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New studies confirm weakening of the Gulf Stream circulation (AMOC)

Filed under: — stefan @ 17 September 2020

Many of the earlier predictions of climate research have now become reality. The world is getting warmer, sea levels are rising faster and faster, and more frequent heat waves, extreme rainfall, devastating wildfires and more severe tropical storms are affecting many millions of people. Now there is growing evidence that another climate forecast is already coming true: the Gulf Stream system in the Atlantic is apparently weakening, with consequences for Europe too.

The gigantic overturning circulation of the Atlantic water (dubbed AMOC) moves almost 20 million cubic meters of water per second – almost a hundred times the Amazon flow. Warm surface water flows to the north and returns to the south as a cold deep current. This means an enormous heat transport – more than a million gigawatts, almost one hundred times the energy consumption of mankind. This heat is released into the air in the northern Atlantic and has a lasting effect on our climate.

But since the 1980s, climate researchers have been warning of a weakening or even a cessation of this flow as a result of global warming. In 1987, the famous US oceanographer Wally Broecker titled an article in the scientific journal Nature “Unpleasant surprises in the greenhouse”. Even Hollywood took up the subject in 2004 in the film “The Day After Tomorrow” by the German director Roland Emmerich. However, there were no measurement data that could prove an ongoing slowdown.

Only since 2004 has there been continuous monitoring at 26°N in the Atlantic (RAPID project). Although the data show a weakening of the current system, the measurement series is still too short to distinguish a possible climate trend from decadal variability. For the longer-term development of the Gulf Stream system, we must therefore rely on indirect evidence.

A long-term AMOC weakening should lead to a cooling in the northern Atlantic. Such a regional cooling in the middle of global warming has been predicted by climate models for a long time. And indeed, the evaluation of data on sea surface temperatures shows that the northern Atlantic is the only region of the world that has escaped global warming and has even cooled down since the 19th century (see graph). In addition, one can see a particularly strong warming off the North American coast, which according to model simulations is part of the characteristic “fingerprint” of a weakening of the Gulf Stream circulation.

Diagram of the Gulf Stream system with the warm surface current and the cold deep current. The actual Gulf Stream off the US coast is a part of this more comprehensive circulation system. The color shading shows the measured temperature trend since the late 19th century. This diagram is based on Caesar et al., Nature 2018 and first appeared in the Washington Post.

This fingerprint is regarded as important evidence, and not least because of this, the Intergovernmental Panel on Climate Change (IPCC) stated for the first time a year ago in the Summary for Policy Makers of its Special Report on the Oceans:

 “Observations, both in situ (2004–2017) and based on sea surface temperature reconstructions, indicate that the Atlantic Meridional Overturning Circulation (AMOC) has weakened relative to 1850–1900.”

New studies support long-term weakening

Two new studies now provide further independent evidence of this weakening. In August a paper by Christopher Piecuch of the Woods Hole Oceanographic Institution on the Florida Current – the part of the Gulf Stream system along the Florida coast – was published. Although continuous measurements of the current have only been available since 1982, Piecuch was able to reconstruct the strength of the Florida Current over the last 110 years from measurements of the sea level difference between the two sides of the current. To do so, he used 46 tide gauge stations in Florida and the Caribbean as well as a simple physical principle: the Coriolis force deflects currents in the northern hemisphere to the right, so that the water on the right side of a current stands higher than on the left. The stronger the current, the greater the difference in sea level. Comparison with measurements since 1982 shows that the method works reliably.

The result: the Florida current has weakened significantly since 1909 and in the last twenty years has probably been as weak as never before. Piecuch’s calculations also show that the resulting reduction of heat transport is sufficient to explain the ‘cold blob’ in the northern Atlantic.

This Monday, in Nature Climate Change a further study appeared, of researchers of Peking University and Ohio State University (Chenyu Zhu and Zhengyu Liu). For the first time, their paper provides evidence for an AMOC slowdown based on data from outside the North Atlantic. Model simulations show that a weakening of the AMOC leads to an accumulation of salt in the subtropical South Atlantic. This is due to the fact that strong evaporation in this region constantly increases the salinity, while the upper branch of the ocean circulation drains the salty water northwards, continually bringing in less salty water from the south. When this current weakens, the water in this region becomes saltier. This is exactly what the measured data show, in accordance with computer simulations. The authors speak of a “salinity fingerprint” of the weakening Atlantic circulation.

