Wikipedia:Reference desk/Archives/Science/2018 July 25

= July 25 =

Why can Labrador get so hot?
List of extreme temperatures in Canada. Also has exceeded the all-time highs of DC, Philly, Toronto, Ottawa, Windsor, Detroit, O'Hare, Indianapolis and Columbus and only 0.9F less than Ontario (108F). Sagittarian Milky Way (talk) 22:48, 25 July 2018 (UTC)
 * Not a complete answer, but there were heat records in many parts of the world this year, with a crisis in Japan at the moment. Co2 levels also fluctuated less, remaining high (with average level higher every year).  Extreme weather events are predicted to rise as global warming pursues.  Forest fires are regular in many areas and increasing, dumping more Co2 and the warming of permafrost is a concern as more methane is not converted before reaching the surface (with a temporary effect higher than that of Co2).  There are fears about reaching tipping points and it's very difficult to determine when one will be attained; runaway changes are considered possible when one or more such tipping points are reached.  About Labrador this year specifically, I'll let others expand (obviously, specific events cannot directly be linked to global trends).  — Paleo  Neonate  – 23:28, 25 July 2018 (UTC)
 * The highest known temperature east of Ontario and New York was not only so far north but also outside the modern warming era or the Dust Bowl which makes it even more unusual. Sagittarian Milky Way (talk) 00:40, 26 July 2018 (UTC)


 * I am intensely skeptical of that information. The table with that value was added on March 21 of this year, with no sources, by an editor who has repeatedly run into trouble due to adding unsourced information to articles. It is not uncommon for locations that are far inland to reach very high temperatures, even if they are far to the north, but for a coastal location to reach such a temperature would really be anomalous. Anything is possible, of course, but I would like to see some evidence. Looie496 (talk) 03:06, 26 July 2018 (UTC)


 * There really seems to be a record of that temperature, the Canadian government list it . There is some similar scepticism of that temperature in this discussion (which was how I worked out to use that site) and . Nil Einne (talk) 12:18, 26 July 2018 (UTC)


 * Further found and sort of . This post in the first discussion  is most interesting as it includes a response from Environment Canada which included an image of the original paper record  confirming it's not simply a modern data entry error. (Although IMO one of the responses in that thread is a little harsh. It sounds like whoever responded primarily felt they were being asked if there was some data entry error and confirmed there wasn't with the original records. They may not have felt it worthwhile going through the process of annotating or removing a single potentially spurious record.) BTW, in case there is some remaining confusion because of PaleoNeonate's post, we aren't AFAIK talking about anything this year or as SMW said anywhere close to modern times but a record from 1914. Nil Einne (talk) 12:39, 26 July 2018 (UTC)
 * Wow. I still think there must be an error somewhere, though. As one of those linked posts says, if the high was 65 the day before and the day after, and it rained on that day, it's very difficult to imagine how the temp could have reached 107. Looie496 (talk) 14:04, 26 July 2018 (UTC)
 * One thing to remember is that climate is complex, and that temperatures (both averages and extremes) are only partly a function of latitude. You can see this sort of thing at U.S. state temperature extremes.  The state with the lowest record high temperature?  Hawaii.  The state closest to the equator.  This is true because temperature is a factor of many things, besides latitude there are wind currents, proximity to large bodies of water, temperature of that water, local terrain, elevation, etc. etc.  Microclimates can also be similarly weird; one of the most famous microclimates in North America is San Francisco, which is frequently 10-20 degrees F colder than places only a few miles away; (There's a frequently mis-attributed aphorism that goes "The coldest winter I ever saw was the summer I spent in San Francisco") the average July high is 66.5F for San Francisco, and 72.0F for Oakland, a 5.5F difference is impressive given that the cities are connected by a bridge.  All that goes to say that simply being far in the north does not disqualify some specific location in Newfoundland from having some unusual microclimate, given the variety of factors at play.  -- Jayron 32 15:20, 26 July 2018 (UTC)
 * It might be useful to examine the temperature records of adjacent stations, also newspapers covering the area - these often contain a day-to-day weather record.  See List of newspapers in Canada.   Here are the figures for five stations in the area:

Date                 Station          Max (°C.)                       Min. (°C.) 1914 August 11       Burin            23.9                            12.8 Fogo            23.3                            15.6 North West River 41.7 X                          10.0 St Georges      24.4                            15.6 St John's       23.9                            19.8

