RealClimate logo


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. 151
    Carrie says:

    143 MA Rodger, I don’t come here to read what Victor thinks and says. I also do not come here to read what you Rodger think about Victor and the rest of the denier camp. Both kinds of comments are waste of everyone’s time including your own. Please go be a Troll somewhere else.

  2. 152
    nigelj says:

    Victor says about his borehole comements “It’s not intended to be taken literally, of course”

    Does that apply to all the other comments? And literally or not, you are still wrong.

  3. 153

    Victor, #139–

    Still dying to know what you think of the correlation (or absence thereof) in these ‘mystery quantities’:

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

    They look correlated to me, but clearly YMMV.

    And a day-old Cinnabon to anyone correctly guessing the identity of the quantities–you pay only S & H!

  4. 154
    Radge Havers says:

    @ ~ 146

    I just went over to that site and found what looks like a graphic arts crime scene.

    If you want to put up a useful and informative website and are unsure about how to design it, go back to fundamentals and examine how Real Climate is put together.

    IMO.

  5. 155
    Victor says:

    147 nigelj: “Aerosols in the middle of last century are not as Victor claims some “complicating factor”. They HAPPENED, and so have to be evaluated scientifically. We have extremely good evidence aerosols like this cause a temporary cooling effect. Victors commentary is worse than useless.”

    The aerosol story is not simply a “complicating factor” but a crude attempt to “burden a failing explanation with an ad hoc hypothesis,” in the language of the Occam’s Razor discussion I quoted above.

    From my blog:

    “The abrupt and rather steep rise in global temperatures from ca. 1979 through 1998 (see the NASA graph above) has typically been attributed to the imposition of pollution control laws in the United States and Europe a decade or so prior. In the lessening of sulfate aerosol emissions from that time on, the “lid” was removed, and, as far as the climate orthodoxy is concerned, the warming effects of CO2 emissions were unleashed without any significant constraints. However, the situation was very different in Asia, where pollution controls were not widely implemented during this same period, aerosol levels continued to rise at the same rate as before, and yet temperatures also soared, in tandem with temperature rises worldwide. Since pollution-based aerosols, unlike CO2 molecules, are short-lived and localized, it’s very hard to see how the same cooling effect claimed for them during the 40 year “hiatus” we’ve been examining would not also have cooled Chinese temperatures during the last 20 years of the previous century, just as they had cooled worldwide temperatures during the earlier period.”

    The evidence on aerosol emissions can be found in an article I was first made aware of by MA Rodger (thanks Mr. R) titled, simply enough, “Air Pollution,” by Hannah Ritchie and Max Roser (https://ourworldindata.org/air-pollution). If you scroll down a bit you’ll find a chart titled “SO2 emissions by world region.” As is evident from this chart, SO2 emissions from the Americas and Europe peaked around 1979, but the graph for Asia is totally different, as it shows a continual rise in SO2 emissions beginning in the 1940’s and persisting till the graph’s upper limit, 2010.

    If SO2 aerosols indeed have a cooling effect strong enough to counter the greenhouse warming alleged for CO2 during the years 1940-1979, then we would expect the growing volume of such aerosols in Asia to continue the same cooling trend well into the late 20th and early 21st centuries. Is that in fact the case? Here’s a graph (https://ars.els-cdn.com/content/image/1-s2.0-S1674927810500029-gr1.jpg) from a paper titled Comparative Analysis of China Surface Air Temperature Series for the Past 100 Years, by Guoli Tang et al (https://www.sciencedirect.com/science/article/pii/S1674927810500029). It is labeled Figure 1 and depicts temperature anomalies for 5 different data sets measuring Chinese surface air temperatures. What we see looks very similar to the worldwide data that’s been so widely disseminated, with the same steep rise in temperatures from the late 70’s to the late 90’s. Clearly, temperatures in China have not abated due to the increasingly high levels of SO2 pollution produced by their many coal burning plants during this entire period.

    Real scientists examine ALL relevant data, not just data that suits their purpose. This is a pattern we see time and again in the climate “science” literature.

  6. 156
    Mal Adapted says:

    Carrie:

    143 MA Rodger, I don’t come here to read what Victor thinks and says. I also do not come here to read what you Rodger think about Victor and the rest of the denier camp. Both kinds of comments are waste of everyone’s time including your own. Please go be a Troll somewhere else.

    Heh. Welcome to RC, Carrie. People come here for lots of reasons. One is to ‘engage freely and robustly’ (albeit virtually) with the AGW-deniers who, thankfully, are a distinct minority of regular commenters. Why do you come here, other than to scold us ;^)?

    Few if any of RC’s regular evidence-based commenters come to learn what others of us think of the AGW-deniers, because we mostly think the same of them already. Victor, OTOH, like a handful of other tenacious deniers, is either here deliberately to obfuscate the scientific case for AGW, or else is severely afflicted by both the Dunning-Kruger effect and the compulsion to exhibit it.