Video animation of ocean currents in the CM2.6 climate model of the Geophysical Fluid Dynamics Lab in Princeton:

In addition to these oceanographic measurements, a number of studies with sediment data indicate that the Gulf Stream circulation is now weaker than it has been for at least a millennium.

These current changes also affect Europe, because the ‘cold blob’ out in the Atlantic also influences the weather. It sounds paradoxical when you think of the shock frost scenario of the Hollywood blockbuster The Day After Tomorrow: but British researchers found that in summer the jet stream in the atmosphere likes to take a route around the south side of the cold blob – this then brings warm winds from the southwest into Europe, leading to heat waves there, as in the summer of 2015. Another study found a decrease in summer precipitation in northern Europe and stronger winter storms. What exactly the further consequences will be is the subject of current research.

However, the latest generation (CMIP6) of climate models shows one thing: if we continue to heat up our planet, the AMOC will weaken further – by 34 to 45% by 2100. This could bring us dangerously close to the tipping point at which the flow becomes unstable.

This article appeared originally in German in Der Spiegel: Das Golfstromsystem macht schlapp

171 Responses to “New studies confirm weakening of the Gulf Stream circulation (AMOC)”

  1. 151
    Susan Anderson says:

    nigelj @~135
    Thanks for the extended discussion about forest fires and compliments to the excellent Daniel Bailey.

  2. 152
    David B. Benson says:

    Barton Paul Levenson @147 — Please reference the easiest undergraduate text so that I can pass along the recommendation as occasion arises elsewhere. Thank you in advance.

  3. 153
    jb says:

    Mack at, well, lots of places:

    Unfortunately, we have to play whack-a-troll with this guy. If he claims that the math is wrong on the calculation of the earth’s no atmosphere temperature, the burden should be on him to show that the VERY simple calculation is wrong.

    The idea is that the energy coming in from the sun equals the energy leaving from the earth, so the equation must look like:

    (solar constant)*(1-albedo)*(pi*earth’s radius^2) = (stefan boltzmann constant)*(earth’s temperature^4)*(4*pi*earth’s radius^2)

    If you solve this for earth’s temperature, you get about 255 kelvin, which is -18 degrees celsius. For Mack to show that this solution is incorrect, he has to show that at least one of these numbers is wrong. Which one? If he can’t answer this, he shouldn’t be permitted to take up white space on this blog.

  4. 154

    M 148: I just get… “infrared radiation”….. no math…. even though you said you’d give me “the math” @38.

    BPL: Okay, I’ll give you the math.

    The surface of the Earth is at 288 K on average, so assuming blackbody emissivity, it radiates 390 watts per square meter by the Stefan-Boltzmann law:

    F = ε σ T^4

    where ε is the emissivity (1 for a blackbody), σ is the Stefan-Boltzmann constant (5.670373 x 10^-8 W m^-2 K^-4 in the SI), and T is the temperature in kelvins.

    The Earth gets 184 W m^-2 in insolation of which it absorbs 161 W m^-2 (i.e., it has a surface reflectivity averaging about 0.125). That means it must be getting 390 – 161 or 229 W m^-2 from some other source.

    And yet we know the Earth constantly loses 80 W m^-2 by evapotranspiration and 17 W m^-2 by pure convection, so it must actually be gaining 229 + 97 = 326 W m^-2 from this other source.

    This other source is, of course, the atmosphere. Using the Stefan-Boltzmann law again, we can calculate that the atmosphere is at an equivalent temperature, as seen from the surface, of 275 K.

    Does that help?

  5. 155

    DBB 152,

    For a really easy one, George S. Philander’s “Is the Temperature Rising?” (1998) is a good one. For more math, John Houghton’s “The Physics of Atmospheres” (3rd ed. 2002) is very thorough without being impossible. Grant W. Petty’s “An Introduction to Atmospheric Radiation” (2nd ed. 2006) is also very good. On the hard side would be Goody and Yung’s “Atmospheric Radiation” (1989).

