Science desk
< September 13	<< Aug \| September \| Oct >>	September 15 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

September 14

'97% Of Climate Scientists Agree' Is 100% Wrong

According to this article, '97% Of Climate Scientists Agree' Is 100% Wrong, the 97% figure commonly cited in favor of scientific consensus on AGW comes from a paper (Cook) which misrepresented several scientist's work. Is there any truth to these papers being mischaracterized? In particular, I'm referring to page 2 of the article. If it is true, how much would it change the 97% figure? A Quest For Knowledge (talk) 13:57, 14 September 2017 (UTC)[reply]

The issue isn't that 97% of climate scientists agree. The issue is what they agree on. What they agree on is that there is a warming trend of up to 0.8 degrees in the last 150 years and they agree that there has been an increase in fossil fuels during the last 150 years. They do not all agree that the warming is completely caused by use of fossil fuels. They do not all agree that the trend will continue. They do not all agree that the trend will accelerate. They do not all agree that ending all use of fossil fuels will reverse the trend. However, this does not mean that less than 97% of climate scientists do believe that global warming is going to be an ongoing trend and that it is caused by man. This is the best analysis that I've seen on the topic of consensus. It makes it clear that while the consensus for any specific subject may be lower (or higher) than 97%, it is still well over 90% in general. 209.149.113.5 (talk) 15:09, 14 September 2017 (UTC)[reply]

An opinion piece is not a reliable source. --Stephan Schulz (talk) 15:39, 14 September 2017 (UTC)[reply]

Also keep in mind what a moving target this is. New scientists are minted every year, scientists die every year, etc. There's really no use in nitpicking exact percentages on something like this. Science isn't a popularity contest. SemanticMantis (talk) 15:52, 14 September 2017 (UTC)[reply]

Also also important: Science is not built on single "gotcha" moments, nor is it built on certitude. It is built on consensus, and it is built on the preponderance of evidence. "I did the calculations, and it's only 96%! HA! It must all be a hoax!" is the sort of bullshit that the creationists and the ID crowd and the climate change deniers engage in. The fact that consensus is clear, evidence is overwhelming, and we're damned sure that climate change is happening and is caused by pollution are not in serious dispute. The disputes are over things like mechanism, degree, small differences in specific theory, and the like. The broad picture is well agreed upon. --Jayron 32 15:59, 14 September 2017 (UTC)[reply]

Basically, if 97% of scientists can be wrong about something, the remaining 3% are probably even more wrong or Not even wrong (if they're even doing science at all). Ian.thomson (talk) 17:06, 14 September 2017 (UTC)[reply]

Rubbish blog talking about no change in the last 15 years. Even Roy Spencer's graphs show the trend even though he believes that God would not allow such a thing and he refuses to put in anything except horizontal average lines on his graphs. Dmcq (talk) 16:32, 14 September 2017 (UTC)[reply]

I am reminded of a discussion on Wikipedia's science reference desk in January 2017 in which we teased apart the actual, factual statistically-meaningful bit about a 95% confidence interval; and deconstructed a sound bite by citing the reliable source of information from which it originated.

The trouble is, certain journalists thrive on the use of imprecise language, weak attribution of claims, and unscrupulous use of statistical fact. These behaviors would be called "weasel words" if an author posted them to Wikipedia. In high-visibility newspapers, authors get paid for using these tactics!

Well-written scientific news carries at least the following characteristics:

clearly-specified factual claims
clear attribution of factual claims to a person or authority of merit
reference to further information, data, and analysis for interested readers to explore the topic in further depth

If you're reading a science-news website that does not do all of those three things, you're not reading a good science news website.

In this case, the author of this Forbes opinion piece constructs a straw man argument. He poses questions that he does not expect us to answer, probably for the sake of promoting doubt. I would call that disinformation - or at the very least, pretty disingenuous, and poor-quality journalism, even for an op-ed piece. He writes: "What exactly do the climate scientists agree on?" Well, if he read the paper he pretends to be criticizing - Quantifying the consensus on anthropogenic global warming in the scientific literature (2013), the paper is pretty specific. "Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming."

Now, if the critics want to attack the methodology, that's fine - they can bring their legitimate criticisms. But if they simply ask obtuse questions - "What exactly do the climate scientists agree on?" ... then there are very easy answers to their ill-informed questions. The climate scientists agree that "humans are causing global warming." This is the statement that Cook et al. found agreement upon. "How do we know the 97% agree?" "We analyze the evolution of the scientific consensus on anthropogenic global warming (AGW) in the peer-reviewed scientific literature, examining 11 944 climate abstracts from 1991–2011... "[Cook et al] classified each abstract according to the type of research (category) and degree of endorsement."

