More than 99.9% of studies agree: Humans caused climate change | Hacker News Reader

More than 99.9% of studies agree: Humans caused climate change

news.cornell.edu

33 pointsbjourne52 comments

That is a high level of consensus for a field where the predictive models (which have been getting published since the 1980s) are extremely bad at predicting the future.

Last time I looked into it was about 10 years ago, but at that time, the models were garbage at actually predicting anything.

The climate is a complex system that is hard to model and hard to predict. Scientists in the field should admit this rather than overstating their certainty about any particular conclusion.

And catch-all statements that "we all agree on X!" seem particularly suspect. The merit of a scientific assertion is established by the clear exposition of reproducible facts, not survey results.

[EDIT] To be clear, the predictive power of the models is relevant to the question of causality because absent a controlled experiment (obviously impossible) or an exhaustive list of relevant statistical controls (also obviously impossible), establishing causality can only be done by developing an accurate (and thus predictive) model and using that model to measure causality.

It's not a prediction about the future, it's based on measuring what has happened. "Humans caused climate change". This statement implies nothing about what will happen in the future

The same approaches and models that are used for predictions are used to establish the attribution of cause. But while the latter cannot be tested, the predictive power of the models can be tested and is thus a suitable proxy for the power of the models to attribute cause accurately.

There are other ways to find causes. For instance CO₂ from burning fossil fuels does not contain ¹⁴C. CO₂ from other sources other than volcanoes does contain ¹⁴C.

If you see the fraction of atmospheric CO₂ that has ¹⁴C going up more than can be accounted for from volcanoes you've got a smoking gun pointing to humans.

Respectfully, you are missing the point. The claim being tested is whether humans caused climate change, not if they increased the CO2 concentration in the atmosphere. Explaining the relationship between the two is point of the model and cannot be tested for accuracy as you suggest.

We know that increasing the CO₂ concentration in the atmosphere increases temperature not because models say it does. We know because we can observe it.

We can measure the intensity and wavelength distribution of incoming solar radiation. We can measure the effects various gases have on that radiation. We can measure what reaches the ground. We can measure the intensity and characterization of what is radiated back out from the ground. We can see that a significant fraction incoming radiation at wavelengths too short to be bothered by CO₂ gets radiated out from the surface at longer wavelengths that CO₂ absorbs, causing the CO₂ to act as an insulator slowing the transfer of radiated energy away from Earth which raises the equilibrium temperature on our side of it.

You present a plausible conceptual model of the core principle of a greenhouse gas. There are numerous questions between your conceptual model and explaining what fraction of the observed warming can be attributed to that effect.

What other side effects do the elevated levels of CO2 have on the climate that might also affect the temperature?

What are the second-order effects from the additional heat introduced to the climate by the greenhouse effect? Does it cause more clouds, and if so, what is the effect of those increased clouds on the radiation balance? Changes in precipitation? Vegetation growth?

What other atmospheric constituents have had changes to their levels that might have also changed the climate?

What other non-greenhouse-gas-related inputs effect the global mean temperature? Solar output? Deforestation? Can we accurately model those inputs so that we can sum up all contributing factors and see that it agrees with the observed record?

What other natural sources of CO2 exist and how much is produced by those now and in the past?

And then there are measurement accuracy questions:

Do we have an accurate measurement of the global mean temperature? How far back is that measurement reasonably accurate? What sampling biases exist due to the siting of airports near large urban areas? Of the 5000 odd airport weather stations for which we have reasonably long historical records, more than 2000 are in the United States and large swaths of Africa and Asia have few to none. How does this affect our ability to reliably measure the global mean temperature? We have very limited measurements of the air temperature over the vast area of the world' oceans. How do we deal with the obvious uncertainties that exist due to this?

