Comments 1 to 40:

1. Evan at 23:45 PM on 5 November, 2023

   Hausfather's recent paper (read here) suggests there is no "warming in the pipeline" should we reach net-zero emissions. Hansen's new paper cited in the above article (read here) uses the very provocative title, "Global warming in the pipeline". Given that one of the leading voices in the climate community (i.e., Hansen) releases a paper now with this provocative title, should give pause to the idea that the warming is in our hands and under our control.

   It is likely that the environmental system is far more sensitive than we are willing to admit.

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2. Rob Honeycutt at 02:23 AM on 6 November, 2023

   Evan... Michael Mann is in pretty firm disagreement with Hansen on this issue. 

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3. Evan at 11:09 AM on 6 November, 2023

   Rob, that does not make Michael Mann correct. "No warming in the pipeline is a theoretical concept that requires us to completely restructure society. Hansen cannot be easily dismissed by simply citing a different researcher. I live my life assuming that we are committed to the level of warming reflected by the current CO2 concentration. I think this is a reasonable approach. I hope I'm wrong and that Michael Mann is correct. But I tend to side with Hansen.

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4. Just Dean at 23:31 PM on 6 November, 2023

   Evan, It is not just Mann that disagrees with Hansen. I believe that Hansen holds the minority position here. Both Zeke and Mann reference the IPCC special report on 1.5C that warming will cease when we get to net zero emissions.  To me, the IPCC represents the consensus thinking. There is a recent paper by Dvorak and Armour that reaches bascially the same conclusion, Ref. , and adresses the aerosol effect.

   If you follow Zeke at theclimatebrink.com and/or X, he has addressed directly Hansen's pipeline paper and his high estimate of climate sensitivity. Also, Zeke's latest analysis of record breaking temperatures relative to the multimodel averages can be found at theclimatebrink.com.

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5. Evan at 23:59 PM on 6 November, 2023

   Dean@4, When the IPCC was just being formed, it was Hansen in 1988 who was sounding the alarm. Hansen has always been at the forefront of climate predictions, preceding the IPCC in his assessment of how severe the climate crisis is and will likely become. The IPCC has always represented a baseline assessment of where we're heading, and not necessrily an accurate assessment of just how bad things could get.

   But let's find common agreement, because I've read the paper by Hausfather (read here) where he shows that temperatures will be frozen if we reach Net 0 emissions. I understand the arguments you're making.; But with CO2 concentrations rising at 2.5 ppm/year, and the state of world affairs leaning ever more to the right, it will be a long long time before I hold any hope for reaching Net 0 emissions. I will continue to encourage others to view our warming commitment as corresponding to the current level of CO2 in the atmosphere. Anything beyond that is contingent on global actions that are still struggling in their infancy. Yes, we have lots of talk and agreements, yes wind power has been increasing, but with CO2 rising at 2.5 ppm/year, apparently we have yet to sufficiently impress the natural world that we're doing enough.

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6. Just Dean at 00:30 AM on 7 November, 2023

   Evan@5, I understand. I prefer to look to the moderate voices in almost any circumstance. To quote Zeke, I am cautiously optimistic about our future and getting to net zero. We have bent the curve on global emissions and according to the IEA and others, e.g. Rystad energy, we may well hit peak emissons this year or at least by 2025.

   I follow the progress of the U.S. electrical sector emissions. Here are three positive facts about our progress.

    

   1. Renewable generation surpassed coal and nuclear in the U.S. electric power sector in 2022, link.

   2. Add nuclear to the renewables and emission-free carbon sources account for almost 40% of the generation in the U.S.

   3. The specific carbon intensity of the US electrical sector has decreased by 40% between 2000 and 2022, falling from 650 kg/MWh to 390 MWh.

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7. Evan at 01:16 AM on 7 November, 2023

   Dean@6, I hope you're correct. Personally, I will only change my view when there is a statistically significant decrease of the rate of increase of CO2, because ultimately the three facts you cite do not determine how the environment will respond. Collectively they are an important component, but only one component that affects the rate of accumulation of CO2 in the atmosphere. Noting that our emissions are only about 4% of natural emissions, we only have to affect natural emissions, or sinks, by a small amount to overwhelm our efforts to control the rate of accumulation of CO2.