    Victor’s ultimate motives are unknown, probably even to him: yet somehow he sees fit to waste RC readers’ time with popular denialist nonsense, much of it undead despite decisive refutation long since by a lopsided consensus of genuine experts. The bulk of what Victor says is obviously ludicrous to anyone who took high school Algebra, but some scientifically-naive lurkers who stumble in here may find a rare comment of his speciously persuasive. Lurkers’ naiveté may extend to the ‘free and robust’ style of engagement in response, which may elicit the lurker’s rejection of the response’s logical content. The more open-minded of them will recognize that scientific culture diverges from popular culture in salient ways. In particular, it’s considered rude to pretend one knoweth whereof one speaketh, when one truly hath not a clue. Equally rude responses can be expected from the clueful.

    You, of course, are similarly unconstrained to respond to any response that offends you. I, for one, wouldn’t virtually silence you even if I could. Of course I can’t, as that’s up to RC’s moderators. I don’t even know where you live ;^D!

  7. 157
    CCHolley says:

    If anyone here has a better proposal to satisfy the demand for radical changes to world civilization that we need to implement RIGHT NOW, in order to forestall total disaster, by all means post it.

    An economy stimulating revenue neutral carbon fee and dividend plan would be a good start.

    https://citizensclimatelobby.org/carbon-fee-and-dividend/

  8. 158
  9. 159
    Hank Roberts says:

    From the CCNF thread: http://climatechangenationalforum.org/ocean-circulation-climate-change-and-arctic-sea-ice-3/

    … the observed decline, shown as the red line in the below figure, is much larger than that predicted by the models. At a recent meeting of oceanographers in Bristol, UK, scientists were wondering what could cause this discrepancy….

    … there appeared to be a consensus building amongst the oceanographers at the Bristol meeting that the recent downturn of the AMOC may be mostly part of a natural variation. Models and reconstructions seem to agree that the AMOC has substantial natural variability on decadal (10-100 years) time scales. In fact some scientists think they can predict that the downturn in the recent past will continue at least 1 or 2 more years and that this could cause a pause, or “hiatus”, in the ongoing Arctic sea ice decline, or even a slight increase. The reason for this is that as the AMOC reduces, there is less heat flushing into the Arctic and thus sea ice can expand.

    We’ll see if these predictions will come to pass. If so, it would indicate important progress in near term climate predictability.

    Cheers from Bristol.

    Andreas

    [Response: I agree that the most recent decline (i.e. over the past 10-15 years) is probably largely part of an oscillation – it is much steeper than the long-term trend which we attribute to global warming. Regarding sea ice, note that we have discussed the anticorreation between AMOC and heat transport into the Arctic, i.e. weaker AMOC -> warmer Arctic Ocean. The mechanism for this anticorrelation has been discussed in the Jungclaus paper which I linked somewhere in the comments. -Stefan]

  10. 160
    MA Rodger says:

    And on he goes with his non-AMOC blather. Presented @153 from the Victor the Troll’s wonderous blog no less:-

    “The abrupt and rather steep rise in global temperatures from ca. 1979 through 1998 (see the NASA graph above) has typically been attributed to the imposition of pollution control laws in the United States and Europe a decade or so prior. In the lessening of sulfate aerosol emissions from that time on, the “lid” was removed, and, as far as the climate orthodoxy is concerned, the warming effects of CO2 emissions were unleashed without any significant constraints. However, the situation was very different in Asia, where pollution controls were not widely implemented during this same period, aerosol levels continued to rise at the same rate as before, and yet temperatures also soared, in tandem with temperature rises worldwide. Since pollution-based aerosols, unlike CO2 molecules, are short-lived and localized, it’s very hard to see how the same cooling effect claimed for them during the 40 year “hiatus” we’ve been examining would not also have cooled Chinese temperatures during the last 20 years of the previous century, just as they had cooled worldwide temperatures during the earlier period.”

    So how much of this is purile gobshite? I’d say pretty-much all of it.

    The global temperature rise in the latter part of the 20th century (which continued into the 21st century, indeed continues to this day) has nowhere ” typically been attributed to … the lessening of sulfate aerosol emissions from that time on.” It is ” typically … attributed to” increasing AGW forcing which pretty-much trebles at the point we see increased temperatures. As the warming of AGW is a global phenomenon, Victor’s purile argument could be used to suggest that continued increasing SO2 levels regional to China may be evident in a rate of warming in China (or parts thereof), a rate below that of regions with falling SO2 levels. Yet Victor, ever the inumerate fool, argues not for a selective reduction of warming but for “cooled Chinese temperatures during the last 20 years of the (20th) century.” Victor’s silly AGW-refuting argument would have a little more credence if he was mindful of China being a big place and pollution no respecter of it borders. Yet there is one place where Victor’s “cooled Chinese temperatures during the last 20 years of the (20th) century” has some evidential basis. But then Victor probably doesn’t want to hear that his strawman is not so easily felled.