See? Easy answers exist to refute an ill-conceived critique.

Perhaps instead of reading opinion-pieces on Forbes.com, our readers would consider reading a better science news website, where interesting and difficult questions about climate and policy are brought forward? Here's a front-page story from the website of the U.S. Energy Information Administration - EIA projects 28% increase in world energy use by 2040. What are we going to do about that? Why doesn't our esteemed op-ed writer tackle that question in his next piece?

Nimur (talk) 18:59, 14 September 2017 (UTC)[reply]

Well, the first page of the article is fairly easy to debunk. It was the second page I was more interested in. I was curious if these quotes were taken out of context or the article was omitting anything. So far, I've researched the first quote and it appears to be accurate. In fact the guy quoted, Richard Tol, did write an interesting article critiquing Cook's methodology: The claim of a 97% consensus on global warming does not stand up. What the Forbes opinion piece neglects to explain is that Tol was only criticizing Cook's methodology, not the scientific consensus on AGW. A Quest For Knowledge (talk) 19:26, 14 September 2017 (UTC)[reply]

The theory that the world is heating up is probably a result of statistical mis-analysis. The temperature records that have survived from 150 years ago are sparse and are heavily weighted in favour of capital cities, which are usually harbour cities and therefore cool. Since the 1960s a boom in technology has allowed the placing of temperature sensors in remote places where readings were never historically taken. A boom in computer technology since 1990 has allowed the storage of all this recent data. What we are seeing is not a rise in temperature but a more accurate figure for the world's temperature. I have never seen any analysis by scientists of the implications of this statistical bias. Akld guy (talk) 19:44, 14 September 2017 (UTC)[reply]

Akld guy, before you self-congratulate as the sole genius who has figured out the grand conspiracy, you should know the following.

You are making certain specific claims that are:

commonplace claims often repeated by ill-informed people
claims that are easily, and commonly, refuted by actual scientific study

Your claims are:

The claim that urban heat islands are responsible for invalid data
The claim that recent data or methodology is inconsistent with older data and methodology

Both claims are wrong.

Urban heat island effect is very well known, very well characterized, and responsible climate-scientists account for this effect. Here is EPA.gov's website on the heat island effect; and here is the National Climatic Data Center's FAQ on temperature data. Refer to "Q5: Are there still biases in the data we use to calculate global and U.S. temperatures?"

Once again, we can easily refute your criticism. Your criticism is neither valid nor correct; and it's not even original. It's the same tired line that has been repeated by many poorly-educated people for, well, a really long time. Before you were even born, uneducated people were saying that urban heat islands perturbed climate science; they were wrong then, and they are wrong now.

Absent any reliable reference for your claim, you should not repeat your claim on this encyclopedia's science reference desk. You say you "have never seen any analysis by scientists of the implications of this statistical bias." Here are six analyses:

Do you really want more, or would you like to rescind your ill-informed commentary?

For your own sake, spend an hour studying climate science before making strong statements about it. Even better - spend a few thousand hours studying it - because that magnitude of formal study is exactly what climate science professionals get.

Nimur (talk) 20:03, 14 September 2017 (UTC)[reply]

Yeah, whatever. Scientists are not statisticians. You do realise don't you that adjusting for bias because of incomplete statistics from long ago is error prone? Extrapolating new figures based on a limited subset is prone to error. In short the comparison is being made on a limited set of figures, expanded out to give a multitude of new figures, versus the latest figures from sensors where readings were never taken. It's just nonsense. Akld guy (talk) 21:42, 14 September 2017 (UTC)[reply]

Scientists can be statisticians, or mathematicians, or whatever.

The author of the first study I linked, Tom Smith, has "degrees in mathematics, meteorology, and oceanography." I'd be willing to bet money that he's got three more degrees than you've got in the geosciences. Multiple universities, organizations, and agencies have validated his credentials; his papers passed peer-review, meaning that panels of experts in climate and statistics checked his work. I also cited many many more authors and publications, so if you don't like the first one, and you don't like the next paper, and you don't like the next author's credentials, and you disagree with the next paper's methodology.... well, the statistics just aren't in your favor, are they? How about 11,000 more research publications, do you still want to nitpick each of the authors' credentials on that stack of research as well?

If you disagree with the majority of experts, you are the ~~fringe scientist~~ crackpot.

This data is vetted by scientists and statisticians. The methodology is correct and sound. You are mistaken, and instead of being argumentative about it, you should take some time to inform yourself.