   I am not really arguing against you, but using this forum to remind the readers of other factors involved. I respect that the facts you're quoting are accurate and come from reliable sources. So I am merely noting that they only represent one piece of the puzzle, and noting that we may still be a bit optimistic about how the natural world will respond to what we have already done and continue to do. I think Hansen differs from other because he has a different view of how sensitive the natural world is to our actions.

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8. Rob Honeycutt at 04:11 AM on 7 November, 2023

   Evan @7... I believe the rate of increase in CO2 concentrations is a different issue than warming in the pipeline, though. Mann (and Hausfather) are taking issue with Hansen's claim there would potentially be decades of warming even after bringing CO2 emissions under control.

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9. Just Dean at 05:33 AM on 7 November, 2023

   Rob@8, Zeke and Andrew Dessler take issue with how Hansen is defining "warming in the pipeline." Basically, he is assuming constant atmospheric concentrations and then he is holding it there for millenia to allow slow feedback mechanisms to kick in, Ref. theclimatebrink.com 5/22/23 . 

   Evan@7, If you wait to see a significant decrease of the rate of increase of CO2, it will be too late. You won't see that until we have made significant progress in reducing man made emissions, see projected CO2 ppm vs emission scenarios, Climate change:Atmospheric Carbon Dioxide .

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10. Rob Honeycutt at 12:46 PM on 7 November, 2023

    Dean... Seems the buried lede is here: "... Hansen’s assumptions will not happen. We are not going to keep atmospheric carbon dioxide and other greenhouse gases fixed for thousands of years. We will definitely stop burning fossil fuels in somewhere between a few decades to a few centuries and the concentration of greenhouse gases in our atmosphere will decline after that."  

    My point here is, you seem to be going off topic talking about the rate of increasing CO2 concentrations (@7) rather than discussing warming in the pipeline.

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11. Evan at 23:51 PM on 7 November, 2023

    Rob@8, can we agree on the following. If the Keeling curve (i.e., plot of CO2 concentration vs year) does no better than level off, then we have warming in the pipeline. Currently the CO2 concentration is accelerating upwards (these are the words that Ralph Keeling himself uses). It is possible that we do many wonderful things to control our emissions and do no better than to simply stop the upward acceleration. In that case, we still have a disastrous situation.

    Even if we do much, much better than to stop the upward acceleration, the next big challenge is to stabilize CO2 concentrations. If we do not better than that, then we have warming in the pipeline.

    My point is simply that it is prudent to assume that we will never do better than to stabilize atmospheric CO2 concentrations, because getting to that point will require a Herculean task. Yes, there are hopeful trends, but there is also a lot of resistance in the world to the kind of change needed to reach Net Zero emissions. These trends could quickly slow down.

    I understand the arguments you and others are making. I just don't believe we have the collective will to do what is needed to make the model assumptions come true. Hence, I will continue to urge people to plan as though current atmospheric concentrations represent our commitment level.

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12. Rob Honeycutt at 00:59 AM on 8 November, 2023

    Evan... Yes, we can agree more or less on everything you've stated there. My point is, that is different from the warming in the pipeline discussion.

    I will say, though, my perspective tends to be more optimistic than yours. I see quite a lot happening toward decarbonizing society. As you say, it is a Herculean task but the pace at which clean technologies are being deployed is also impressive. It's not yet enough. We have a long hard road ahead in the coming decades. But I think we're going to get there.

    I believe it's important to communicate the incredible challenges we face but without instilling in people's minds the idea it's already a lost cause. 

    On the warming in the pipeline issue, I think Zeke and Andrew get it. If Hansen is discussing millennial level warming in the pipeline as steady concentrations, it's important science to understand, but functionally irrelevant to the challenge of the coming decades.

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13. michael sweet at 02:39 AM on 8 November, 2023

    I don't think Hansen is worried about thousands of years in the future.  He has been saying for decades that aerosols are reflecting a lot of energy back into space, cooling the planet.  Reducing fossil fuel use reduces aerosols.  The loss of aerosols causes rapid warming.  Hansen projects that 1.5C will be exceeded by 2030 and 2.0 C will be exceeded by 2050.  He is concerned about changes that will occur while people alive now are still around, about 100 years.  He is concerned about multimeter sea level rise by 2100.  If Hansen is correct about aerosols the next 30 years will have substantial extra heating.

    I respect Zeke and Mann but their explainations for the extreme heat the past 6 months are pretty weak.  While the current temperatures are inside the error bars for the models, the temperature this year is extraordianrily hot comnpared to all previous years.  I note that the IPCC generally emphasizes what a consensus of scientists think is the minimum amount of change in the climate and temperature.  That means that a majority of scientists  think it will be worse than the IPCC projections.