  11. 161
    CCHolley says:

    If anyone here has a better proposal to satisfy the demand for radical changes to world civilization that we need to implement RIGHT NOW, in order to forestall total disaster, by all means post it.

    A revenue neutral, economic stimulating, carbon fee and dividend plan is a good start.

    https://citizensclimatelobby.org/basics-carbon-fee-dividend/

  12. 162
    Nemesis says:

    @Carrie

    I agree with you that it’s futile to discuss with deniers for many reasons. But it’s just as useless to try to convince some people (who want to have a discussion with deniers) that it’s futile to discuss with deniers. Deniers want to discuss things (for whatever reasons) and they will always find someone who likes to try to convince these deniers. And you know what? Sometimes I can’t resist and start a discussion with a denier. And you know what? I even accomplished to convince some deniers. The most important person I managed to convince some years ago was my nephew. It took some months of hard work, but finally he woke up and realized anthropogenic climate heating is real. And I convinced some real hardcore deniers on youtube also. So, I contravened against my very own principle (no discussions with deniers anymore) at times and were even successful :D But I’m sure there are some professional deniers out there who know very well that AGW is real, but they have an agenda, they try to confuse discussions, they want to create discordia. There’s surely no chance to convince these kind of professional deniers, it’s absolutely futile to try to convince these kind of professional deniers.

    After all, it’s easy to simply ignore deniers one doesn’t want to talk to, it takes just a little movement of my mousewheel :)

  13. 163
    Al Bundy says:

    Hank,
    Extrapolating from your comment, it appears that arctic sea ice is in worse shape than the data suggests. My, what a “choice” we have: degradation of ocean life and reduction of CO2 absorption via the slowdown of the AMOC -or- the hastening of Day Zero for arctic sea ice.

  14. 164

    Victor, #153–

    Oh, bosh. (Again.)

    Aerosol forcing have been examined intensively, and continue to be–as in, 2,400+ papers related to that topic published so far *this year*.

    https://scholar.google.com/scholar?as_ylo=2018&q=aerosol+forcing+data&hl=en&as_sdt=0,34

  15. 165
    Victor says:

    157 MA Rodger says: “The global temperature rise in the latter part of the 20th century (which continued into the 21st century, indeed continues to this day) has nowhere ” typically been attributed to … the lessening of sulfate aerosol emissions from that time on.” It is ” typically … attributed to” increasing AGW forcing which pretty-much trebles at the point we see increased temperatures.”

    More obfuscation from my favorite RC obfuscator (and biggest fan), the Hapless MA Rodgers. Where, Mr. Rodgers, is your evidence for a trebling of AGW forcing “at the point we see increased temperatures”? Here is a graph, courtesy of NOAA, representing the steady increase in CO2 levels since 1960, when the burning of fossil fuels began to take off in a big way:

    http://assets.climatecentral.org/images/made/5_2_13_news_andrew_keelingcurve_475_367_s_c1_c_c.jpg

    What I see is a steady increase. Nowhere in the entire extent of that diagonal line is there any hint of a sudden leap, twofold, threefold or whatever, occurring in or around the “point we see increased temperatures” (late 1970’s) or anywhere else.

    The standard story we’ve heard over and over again is that the warming effect of CO2 forcings was masked from ca. 1940 – ca. 1979 by industrially produced aerosols, which dissipated significantly after 1979 due to strict pollution controls enacted in the US and Europe. Here’s one example of many that could be cited:

    “The mid-century cooling appears to have been largely due to a high concentration of sulphate aerosols in the atmosphere, emitted by industrial activities and volcanic eruptions. Sulphate aerosols have a cooling effect on the climate because they scatter light from the Sun, reflecting its energy back out into space.

    The rise in sulphate aerosols was largely due to the increase in industrial activities at the end of the second world war. In addition, the large eruption of Mount Agung in 1963 produced aerosols which cooled the lower atmosphere by about 0.5°C, while solar activity levelled off after increasing at the beginning of the century

    The clean air acts introduced in Europe and North America reduced emissions of sulphate aerosols. As levels fell in the atmosphere, their cooling effect was soon outweighed by the warming effect of the steadily rising levels of greenhouse gases.” (https://www.newscientist.com/article/dn11639-climate-myths-the-cooling-after-1940-shows-co2-does-not-cause-warming/)

    So yes, “the global temperature rise in the latter part of the 20th century” HAS indeed “typically been attributed to … the lessening of sulfate aerosol emissions.”

    And yes again (one more time): “Since pollution-based aerosols, unlike CO2 molecules, are short-lived and localized, it’s very hard to see how the same cooling effect claimed for them during the 40 year “hiatus” we’ve been examining would not also have cooled Chinese temperatures during the last 20 years of the previous century, just as they had cooled worldwide temperatures during the earlier period.”