Nimur (talk) 21:53, 14 September 2017 (UTC)[reply]

Just to add a little bit here: the blogger Anthony Watts believed this exact thing - that urban heat island was affecting temperature records. To his credit, he investigated this scientifically, sending people to photograph weather stations and see how the environment around them had changed. In the end, the weather stations in urban areas didn't give a significantly different reading to those in rural areas (they gave slightly warmer night time temperatures and cooler day time temperatures, but these effects cancelled out), and even the best-sited weather stations showed a warming effect - see Anthony Watts (blogger)#Surface Stations project. Despite this, Watts continues to believe that global warming isn't happening, which pushes him "sceptic" to "denier" in my books. Smurrayinchester 09:24, 15 September 2017 (UTC)[reply]

The 97% figure does not just come from one paper. Four separate papers have estimated consensus at 97%, and three other papers came up 91%, 93% and 100%. Adrian J. Hunter^{(talk•contribs)} 10:08, 15 September 2017 (UTC)[reply]

So, the counter-argument I'm facing is that these studies misrepresent the papers. If you look at page 2 of the article, there are a series of quotes from scientists who say that Cook miscategorized their papers. I've been able to validate the first quote from Tol as accurate, albeit misleading. Tol does dispute Cook's methodology but not the scientific consensus on AGW. A Quest For Knowledge (talk) 10:29, 15 September 2017 (UTC)[reply]

Lighting a match in a hydrogen filled room

Imagine a room completely filled with hydrogen and no oxygen. A match is somehow struck in this room. Does it light? Does the room explode with flame? Or is oxygen needed for the reaction? Basically, does hydrogen require oxygen to burn? †dismas†|^(talk) 19:15, 14 September 2017 (UTC)[reply]

Hydrogen requires oxygen to burn. Flame, in the conventional sense, requires the three parts of the fire triangle: fuel (hydrogen); oxidizer (from the oxygen in the air); and a spark (the heat from friction during the strike of the match).

Interestingly, though, a match probably does not require oxygen from the air - depending on the type of match, it may contain (or may be struck against) an oxidizing chemical, allowing the flame reaction to occur (for a brief time) independent of any oxygen in the air. If the room is totally oxygen-free, that flame will rapidly extinguish.

Nimur (talk) 19:23, 14 September 2017 (UTC)[reply]

According to Flammability limit, the upper flammability limit of hydrogen in 75% in air, so no, the room does not explode. Yes, hydrogen requires oxygen to burn. shoy (reactions) 19:27, 14 September 2017 (UTC)[reply]

For the record, we're restricting to discussion of conventional chemical combustion. You need an oxidizer; in a normal room on Earth, that oxidizer is usually oxygen.

Chemical combustion ("flame") can also exist in an atmosphere of chlorine or fluorine; or in appropriate mixtures of perchlorate, and so on. In yet another case of chemistry that is more difficult than the version we learned in high school, sulfur can burn hydrogen under certain conditions; sulfur acts as a weird simultaneous "fuel-and-oxidizer" in that reaction. If you mix hydrogen and sulfur dioxide, sulfur will even un-oxidize from the oxygen and re-oxidize with the hydrogen; under other conditions, the reaction goes the other direction [7]. All of those chemicals will "burn" hydrogen in a chemical reaction. A 100.0% hydrogen atmosphere, however, can not sustain a flame.

If you want to start mincing words, we can also redefine the plain english word, "burn", to encompass the totally-different physics and nuclear chemistry called hydrogen fusion. This is actually a commonplace abuse of language among people who study stars, for example: if you read our article on Stellar nucleosynthesis, you see the word "burn" used throughout the article.

Nimur (talk) 19:43, 14 September 2017 (UTC)[reply]

Well they were both faster than me, so I'll just say Nimur and Shoy are right (well, Nimur might be right or wrong about specialty matches, I don't know). But while we're all here, anyone know why the the table at Flammability limit#Examples has different values for UFL and UEL for hydrogen? I noticed it while preparing my now-superfluous reply. UEL=58%, UFL=75%. The source has the same thing: [8]. None of the other materials have different values (some have ranges). And the way I use UFL and UEL in real life (admittedly not pure chemistry, and not with hydrogen) they're defined identically. --Floquenbeam (talk) 19:48, 14 September 2017 (UTC)[reply]

My understanding is that flammable limit is "sustain combustion" where as explosive limit is "deflagrate/detonate". The distinction is probably not that important if your only goal is keeping things safe. shoy (reactions) 15:04, 15 September 2017 (UTC)[reply]

At the risk of sounding like a commercial endorsement, these matches burn underwater (and in sand). To scale back my earlier claim, these matches are specialty-items and are not commonplace.

