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If you doubt that the AMOC has weakened, read this

A few weeks ago, we’ve argued in a paper in Nature that the Atlantic overturning circulation (sometimes popularly dubbed the Gulf Stream System) has weakened significantly since the late 19th Century, with most of the decline happening since the mid-20th Century. We have since received much praise for our study from colleagues around the world (thanks for that). But there were also some questions and criticisms in the media, so I’d like to present a forum here for discussing these questions and hope that others (particularly those with a different view) will weigh in in the comments section below.

Exhibit #1, and the prime observational finding, is a long-term cooling trend in the subpolar Atlantic – the only region in the world which has cooled while the rest of the planet has warmed. This ‘cold blob’ or ‘warming hole’ has been shown in IPCC reports since the 3rd assessment of 2001; it is shown in Fig. 1 in a version from the last (5th) IPCC report. In fact it is Figure 1 of the Summary for Policy Makers there – you can’t get more prominent than that.

Fig. 1 Observed temperature trends since the beginning of the 20th Century (Figure SPM1 of the last IPCC report).

I think there is a consensus that this is a real phenomenon and can’t be explained away as a data problem. According to NOAA, 2015 was the coldest year in this region since record-keeping began in 1880, while it was the hottest year globally. The key question thus is: what explains this cold blob?

In 2010, my colleagues Dima and Lohmann from Bremen were the first (as far as I know – let me know if you find an earlier source) to suggest, using sea surface temperature (SST) pattern analyses, that the cold blob is a tell-tale sign of a weakening AMOC. They wrote that

“the decreasing trend over the last seven decades is associated to the weakening of the conveyor, possibly in response to increased CO2 concentrations in the atmosphere”

(with ‘conveyor’ they refer to the AMOC). One of several arguments for this was the strong anti-correlation pattern between north and south Atlantic which they found using canonical correlation analysis and which is the well-known see-saw effect of AMOC changes.

I have since become convinced that Dima and Lohman were right. Let me list my main arguments upfront before discussing them further.

  1. The cold blob is a prediction come true. Climate models have long predicted that such a warming hole would appear in the subpolar Atlantic in response to global warming, due to an AMOC slowdown. This is seen e.g. in the IPCC model projections.
  2. There is no other convincing explanation for the cold blob. There is strong evidence that it is neither driven by internal atmospheric variability (such as the North Atlantic Oscillation, NAO) nor by aerosol forcing.
  3. A range of different data sets and analyses suggest a long-term AMOC slowdown.
  4. Claims that the slowdown is contradicted by current measurements generally turn out to be false. Such claims have presented apples-to-oranges comparisons. To the contrary, what we know from other sources about the AMOC evolution is largely consistent with the AMOC reconstruction we presented in Nature.

Let us look at these four points in turn.

A climate prediction come true

The following graph shows climate projections graph from the last IPCC report.

Fig. 2 Global warming from the late 20th Century to the late 21st Century (average over 32 models, RCP2.6 scenario) – Figure SPM8a of the IPCC AR5.

The IPCC writes that “hatching indicates regions where the multi-model mean is small compared to natural internal variability (i.e., less than one standard deviation of natural internal variability in 20-year means.)” The subpolar North Atlantic stands out as the only region lacking significant predicted warming even by the late 21st Century. The 4th IPCC report included a similar graph (Fig. TS28).

In our paper we have analysed the ‘historic’ runs of the CMIP5 climate models (i.e. those from preindustrial condition to the present) and found that the observed ‘cold blob’ in this region is consistent with what the models predicted, with the amount of cooling in the models depending mainly on how much the AMOC declines (see below). In the mean of the 13 models we examined (Fig. 5 of our paper), the downward trend of the AMOC index is -0.33 °C per century, in the observations we found -0.44 °C per century. (Our AMOC index simply consists of the difference between the surface temperatures of the subpolar Atlantic and the global ocean). The models on average thus predicted three quarters of the decline that the observational data indicate. (In fact most models cluster around the observed decline, but three models with almost zero AMOC decline cause the underestimation in the mean.)