    MA: Yet there is one place where Victor’s “cooled Chinese temperatures during the last 20 years of the (20th) century” has some evidential basis. But then Victor probably doesn’t want to hear that his strawman is not so easily felled.

    V: The paper you cited is limited to one relatively small region of China where temperatures have cooled — in contrast to the rest of China (and all of Asia generally) where temperatures rose dramatically during the last 20 years of the previous century, in tandem with world temperatures generally.

    From the paper he cited:
    “For most of East Asia the value of AT is positive, indicating a warming in recent decades consistent with the general trend observed for northern hemisphere
    temperature. The most striking exception is an area of pronounced cooling over the Sichuan Basin, highly localized and seemingly not related to larger scale temperature change patterns.” MA Rodgers has aptly demonstrated his cherry-picking skills, which are indeed considerable.

  16. 166
    CCHolley says:

    Victor @153

    Real scientists examine ALL relevant data, not just data that suits their purpose. This is a pattern we see time and again in the climate “science” literature.

    Pure baloney. It is Victor that continually ignores relevant data, not climate scientists.

  17. 167
    MA Rodger says:

    Victor the Troll @165,
    Off you go again. ‘Yea but No but Yeah but…’ All off-topic.
    I do appreciate you are a very ignorant and a very stupid person. As daft as they come, which is of course the stuff of common-or-garden AGW denial. Yet you present yourself here with the assertion of some high-&-mighty commentator who supposedly knows what he is talking about.
    You tell us @154 “Real scientists examine ALL relevant data, not just data that suits their purpose. This is a pattern we see time and again in the climate “science” literature,” and so-saying accuse climatology of being ‘non-scientific’.
    But now @165 you ask “Where, Mr. Rodgers, is your evidence for a trebling of AGW forcing “at the point we see increased temperatures”?” Come on, Victor. You are such a dunderhead not to know this.
    It is plastered all through that literature you so dispise. Indeed, you can work it out for yourself as annual CO2 levels are readily available and the calculation is hardily complicated.
    But the first-stop for such data would usually be the IPCC and in AR5 Aii Table 1.2 we find annual CO2 forcing and they yield decadal forcing increases as follows.
    Period ….F(CO2)
    … …. ….increase.
    1900-10 … 0.044
    1910-20 … 0.066
    1920-30 … 0.063
    1930-40 … 0.064
    1940-50 … 0.039
    1950-60 … 0.050
    1960-70 … 0.112
    1970-80 … 0.176
    1980-90 … 0.237
    1990-00 … 0.224
    2000-10 … 0.267
    That pretty-much turns all you say @ 165 into gobshite, excepting the China issue, but in that you just spew nonsense rather than make any sensible or substantive points.

  18. 168
    Hank Roberts says:

    Sigh. Victor comes here to polish his stories so they sound more “sciency” when he peddles them elsewhere.
    Much more along the lines of this and he’ll qualify for an Administration job.

  19. 169
    CCHolley says:

    Victor @165

    Most of the industry in China is on the coast. The rest of China is vast and mostly rural. Plus any cooling effect is fighting a much larger CO2 signal than the previous period.

  20. 170
    Dan says:

    Victor’s “From my blog…”.

    The absolute definition of promoting scientific ignorance. You are unable to admit that you are completely, utterly wrong as has been pointed out numerous times on various specific issues. Classic core insecurity. Textbook in fact.

    How is that explanation of why the stratosphere is cooling going, junior? You were given that homework assignment long ago and of course since you could not answer it because you do not understand the science (without violating the first law of thermodynamics…oh, sorry, look it up) you diverted away from it. Can’t admit to not having a clue, once again, we see. What an embarrassment to any science educator you may have had.

  21. 171
    Arun says:

    https://www.nature.com/articles/d41586-018-04086-4
    Quote:

    Thornalley et al….found that the strength of the AMOC was relatively stable from about ad 400 to 1850, but then weakened around the start of the industrial era. This transition coincides with the end of the Little Ice Age — a multicentennial cold spell that affected many regions of the globe10. Thornalley and colleagues infer that the weakening of the AMOC at that time was probably a result of the input of fresh water from the melting of Little Ice Age glaciers and sea ice. They estimate that the AMOC declined in strength by about 15% during the industrial era, relative to its flow in the preceding 1,500 years.

    However, the roughly 100-year difference in the proposed timing of the start of the AMOC decline in these two studies has big implications for the inferred trigger of the slowdown. Caesar et al. clearly put the onus on anthropogenic forcing, whereas Thornalley et al. suggest that an earlier decline in response to natural climate variability was perhaps sustained or enhanced through further ice melting associated with anthropogenic global warming. Nevertheless, the main culprit in both scenarios is surface-water freshening.

    End quote.

    Any thoughts on that?