Speaking of the global mean temperature, what exactly is the definition? You can't actual measure that directly, so you need to carefully define what it is, create a model to allow its computation, and then apply that model to the raw data. Here's an example: Global mean temperature at a given time is the instantaneous integral of the air temperature at 2 meters above the surface of the Earth. But we just have hourly sampled temperatures (that are not even at a consistent time within each hour) at a few thousand locations worldwide, so our model will be to correct the time offsets by linear interpolation with the temporally adjacent samples. To be able to sample the Earth uniformly for the numerical integral, we'll need to interpolate between triangulated stations and correct for elevation changes and proximity to large bodies of water (both of which are extremely complex models themselves). All this doesn't even deal with missing data (extremely common) from the station network. And what do we do over the ocean?

How far back do we have accurate measurements of CO2 concentration in the atmosphere?

Do we have a good measurement of the integrated reflective spectrum across the Earth's surface?

All of the above combined requires a complex physical and numerical model that is very far from your toy example of pure measurement. Such a model is necessarily an approximation with unknown inaccuracies, and the only way I can think to test any proposed model is to wait and see how well it predicts the future.

I'm not asserting that global warming is not happening or that it is not caused by humans. I've just not read or heard anything that answers that question in a convincing manner and I can think of no way to get to a firm answer than producing a model of the global climate that can accurately predict the future and to use that model to measure the fraction of observed warming that has been caused by human-produced greenhouse gasses (and other human-caused climate inputs). And some statistics on a keyword search of climate science papers by social science researchers is not going to convince me or anyone else capable of critical thinking.

How do you get any scientific field to agree 99.9%? I don't think you could even get these numbers for particle physics. Is science no longer about attempts at falsification? Or is the game derision of those with non-apocalyptic perspectives?

The article explains that they searched 88k peer-reviewed studies.

You think more than one in a thousand studies particle-physics studies deny the existence of the electron? The studies might disagree around the edges, but I think there's overwhelming consensus on theories for which there's overwhelming evidence.

The words "deny" and "evidence" cannot be used with scientific models. "deny" presupposes truthfulness of a proposition (a big no-no), and "evidence" is not the same as "absence of falsifying observations".

To be honest peer consensus means nothing unfortunately. For example scientific consensus in Medieval Europe was that the Earth is flat. Dogmas are dangerous and I'm afraid this one is very dangerous too.

Even if what is being pushed turns out to be true, this method sets a very dangerous precedent and the "believe in science" is creating a new religion.

Wikipedia [1] has that covered.

[1] - https://en.wikipedia.org/wiki/Scientism

This is incorrect. From https://en.wikipedia.org/w/index.php?title=List_of_common_mi...:

> Medieval Europeans did not believe Earth was flat. Scholars have known the Earth is spherical since at least 500 BC.[179] This myth was created in the 17th century by Protestants to argue against Catholic teachings.[180]

But the Church was pushing its Dogma and pressuring scientists to support it. Ofc some scholars knew it.

Can you give a source for your claim?

Further from another Wikipedia article (https://en.wikipedia.org/w/index.php?title=Myth_of_the_flat_...):

According to Stephen Jay Gould, "there never was a period of 'flat Earth darkness' among scholars, regardless of how the public at large may have conceptualized our planet both then and now. Greek knowledge of sphericity never faded, and all major medieval scholars accepted the Earth's roundness as an established fact of cosmology."[5] Historians of science David Lindberg and Ronald Numbers point out that "there was scarcely a Christian scholar of the Middle Ages who did not acknowledge [Earth's] sphericity and even know its approximate circumference".[6]

>Can you give a source for your claim?

That's what we were taught in school in Europe.

I don't know source/s for Church supporting Flat Earth but I know that Medieval Church was supporting Geocentric model and opposing Heliocentric astronomical model.

Galileo Galilei was victim of this dogma:

"Galileo's championing of Copernican heliocentrism (Earth rotating daily and revolving around the sun) was met with opposition from within the Catholic Church and from some astronomers. The matter was investigated by the Roman Inquisition in 1615, which concluded that heliocentrism was foolish, absurd, and heretical since it contradicted Holy Scripture."