  6. 156
    Johann G. K. Gizurarson says:

    Hi guys,

    If the AMOC is weakening (which I’m quite compelled to believe given various well presented data throughout couple of years), why isn’t the climate here in Iceland cooling down? E.g. summer of 2019,2016,2012,2011,2010,2008,2007,2003 were all extremely warm on any timescale here in the city of Reykjavik.
    According to IPCC even if it [AMOC] weakens there will still be warming over land. However, Reykjavik is at the coast (one of the nearest “big” places to the famous cold blob) and there has no cooling happened. If we compared all months all years from 2000 to 2020 almost every month has been warmer in Reykjavik than the 1961-1990 average. When are we going to see cooling here? Or are we only going to see reduced warming compared with if the AMOC wasn’t changing?

    With regards,

    Jóhann (Stefan & co; thanks for great work!)

  7. 157

    #149, Mack–

    I’m thinking of writing a REAL science book myself…

    Yeah, keep us updated. I want to make sure I have a good supply of popcorn when it comes out.

    If it comes out!

  8. 158
    MA Rodger says:

    I see Maniac Mack @148 is again trying to re-write this comment thread to suit his personal fantasies. Perhaps I should set him straight.

    Mack @148,
    You are wrong.
    Nobody said @38 they were going to give you “the math”. You were simply asked if you wanted “the math”. Your response @47, you will recall, was to say:-

    I know the math. Maybe you and all the experts have made a mistake in “the math” Reality doesn’t always agree with “the math”.

    Subsequently, when @57 it was suggested that your comments showed you “don’t actually understand the math,” your response @63 was:-

    I do understand the math and I do know the mistake in the math. You are obviously still ignorant of the mistake in the math. A mistake so bad we have supposedly intelligent people like yourself trying to tell me that the ATMOSPHERE is keeping the oceans in liquid state.

    Yet, when asked to set out this “math” you understand, complete with the “mistake so bad”, you are unable to oblige.

    It was only after all this nonsense from you up-thread that @120 that you finally agreed that you do “want the math” saying:-

    “Well, yes, I think I’m prepared for you to hit me with the math. Go ahead, make my day.”

    And to be pedantic, you had only been asked if you “want the math” which isn’t entirely the same as somebody saying they would “give” you this “math”.

    True, you do complain @136 that other “math” provided is not the same as the ‘ocean-melting’ “math” you admitted @120 you were “prepared for” receiving. But I would suggest that you probably are not “prepared,” as you give all the signals of somebody with zero understanding of “math” (a view also expressed by Barton Paul Levenson @57, and reinforced by you successfully demonstrating elsewhere @RealClimate your total ignorance of the Laws of Thermodynamics).
    Of course, I am always happy to amend my views to suit available evidence. So do feel free to consider responding to my comment @76 which anybody with the slightest ability in mathematics would not have found unreasonable. You may recall it ended:-

    “So a gentle nudge, chum. Set out this alleged mathematical mistake you are bleating on about, or shut you cake hole!!”

  9. 159
    William B Jackson says:

    #158 I make no claim to great knowledge of math but I find Mack positively Trumpian in his denial of objective reality. Luckily while Trump’s denial leads to unnecessary deaths Mack’s leads only to time wasting nonsense posts.

  10. 160
    Mack says:

    @158 MA Rodger

    @154 BPL
    Thanks for the math, BPL,
    The first mistake you’ve made is the Earth with an emissivity of 1…sorry,the entire surface of the Earth is not covered in black asphalt. The Earth’s total emissivity has been measured at 0.82…we are a blue planet.
    The second mistake you’ve made is the 161 watts/sq.m insolation at the Earth’s surface. You are following Trenberth’s looney Earth Energy Budget diagrams showing only 161 w/sq.m absorbed at the Earth’s surface…. totally insufficient. That’s the big mistake. Reality is .. it’s about that 340 watts/sq.m you thought was at the Top of the Atmosphere (TOA). You’re confused between the surface of the Earth and the “surface of the Earth” as designated by Trenberth to be at the TOA.
    So, if you slot those numbers into the Stefan-Boltzmann equation, BPL…. ie emissivity = 0.82 , area = 1 sq.m , Radiative energy = 340 watts/sq.m… you’ll arrive at about 292K or 19deg C. at Earth’s surface.
    The 340 watts/sq.m. you knew, of course, comes from taking the TSI, which exists at the TOA, of 1360 watts/sq.m and then geometrically “attenuating” it down, first by halving for day/night, the 1/2 again for the lit side Earth curvature….divide by 4.
    The 292K or 19deg C, is still a bit higher than the GAT, measured at about 15deg.C …so the further reduction is accounted for by atmospheric attenuation… gases ,vapour, aerosols, clouds etc … which you can figure out from the S-B equation to be about 20watts/sq.m.
    Geometric “attenuation” plus atmospheric attenuation on the real,measured 1360 watts /aq.m that exists at the TOA, using the Stephan-Boltzmann equation, provides us with the real global average temperature, without the need for any atmospheric “greenhouse effect.”
    Anything else you need to know, BPL?

  11. 161
    MA Rodger says:

    I see that Maniac Mack has set out two alleged mistakes. (Perhaps they collectively constitute the AGW-science-confounding “mistake so bad” he has mentioned upthread.) While for the “second mistake”, he sets out is an embarrassingly stupid account, the “first mistake” involves a less widely-discussed value, the emissivity of the Earth’s surface.

    Maniac Mack tells us “The Earth’s total emissivity has been measured at 0.82…we are a blue planet.” This likely does no more than repeat the denialist blather of Jennifer Marohasy who also says in a 2011 blogpost “The emissivity of the surface has been measured, not assumed, and it is 0.82.”
    This particular blogpost never manages to say who did this ‘measuring’ but a second 2011 blogpost from the same author goes into the subject a little differently and names two references for the statement “The surface has a measured emissivity of 0.82; it means that the surface emits 82% of the energy it absorbs.”
    Ignoring the obvious misunderstanding of the physics, the references to measured emissivity are to the URL of an obsolete webpage and Modest (2003) ‘Radiative heat transfer’, the latter hardily the go-to reference for a measured emissivity value for the Earth’s surface. And if it did set out this 0.82 value, it is unlikely to be more than a point measurement as measurements of ocean & land surface seldom find such values outside desert regions.

    Of course, Maniac Mack may be thinking of some other source for his measured emissivity of Earth’s surface. So the question remains – Is there another source to back his bold assertion on emissivity that actually exists outside his warped imagination?

  12. 162

    M 160,

    Well, you’ve responded with your own “math.” There are so many mistakes, it’s hard to know where to start. I’ll try to tackle them in order.

    M: The first mistake you’ve made is the Earth with an emissivity of 1…sorry,the entire surface of the Earth is not covered in black asphalt. The Earth’s total emissivity has been measured at 0.82…we are a blue planet.

    BPL: I was talking about emissivity at the surface, which has been measured with instruments. Various estimates range from about 0.9 to 1.0, with most clustered near the upper end. Roeckner et al. (1993) get 0.996, for instance.

    M: The second mistake you’ve made is the 161 watts/sq.m insolation at the Earth’s surface. You are following Trenberth’s looney Earth Energy Budget diagrams showing only 161 w/sq.m absorbed at the Earth’s surface…. totally insufficient. That’s the big mistake. Reality is .. it’s about that 340 watts/sq.m you thought was at the Top of the Atmosphere (TOA). You’re confused between the surface of the Earth and the “surface of the Earth” as designated by Trenberth to be at the TOA.

    BPL: No, of that 340 W m^-2 at top of atmosphere, about 25% is reflected away by clouds and Rayleigh scattering before it ever gets to the surface. Actual insolation is 184 W m^-2, and 23 W m^-2 of that is reflected by the surface, mostly by ice near the poles but also by land and, to a tiny extent, water.

    M: So, if you slot those numbers into the Stefan-Boltzmann equation, BPL…. ie emissivity = 0.82 , area = 1 sq.m , Radiative energy = 340 watts/sq.m… you’ll arrive at about 292K or 19deg C. at Earth’s surface.