Is there an alternative explanation?

If the ocean temperature in any region changes, this can only be due to a change in heat supply or loss. That can either be a change in heat flow via ocean currents or through the sea surface. Thus the subpolar Atlantic can either have cooled because the ocean currents are bringing less heat into this region, or alternatively because more heat is being lost to the atmosphere. So how do we know which of these two it is?

First, we can analyze the heat flux from ocean to atmosphere, which can be calculated with standard formula from the sea surface temperature and weather data. Halldór Björnsson of the Icelandic weather service has done this and presented the results at the Arctic Circle conference 2016 (they are not published yet). He showed that the short-term temperature fluctuations from year to year correlate with the heat exchange through the sea surface, but that this does not explain the longer-term development of the ‘cold blob’ over decades. His conclusion slide stated:

Surface heat fluxes did not cause the long term changes and are only implicated in the SST variations in the last two decades. Long term variations are likely to be oceanic transport but not due to local atmospheric forcing.

That’s exactly what one expects. Weather dominates the short-term fluctuations, but the ocean currents dominate the long-term development because of the longer response time scale and “memory” of the ocean.

Nevertheless some have suggested that the main mode of atmospheric variability in the north Atlantic, the North Atlantic Oscillation or NAO, might have caused the “cold blob”. In our paper we present a standard lagged correlation analysis of the NAO with the “cold blob” temperature (in form of our AMOC index). The result: there is indeed a significant correlation of the NAO with subpolar Atlantic surface temperatures. But on the longer time scales of interest to us (for 20-year smoothed data), changes in the sea surface temperature lead the NAO changes by three years. We conclude that changes in sea surface temperatures cause the changes in NAO and not vice versa. (And we’re certainly not the first to come to this conclusion.)

And a third point: in summer, the effect of heat flow through the sea surface should dominate, in winter the effect of ocean currents. That is because the well-mixed surface layer of the ocean is thin, so only the uppermost part of the ocean heat transport gets to affect the surface temperature. But the thin surface layer still feels the full brunt of atmospheric changes, and even stronger than in winter, because the thermal inertia of the thin summer surface layer is small. In our paper we analysed the seasonal cycle of the temperature changes in the subpolar Atlantic. The cooling in the “cold blob” is most pronounced in winter – both in the climate model (where we know it’s due to an AMOC slowdown) and in the observations. That yet again suggests the ‘cold blob’ is driven from the ocean and not the atmosphere.

There is another well-known mode of Atlantic temperature variability known as AMO, which correlates strongly with our AMOC index. Its established standard explanation in the scientific literature is… variations in the AMOC. (The NAO and AMO connections are discussed in more detail in the Extended Data section of our paper.)

There may be the possibility that some ocean heat transport change other than an AMOC change could be responsible for the ‘cold blob’ in the subpolar Atlantic, and I wouldn’t argue that we understand the ocean current changes in detail. But if you take a ‘big picture’ view, it is a fact that the AMOC is the dominant mechanism of heat transport into the high-latitude Atlantic, and the region that has cooled is exactly the region that cools in climate models when you slow down the AMOC. We have analysed the ensemble of CMIP5 “historic” model simulations for the past climate change from 1870 to 2016. For each of these model runs, we computed the AMOC slowdown over this time as diagnosed by our AMOC index (i.e. based on subpolar ocean surface temperatures) as well as the actual AMOC slowdown (which we know in the models, unlike in the real world.) The two correlate with a correlation coefficient R=0.95. Thus across the different models, differences in the amount of AMOC slowdown nearly completely explain the differences in subpolar Atlantic temperatures. If you doubt that what the temperatures in the Atlantic are telling us is a story of a slowing AMOC, you doubt not only that the high-resolution CM2.6 climate model is correct, but also the entire CMIP5 model ensemble.