"Galileo later defended his views in Dialogue Concerning the Two Chief World Systems (1632), which appeared to attack Pope Urban VIII and thus alienated both the Pope and the Jesuits, who had both supported Galileo up until this point. He was tried by the Inquisition, found "vehemently suspect of heresy", and forced to recant. He spent the rest of his life under house arrest."[0]

I would need to further research or ask some historians what was Medieval's Church formal(official) and informal(unofficial) opinion on Flat Earth vs Spherical Earth.

[0] https://en.wikipedia.org/wiki/Galileo_Galilei

I was also taught this thing (flat earth in the medieval ages) in school (in Germany). I was also taught that Christopher Columbus believed the Earth was flat and we even played Christopher Columbus's trying to convince others of a spherical earth.

But it just seems that it is wrong. That apparently happens in school.

Yes, in the medieval ages, heliocentrism was questioned.

And instead of dealing with climate change (with EASY and ROI-positive approaches like incentivizing wind/solar adoption, pushing electric cars along, etc.) we focus our energy on getting rid of straws.

Or...instead of working across the aisle to peel off a moderate Republican (tell me there isn't one Republican that won't go for a bill that gives their district a new military base or national lab?), we bend over backwards to coal interests (Manchin) instead of passing a climate-oriented bill!

It's like our politicians just want to bluster and point fingers instead of actually working to pass sensible legislation...

You need one Republican Senator who doesn't have a district to bribe - he/she represents an entire state. I'm sure if the Democrats could find one and not deal with Manchin, they absolutely would -- but the nature of a 50:50 Senate for reconciliation and the filibuster threat on stand-alone bills for a highly ideological issue means there are zero Republicans who will join them.

This demonstrates the issues with American politics very pointedly though. Even though 49/50 Democrats in the Senate want to pass the bill you describe, since 1/50 opposes it (along with 50/50 Republicans) - you blame "our politicians". The blame for inaction lies entirely on one political party but we have to pretend like it's some sort of failure by both sides to negotiate.

> Even though 49/50 Democrats in the Senate want to pass the bill you describe, since 1/50 opposes it (along with 50/50 Republicans)

Yes, when 51% of the votes are opposed to a course of action it is not followed. Are you advocating that for a submajority vote to suffice? That seems like it would have interesting consequences.

Nah, just saying that when 98% of one party's higher chamber wants to make minimal progress toward doing the right thing, and 0% of the other one does -- it's pretty dumb in an /r/enlightenedcentrism kind of way to blame "our politicians" for failing to take action.

Given the responses in this thread - it makes sense why hapless "both sides" politicians like Andrew Yang were so popular on HN.

> 98% of one party's higher chamber

The parties don't have chambers; the legislative branch does (and as noted, it is not 98% of the higher chamber which is stymied but rather 49%). Moreover, the U.S. is not a parliamentary democracy, but rather a representative democracy: the politicians represent not parties but districts and states. Whereas in parliamentary systems party discipline is the norm and free voting is the exception, in the U.S. system free voting is far more common, although of course there are still party whips. While in a parliamentary system a majority of the majority party may still control the country, in the U.S. system a shorter way of saying 'a majority of the majority' may often be 'a minority.'

> progress toward doing the right thing

That's begging the question, isn't it? In this case 51% of the chamber think a proposed course of action isn't the right thing, while 49% do. N.b.: I am not taking any position on the rectitude or not of the proposed course of action, just noting that it has not gained support of a simple majority of the chamber.

The bill in congress is a nightmare. It is not simply an environmental bill, it is a hodge podge of grift and special interests.

The climate portion includes renewable energy, nothing about base load resolutions. If we are going to electrify the nations transportation, we need dedicated base loads. Nuclear is the way. Initial talks were not including nuclear. Without this, the bill will be Solyndra’s and New York Tesla Solar all the way down.