    BPL: Right, but those numbers are wrong, so the fact that you get something roughly like the right answer, though not identical to it, is a coincidence. You’ve merely taken a too-low emissivity and compensated for it with a too-high insolation.

    M: The 340 watts/sq.m. you knew, of course, comes from taking the TSI, which exists at the TOA, of 1360 watts/sq.m and then geometrically “attenuating” it down, first by halving for day/night, the 1/2 again for the lit side Earth curvature….divide by 4.

    BPL: Right. Well done.

    M: The 292K or 19deg C, is still a bit higher than the GAT, measured at about 15deg.C …so the further reduction is accounted for by atmospheric attenuation… gases ,vapour, aerosols, clouds etc … which you can figure out from the S-B equation to be about 20watts/sq.m.

    BPL: You’re forgetting reflection and scattering.

    GM: Geometric “attenuation” plus atmospheric attenuation on the real,measured 1360 watts /aq.m that exists at the TOA, using the Stephan-Boltzmann equation, provides us with the real global average temperature, without the need for any atmospheric “greenhouse effect.”

    BPL: You can’t use the 1360 W m^-2 because the Earth receives solar energy on its cross-section, which is a disk, but has a total surface area four times greater, because it’s (roughly) a sphere.

  13. 163

    #160, Mack–

    A ‘lovely theory slain by ugly fact.’

    The energy at Earth’s surface is pretty well-constrained with good old empirical measurement using (inter alia) such as these:

    https://www.campbellsci.com/blog/pyranometers-need-to-know

    As one random analysis in the literature (Wild et al., 2012) puts it:

    …we make extensive use of the growing number of surface observations to constrain the global energy balance not only from space, but also from the surface.

    https://link.springer.com/article/10.1007/s00382-012-1569-8

    And their bottom line?

    Our analyses favor global mean downward surface solar and thermal radiation values near 185 and 342 Wm−2, respectively, which are most compatible with surface observations. Combined with an estimated surface absorbed solar radiation and thermal emission of 161 and 397 Wm−2 respectively…

    It’s not likely that an entire set of scientific disciplines would “confuse” shortwave and longwave radiation. Random blog commenters, well, that’s another story.

  14. 164
    Astringent says:

    Mack at #160 And the first mistake that dear Mack has made is thinking that term ‘blackbody radiation’ is something to do with an object’s colour. It’s not! It’s dependent on temperature. While ε for the earth isn’t exactly 1 it’s close enough to be nearly immaterial in the calculations. like to critique the rest of his ramblings, but they aren’t coherent enough to be critiqued.

  15. 165
    Victor says:

    BPL: “The amount of heat involved in a one degree increase is therefore about 5.179 x 10^21 joules. This is an amount of energy equivalent to 13.68 trillion Hiroshima bombs.”

    V: Well that explains the explosion I heard this morning. Or was it the garbage truck going by?

    Kevin McKinney: Victor, thank you for confirming in tediously irrelevant detail what I said in my #109: land areas are warming at roughly twice the rate of the world as a whole. (I.e., land plus ocean.) Can I now assume you understand that piece?

    V: As I recall, the standard “scientific” response to the notorious “hiatus” involved all that missing heat diving down from the atmosphere into the ocean. That was a period of roughly 16 years when land temps. were relatively flat, but (according to the “experts”) the ocean was heating up drastically.

    K: In reference to the sneer about Arctic ‘databases’, I find it hard to believe that you don’t know full well that every analysis of global temperature save Hadcrut includes the Arctic. So I’m assuming the comment wasn’t actually moronic, but merely disingenuous in the extreme.

    V: No, you are the one who’s being both disingenuous AND moronic. I was not referring to official “scientific” databases, as should have been obvious. I was (sarcastically) wondering how an inanimate object such as “the Arctic” is able to determine whether temperatures have been rising over the past several years without maintaining a database in which yearly temps. are duly recorded. Obviously “the Arctic” is incapable of maintaining such a database, thus has no way of determining relative warmth from year to year. Thus your claim that what really counts is changing temperatures over time rather than immediate atmospheric conditions is not only spurious but silly.