A range of different data sets and analyses suggest a long-term AMOC slowdown

A number of different SST data sets and analyses support the idea of the AMOC slowdown. That is not just the existence of the subpolar cooling trend in the instrumental SST data. It is the cross-correlation with the South Atlantic performed by Dima and Lohmann. It is the fact that land-based proxy data for surface temperature suggest the cold blob is unprecedented for over a millennium. It is the exceptional SST warming off the North American coast, an expected dynamical effect of an AMOC slowdown, and strong warming off the west coast of southern Africa (see Fig. 1 in my previous post).

In addition we have the conclusion by Kanzow et al. from hydrographic sections that the AMOC has weakened by ~ 10% since the 1950s (see below). And the Nitrogen-15 data of Sherwood et al. indicating a water mass change that matches what is predicted by the CM2.6 model for an AMOC slowdown. And the subsurface Atlantic temperature proxy data published recently by Thornalley et al. Plus there is work suggesting a weakening open-ocean convection. And finally, our time evolution of the AMOC that we proposed based on our AMOC index, i.e. based on the temperatures in the cold blob region, for the past decades matches evidence from ocean reanalysis and the RAPID project. Some of these other data are shown together with our AMOC index below (for more discussion of this, see my previous post).

Fig. 3 Time evolution of the Atlantic overturning circulation reconstructed from different data types since 1700. The scales on the left and right indicate the units of the different data types. The lighter blue curve was shifted to the right by 12 years since Thornalley found the best correlation with temperature with this lag. Our index is the dark blue line starting in 1870. Graph: Levke Caesar.

Do measurements contradict our reconstruction?

Measuring the AMOC at a particular latitude in principle requires measuring a cross-section across the entire Atlantic, from surface to bottom. There are only two data sets that aspire to measure AMOC changes in this way. First, the RAPID project which has deployed 226 moored measuring instruments at 26.5 ° North for that purpose since 2004. It shows a downward trend since then, which closely matches what we find with our temperature-based AMOC index. Second is the work by Kanzow et al. (2010) using results of five research expeditions across the Atlantic between 1957 and 2004, correcting an earlier paper by Bryden et al. for seasonal effects and finding a roughly 10% decline over this period (in terms of the linear trend of these five data points).

Some other measurements cover parts of the overturning circulation, and generally for short periods only. For 1994-2013, Rossby et al. (2013) – at the Oleander line between 32° and 40° North – found a decrease in the upper 2000m transport of the Gulf Stream by 0.8 Sverdrup (a Sverdrup is a flow of a million cubic meters per second). It is important to realize that the AMOC is not the same as the Gulf Stream. The latter, as measured by Rossby, has a volume flow of  ~90 Sverdrup, while the AMOC has a volume flow of only 15-20 Sverdrup. While the upper northward branch of the AMOC does flow via the Gulf Stream, it thus only contributes about one fifth to the Gulf Stream flow. Any change in Gulf Stream strength could thus be due to a change in the other 80% of Gulf Stream flow, which are wind-driven. The AMOC does however provide the major northward heat transport which affects the northern Atlantic climate, because its return flow is cold and deep. Most of the Gulf Stream flow, in contrast, returns toward the south near the sea surface at a similar temperature as it flowed north, thus leaving little heat behind in the north.

Likewise for 1994-2013, Roessler et al. (2015) found an increase of 1.6 Sv in the transport of the North Atlantic Current between 47° and 53° North. This is a current with a mean transport of ~27 Sverdrup, 60% of which is subtropical waters (i.e., stemming from the south via the Gulf Stream). For this period, our reconstruction yields an AMOC increase by 1.3 Sv.

For 1994-2009, using sea-level data, Willis et al. (2010) reconstructed an increase in the upper AMOC limb at 41°N by 2.8 Sv. For this period, our reconstruction yields an AMOC increase by 2.1 Sv.

Finally, the MOVE project measures the deep southward flow at 15° North. This is a flow of ~20 Sverdrup which can be considered the sum of the north Atlantic overturning circulation plus a small component of returning Antarctic Bottom Water (see Fig. 1 in Send et al. 2011). The following graph shows all these measurements together with our own AMOC index (Caesar et al 2018).