I am really suspicious of this 99.9% number. Most journals allow a ~5% margin of error so even if humans caused climate change (which they most likely did) we should only see 95% of these studies finding this result. Also this doesn't account for the fact that people and organizations have their own biases and that it's possible to construct "experiments" to give you whatever result you want, so we should be seeing some experiments showing that climate change isn't real or whatever, bringing that 95% number down even further.

If this number is accurate and not just chosen for PR reasons, it would lend credence to the idea that anti-human-climate-change research is being suppressed. Is this bad? Probably not, but it's probably a more accurate conclusion than declaring climate change the correct conclusion.

Did you even read the article? It gives a brief explanation of the methodology. The full paper is found here: https://iopscience.iop.org/article/10.1088/1748-9326/ac2966

I'm not saying that the authors were dishonest I'm saying that if this is an honest outcome from the paper's authors (which it probably is) then the result we should expect should be closer to 95% than 99.9%. That it's this off from the expected value indicates that something external to this paper is inaccurate, even if these authors measured the inaccuracies correctly.

> Most journals allow a ~5% margin of error so even if humans caused climate change (which they most likely did) we should only see 95% of these studies finding this result.

Well, for a phenomenon strong enough, any measurement you make will find it. It's like taking a 1m long board and trying to assert the hypothesis that it's 20cm long. It doesn't matter that you accept a 0.05 p-value, you don't have an instrument noisy enough to reach it.

That's not how statistical significance works. :) By the same logic, 5% of all historical studies on the Holocaust should state that it is a hoax or else Holocaust denial is being suppressed. Furthermore 5% is a very low significance level, way below what is used by most reputable journals.

So if a study were done on whether humans could fly (without planes/gliders), there'd be 5% of studies finding that people can indeed fly, and publish that as real science?

While I agree with the thesis, that humans are more likely than not to have caused climate change, I’m also forced to note that consensus is not a scientific approach for establishing matters of fact.

It does discredit to scientific research to publish papers like this and claim that “the science is settled.”

It's a funny feeling to try to live life as if nothing is happening while knowing that I'll see a blue ocean event in somewhere between 5 and 20 years, causing runaway warming and all the incredible impacts it will have on human civilization. I feel completely powerless to do anything about it.

The climate scientists I talked to are off the impression that a blue ocean event is not a thing they are concerned about. There are certainly experts who think it is a problem but I am not sure how fringe those are compared to the ones not worried about a blue ocean event.

> The research updates a similar 2013 paper revealing that 97% of studies published between 1991 and 2012 supported the idea that human activities are altering Earth’s climate.

That was a fraudulent or at least dishonest claim already (everyone knows right?!), so I doubt this new one does any better. Just the line "caused climate change" is dishonest: It implies every person which worked on a study and who falls into the 99,9%, believes that the rising temperatures are 100% caused by humans, while the other faction apparently denies any influence or denies climate change as a whole. That's just BS.

Devils advocate:

The eocene period https://en.wikipedia.org/wiki/Eocene was roughly 50 million years ago and the Earth was 15 celcius warmer than it was today. We are worried about 1.5celcius, not 15 celcius.

From that time, the Earth became ~20 celcius colder about 20,000 years ago. https://en.wikipedia.org/wiki/Last_Glacial_Maximum

Which was 6 celcius colder than today. Did humans cause the 6 celcius in warming between 20 and 10 thousand years ago?

For the last 10,000 years the Earth has bounced around +- 1 celcius and current day climate change in the last couple hundred years ago is less than that bouncing back and forth.

What exactly have humans caused? The standard deviation of temp in the last 10,000 years has not changed. We can't be blamed for any of the other actual climate change.

The climate changes and so far humans havent changed anything.

The more interesting debate is whether the purported solutions to climate change are worthwhile, worse, or better than the status quo. There is a lot of money to be made in this space, and so I am skeptical of anyone who presents their magic device or process, as a tangible solution.