  22. 172
    Hank Roberts says:

    Those who want to deny the reality of global warming will use any excuse to create doubt about our understanding of recent climate change. The mid-20th-century warming pause is one of their favorite excuses, and even when its cause is explained to them they still dispute it. The question is valid: were sulfate aerosols really that much higher during the 20th century than before the industrial revolution? Where’s the data?…

    …sulfates are mostly in the northern hemisphere, that means that there should have been a stronger mid-century cooling effect in the north than in the south — and that’s exactly what we observe ….

    … To the question: were sulfate aerosols really that much higher during the 20th century than before the industrial revolution? The answer is: definitely yes. To the question: did sulfate emissions really level off, even decline, around 1975? The answer is: definitely yes.

    https://tamino.wordpress.com/2010/08/23/antrhopogenic-global-cooling/

  23. 173
    nigelj says:

    Victor @155. MAR has responded so I don’t need to say much. As I said sulphates have a cooling effect. The paper on aerosols in one region of China makes the point that they provably have a cooling effect, added to tons of other evidence. This is what you have to deal with, but refuse to because it doesn’t fit your grand and completely deluded theory.

    I will just try to make the points slightly differently in a historical way which might be simpler. The implementation of pollution controls on sulphate aerosols during the 1970s is not the ‘only’ reason temperatures started increasing at that point. CO2 concentrations had also built up to a level (they accumulate in the atmosphere) until they were sufficient to overwhelm the effects of sulphates. Oil burning which has low sulphates was also increasing.

    So these various factors coincided by chance to influence climate. Once again they HAPPENED, and are not inventions being used to justify anything. Occams razor does not say simplify by ignoring reality. This is whats happened in asia as a whole, so there’s overall warming, but some regional cooling where there’s a lot of coal fired power.

  24. 174
    Victor says:

    143 MA Rodger says:
    And“Yeah-but-No-but” Vic . . . may remember that was also the point when he was provided with a CO2-v-SAT graph (https://sites.google.com/site/housman100resultstemperarypost/home/test-page-for-jpeg-storage/temp14.jpg?attredirects=2 — usually two clicks to ‘download your attachment’), the one he should be waving to demonstrate any lack of correlation, that assuming it supports his bold assertion that there is a ‘lack of correlation’

    V: For some reason my earlier response to this post by MA Rodger seems to have gotten lost, so I’ll give it another try.

    MA, the “correlation” you’ve come up with makes no sense in terms of what we know about the temperature record, which includes roughly 40 years of NO warming while CO2 levels soared. Care to explain?

    As I recall, I posted a scattergram compiled by a real statistician some time ago that DOES make sense in terms of the data. Here it is again, one more time: https://wattsupwiththat.files.wordpress.com/2014/09/clip_image006_thumb2.jpg

    From an article by Danley Wolfe: https://wattsupwiththat.com/2014/09/12/a-look-at-carbon-dioxide-vs-global-temperature/

  25. 175

    #168, Hank–“Much more along the lines of this and [Victor]’ll qualify for an Administration job.”

    OT, but brief: I don’t know about that. While he is already qualified on the denialism front, IMO–sophistication in this doesn’t seem to be required, unless perhaps in confirmation hearings–I see no evidence that his abilities to toady are sufficiently developed actually to survive in the Administration for any length of time.

  26. 176
    Al Bundy says:

    Folks comment here to get the flush of adrenaline that accompanies dissing someone one considers inferior. BPL, Victor, and I, as well as everyone else who regularly comments here have entirely unJesuslike motivations. Personally, I’m still striving to overcome the horrendous abuse that was my childhood. Unfortunately people naturally hate abused children once they turn 18 and isolation isn’t conducive to healing.

    So, Stefan’s excellent and clear post has been dragged through our muck. Shame on us.

    And I’m still wondering about the Southern Ocean’s CO2 uptake as compared to the AMOC. My searches so far seem to say that there’s little data available. My feel is that the AMOC’s reduction in CO2 uptake is an accurate microcosm for the entire system. (Feel free to show your superiority to an abused child by dismissing my thoughts)

  27. 177
    nigelj says:

    Al Bundy @173

    Regarding climate denialism and whether to respond to these people, theres a well known very old quotation “For evil to flourish, it only requires good men to do nothing”

  28. 178
    Victor says:

    172 Hank Roberts says (quoting Tamino):

    “…sulfates are mostly in the northern hemisphere, that means that there should have been a stronger mid-century cooling effect in the north than in the south — and that’s exactly what we observe …”

    Sorry, Charlie — but that is NOT what we observe:

    https://www.nasa.gov/images/content/418334main_hemi-temp-full.jpg

    Note the precipitous dip in global temperatures from 1940 through 1950, with the south cooling at roughly the same rate as the north. Given the difference in sulfate emission between those two hemispheres, as Tamino reminds us, there must have been some other reason than cooling due to industrial aerosols. Tamino has in fact provided us with a very effective argument against the aerosol hypothesis he wants us to accept. As for the rest of the period in question, there is only one stretch where the two datasets move in opposite directions: from around 1970 to 1980. In all other cases they move, more or less, in the same direction.