    The scientists who project damages substantially exceeding the IPCC reports are in the minority.  It is very concerning to  me that they exist at all.  Especially since the last 6 months have been so hot and next year is projected to be even hotter.  El Nino does not usually strongly affect temperature until the end of the year.

    I agree that "it's important to communicate the incredible challenges we face but without instilling in people's minds the idea it's already a lost cause."  But politicians still are not taking action seriously.

    What is the IPCC defination of "consensus".  It has to be a lot higher than 50%.  Is it 80%, 90%?  They must have it written down somewhere.

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14. nigelj at 05:28 AM on 8 November, 2023

    I believe Hansen has to be right to the extent there will be more warming in the pipeline due to sulphate aerosols reducing, over the immediate short term future. Aerosols cause a cooling effect so if you cut them you must get a warming effect. However its a question of how much warming would be in the pipeline, and I went looking and found this a few days ago: "Cutting air pollution would not cause ‘near-term spike’ in global warming"

    www.carbonbrief.org/cutting-air-pollution-would-not-cause-near-term-spike-in-global-warming/

    The study appears to say that if sulphate aerosols were all cut to zero immediately you would get a significant spike in warming lasting about a decade or so, but if they are phased out over several decades (which is the far more realistic scenario) additional warming  would be zero or quite small.

    We have had a couple of hot years and significant heatwaves and Hansens argument appears to be this relates to reduced aerosols from shipping (?). While I have huge respect for Hansen, I struggle to believe something like that would cause enough warming, and haven't seen anyone come up with numbers on it.

    Manns concern appears to be that people will give up on mitigation if they begin to believe a lot of warming is already baked into the system or that we are already doomed. And IMO hes right. Therefore its important to be accurate about exactly how much warming is baked into the system and not exaggerate and speculate unnecessarily.

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15. MA Rodger at 21:23 PM on 8 November, 2023

    This Hansen et al (2023) paper was pre-published back in January and did result in a bit of discussion here at SkS. And there was supposed to be a second paper specifically on SLR.

    Hansen et al rattle through a pile of stuff, some of which I would agree has merit and some which I find difficult to accept, some very difficult. The high ECS is one of the very difficult ones. (Perhaps the point that the big part of the difference between high ECS values and the IPCC's most likely value ECS=3ºC, [something the IPCC tend not to identify preferring a range of values as in AR6 Fig1.16]: the difference is due to warming that follows the forcing by a century or more. That time-lag is one of the reasons the ECS estimates are not better nailed down and still has its 'fat tail' . It also would give mankind a fighting chance of dodging it.)

    SLR is certainly a big subject of concern. It is a long-term problem, multi-century. The equilibrium position for a +1.5ºC is perhaps 3m and the threat of setting Greenland into unstoppable meltdown at higher levels of warming would triple that. I do tend to get irked by the SLR by 2100 being the sole subject of discussion.

    Of course, predictions of that 2100 SLR being massive (5m) is one of Hansen's foibles. The worry is, I think, specific to Antarctica and it is a genuine worry. But to achieve 5m by 2100 would need massive numbers of icebergs bobbing around in the southern oceans and result in global cooling. And there is also the awkward point for climatologists that increased snowfall over Greenland/Antarctica could provide a significant reversal of SLR.

    The final issue raised by Hansen et al (2023) is the impact of the reduction of aerosols from our falling SO2 emissions. Quantifying the impact of SO2 emissions is not entirely global a thing, so emissions in, say, China may induce more cooling than, say, Europe. But that said, global SO2 emissions data I identify tends to be way out-of-date. The most recent is this one from a Green Peace publication. This shows the reduction in SO2 is well in hand over the last decade. And the CERES data showing EEI does show a drop in albedo (yellow trace in the 2nd graphic) through that period. My own view of these CERES numbers is that they include a lot of bog-standard AGW-feedback-at-work.

    

    

    There is also the last 5 months of crazy global temperatures (so post-dating Hansen et al's pre-publication). I don't see these as being sign of things to come. I'd suggest it is casued by the January 2022 Hunga Tonga eruption which threw both SO2 and H2O into the stratosphere, the cooling SO2 dropping out leaving the warming H2O to do its thing before eventually it too dropping out.