You will note the red "X" against the North West River maximum. This suggests it was picked up as an anomaly at the time. 86.133.26.146 (talk) 17:32, 26 July 2018 (UTC)


 * There is also a red X by the original data record for "107" above. Also note there is a column "Range" to the right, which has an entry "57" (which is "107" - "50").  The weather was given as some letter, which I assume means clear, for the morning, with "overcast" in the afternoon, and "rain and heavy thunderstorm" as a note.  Which is what you'd expect with that kind of high temperature!  Finally, note the sequence of high temperatures:  97 62 63 71 70 64 65 66 75 107+ 65 86 76 62 63 65 63 65 50 49 68 65 63 74 78 74 .  Putting those in LibreOffice Calc and doing STDEV.S(that range of values) I get 12.41, which sounds at least about right.  The average is 69.46, so this value is at 3.02 standard deviations out.  That means there is only a 0.27% (1/370) chance of such a value occurring, according to standard deviation.  (It seemed faster to check that table than remember the function name...)  Nonetheless, in a dozen such months, one time it could happen by chance.  The value is still suspect, of course, because any 1% chance of error is more likely than that it is correct (that is, until you read the post above; with confirmation, its chance of being correct is much higher than the 1% error) -- but we certainly don't know it is wrong. Wnt (talk) 22:27, 26 July 2018 (UTC)
 * To me it looks more like a + or straight cross than an x unless it was added at an extreme angle. See also this rotated version. . I was thinking of it before and it seems to be a clear highlighting. But whether it was intended to indicate the value was in doubt or could be an error or an anomaly, or simply noting it was unusual high or maybe that it was the highest value, I'm not sure. I'm leaning towards it simply being because it's the highest value. There look to be two bars which similar denote the lowest minimum values. I was originally confused about these because I thought they were underlining two random values with nothing special. But looking more carefully I realised they are probably a bar above the two 38 values which are the lowest minimum values for that month. Nil Einne (talk) 10:21, 27 July 2018 (UTC)

Not sure why this doesn't break the Second Law of Thermodynamics
I'll assume it doesn't, but I can't see why. Advice welcome, I've been scratching my head for a decade.

Imagine the Earth were so far from the Sun, that there was no solar heating, and it had no internal radioactive decay ; would its atmosphere ( probably needing to be only Helium, to be a gas at 6 Kelvin ) be the same temperature on the surface, as at say 10 kilometres altitude ? If so, how would a molecule of air moving vertically, in the Earth's gravitational field, keep the same kinetic energy ( and hence velocity and hence temperature ), as it gained or lost the gravitational potential energy, of that 10 km of height ? Air molecules may well interact, sharing and equalising their kinetic energy ; but over any finite change of height, there must be an equal and opposite change of kinetic energy. If this were not true, a molecule of air which was moving upwards, would continue at the same speed, indefinitely, until it escaped to space ; and that would seem to break the even-more unbreakable First Law.

If the gas particles do exhibit "ballistic" behaviour ( like mortar shells ), and this maintains a permanent temperature gradient with height, which could be used to drive a heat engine ; a planet with such an atmosphere, could continuously generate mechanical power, as it absorbed heat energy from the 6 Kelvin afterglow of the Big Bang.

The continuous absorption of heat to generate power, would seem to break the Second Law.

Thanks. GeoffAvogadro (talk) 23:21, 25 July 2018 (UTC)


 * I think you're getting lost in complexities, but the clean and simple answer is that air temperature decreases with height: this is called the adiabatic lapse rate. The physical reason for this is that at lower altitudes, there is more gravitational potential energy; at higher altitudes, individual molecules have expended kinetic energy to work against gravity.
 * There are many confounding extra details that make atmospheric science so much fun; but at the basic level, there absolutely is a statistical reduction in kinetic energy for air molecules as their altitude increases.
 * Above a certain height, the sparsity of the gas molecules becomes very low, and some different properties of thermal and chemical physics begin to dominate: this region is called the ionosphere (and/or the thermosphere, or magnetosphere, depending on which classification scheme you're using; these terms are sometimes used interchangeably, but they actually specify sub-regions that describe the details of the molecules and ions at specific altitudes and atmospheric conditions).
 * Nimur (talk) 23:34, 25 July 2018 (UTC)