    K: Victor asked:

    Thus, according to “the science,” we would expect to find more extreme weather-related events in the lower latitudes as we review Earth’s history. So permit me to repeat my earlier question: is that the case?

    Let me repeat my answer:

    No.

    But maybe a longer answer would help.

    V: Actually your longer answer is no help at all as it’s obvious you don’t know what you’re talking about.

    K: First, what is meant by “extreme weather events?”

    Since “weather” refers to specific conditions at a particular place and time, it’s evident that we must here be considering events as defined with reference to local norms.

    V: That’s precisely my point. If temperature were driving extreme weather then norms associated with particular localities would have reflected that. And since a 1 degree (or 2 degree) difference in temperature can, according to you, mean the difference between tolerable conditions and intolerable conditions then populations would be fleeing from the warmer regions to the cooler ones. We’d be seeing a mass migration from, say, Florida to Canada. Seems to me the migration has tended to go in the opposition direction. Do you wonder why?

    K: So, presumably, 5mm of precipitation would be considered “extreme” were it falling on Santa’s workshop, whereas on Aruba it might be completely unremarkable.

    So, bottom line here: both Aruba and Santa’s workshop experience “extreme” precipitation at one time or another, but the amounts for the former are going to be much larger than for the latter.

    V: Sorry Kevin, but I presumed we were talking about an “existential” threat to life on this planet, not relative differences in normal precip. from one region to the next.

    K: The foremost example would be tropical cyclones (AKA hurricanes). As explained in Brittanica, tropical cyclones have specific physical characteristics which are dependent upon the tropical marine environment. It’s possible for tropical cyclones to persist as entities after exiting the tropics, but they lose those specifically tropical characteristics (most obviously, the famous “eye”) and become more diffuse “extra-tropical cyclones.”

    Obviously, this is one example of an “extreme weather event” which, indeed, is found “more… in the lower latitudes,” to use Victor’s words.

    V: Yes indeed. And on this we can agree.

    K: However, the context of this whole discussion was drying/evaporation/wildfire, not hurricanes.

    V: Exactly.

    K: In that context, the extremes would be expected, just as I said, where the *change* is greatest–i.e., the Arctic. A salient example there would be wildfire on the tundra, as mentioned above.

    V: So what you are saying is that “the Arctic” made a mental note of the fact that the climate has changed over the years and thus decided to set itself on fire as a response. (Sarcasm, in case you fail to notice.)

  16. 166
    nigelj says:

    Victor @165

    “That’s precisely my point(talking to KM). If temperature were driving extreme weather then norms associated with particular localities would have reflected that. And since a 1 degree (or 2 degree) difference in temperature can, according to you, mean the difference between tolerable conditions and intolerable conditions then populations would be fleeing from the warmer regions to the cooler ones. We’d be seeing a mass migration from, say, Florida to Canada. Seems to me the migration has tended to go in the opposition direction. Do you wonder why?”

    I can’t recall KM ever saying anything remotely like that. Care to copy and paste what you accuse him of saying?

    We have had about 1 degree of warming thus far, and nobody has ever claimed such a thing would cause cause significant migrations of people, and surprise surprise we havent seen any. So you have just created huge, boring, tatty old strawman.

    We have seen some very small pacific island communities partly relocate due to sea level rise thus far, and some quite noticeable sea level rise impacts In Florida. Google it. And we have already seen heatwaves increase in frequency and intensity, and level 5 hurricanes increase in number off Americas coast.

    If we get over 2 degrees of warming, the frequency and intensity of heatwaves is expected to become seriously concerning and will lead to life threatening conditions through tropical regions as below:

    https://www.theguardian.com/environment/2017/aug/02/climate-change-to-cause-humid-heatwaves-that-will-kill-even-healthy-people

    The more warming above 2 degrees, the worse it gets, obviously. I think this could lead to significant migration from tropical regions of the world to cooler climates. This probably won’t happen in a place like Florida because people will just spend more on air conditioning, but people in poor tropical countries cant always afford this.

    It’s a potentially grim huminatarian picture and mass migrations cause all sorts of geo political problems as we have seen recently in the middle east / Europe. It’s made worse by the potential for tropical cyclones to become more frequent and intesne at the same time and same places, and many pacific islands are also particularly susceptibe to sea level rise, so its a triple blow for them.