  29. 179
    Hank Roberts says:

    >Victor … scattergram … WTF …. real statistician

    Real statisticians don’t publish their work at WTF, Victor.

    You’re confusing yourself again. But thanks for making clear which barrel you’re scraping from.

  30. 180
    MA Rodger says:

    Yeah-but-No-but-Yeah-but @174,
    I see you continue you purile off-topic nonsense, now with a return to the Wattsuppian blather of Danley Wolfe who you describe as “a real statistician.” If he is such, he sould know better than manufacture such gobshite graphics.
    Victor, you have more-than-once trolled this Danley Wolfe here in times gone-by. The response remains as damning today as it ever was. So I will simply repeat the reply I made the last time you paraded this gobshite here:-

    “We have been here before with that gobshite you serve up, both with the cretin that devised it as well as later with you. Here is the rebuttal provided back then (usually 2 clicks to ‘download your attachment’). Nothing has changed since.”

  31. 181
    Mal Adapted says:

    @Stefan, inline to Hank Roberts: may we conclude you implicitly approve Dr. Schmittner’s very clear, concise narrative of the mechanics of global ocean circulation? Paraphrasing somebody or other, it’s as simple as it can be and no simpler. With such a straight logical path to follow, it ought to be hard for AGW-deniers to argue with projections of a slowing AMOC, with its probable consequences for Europe’s people. We fully expect Victor’s ilk to give it the old middle-school try, though ;^D.

  32. 182
    Victor says:

    170 Dan “How is that explanation of why the stratosphere is cooling going, junior? You were given that homework assignment long ago and of course since you could not answer it because you do not understand the science (without violating the first law of thermodynamics…oh, sorry, look it up) you diverted away from it. Can’t admit to not having a clue, once again, we see. What an embarrassment to any science educator you may have had.”

    The embarrassment is all yours, Dan. I responded some time ago but you seem to have missed it. Once again:

    4. The temperature variations recorded in the lowermost troposphere are generally reflected at higher altitudes also, and the overall temperature ‘pause’ since about year 2002 is recorded at all altitudes, including the tropopause and into the stratosphere above. In the stratosphere, however, the temperature pause had already begun by around 1995; that is, 5–7 years before a similar temperature pause began in the lower troposphere near the planet’s surface. The stratospheric temperature pause has now existed without interruption for about 23 years, with no explanation offered by the climatological community. From https://www.thegwpf.org/content/uploads/2018/03/State-of-the-Climate2017.pdf

    To make it real easy for you, see the graph displayed here:
    http://www.theclimateconsensus.com/content/satellite-data-show-a-cooling-trend-in-the-upper-atmosphere-so-much-for-global-warming-right

    NB: No significant stratospheric cooling since 1995.

    [Response: Wrong.

    https://twitter.com/ClimateOfGavin/status/978667693736910848

    – gavin]

  33. 183
    Victor says:

    179 Hank Roberts says:

    “>Victor … scattergram … WTF …. real statistician

    Real statisticians don’t publish their work at WTF, Victor.

    You’re confusing yourself again. But thanks for making clear which barrel you’re scraping from.”

    A scattergram is a scattergram, Hank, no matter where it’s been published — the process is pretty straightforward. If you’re not happy with Wolfe’s version, try making one yourself. He provides links to his (perfectly respectable) data sources in the article.

  34. 184
    nigelj says:

    Victor @178 “Note the precipitous dip in global temperatures from 1940 through 1950, with the south cooling at roughly the same rate as the north.”

    Absolute nonsense. Its clear that the north cooled more that the south, with a clearly steeper drop in the red line trend, as you would expect as more coal was burned there. Victor can’t even read a simple graph.

    Also the link he posted on correlations on wattsup is some rubbish stating the obvious that theres no correlation between CO2 and the pause after 1998. Of course there wouldnt be, but to get any insight on correlations you look at longer time frames that relate to the issues we are interested in, so the entirety of 1900 – 2018, and then you see a significant correlation. Victor has the scientific awareness of a child.

  35. 185
    Hank Roberts says:

    Poor Victor. He’s started citing his denial-site sources now, lacking any other support for his beliefs.

  36. 186
    Hank Roberts says:

    it’s amazing how facile Victor is — he finds a chart he can eyeball, claims it shows no stratospheric cooling since 1995, and ignores the text on the page

    … stratospheric temperatures reached a record low in 2016…

  37. 187
    Hank Roberts says:

    Victor tries his usual “who you gonna trust, statistics or my lying eyes” approach to argument, looking at a short section out of a larger chart to claim no change over time, ignoring the text surrounding the picture that so captures his imagination.

  38. 188
    Dan says:

    re: 182.
    As for “embarrassment”, sport, you have done what is classically known as “projection”. In simple words you might comprehend: busted! Your insecurity to admit to being completely wrong is telling. Let alone your failure to want to learn how science is conducted. Or your failure to understand the First Law of Thermodynamics. Stop flaunting your ignorance.