    And the in-the-pipeline thing. Climatology is/has-been saying we need to halve CO2 emissions b 2030, and following the point of net zero in mid century we enter a century-plus of net-negative CO2 emissions. That would see all emissions 2008 to year-of-net-zero removed by human hand and stored away safely. So that is on top of the natural draw-down of CO2 into the oceans. And if we don't do that, it will not be from ignorance of the situation.

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16. Just Dean at 23:59 PM on 8 November, 2023

    Michael@13, I'm not sure I agree or understand your statement about Zeke's explanations for the recent warming as "pretty weak."  He has given it the most thorough treatment that I have seen both at The Climate Brink and at CarbonBrief .  Factors include El Nino, uptick in 11-year solar cycle, Hunga-Tonga and reduction in aerosols due to 2020 phaseout of sulphur dioxide.

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17. Andrew741 at 03:59 AM on 10 November, 2023

    Absolutely, the discussion around the warming in the pipeline is a nuanced one. It's refreshing to see your optimism amid acknowledging the Herculean task of decarbonization. The pace of clean tech deployment is impressive, and while the road ahead is long and challenging, your belief in reaching the destination is encouraging. Balancing awareness of the challenges without painting it as a lost cause is key. It's a delicate dance, but a necessary one for fostering both awareness and hope in the face of daunting environmental issues.

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18. Andrew741 at 04:01 AM on 10 November, 2023

    @Evan
    Your perspective on the Keeling curve and the challenges ahead is thought-provoking. Acknowledging the current upward acceleration in CO2 concentrations and the potential difficulty in even stabilizing them paints a stark reality. Your caution about assuming we can achieve more than stabilization is a call to recognize the Herculean task at hand, balancing hopeful trends with the resistance to necessary change. It's a sobering reminder to plan for the worst while striving for the best, given the uncertainties and the collective will required for significant global shifts,

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19. michael sweet at 07:28 AM on 10 November, 2023

    Dean,

    I think the explaination of current heat caused by " El Nino, uptick in 11-year solar cycle, Hunga-Tonga and reduction in aerosols due to 2020 phaseout of sulphur dioxide" is not very satisfying. 

    The El Nino has just started.  Usually the effect of El Nino is felt most at the end of the year and the year following.  That means we are just now feeeling the El Nino effect.  In addition, the current El Nino is described as moderately strong, not extremely strong source.  To me that means that only a little of the extrordinary heat of the past 4 months could be attributed to El Nino.  Dr. Zeke Hausfather here primarily attributes the current extreme record temperatures to El Nino.  I doubt the El Nino has contributed so much heat so early in the cycle.  We will see how much hotter next year is.  I think El Nino contributes less than 0.1 C.  

    The solar cycle only contributes about 0.2 C to warming from the top of the cycle to the bottom.  While the cycle has increased a lot this year, it is still not peaking out.  The solar cycle is not much different from earlier record years.  This contribution is also less than 0.1 C.

    The volcano is harder to evaluate.  Most volcanoes cool the surface but this one shot a bunch of water into the Stratosphere.  Since that has not happened before it is hard to estimate.  I think the volcano contributes less than 0.1 C.  

    October was 0.4 C above the previous record year which had a much stronger El Nino, September was 0.5 C above record, August 0.3 C, July 0.43 C higher.  These records are usually broken by hundredths of a degree.  The past years had stronger El Ninos and the solar cycle was comparable.  

    Hausfather's estimates of all the forcings do not add up to 0.5C for September.  Hansen has been saying for decades that aerosols reduce temperature much more than the models indicate.  I fear that Hansen is correct and the unaccounted for warming is coming mostly from the reduction in aerosols.  This is due primarily to the change in marine fuels with some coming from polllution controls in China.

    If the record heat is caused primarily by the reduction in aerosols it will be permanent.  Next year will be hotter because of the  El Nino.   Future years will build off a new base that is about 0.4 C higher than it was three years ago.  Hansen predicted before this year that 1.5 C would be exceeded before 2030.  If this year is above 1.5 C becasue of aerosol reduction than by 2030 it is very likely all years will be above 1.5 C and Hansen will be correct.  If the volcanoes effects have been underestimated than after next year the temerature should go down for a few years.

    Pray that Hansen is incorrect and the volcano caused this years extraordinary temperatures.

    Keep strongly in mnd that Drs Mann, Hansen and Hausfather are way more informed about these matters than individuals who post on the internet, including me.  I recommend you try to read as many of their postings as possible to determine who you think is being the most consistent.