    Since you claim to be left leaning and have a bleeding heart for poor people, you might want to consider all this. And there I will leave it for now. I’m only bothering to put in the effort to respond because other people might find the guardian article interesting. Don’t think its just for you and your trolling.

  17. 167

    #165, Victor–

    I must invoke the Stravinsky clause again: “I don’t wish to criticize, etc., etc.” However, let’s clear one thing up. Obviously, science and logic are very difficult for you, Victor, but maybe you’ll do better with a syntactic issue. So, back to your #134:

    K: No, one would expect to see the more extreme effects in regions where the *change* in temperature is most marked, i.e., the Arctic.

    V: So “the Arctic” maintains a database, telling it how much its temperature has changed over the last several years? Pray tell, how does it do that? And as for that change being “most marked” in the Arctic . . .

    Obviously–perhaps even to you?–it is not the Arctic that maintains databases, but human scientists. They do so in order (inter alia) to be able to discern “where the *change* in temperature is most marked.”

    Definitions:

    marked
    /märkt/

    1. having a visible mark.
    “plants with beautifully marked leaves”
    (of playing cards) having distinctive marks on their backs to assist cheating.
    Linguistics
    (of words or forms) distinguished by a particular feature.
    “the word “drake“ is semantically marked as masculine; the unmarked form is “duck.””

    2. clearly noticeable; evident.
    “a marked increase in sales”

    Obviously, in context, the second sense is the relevant one. So, temperature change is most “clearly noticeable,” most “evident”, in the Arctic, where its magnitude has been roughly double that of the rest of the planet. This is thanks to the tireless labors of numerous scientists compiling those databases, since without those efforts, we would not know how much warming had occurred.

    This is shown graphically in such places as this:

    https://data.giss.nasa.gov/gistemp/maps/index.html

    So, let me again try to dumb it down sufficiently that you can actually understand it, instead of concluding in your incomprehension that I must not know what I’m talking about:

    Temperature-sensitive changes in extreme weather are a function not primarily of the temperature at a particular location, but of the *change* in temperature at that location.

    For example, the link above shows that north of 79 degrees N latitude, warming has exceeded 3 C, with respect to a 1951-1980 baseline. That’s the largest magnitude of warming seen anywhere. The least is south of 83 degrees south, on the Antarctic ice sheet (0.19 C), with another significant low in the band from 45 to 55 S (0.25-0.31 C).

    I don’t think I can make it simpler than that. And remember, I’m going to considerable lengths here to answer in good faith–albeit by now with an irritation that I’m not bothering to mask–a question that *you asked.*

  18. 168
    Piotr says:

    163 Kevin McKinney says about #160, Mack: A ‘lovely theory slain by ugly fact.’

    Or more precisely: a full of himself ignoramus^* – got slain by the very person he thought he was slaying (see BPL # 162).

    Lovely job, BPL.
    —-
    ^* a full of himself ignoramus to BPL, examples only from one post:
    -“The first [second, big] mistake you’ve made”
    – “you are following Trenberth’s looney Earth Energy Budget diagrams showing only 161 w/sq.m absorbed at the Earth’s surface…”
    – “you are confused”
    – “Anything else you need to know, BPL?”

    Me, me, me! Mack, how does it feel to have your ass handed to you, just when you thought it were the others who made fools of themselves? Ignorance is one thing, ridiculing others based on your own ignorance – quite a different one.

  19. 169
    Ray Ladbury says:

    Not to feed the troll, but one needs to be careful in answering any question from Weaktor. He tends to ignore or even switch between definitions of terms. He asked if we see more severe weather effects in the tropics. Now, if what he is asking about is climate–we certainly see more severe weather there. There is really no analog to Tropical Storms at temperate latitudes, and even a run of the mill tropical rain tends to put a Midwest gullywasher to shame. However, that is not especially germane to what happens due to climate change.