  39. 189

    Victor says: “the south cooling at roughly the same rate as the north.”

    In whose fantasy world? What happened to the vaunted acuity of the Victorian eye?

    Or maybe the eye isn’t the problem here.

    So let’s try a little logic. ~1940, the NH is the warmer hemisphere by more than 0.1 C; ~1970 sees the hemispheres at approximately the same anomaly. Only the most rudimentary calculus is required to show that NH has therefore declined more over said span.

  40. 190
    Victor says:

    180 MA Rodger says:

    “Yeah-but-No-but-Yeah-but @174,
    I see you continue you purile off-topic nonsense, now with a return to the Wattsuppian blather of Danley Wolfe who you describe as “a real statistician.” If he is such, he sould know better than manufacture such gobshite graphics.
    Victor, you have more-than-once trolled this Danley Wolfe here in times gone-by. The response remains as damning today as it ever was. So I will simply repeat the reply I made the last time you paraded this gobshite here:-

    “We have been here before with that gobshite you serve up, both with the cretin that devised it as well as later with you. Here is the rebuttal provided back then (usually 2 clicks to ‘download your attachment’). Nothing has changed since.”

    V: You have an amusing “tell,” MA. The more insults you spout the more likely it is you’re bluffing. In this case the bluff is just as obvious as it was when you first posted those graphs.

    The data you present tell essentially the same story as the data I linked us to, by that “cretin” Danley Wolfe. Both tell the same story, only yours is conveniently squished (“to hide the incline”?), and you’ve omitted Wolfe’s trendlines (which then reappear for some reason on your bottom-most display). And no, Wolfe’s trendlines are not bogus. The picture is quite clear even in the absence of trendlines, as is all too evident in your topmost scattergram.

  41. 191
    Victor says:

    182 V: No significant stratospheric cooling since 1995.

    [Response: Wrong.

    https://twitter.com/ClimateOfGavin/status/978667693736910848

    — gavin]

    Interesting. An in-depth study by an experienced climatologist refuted by a tweet from the twitter account of a mathematician/media outreach specialist.

    [Response: Not interesting. Actual data refuted by a random blog commenter with an ad hom. Yawn. – gavin]

  42. 192
    Victor says:

    186 Hank Roberts says:

    “it’s amazing how facile Victor is — he finds a chart he can eyeball, claims it shows no stratospheric cooling since 1995, and ignores the text on the page

    … stratospheric temperatures reached a record low in 2016…”

    Citing a “record low” in a single year is what is facile, Hank. What is meaningful is the observation by a highly trained professor of Geosciences that “The stratospheric temperature pause has now existed without interruption for about 23 years, with no explanation offered by the climatological community.”

  43. 193
    Hank Roberts says:

    Victor, record annual temperature events occur in single years.
    Facile? You’ve learned a new word.

  44. 194
    nigelj says:

    Victor @192, you are completely missinterpreting this entire stratospheric issue.

    Start at the beginning: Climate models predict the surface and troposphere will warm long term due to CO2 emissions, and that the stratosphere will COOL long term.

    The surface and troposphere have warmed over the last 120 years approx. The so called pause is almost nothing and hasn’t changed that.

    The stratosphere has been cooling since at least the 1960’s as below. I have no idea what your claimed “expert” is going on about.

    https://www.google.com/search?q=graph+of+cooling+stratosphere&safe=strict&client=firefox-b&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwj2oYaR1ePbAhXBG5QKHeY_B04QsAQIKQ&biw=1010&bih=587

    The greenhouse effect explains both the warming surface and troposphere and cooling stratosphere. The question was where is your alternative explanation as to why the surface / troposphere would warm and stratosphere cool? You still haven’t answered it.

  45. 195
    nigelj says:

    Victor @192, regarding your geosciences professors concern that stratospheric cooling has stalled over the last 23 years.

    The stalled period of stratospheric cooling over the last two decades is related to the ozone issues. The following research has a rather good explanation that its a temporary stalled period of temperatures, related to the ozone “hole” issue and the subsequent recovery of the ozone layer:

    https://ore.exeter.ac.uk/repository/bitstream/handle/10871/17282/rev2.pdf;sequence=2

    It may also be due to the effect of natural and human aerosols causing a lot of roughness in the long term trend.

    Look at the whole series from 1950 to this decade, and its a very jagged trend but the overall linear trend for the full period is still downwards. Don’t loose sight of that.

    Some other detail on why the stratosphere cools with greenhouse warming:

    https://www.skepticalscience.com/Stratospheric_Cooling.html

  46. 196
    MA Rodger says:

    Victor the Troll @190.
    You respond to the debunking of Danley Wolfe (usually 2 clicks to ‘download your attachment’).