Fig 4. Our AMOC index in black, compared to five different measurement series related more or less strongly to the AMOC. The dashed and dotted linear trends of our index can be directly compared to the linear trends over corresponding data intervals. The solid black line shows our standard smoothed index as shown in our paper and in Fig. 3. Graph by Levke Caesar.

First of all, it is clear that these data contain a lot of year-to-year variability – which doesn’t correlate between the different measurements and for our purposes is just ‘noise’ and not a climate signal. That is why for our index we generally only consider the long-term (multidecadal) changes in SST to reflect changes in the AMOC. Thus, we need to look at the trend lines in Fig. 4.

Given that even these trends cover short periods of noisy data sets and thus are sensitive to the exact start and end years, and that lags between the various parts of the system may be expected, all these trends are surprisingly consistent! At least I don’t see any significant differences or inconsistencies between these various trends. Generally, the earlier trends in the left part of the graph are upward and the later trends going up to the present are downward. That is fully consistent with our reconstruction showing a low around 1990, an AMOC increase up the early 2000s and then a decline up to the present (compare Fig. 3).

Claims that any of these measurements are at odds with our index or even disprove the long-term AMOC decline are thus baseless (and thus rightly fit into Breitbart News where they were raised by the notorious James Delingpole).

One interesting question for further research is how the AMOC in the Atlantic is linked to the exchange with the Nordic Seas across a line between Greenland, Iceland and Scotland. In our 2015 paper we showed a model result suggesting an anti-correlation of these overflows with the AMOC, and our new paper suggests a similar thing: a warm anomaly off Norway coinciding with the cold anomaly in the subpolar Atlantic, both in the high-resolution CM2.6 model and the observations.

So, while there is obviously the need to understand the ocean circulation changes in the North Atlantic in more detail, I personally have no more doubts that the conspicuous ‘cold blob’ in the subpolar Atlantic is indeed due to a long-term decline of the northward heat transport by the AMOC. If you still have doubts, we’d love to hear your arguments!

221 Responses to “If you doubt that the AMOC has weakened, read this”

  1. 201
    Victor says:

    196 & 197. More bluff and bluster from MA Rodger. I guess he’s hoping his many insults will distract from the weakness of his arguments.

    MA: The line your moron-of-an-expert provides is drawn in simply to connect his cherry-picked top-&-bottom ones. It has no evidential basis.

    V: The lines are there to emphasize the difference between the three periods in question (ca 1957 through ca. 1975; ca. 1975 through ca. 1999; ca. 1999 through ca. 2015). The first reveals no correlation, the second reveals a strong correlation, the third reveals no correlation. The differences are obvious even without Wolfe’s guidelines, but Rodger prefers to ignore them, assuming for some odd reason that what one can observe with one’s own eyes doesn’t really count as science.

    The line he’s drawn is a perfect example of misdirection, a crude attempt to obscure meaningful evidence by distracting our attention away from it. Science is about working with the evidence at hand, not obscuring it.

    MA: Here is how the graphic you say “makes no sense” fits the monthly data mis-used by Wolfe, it now being updated to show both data sets (usually 2 clicks to ‘download your attachment). Assuming I catch you with your sensible head on and have not been out halucinating with those gobby Leprechauns, does it all make sense now?

    V: Ok, thanks. Remarkable. I can now see more clearly how effectively the lines you’ve drawn distract from the pattern produced by the actual data. Maybe Leprechauns exist after all.

  2. 202

    In a perfect world, Victor would be able to learn what “correlation” actually means and wouldn’t keep using his own private definition for the word.

  3. 203
    Ray Ladbury says:

    Weaktor: “According to at least one authority on this matter (Ole Humlum)…”

    Bwaaaaahaaaahaaaaaa. Oh, dude. Stop. You’re killin’ me…

    Weaktor, when you gonna take this performance art piece on the road?

  4. 204

    So, Victor, still awaiting your expert opinion on whether these two time series are correlated or not?

    http://i1108.photobucket.com/albums/h402/brassdoc/Mystery%20quantities.png

  5. 205

    Victor–Correlated? Or no?

    http://i1108.photobucket.com/albums/h402/brassdoc/Mystery%20quantities.png

    (Not sure the original post went through, or whether the link made it in.)

