nothing like the models from 20-30 years ago". "Nothing" seems a bit harsh. https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming/ do you have other sources?  
> **username_19**: "Seems more like political grandstanding than genuine science." I cannot blame the IPCC. They wrote 5 reports over 30 years, explaining us very clearly "There's a large concrete wall just ahead of us. We might want to not crash into it". And all they got as an answer was "Braking is bad for the economy", "There's no wall", "The wall has always been here", "How do you know crashing into a wall is bad for us?", "Is the wall 2m or 3m thick?", "How will my car look like, exactly, after it hits the wall?". No wonder the IPCC now writes "CRASH IS IMMINENT. EMERGENCY BRAKE, NOW!!!!"  
> **username_7**: Trying to say that climate change science is as mature as gravity science is a nonsense. Gravity theory is testable to umpteen sigmas.  
> **username_11**: @supecat can you remove that line "when temperatures fell" - this is a statement that *is* not true and thus misinformation. You are incorrect and using that as argument breaks down any discussion one can have. -- Or you have to show the truth that temperatures fell.  
> **username_18**: @username_11: Some record low temperatures as well as record high temperatures have been set in many places in the last twenty years, and the response was often to say that the presence of high temperatures in some places would change wind patterns in ways that caused record low temperatures, a notion which while plausible *was not part of climate modelers' predictions*.  A fundamental requirement of a scientific theory is identifying what possible future observations would be consistent with it, and what *what possible future operations would be inconsistent with it*.  
> **username_18**: @username_11: While there may have been some climate modelers somewhere that were properly employing scientifiic principles, the scientific methodology of those covered by the press was severely lacking.  Further, those who complained about the sloppy "science" were branded as heretics without making any effort to address their legitimate concerns.  
> **username_19**: @username_18: "Some record low temperatures". You're talking about weather, we're talking about climate. Weather is a chaotic system : adding more energy to it will raise the average temperature, but will also lead to extreme events with more frequency and intensity than before. So record lows, record highs, record droughts, record hurricanes are expected, and have been predicted by climate models for a long time now. The opposite of global warming would be : lower average temperatures, fewer extreme events, "boring", stable winters and summers, with small temperature variations from day to day.  
> **username_18**: @username_19: Do you think the media's reporting has adequately described predicitons and associated null hypotheses in such a way that predictions would likely fail if observed warming had been purely coincidental?  Do you think that the models have been sufficiently rigorous in compensating for phenomena such as the heat island effect or changes to measurement methodology that any apparent temperature increase could only caused by CO2 and not by other real factors (like heat islands) or imaginary ones (changing methodologies)?  
> **username_19**: @username_18 what is your point, exactly? All the scientists who contributed to IPCC reports are stupid, corrupt, or both? That they only use weather stations if they are close to the exhaust of an air conditioner? How do you explain that large glaciers are disappearing? You don't need to trust anyone for this example, you simply need to watch them shrink from one year to another.  
> **username_18**: @username_19: The portion of the research covered by the media is scientifically unsound.  That is likely, at least in part, because the media are prone to view scientifcally-dubious studies that yield dramatic conclusions as more newsworthy than scientific studies which yield more timid conclusions.  I don't know whether the climate modelers did shody work, or wehther scientists did good work but the media only presented an unsound collection of snippets from it, but the overall reporting has been objectively terrible from the standpoint of scientific soundness.  
> **username_14**: @username_19 "I cannot blame the IPCC." Why not? The reason no one has taken their "wall" seriously so far is every time they claim its "right here", its been more like a gentle hill. I personally believe 100% we need to invest in green technologies and make an effort to reduce carbon footprints etc to build a sustainable future that is worth living in. If I consider time scales and the relatively limited amount of actual data collected on the topic, I would never make aggressive, seemingly fear-mongering statements that once again, seem more like political grandstanding than actual science.  
> **username_14**: @username_7 I've edited the answer slightly. I think gravity is a near perfect comparison as described prior in the comments. We have a ridiculous amount of evidence it exists but that's about all we have evidence and a *great* understanding of. The rest are theories that we shouldn't dismiss but rather research and test extensively rather than claim "we're going to make the earth void of human life in [always 10-30 years later] if we don't act RIGHT NOW". Hopefully that helps explain the comparison? Open to a better one if you have suggestions?  
> **username_19**: @username_14: I don't know where you live or how old you are. I'm 40, and live in western Europe. I remember seeing large glaciers and lakes as a kid which have now completely disappeared. The last few years have been so dry that the region I live in (in Germany) now looks like southern Spain. There were large wildfires in Brittany this year, in a region known for typically being very rainy. If that's a gentle hill to you, I do not want to know what a wall looks like. Atmosphere+oceans have such a large inertia, if we wait until we notice that we overshot, it will be *way* too late.  
> **username_19**: @username_14: https://xkcd.com/1379/ We're already at +1.2°C, and the effects are highly non linear.  
> **username_7**: @username_19 - If we go back 10,000 years, your house is a mile under ice.  
> **username_7**: https://mobile.twitter.com/JohnBri64148431/status/1551961365744607233/photo/1  

---

### Answer by username_20 on 2022-07-20. Score: 15

Just because a "small number" of scientists knew about something in the mid 1820s doesn't mean it was initially accepted by other scientists. You also have to consider the means of disseminating information and knowledge then and since. You also have to consider what other attitudes prevailed.