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20. Just Dean at 10:02 AM on 10 November, 2023

    Michael,

    I basically read everything Zeke write's including every post at CarbonBrief, theclimatebrink.com, and his October 13th NYTimes article and some of his recent peer-reviewed journal articles.

    Zeke has basically been giving his readers and followers a play by play of this, "Staggering. Unnerving. Mind-Boggling. Absolutely gobsmackingly bananas" year.

    You may want to remember that we need to wait until 2023 is over before we can plot the average temperature for the year by all the different sources, on the global temperature series .  To me it appears that 2023 will be high right in line with the two year duration of the El Ninos of 1998 and 2016 where basically the average temperatures jumped by 0.3 C.  

    I don't I think I need to read anymore of Zeke's work but maybe you want to consider it. 

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21. MA Rodger at 20:48 PM on 10 November, 2023

    Just Dean @20.

    It is not correct to make a comparison of 2023 with El Niño years 1998 & 2016. We are in the first year of a 2023/24 El Niño and the earlier ones were 1997/98 and 2015/16. 2023 is not the El Niño year in which the temperatures jump.

    (Using ERA5 numbers), if we assume the October anomalies coutinue for Nov/Dec, 2023 would show a record year averaging +0.16ºC above all previous years. 1998 & 2016 saw similar +0.15ºC & +0.18ºC respectively. But 2023 is not another 1998 or 2016. We would have to wait for 2024 to make a comparison with previous El Niño years. And the coming El Niño is not looking anything like 1998 or 2016. It is forecast to be "moderate El Niño event", so more like 2010.

    That is why 2023 is being described as "Staggering. Unnerving. Mind-Boggling. Absolutely gobsmackingly bananas." The big question, which is yet to be answered, is 'Why?'

    

    You'll be familiar with this graphic if you follow Jason Box. It well-explains the temperature rise 2014-2023 but it does not show anything that would explain the "staggering, unnerving, mind-boggling & absolutely gobsmackingly bananas" temperatures we've seen over the last five months.

    (If you want to see how bananas, have a play on the UoMaine Climate Reanalyser and compare 2023 with previous years, then blank off 2016-23 and repeat for 'pre-El Niño' 2015. And again for 1997.)

    My suggestion as to 'Why?' is that the Jan 2022 Hunga Tonga eruption which was exceptionally large and being sub-ocean blew large amounts of both SO2 and H2O into the stratosphere. These two would cancel each other out so the rather chilly 2022/23 winter (globally) with the SO2 marginally more powerful. But that SO2 has dropped out now and the remaining H2O is still there providing us the bananas. If this is the situation (& there is satellite data showing SO2 dropping out quicker than the H2O), the bananas do thankfully have a shelf-life.

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22. Just Dean at 23:36 PM on 10 November, 2023

    MA Rodger,

    If you read my previous comment closely, you will see that I understand we are in the first year of an El Nino event. I am indeed comparing 2023 to 2015 or 1997. 

    If you look at the global temperature series referenced in Zeke's July 26 CarbonBrief article, you will saw-tooth like structures for both the 1998 and 2016 El Nino events. The total temperature excursion over the two years was about 0.3 C, with each year adding about 0.15 C.  I realize that 2023 is extraordinary and might be closer to a jump of 0.2 or 0.25 C  but we need to see how this year and 2024 play out.  To quote Zeke from his 10/31 post on The Climate Brink, "It remains to be seen if we will see more exceptional warmth in the latter part of this year and early next as the El Nino event peaks or if this El Nino is behaving differently – potentially contributing more warming early on due to the rapid transition out of unusually persistent La Nina conditions – than we’ve seen in past events."

    We are observers in an unfortunate global warming experiment. We will need wait to see how it unfolds. To my earlier point to Michael, Zeke is trying his best to interpret this in real time, and allowing us to look over his shoulder, basically giving updates on a weekly or biweekly basis. I am not aware of any other climate scientist that is sharing insight that frequently. Between Zeke, Mann and Hansen, I find Zeke to be the most moderate, consistent and coolheaded. Yes, I'm a fan.

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23. Bob Loblaw at 00:08 AM on 11 November, 2023

    Back in 2016, I created this graphic regarding the spike in global temperatures, and how the denial industry would respond.