  6. 206
    Victor says:

    205 Kevin McKinney says:

    “Victor–Correlated? Or no?”

    You’re trying to trick me, so it’s hard to take your challenge seriously. In any case, I see no reason to make a decision one way or the other. If the lines are correlated, it certainly isn’t obvious. The lack of correlation between global temperatures and CO2 levels IS obvious, however. How would YOU go about evaluating that graph?

  7. 207
    Victor says:

    203 Ray Ladbury says:

    “Weaktor: “According to at least one authority on this matter (Ole Humlum)…”

    Bwaaaaahaaaahaaaaaa. Oh, dude. Stop. You’re killin’ me…”

    Interesting. That’s my reaction to most of YOUR posts, Ray.

  8. 208
    nigelj says:

    Victor @199, you almost summed it up yourself. There are excellent explanations for all the various “pauses” in the longer term temperature records. You scream “greenhouse effect wrong” or the like ever so eagerly, the rest of us think maybe there are other explanations, lets not be stupid and jump to conclusions, and there are other excellent explanations.

    You don’t trash a compelling theory like the greenhose effect too easily. Remeber all that hysteria when some particle accelerator had discovered faster than light speed? Oh dear Einstein was wrong. It turned out to be a short circuit.

    You claimed the scatterplot diagram you posted from WUWT shows no correlation. Although its a distorted, useless piece of work as people have pointed out it actually still shows a correlation. I suggest you swot up on scatterplots as below, because right now you simply dont understand the issue. They exist on a scale, as opposed to being a correlation or not a correlation, and you look at all the data, not some cherry picked short period. You exist in a world of your own on correlations allright, thats an understatement.

    http://mste.illinois.edu/courses/ci330ms/youtsey/scatterinfo.html

  9. 209
    Ray Ladbury says:

    Why thank you, Weaktor. I try to keep my insults of you entertaining. Frankly, from your blather on here, I would have guessed you aren’t intelligent enough to even perceive and intelligent insult, let alone appreciate one.

    I would have thought that The Stooges were more your speed.

  10. 210

    Victor, #206–

    “How would YOU go about evaluating that graph?”

    I’d do the statistics. But I’m not the one who claims a magic eye that can better assess correlations than the mathematics can.

    However, I find your response that “If the lines are correlated, it certainly isn’t obvious,” interesting, since my eye–FWIW–does find an obvious (if imperfect) correlation.

    It suggests to me that your criteria for visual ‘correlation’ allow for very little divergence between data sets, and hence are not very useful in teasing the factors of a complex system in which there are multiple inputs and causation loops, such as the climate system.

    (As an aside, I think that ‘trickery’ is a very interesting framing of my question–and not a phrasing that would have occurred to me. “Testing,” maybe, but not “tricking”.)

    The quantities? CO2 and temperature, early 20th century. I was curious to see whether a graph that highlighted the period previously under discussion, and aligned over the period in question, would appear to you to be more closely correlated, particularly when anonymised.

    http://i1108.photobucket.com/albums/h402/brassdoc/Mystery%20quantities.png

    As I say, my eye does see a correlation, though clearly not one accounting for all the variance. Why that huge divergence at the beginning of the period, for example? Clearly there are other factors involved.

    And I’ll readily admit that I didn’t really baseline the curves properly, as described in the recent ‘models v. obs’ thread just posted; it’s possible that if I had, the divergence there would have been less, and that it would consequently have been greater somewhere else.

    (On the other hand, what I did do was to best align the curves visually when deriving the display offset value, which is actually analogous to the proper method in the sense that the visual adjustment operates over the entire 40-year span of the data–and is moreover *thoroughly* analogous to eyeballing a curve for correlation.)

  11. 211
    MA Rodger says:

    So let’s make Victor the Troll yet again look ridiculously stupid.