Based on the pie chart on this page, it seems like a greedy approach and tackling energy (via something like nuclear power) is going to be a large part of the solution, yet I almost never hear climate activists prioritize it, which leads me to agree that the problem is very real, but the purported solutions appear to be hoaxes either intentional or misguided/unintentional.

https://ourworldindata.org/ghg-emissions-by-sector

I'm not sure what the point of this study is. Despite serious efforts at obfuscation by the fossil fuel sector over the past 40 years, it's now widely know that the basic science of climate was solved by the late 1970s (1). Everything since then has been a refinement of the fundamental concept, i.e. that infrared-absorbing atmospheric gas concentraion is a primary control on a planet's surface temperature (along with other factors like albedo, soot and dust levels, etc.).

Humans have, primarily by the combustion of fossil fuels, steadily pushed towards a doubling of the levels of the long-lived IR-absorbing gases CO2 and CH4 in the atmosphere. This should take place (we hit 560 ppm) around 2050 at the earliest. Perhaps a betting pool would be the thing?

Fossil fuel combustion is the main driver of global warming, as we can see by noting the reduction in 14C in the atmosphere due to dilution with 14C-lacking fossil-sourced CO2 emissions. That also was known by 1980 (2).

1. https://www.princeton.edu/news/2021/10/05/princetons-syukuro...

2. https://www.cambridge.org/core/journals/radiocarbon/article/...

Isn't Climate Change a pleonasm ? It's a bit obvious a temporary thing changes.

Also there is very little doubt that humanity as a whole is a major force accelerating it. Yet, I don't think that CO2 models proven to be accurate. It's way more likely that the Ultra Urban Cities are a big factor. Displacing all fauna and flora, creating a micro climate surrounding it and tons of garbage daily.

Without stirring up any controversy I think we can confirm the giant island of plastic in the Pacific ocean is caused by humans.

Not trying to be the devils advocate, but at one point almost everybody agreed that the sun revolved around the Earth.

To be fair, most physicists today will agree that the geocentric and heliocentric world views are equivalent, they are just different frames of reference, both non-inertial.

The amount of immediate unsupported skepticism showing up in these comments is incredibly disheartening.

I feel rather certain at this point humanity as a whole is unable/unwilling stop this impending disaster due to the perverse insentives that existm that allow people to continue to bury their heads in the sand, and pretend everything is fine.

Skepticism doesn't require being supported. It is the default perspective when facing a scientific assertion.

Conversely, affirmative scientific assertions require the support of relevant reproducible facts. Appeals to authority or consensus are not a source of such support, and should not form part of our scientific discourse.

The disaster you imagine is not materializing.

The CO2 is having a greening effect on planet earth: https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fer...

Deaths from natural disasters are still near historic all time lows (despite population being at all-time highs): https://ourworldindata.org/grapher/number-of-deaths-from-nat...

Sea level rise trend is consistent (and not accelerating) at 2.24mm / year for the last 120 years. That's equivalent to a change of 0.73 feet in 100 years (not an emergency by any stretch): https://tidesandcurrents.noaa.gov/est/est_station.shtml?stni...

Crop yield and productivity is up 50% or more since 1991:

Corn - https://www.nass.usda.gov/Charts_and_Maps/Field_Crops/cornyl... Rice - https://www.nass.usda.gov/Charts_and_Maps/Field_Crops/riceyl... Soybeans - https://www.nass.usda.gov/Charts_and_Maps/Field_Crops/soyyld... Wheat - https://www.nass.usda.gov/Charts_and_Maps/Field_Crops/wwyld....

Of course, that's to be expected, because CO2 (essential ingredient of photosynthesis) and warmth are generally good for plants, so long as there's sufficient sunlight and precipitation, which there has been.

So tell me, how is your life worse off than your ancestors from the pre-industrial era?

Of course they agree, otherwise they would be cancelled.

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