    “Hide the decline”? How does that work when the data from your moron-of-an-expert appears <i."mysteriously" in the identically-scaled bottom panel? Wolfe’s graph is re-presented faithfully, even to his ignoring of annual CO2 cycle (which introduces a significant amount of fuzziness). The only ‘convenient squishing’, Victor, is in your denialistical brain!!
    “And no, Wolfe’s trendlines are not bogus.”? How do you manage that? 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. The line that should be drawn, the one that does fit the data, is the thin black line marked in the central section of the yellow line (roughly using data from the period 1980-2002). Using the data (rather than being driven by denilaist fantasy) presents a very different line from your mornon-of-an-expert.

    Of course, you do have the opportunity here to explain your interpretation of this situation. But I fear it is, as ever, a waste of everybody’s time. Even if you did feel inclined to provide it, you struggle to grasp the most basic of points. But normal people with a better grasp of reality than you, Victor, they will appreciate the debunking of your moron.

  47. 197
    MA Rodger says:

    Victor the Troll,
    For completeness, your comment @174 was accusing the graphic I presented @143 of making “no sense in terms of what we know about the temperature record, which includes roughly 40 years of NO warming while CO2 levels soared. Care to explain?” This of course was the point where you then presented (yet again) the nonsense of the Wattsupian moron Danley Wolfe (who you incredibly described as a “real statistician”), egregious nonsense that needed addressing.
    So let me now address that question you posed @174, the explanation.
    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?

  48. 198
  49. 199
    Victor says:

    194 nigelj: The greenhouse effect explains both the warming surface and troposphere and cooling stratosphere. The question was where is your alternative explanation as to why the surface / troposphere would warm and stratosphere cool? You still haven’t answered it.

    V: Yes I have. My answer is very simple. According to at least one authority on this matter (Ole Humlum) the stratosphere has NOT cooled over the last 23 years, an observation supported by just about all the graphs you linked to above.

    195 nigelj: The stalled period of stratospheric cooling over the last two decades is related to the ozone issues. The following research has a rather good explanation that its a temporary stalled period of temperatures, related to the ozone “hole” issue and the subsequent recovery of the ozone layer:

    https://ore.exeter.ac.uk/repository/bitstream/handle/10871/17282/rev2.pdf;sequence=2

    It may also be due to the effect of natural and human aerosols causing a lot of roughness in the long term trend.

    V: Ah yes, nigel. True to form. Whenever it’s demonstrated that one of the treasured assumptions supporting AGW is incorrect (or at best questionable), some ad hoc notion is offered in an attempt to explain it away.

    Global temperatures rose precipitously during the first 40 years of the 20th century while CO2 levels were rising at only a modest rate, demonstrating that temperatures can rise significantly without much help from CO2 emissions. — Uh, that can be explained by low volcanic activity and increased solar radiance.

    Global temperatures dropped and then stalled for 40 years during the 20th century, despite the fact that CO2 levels were soaring during this same period. — Uh, that was due to the cooling effect of industrial pollutants.

    While temperatures soared during the last 20 years of the previous century, the rate of increase dropped dramatically from 2000 on. — Uh, that’s because most of the heat got (somehow) transferred into the oceans; or it was due to a combination of ENSO, volcanic eruptions and solar variability; or it’s just a fluke easily corrected by cooking up some fancy statistical formula; or it’s due to errors made while the data was being collected; or, or, or . . . As of 2014, there were 63 “explanations” for this notorious “hiatus”: http://hockeyschtick.blogspot.com/2014/07/updated-list-of-29-excuses-for-18-year.html

    Aside from the last 20 years of the previous century, we see no correlation between CO2 levels and global temperatures. — Uh, that can be fixed if we focus on the “long-term,” drawing a nice simple diagonal trend line beginning at 1900 and ending in 2018, conveniently ignoring the ups and downs in between, which don’t really count.

    Even in the unlikely event that all the explanations offered above might have some basis in reality, we must not forget that an attempt to explain the absence of evidence is no substitute for actual evidence. Thus any attempts to explain why we see no evidence of stratospheric cooling in recent years, as convincing as you might find them, do not in fact constitute actual evidence, meaning that the claim associating stratospheric cooling with troposcopic warming cannot be maintained, as the supporting evidence is not there.

  50. 200
    MA Rodger says:

    Hank Roberts @198,
    I was always of the opinion that Wolfe’s grand work was using the CO2/Temp plot to stretch out the recent years and thus lower the apparent rate of temperature rise. Compared with the tick-tock of time, CO2 has been rising faster with time, stretching out that x-axis, reducing the slope of rising temperature. The only actual analysis Wolfe carries out is an OLS through 2001-14, this erroneously presented as proof-positive that there had been no warming “for the period 1998-2014” (You will note his bold-as-brass assertion presents a time period that doesn’t tally with the OLS analysis. He doesn’t seem to care. Indeed most of his graphical anotation is simply bogus, thus very Wattsupian.) Beyond that, the big no-no he perpetrates his presenting his splurge of graphed data points with zero analysis. Eyeballing such splurges is a very poor way of identifying trends.