    

     

    With 2023 showing such a high temperature anomaly, you can bet that all the web sites and reports that claim "no warming since..." will be running an exercise similar to this:

    

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24. michael sweet at 05:03 AM on 11 November, 2023

    Just Dean:

    If you like Dr Hausfather's posts you will be in good hands.  I also like his detialed and timely posts.  As I said above, read as much as you can and focus on the people you think are most consistant.  There are currently several competing scientific explainations of the high temperatures in 2023.  More time will determine which is correct.

    I agree with MA Rodger that the current data does not explain the extraordinary high temperatures of 2023.  (I rarely post about temperatures on Skeptical Science any more because I usually agree with MA Rodger).  I hope he is correct that the unusual heat is caused by the volcano.  I fear that Hansen might be correct that aerosols have been obscuring more warming than is currently modeled.   Hausfather is a very skilled scientist and he thinks it might be an unusual El Nino.  This El Nino is following an unusually long La Nina period, perhaps that expalins the unusual change.  It could just be random natural variation (I doubt that).  I think the scientific literature supports all of these possibilities.

    In this case I expect that in two or three years the extraordinary heat this year will be explained.  If is is an unusual El Nino we should know in 2024 or 2025.  If it was the volcano the temperatures in 2025 should return to the previous trend.  If it is aerosols they will stay elevated.  This is an unusually short time to determine a scientific explaination.  The data might be muddled and we will need another few years to determine the best answer.

    This is how science advances!!  Competing hypothesis are tested against the data.  People initially take sides.   As more data becomes available one hypothesis is more supported by the new data.  Most people accept the most supported hypothesis.

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25. michael sweet at 05:04 AM on 11 November, 2023

    Bob:

    The denialists will have to wait and see how warm 2024 is before they changne their posts!!

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26. MA Rodger at 10:04 AM on 11 November, 2023

    Just Dean @22,

    My apologies for misreading your comment @20.

    The climatology community do not generally spend their time awaiting monthly global temperature anomalies and (as in the kerfuffle with the so-called 'hiatus' a decade back) tend to react to issues after they have arisen; and then not very fluently. So in that regard Jason Box is an oddity.

    Concerning the contribution of El Niño to 2023 global temperatures, it is true that there were stronger La Niña conditions in mid-2022 than there was in mid-1996 and particularly in mid-2014. Thus the change from a cooling La Niña would perhaps suggest more resulting warming in 2023. But the flip side of that is the La Niña conditions so far in 2023 being far weaker than 1997 & 2016 suggesting less resulting warming. (Note the 2009-10 El Niño also began from strong La Niña conditions in 2008.) The net effect for 2023 should then perhaps be 1997 or 2015-like. But they are not.

    Thus I would suggest there is ample evidence from the global temperature record to indicate something with perhaps even more warming impact on global temperatures than the coming La Niña.

    If the temperature rise (using ERA5 with assumed Nov/Dec 2023 anomalies as per @21) the global temperature rise through the first year and then the additional second year rise run as follows:-
    1996-97 ... +0.12ºC ... ... 1997-98 ... +0.19ºC
    2008-09 ... +0.13ºC ... ... 2009-10 ... +0.10ºC
    2014-15 ... +0.15ºC ... ... 2015-16 ... +0.18ºC
    2022-23 ... +0.30ºC ... ... 2023-24 ... +???ºC

    Perhaps it would be worth setting out the same data for was the most powerful El Niño of recent decades. This was overwhelmed by the El Chichón eruption of April 1982 which resulted in a cooling in 1982:-
    1981-82 ... -0.20ºC ... ... 1982-83 ... +0.19ºC

    So perhaps the Jan 2022 Hunga Tonga eruption and its water vapour is acting as a booster for 2023. (I mentioned satellite data @21 supporting this contention. See th 6 min video from Andrew Dessler here. It's now 3 months old.)

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27. Just Dean at 23:24 PM on 13 November, 2023

    MA Rodger,

    I looked at the video from Dessler. I don't understand why you cited that. That video is an explaination video cited by Dessler in his post from The Climate Brink where he concludes that Hunga-Tonga is "not reponsible for the blistering temperatures we're experiencing."  

    Or as his last sentence states, " If you’re sweating right now, don’t blame HT. Blame fossil fuels."

    Again, I think the jury is still out but I tend to trust the experts and from what I read most feel that Hunga Tonga is not repsonsible for this year's heat wave - Ref. From what I read an aerosol effect should play out over years not months and contribute a "baseline offset" if there is an effect. According to Stuart Jenkins, it is maybe on the order of 0.04 - 0.05 C. 