    The energetics of weather phenomena are complicated. Release of latent heat as water changes phase may play a more important local role than local insolation. I do not expect Weaktor o understand such subtleties, just as I do not expect him to comprehend the scales of the effects and systems under discussion. He doesn’t care enough about understanding. What I expect is that he will do what he has always done–exploit ambiguities in the replies to him in out of context copy-pasta to make it appear that everyone is as clueless as he is. That is why it is criticalto be precise if you do choose to engage with him.

  20. 170

    #168, Piotr–

    Absolutely right, Piotr!

    But let me underline the point I was trying to make, and fill out the context a bit more, too.

    Mack’s notion–which I ironically called a “lovely theory,” alluding to an epigram of Thomas Huxley’s–suffers from completely neglecting frequency.

    BPL said, correctly:

    You’ve merely taken a too-low emissivity and compensated for it with a too-high insolation.

    And the “ugly fact”–from Mack’s perspective, and as you and many others here know perfectly well, but apparently Mack does not–is that the “emissivity” and the “insolation” are in very distinct frequency bands!–or, to phrase it conversely, have very distinct ranges of wavelengths.

    (Some may appreciate a graphic illustrating this fact; if so, the second figure here should serve. As one can see, solar radiation lies roughly from 0.2 nm-2 nm, whereas Earthly thermal radiation spans something like 3-70 nm.)

    Further, these ranges are well-constrained by measurement at the surface, as my reference to pyranometers was intended to convey. There’s a history of measurement of solar and atmospheric radiation that goes back deep into the 19th century.

    In fact, I have written about that at some length, here:

    https://hubpages.com/education/Fire-From-Heaven-Climate-Science-And-The-Element-Of-Life-Part-Two-The-Cloud-By-Night

    It’s an incomplete survey, but I think will be eye-opening for many, as it traces some of the thread of the research perhaps a bit less well-known in relation to climate science history. Significant researchers I covered in relative depth in the article:

    –William Charles Wells (1814)
    –Anders Knut Angstrom–not his famous grandfather, Anders J. Angstrom, nor yet father Knut Angstrom, the scientific opponent of Svante Arrhenius! (1918)
    –W.H. Dines (1929)
    –Guy Callendar (1938)
    –Walter M. Elsasser (1942)

    Mack had remarked on “the real,measured 1360 watts /aq.m that exists at the TOA…” That leads me to think he is unaware–like a great many denialati who, well, deny that any such thing can exist–that “back radiation” is not some sort of invention by contemporary computer modelers, but rather a reality that has been under empirical study since the day of the Napoleonic wars.

    In fact, that empirical study was a necessary *prerequisite* for the development of numerical modeling of climate and weather in the first place.

  21. 171
    Barry Finch says:

    Since the comments concentrated on the so-called “greenhouse effect” rather than AMOC and nobody else mentioned the FTIR spectral analysis from the IRIS and HIRS infra-red spectrometer instruments on some of the Nimbus satellites:
    —————————
    Nimbus-1 (1964 – 1964)
    Nimbus-2 (1966 – 1969)
    Nimbus-3 (1969 – 1972)
    Nimbus-4 (1970 – 1980)
    Nimbus-5 (1972 – 1983)
    Nimbus-6 (1975 – 1983)
    Nimbus-7 (1978 – 1994)
    Nimbus-3 (1969 – 1972) IRIS-B Infra-Red Interferometer Spectrometer – B
    Nimbus-6 (1975 – 1983) HIRS High-resolution Infra-Red Sounder
    —————————
    Example measured FTIR power flux vs wave-length spectra with the notches, H2O broad-band suppression & atmospheric window at:
    http://climatemodels.uchicago.edu/modtran/modtran.doc.html (IRIS-C spectrum on the Nimbus 3 satellite over the Sahara Desert to demonstrate the U.S. Armed Forces MODTRAN model’s general accuracy)
    https://publishing.cdlib.org/ucpressebooks/view?docId=ft8r29p2m6;chunk.id=d0e1726;doc.view=print (Sahara Desert as observed by IRIS-D instrument on the Nimbus-4 satellite)
    https://www.youtube.com/watch?v=Oog7-KOtpEA&t=1713s at 18:07 (4 FTIR samples for western tropical Pacific Ocean, Sahara Desert, Antarctica & southern Iraq)

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