 * The answer is that in that scenario the entire atmosphere would be in thermal equilibrium with the cosmic background radiation, at a temperature of 2.8 K. But basically there wouldn't be any atmosphere -- even helium would be in a liquid state at that temperature. You would only have a few stray molecules that randomly escape from the surface, hardly denser than outer space. Looie496 (talk) 02:45, 26 July 2018 (UTC)
 * Helium is a liquid at that temperature at atmospheric pressure. You'd need to check the phase diagram of helium to see what state it would be in at the pressures you are thinking of.  Also, if helium is escaping from the surface and dissipating into the atmosphere at a greater rate than it is condensing, it is not in equilibrium; your planet is losing mass, which means even at the same temperature, you're losing thermal energy.  -- Jayron 32 18:03, 27 July 2018 (UTC)
 * Good point about pressure. Looking at the phase diagrams at http://ltl.tkk.fi/research/theory/helium.html, it appears that at the cosmic background temperature, you could have an atmosphere of up to two Earth-atmospheres in pressure composed almost entirely of 3He, above an ocean of liquid helium. The other stable isotope, 4He, would be liquid down to a much lower pressure. Looie496 (talk) 20:42, 27 July 2018 (UTC)
 * It is true that in the absence of surface heating the atmosphere will gradually become isothermic. So, there is no contradiction with the second law. Molecules going up will be slowed by the gravity but will gain energy in collisions with molecules going down and therefore accelerated by the gravity. This picture is only true on spatial scales above the mean free path length in gas. Below this length the gas kinetic model (and thermodynamics generally) is not applicable and the gas behaves like a cloud of free particles which happens, for example, in exospheres. Ruslik_ Zero 06:46, 26 July 2018 (UTC)
 * Uh, unless there's some subtlety I'm missing here, you couldn't drive a heat engine with the atmospheric temperature gradient because to move the hotter air away from the surface you have to do work against Earth's gravity. Also, I know this is a spherical cow kind of thought experiment, but as Looie496 noted, at that temperature you'd just have frozen volatiles on the planet's surface, with a tiny amount of sublimated vapor, as seen on worlds like Pluto. And there'd be no appreciable amount of helium; Earth's gravity is too weak to hold on to hydrogen or helium. --47.146.63.87 (talk) 06:59, 26 July 2018 (UTC)


 * I thought that the cosmic background radiation plus starlight gave a higher equilibrium temperature than the cosmic background radiation alone. Obviously this would differ (in the galaxy core? in the empty spaces between galaxies? Any large clouds nearby?) but the interesting number would be for a planet in the spiral arm, roughly where our sun is. --Guy Macon (talk) 06:59, 26 July 2018 (UTC)
 * The vast majority of cosmic rays originate from outside our own galaxy. The intensity may actually increase as you move to regions of lower stellar density, due to reduced shielding from cosmic rays by stellar magnetic fields. Someguy1221 (talk) 22:28, 27 July 2018 (UTC)
 * "Cosmic background radiation" properly refers to the relic radiation from photon decoupling that pervades the universe. This is what the original poster was referring to. I don't doubt sometimes the term is used sloppily to include cosmic rays, but in strict scientific terms this is wrong, as they're two totally different things. --47.146.63.87 (talk) 06:39, 28 July 2018 (UTC)
 * Nah, i just had a total brain fart reading Guy's post, and thought he wrote 'cosmic rays'. Someguy1221 (talk) 19:32, 28 July 2018 (UTC)
 * Yes, obviously this depends on distance. Pluto for instance gets down to about 33 kelvin; the heat sources are a mixture of the Sun's heat, Pluto's internal heat, and probably some tidal flexing from Charon. --47.146.63.87 (talk) 06:39, 28 July 2018 (UTC)
 * Assuming the background temperature was enough to keep helium a gas then the temperature of the air would be the same at all heights. It being different on earth is because the earths atmosphere is nowhere near an equilibrium, we have the sun shining down and various interactions between the gas and the radiation. The energy of the molecules would get spread out, they don't just fall from space to the ground. Just having molecules falling straight up and down isn't a stable equilibrium. Dmcq (talk) 11:37, 26 July 2018 (UTC)