Charles Darwin's Theory of Evolution was vigorously opposed by many eminent people because of religious beliefs. In some places it still is.

Personally, I first became aware of global warming via the mass media many years *after* I completed my university studies. I was taught other scientific things - there's a lot to learn - and I still think I had a good education.

I became aware of Darwin's Theory of Evolution in high school, but no-one mentioned global warming or the heat retaining potential of carbon dioxide or methane, or whatever else. It wasn't part of the science curriculum, other things were.

People may have been warning about global warming before that, but from what I'm aware of they were few in number, they didn't captivate the attention of the mass media and they were essentially voices in the wilderness. There's a saying "the squeaky wheel gets the oil", they weren't squeaky enough.

> **Comments:**
> **username_21**: "but no-one mentioned global warming or the heat retaining potential of carbon dioxide or methane" - greenhouse gasses were part of my high school curriculum in the 70s - water vapor, then methane, then CO2.  
> **username_2**: [*Planet Earth*](https://en.wikipedia.org/wiki/Planet_Earth_(1986_TV_series)), aired on PBS in 1984. I've watched it *at least* once a year for the last ~30y. It's so jammed packed with information I'm still learning things from it. Via that series, I *knew* all these things before HS, but it's still an ongoing process to understand all their affects on our world.  
> **username_2**: Titles of some of the episodes: "The Living Machine" (the Biosphere), "The Climate Puzzle" (the effect of on biosphere), "Gifts from the Earth" (our effects), "The Fate of the Earth" (and *the end*.) ... Then there's the original *Cosmos*, but that's hellbent on worrying about nuclear war.  
> **username_22**: @username_2 Oh yeah, Sagan was _very_ vocal about it, and there was his famous and memorable address to the US congress in 1985.  
> **username_17**: The "squeaky wheel" often gets mischaracterized or gets seriously derogatory stereotyped. "Hippies", "tree huggers", and other counter culture terms were often made synonymous with drug use, violent behavior, craziness, or other negative aspects of life. Women were a big part of this "squeaky wheel", and have been (and still are) ostracized and ignored simply because of their gender. "Those who knew better" simply couldn't be bothered with caring about the "distant future of 40+ years", since they spent all of their time "bringing home the bacon". There's still a lot of that happening, too.  
> **username_2**: PBS doesn't captivate the attention of the masses, is the problem. If everyone had religiously watched [*The Mechanical Universe*](https://www.youtube.com/watch?v=XtMmeAjQTXc&list=PL8_xPU5epJddRABXqJ5h5G0dk-XGtA5cZ) we wouldn't have this flat Earth non-sense and there'd be a lot more engineers. - What I haven't seen in about 20y is anyone who works for an energy company being in a documentary.... Fastest way to get fired from Exxon? Do an interview about climate change.  

---

### Answer by username_23 on 2022-08-09. Score: 1

Svante Arhennius' crude calculations published in 1896 of the likely global temperature changes from halving and doubling CO2 (based on prior work by Tyndall, Foote and Fourier) were considered speculative - amongst other speculations about climate - and were not taken seriously at the time or for a long time after. In part because the prevailing view was nothing humans could do could change the climate but also, in science terms, through incorrect understandings around "saturation" of Infrared absorption and ocean uptake (drawdown?) of CO2.

The re-emission of IR from greenhouse gas molecules within the atmosphere was not fully accounted for, leading to the incorrect conclusion that with enough CO2 to catch 100% of IR on the way to space adding more would make no difference.

With respect to ocean uptake of CO2, the [Revelle Factor](https://en.wikipedia.org/wiki/Revelle_factor) - resistance of the ocean surface layer to taking in CO2 - was not known until 1957; it was assumed rapid ocean uptake would prevent CO2 concentrations rising significantly in the atmosphere.

By the early 1970's most factors that are now deemed capable of causing "inadvertent climate modification" were known - including that aerosols from fossil fuel burning had a reflective effect that reduced solar intensity, ie a cooling influence - but not it's relative strength over time compared to enhanced greenhouse effect. The relative strengths of all the known factors and the impacts of interactions and feedbacks within the global climate system were not known with sufficient precision for it to be possible to be sure, even into the 1970's.

From "Understanding Climatic Change: a Program for Action" - US National Academy of Sciences, 1975 -

> "Unfortunately, we do not have a good quantitative understanding of
> our climate machine and what determines its course. Without this
> fundamental understanding, it does not seem possible to predict
> climate — neither in its short-term variations nor in its larger
> long-term changes."

The "Program for Action" was intended to achieve that better "quantitative understanding" and by the 1980's had done so well enough for then still current "little ice age" fears to be put to rest. Unfortunately the reason why - warming was expected to dominate - was not so reassuring as was hoped.

A lot of debate and dispute has followed but every high level science based report and study from the world's leading science and climate science institutions since then (about 4 decades so far) has consistently concluded that we have global warming and can expect more so long as we keep burning fossil fuels and adding CO2 (and methane) to the atmosphere.


---