These matches are a real-world example proving that some flames cannot be extinguished. Such materiel embeds the oxidizing chemical into the fuel and once ignited, the fire cannot be extinguished because it self-completes the fire-triangle. Nimur (talk) 19:56, 14 September 2017 (UTC)[reply]

Cannot? I bet you could so it if you had a sufficient supply of liquid helium and a way to pump it onto the flame. Just sayin'. --69.159.60.147 (talk) 21:46, 14 September 2017 (UTC)[reply]

Okay, if you can cool it fast enough, by blowing inert gas over the fuel/oxidizer mix, you can make the reaction unsustainable. Moving the ambient air might prevent it from incandescing, and the flame might go out. Nimur (talk) 22:02, 14 September 2017 (UTC)[reply]

In some cases, you can also disrupt the reaction with things like Halon. 2601:646:8E01:7E0B:3DB7:8D6E:A762:14CC (talk) 09:06, 17 September 2017 (UTC)[reply]

I can't get youtube here...do they say what the chemical mixture is? Might be possible to quench the reaction with...radical trap, alternate oxidizer or reducing agent that gets the process out of some self-sustaining chemical pathway, etc. How far can we destabilize via the fourth side of the fire tetrahedron? DMacks (talk) 21:08, 16 September 2017 (UTC)[reply]

A safety match should strike and burn in a hydrogen filled room. (A weird thing is that the ignition of a humble safety match is chemically the same as Armstrong's mixture, which is perhaps the most infamously hazardous thing a pyrotechnics wannabe can attempt to make. But the match and striker are physically separated. Wnt (talk) 00:55, 15 September 2017 (UTC)[reply]

To be clear, it will strike and burn as along as there is oxidizer remaining on the match. After it runs out of oxidizer, it will go out. shoy (reactions) 14:57, 15 September 2017 (UTC)[reply]

Would the heat of the striking cause the oxidizer to react with the hydrogen atmosphere at all? I have a mental image of striking the match, and having both the box and the match burst into flames (assuming that the reaction of oxidizing gas with fuel solid would look similar to the reaction of oxidizing solid with fuel gas... which is also an interesting question). MChesterMC (talk) 15:17, 15 September 2017 (UTC)[reply]

Cassini

is there any prediction of what happens when she crashes through Saturn? Treasure trove of data coming in 20+ hours but would be nice for the article to compare what is expected.

also any word on future missions.

Thanks.Lihaas (talk) 20:20, 14 September 2017 (UTC)[reply]

JPL has a great website on the event: JPL's Saturn Website main page presently has a special - Cassini: The Grand Finale. Here's an interview with several of the program scientists, including a description of what's about to happen in the next few hours as the spacecraft enters Saturn atmosphere. The spacecraft will begin to aerodynamically tumble, eventually enduring aerodynamic stresses beyond its ability to maintain directional control. The spacecraft will no longer be able to point its antenna toward Earth; and will tumble unpredictably before ultimately breaking apart. Here's a more detailed overview: Cassini Spacecraft Makes Its Final Approach to Saturn.

"Within about 30 seconds following loss of signal, the spacecraft will begin to come apart; within a couple of minutes, all remnants of the spacecraft are expected to be completely consumed in the atmosphere of Saturn."

Here's a long-form documentary, (about 15 minutes long), from earlier this summer; it includes some stunning animations representing what NASA's digital artists think the spacecraft break-apart would look like if you could watch it with your own eyes at Saturn.

It's a little hard to understand intuitively, but the material of the spacecraft will be hitting atmospheric gas, as dense as Earth's sea-level atmosphere, while it's still moving at orbital entry speeds - about 70,000 miles per hour (or about twenty miles each second). At those speeds, the heat of aerothermal friction is so high that even space-grade metals - like titanium - or ceramic or composite structures - just can not withstand the heat and stress. Hitting air molecules at that speed can be as destructive as slamming into a solid object.

This link - JPL's Cassini Grand Finale interactive feature - is a fun tour of the last hours of mission operation, full of cool animations and brief descriptions. The feature explains which parts of the spacecraft are expected to break off first, using language that's accessible to an average science enthusiast.

"Cassini’s gold-colored multi-layer insulation blankets will char and break apart, and then the spacecraft's carbon fiber epoxy structures, such as the 11-foot (3-meter) wide high-gain antenna and the 30-foot (11-meter) long magnetometer boom, will weaken and break apart. Components mounted on the outside of the central body of the spacecraft will then break apart, followed by the leading face of the spacecraft itself."