    Voctor the Troll @201,
    You say of me:-

    “The line he’s drawn is a perfect example of misdirection, a crude attempt to obscure meaningful evidence by distracting our attention away from it. Science is about working with the evidence at hand, not obscuring it.”

    So Victor, would you care to explain why you call me a bare-face liar? Is it just some part of your trolling method. Or is there a “line” that I have graphed somewhere that you actually feel are misplaced?
    (A note that I have corrected a minor ‘misplacement’ in that the moron Wolfe used data to May 2014, not May 2015 as originally poltted on the ‘single-pannel’ CO2-v-Temp graphic.)
    Further, and perhaps more specifically, you tell me that “the lines” I’ve drawn (and I assume these said “lines” are on this graphic [usually 2 clicks to download]) “distract from the pattern produced by the actual data.” As every jot-&-tittle on that graph is derived numerically from the data, this is very hard to accept as being anything more than your anti-AGW leprechaun-blather. Perhaps asking you to describe which particular “lines” you object-to is a small ask and within your limited abilities, this assuming you are happy to take a break from your trolling. Asking you for the basis of your objection may be asking too much of your limited intellect but please feel free to contribute your angle to the discussion, for once.

    And this leads to a little compare-&-contrast. You object loudly to my wholly-numerically-derived graphic but then wax lyrical over the gobshite-graphic presented by the wonderous Wolfe of Wattsupia. Let us examine the work of the wonderous Wolfe.

    You tell us of Wolfe’s graph “The lines are there to emphasize the difference between the three periods in question (ca 1957 through ca. 1975; ca. 1975 through ca. 1999; ca. 1999 through ca. 2015).” So let us examine the lines presented.
    The data covers the period 3/58 to 5/14. That is 56 years 2 months which matches the tally of time set out by the moron Wolfe – 18yrs+21yrs+17yrs= 56 years. But the lines he provides dividng these three periods are set at 337.55ppm and 373.20ppm. By maintaining the annual cycle in his data moron Wolfe introduces some ambiguity (+/-1yr) but they are best placed at 8/1979 and 7/2002 making his tally 21yr+23yr+12yrs = 56 years.
    Now moron Wolfe does manage to carry out one OLS regression on the most-recent of his three periods and that he chose to begin on 4/2001, so almost within his fudge zone. He makes a botch of presenting the results (beyond the typo-missing 0) by using the variance of the trend instead of the trend itself.
    Worse still, his central period trend is plotted 50% steeper than reality and the early period he shows flat does have statistically significant trend, lower than the long term (about a thrid the value) but certainly it is not flat.
    So of the five lines drawn by moron Wolfe, one is cherry-picked and the other four are plainly bogus. But then Wolfe is not the proper-world “real statistician” that Victor insists. Wolfe comes from that realm of fakism Whattsupia so bogus fakism is pretty-much par for the course.

  12. 212
    Simon F says:

    Hello,
    Thank you very much for this summary.
    I understand that the AMOC decline is uncovered after multi-decadal filtering only and this proves that so many real-time/short-term maps and graphs, including RAPID data, highlight a signal which is mostly the variability of the ocean state and not the AMOC decline.
    To me, the term “cold blob” is not useful anymore now everything makes sense. There is a “visible” short-term cold mode (RAPID data and mainstream sea temperature charts) adding to the “invisible” AMOC decline, both being collocated. What we are seeing now is the cold mode, what deserves to be monitored for decades is the AMOC decline.

  13. 213
    Victor says:

    208
    nigelj says: Victor @199, you almost summed it up yourself. There are excellent explanations for all the various “pauses” in the longer term temperature records. You scream “greenhouse effect wrong” or the like ever so eagerly, the rest of us think maybe there are other explanations, lets not be stupid and jump to conclusions, and there are other excellent explanations.

    V: It’s always possible to cook up some explanation or other when the evidence fails to support your pet theory. But when the evidence DOES support your theory, do you then look just as carefully to find reasons why you could be wrong? The tendency to cast about for anything and everything that might support a weak hypothesis while at the same time ignoring anything that might further weaken it is called confirmation bias. And this is what I see over and over again in the climate science literature. The industrial aerosol theory is a perfect example. The cooling effect of such aerosols is well known, but when you apply it ONLY where it helps your theory and ignore the evidence (e.g., from Asia) that contradicts it, that is confirmation bias, sorry.

    Moreover, as I’ve argued many times, an attempt to explain the absence of crucial evidence, no matter how reasonable it might seem, is NOT the same as producing such evidence. One can’t, for example, claim a “long-term” warming trend over 120 years due to CO2 emissions, when we see little to no evidence of CO2 induced warming for the first 80 years of that period. Regardless of how one might want to explain it, the evidence is STILL not there, and science is based on evidence, not reasons for lack of same.

    nj: You don’t trash a compelling theory like the greenhose effect too easily. Remeber all that hysteria when some particle accelerator had discovered faster than light speed? Oh dear Einstein was wrong. It turned out to be a short circuit.

    V: The evidence for relativity is overwhelming, so the discovery of a single alleged exception must be taken with a huge grain of salt. The evidence for AGW, on the other hand, is dubious at best, and in many cases simply not there. HUGE difference.

    nj: You claimed the scatterplot diagram you posted from WUWT shows no correlation.

    V: No. The scatterplot reveals that only one 20 year period out of 58 shows evidence of correlation.

    nj: Although its a distorted, useless piece of work as people have pointed out it actually still shows a correlation. I suggest you swot up on scatterplots as below, because right now you simply dont understand the issue. They exist on a scale, as opposed to being a correlation or not a correlation, and you look at all the data, not some cherry picked short period. You exist in a world of your own on correlations allright, thats an understatement.

    V: Real science, as opposed to pseudoscience, is not based on black box outcomes derived from simple minded formulas, but the careful analysis and evaluation of all the evidence based on critical thinking, a skill rarely demonstrated on this blog.

  14. 214
  15. 215
    Hank Roberts says:

    Victor says:
    22 Jun 2018 at 10:30 PM

    … How would YOU go about evaluating that graph?

    There’s your problem. Assuming the ol’ Mark One Eyeball is the right tool and the picture/graph is the correct thing to evaluate.

    Wrong. Where are the numbers that were used to create the graph?
    How many, at what intervals, and how much variability in the collection?
    Then you do the basic statistical arithmetic.

    But you’ve been told this before, more than once. And you just don’t learn.

  16. 216

    V 206: The lack of correlation between global temperatures and CO2 levels IS obvious

    BPL: Only in your delusional worldview, where you use your own definition of “correlation” and ignore the actual definition. I’ve been over this with you more times than I can count and you stubbornly refuse to learn. You’re like a creationist who keeps repeating that evolution is “only a theory” even after ten people have explained what “theory” really means.

  17. 217
    Hank Roberts says:

    https://www.washingtonpost.com/news/energy-environment/wp/2018/06/26/a-huge-stretch-of-the-arctic-ocean-is-turning-into-the-atlantic-right-before-our-eyes/

    Scientists studying one of the fastest-warming regions of the global ocean say changes in this region are so sudden and vast that in effect, it will soon be another limb of the Atlantic Ocean, rather than a characteristically icy Arctic sea.

    The northern Barents Sea, to the north of Scandinavia and east of the remote archipelago of Svalbard, has warmed extremely rapidly — by 2.7 degrees Fahrenheit just since the year 2000 — standing out even in the fastest-warming part of the globe, the Arctic.

    “We call it the Arctic warming hot spot,” said Sigrid Lind, a researcher at the Institute of Marine Research in Tromso, Norway.

    Now Lind and her colleagues have shown, based on temperature and salinity measurements taken on summer research cruises, that this warming is being accompanied by a stark change of character, as the Atlantic is in effect taking over the region and converting it into a very different entity.

    Their results were published this week in Nature Climate Change by Lind and two colleagues at Norway’s Institute of Marine Research and University of Bergen. They underscore that the divide between the Atlantic and the Arctic isn’t just a geographical one — it’s physical in nature.