Nimur (talk) 20:29, 14 September 2017 (UTC)[reply]

@Nimur: fascinating, and I am an "average science enthusiast," but I thought that the atmosphere is way stronger than ours?

Further, is there a remote possibility (in probability theory there are no absolute certainties (or vice versa) she can survive to send back more data? I realize even at this point IFF it happens she;;ll [almost] certainly never leave Saturn.Lihaas (talk) 20:55, 14 September 2017 (UTC)[reply]

Saturn is an enormous planet. The spacecraft's orbit will take it over the "cloud tops," and as it descends, it will encounter denser atmosphere. The air will get about ten times as thick for each minute the spacecraft falls.

There is no realistic way for this spacecraft to survive the plunge into the planet's atmosphere. It is not structurally designed for reentry; it has no heat shield.

Even if the spacecraft survived, it will begin tumbling as soon as the atmosphere becomes thick enough. Once the spacecraft is tumbling, it cannot point its antenna at Earth, so we can not hear any messages it sends to us. We'll be pointing the most sensitive antennas on our planet - Deep Space Network - using an antenna in California and another in Australia. Even with our most sensitive antennas, we can't detect Cassini's signals after it starts tumbling.

The mission planners know that is going to happen - so they've configured the spacecraft to send as much data as possible before it hits the planet; and to transmit as much as possible on the way in.

No part of the spacecraft will remain intact: it will be evaporated by the intense heat, like a meteor.

Is any other outcome possible?

No.

Several years ago, after I read the Wikipedia article on "almost surely", I had a long and boring conversation with my mathematician friend. We took that article apart piece-by-piece. We did a verbal epsilon-delta proof. We constructed a Lebesgue measure for the probability integral. We took the language apart, constructed a grammar, used axiomatic set theory. We talked about alternative views on the issue, colored by my various backgrounds in physics, in engineering, in philosophy. We talked about using probabilities as inputs to decision problems in game theory. We talked about plain English words, and the very same words used in technical mathematical parlance. We talked about "certainty," and "good-enough-certainty." We came to no new profound understanding.

Almost surely, the spacecraft will break apart.

Nimur (talk) 21:10, 14 September 2017 (UTC)[reply]

Quibble regarding "the heat of aerothermal friction" -- my understanding is that friction plays a small part in the heating of a spacecraft (or meteor) on atmospheric entry. The main heating effect is caused by the compression of the air in front of the object. Atmospheric entry says "Direct friction upon the reentry object is not the main cause of shock-layer heating. It is caused mainly from isentropic heating of the air molecules within the compression wave." CodeTalker (talk) 22:17, 14 September 2017 (UTC)[reply]

Good observation; I'm lumping all of the aerodynamic heating effects together. Reentry thermodynamics, as you point out, become very complicated. Nimur (talk) 23:06, 14 September 2017 (UTC) −[reply]

Any chance bacteria can survive? There are water vapor clouds and comfortable temperatures near the bottom of the observable cloud layers. (The gravity is Earthlike also, so any relevant microbes need to be able to hang aloft for long durations) Wnt (talk) 00:57, 15 September 2017 (UTC)[reply]

No, the chance is extremely low. NASA's Planetary Protection Office specifically researches how to prevent biological contamination of worlds we explore, even when we send robotic probes like Cassini.

Here's their brief overview on bioprotection for Saturn's moons.

Nimur (talk) 12:56, 15 September 2017 (UTC)[reply]

After we crash our satellite into Saturn, I expect angry Saturnians to fire back at Earth. (Those same Saturnians were also angered by the civilizations on some of their ~~larger~~ moons, and those moons are now rings.) :-) StuRat (talk) 03:33, 15 September 2017 (UTC) [reply]

Actually the Rings of Saturn article says that all the particles together would be a moon a little smaller than Mimas, though it also says that Cassini gave some indications that's a bit of an underestimate. Wnt (talk) 11:33, 15 September 2017 (UTC)[reply]

Have Cassini or any other of our probes ever gotten close enough to the rings to get pictures of some individual pieces of them? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:43, 15 September 2017 (UTC)[reply]

Textures in the C Ring; Waves and Small Particles in the A Ring; Moon-Made Rings; A Lone Propeller; Daphnis. Many photos exist from a long and accomplished scientific mission. Some of our useful information about ring material comes from non-photographic data - such large areas can be understood by imaging them with radio and other instruments - but the picture we get is a little different than a photograph. Nimur (talk) 14:27, 15 September 2017 (UTC)[reply]