  18. 218
    nigelj says:

    Victor @213

    “But when the evidence DOES support your theory, do you then look just as carefully to find reasons why you could be wrong? ”

    If the evidence totally supports a theory, there is little to be gained by constantly reexamining the theory. Should we reexamine whether the earth is flat or round?

    If the evidence seems to support a theory reasonably well, or we are 95% sure, then obviously you always keep an open mind, and look for reasons to falsify a theory. All scientists are trained to do this. They only come down on the side of agw, because they have tried to demolish agw and cannot find a flaw in the basic theory!

    I first looked at this climate change issue about 25 years ago, and I had the same sceptical doubts as you on much the same issues. I looked hard at both sides of the debate and came down on the side of agw. My critical thinking skills are just fine.The IPCC has done the same and they are more qualified than both of us.

    Obviously I still keep an open mind on the issue, but it looks very unlikely now that agw would ever be fasified, and temperature predictions look ominously accurate. If you cannot see the strong warming trend in the temperature data since 1980 and also the correlation with CO2 you have a basic problem with visual perception or visual graph analysis. The maths also shows both a strong warming trend and a correlation.

    You also need to appreciate its normal to look for evidence that supports a theory, or provides explanations for things like pauses, and this is not confirmation bias – provided you also have a good look at evidence that could ‘falsify’ the theory and sceptical evidence. Its really about looking very objectively at all the evidence, at both sides of debates, which is what I do. It also means you have to look at all the research related to a specific issue and not just papers that you “like” and then weight it up carefully.

    “Aerosols”

    Several people have explained to you why your understanding of asia and aerosols is totally flawed. I can’t help it if you can’t grasp it.

    “One can’t, for example, claim a “long-term” warming trend over 120 years due to CO2 emissions”

    Nobody has claimed the warming trend since 1900 is ‘entirely’ CO2 emissions. Just that it mostly is.

    “The evidence for AGW, on the other hand, is dubious at best, and in many cases simply not there”

    No it isn’t dubious. The evidence is overwhelming. I have already given you several references to greenhouse fingerprints so you are being disingenuous. There are more than 10 separate lines of evidence pointing at AGW :

    https://www.skepticalscience.com/10-Indicators-of-a-Human-Fingerprint-on-Climate-Change.html

    “Real science, as opposed to pseudoscience, is not based on black box outcomes derived from simple minded formulas, but the careful analysis and evaluation of all the evidence based on critical thinking, a skill rarely demonstrated on this blog.”

    There’s no such thing as “simple minded formulas” and science is by its very nature based on formulas. The IPCC looks hard at all the evidence, including sceptical leaning research papers. So their critical thinking skills are just fine. Its you who have poor critical thinking skills, I could speculate on why but I won’t.

  19. 219
    Victor says:

    218 nigelj: If the evidence totally supports a theory, there is little to be gained by constantly reexamining the theory. Should we reexamine whether the earth is flat or round?

    V: OMG, what incredible arrogance! I’ve seen AGW compared with Newton’s laws of motion, Darwinian evolution, gravity and God knows what else. So why not go all out and compare it with our certainty that the Earth isn’t flat? Which would make any doubters comparable to flat-earthers I suppose. My oh my, where is this unprecedented self-confidence coming from? Even Darwin had some doubts.

    You’ve got a whole raft of experienced, highly accomplished scientists from many fields, including physics and, yes, climate science, challenging your many assumptions, on the basis of the FACT that they are either wrong or unproven. But in your colossal arrogance you insist that you cannot possibly be wrong. And then get really upset and emotional when so many rational people refuse to buy it. Get a shrink!

  20. 220

    V 219: Even Darwin had some doubts.

    BPL: Not about evolution having taken place. About whether his theory of it covered all the details.

  21. 221
    nigelj says:

    Victor @219, I didn’t say agw climate change was as certain as the earth is round.

    The clue was in the second paragraph where I obviously meant agw climate science: “If the evidence seems to support a theory reasonably well, or we are “95%” sure, then obviously you always keep an open mind,……”

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