     

     

     

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28. nigelj at 04:49 AM on 14 November, 2023

    Just Dean @27

    Regarding the experts allegedly blaming the warming this year (particularly July to October) on climate change plus a bit from el nino. This doesn't sound convincing to me. El Nino has barely even started so wouldnt have much effect (as others point out) , and greenhouse gas warming and its realted feedback mechanisms is a gradual process that wouldn't cause a sudden spike in warming in a few months of one year.

    The reduction in industrial aerosols from the new shipping rules in 2020 is also not a good explanation for this years warming.  The reduction in aerosols stared immediately in 2020 and increased from there, so You would expect it to have had a fairly immediate effect and an effect over the three years. Its hard to see why it would create a sudden warming spike three years later.

    I think MAR has a good explanation that the Tongan Volcano's aerosols have all fallen out of the atmosphere and remaining water vapour has thus caused a spike in warming. I did a google search a few days ago, and aerosols decrease over a period of a couple of years following a reverse exponential curve and water vapour can remain in the stratosphere for a couple of years. All it would need is for a large part of the water vapour to remain a little bit longer than the aerosols.

    But I think that the global warming trend will accelerate and may have already accelerated, due to the reduction in industrial aerosols and various feedback mechanisms, but it is not something we would be able to detect in just a couple of years temperatures. And its most likely going to be a gradual process, rather than a step change in just one year.

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29. Just Dean at 06:41 AM on 14 November, 2023

    nigelj,

    I'm not sure what I else I can say. I'm not an expert but I'm telling you that based on what I can find on the web, the consenus by climate scientists appears to be that Hunga-Tonga is not reponsible for our the spike in surface temperatures, contributes but is not a major factor. If you have not visited Dessler's post at The Climate Brink, I encourage you to do so. I'm sure he would still welcome questions or comments if either you or MA Rodger wish to discuss it with him.

    I referenced a paper by Stuart Jenkins @27. I don't have access to the paper but I found a detailed article about the paper at CarbonBrief . It has a nice plot of the projected increase in surface temperature as a function of time after the eruption. It causes a very slight increase over several years and then dissipates.

    This is the only study cited by Dessler that claims Hunga-Tonga added to heating. Two others actually believe it would cause slight cooling. Dessler claimed he was working on a peer-reviewed paper but I don't expect any surprises there. 

    I'm tapped out. I've gotten nothing else that I feel like I can contribute to this discussion.

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30. michael sweet at 08:48 AM on 14 November, 2023

    Just Dean,

    The main scientific explainations for the extreme heat this year are: the start of El Nino, the volcano, aerosols and natural variation.  I think that in this thread you and others have posted data supporting the idea that the El Nino is too early to provide so much of an increase in temperature.  The volcano does not produce enough forcing to account for the increase in temperature and aerosols do not provide enough forcing for the observed temperatures.  I think "natural variation" is short hand for we don't know the cause.

    Obviously something has caused the extreme heat this year.  I think it probably is El Nino, the volcano or aerosols.  I think the data is not definative yet as to which is actually the cause.   Great scientists are divided on what they support.  We will have to wait two or three years.  During that time more data will become available.  That data will give us clues about what the true cause is.   I hope that it is El Nino or the volcano.  I fear it might be aerosols.  We need more data to decide.

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31. Just Dean at 23:14 PM on 14 November, 2023

    Michael,

    Fine, but my money is on Zeke and the moderate, mainstream climate scientists.  I'm just not buying the theory of Simons and Hansen of an "aerosol termination shock."  

    As I say I'm not an expert, but I am a retired research engineer who worked with fusion scientists and high-energy-density physicists for 34 years, so I've seen a thing or two and this just seems too speculative to me.

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32. nigelj at 05:28 AM on 15 November, 2023

    Just Dean @31, I agree that the spike in warming this year around july - october is unlikely to be caused by  the reduction in industrial aerosols. The so called  termination shock.

    The reduction in shipping aerosols started back in 2020 and fuels were changed immediately so if anything you would expect a sudden spike in temperatures back in 2020 - 2021 not this year. Other reductions in industrial aerosols like Chinas  introduction of scrubbers is phased in so would have  a gradual effect over time and doesnt really expain a sudden spike.

    I do  think the reduction is industrial aerosols will have a longer term warming effect but it will be gradual and seen more in hindsight. And the mainstream view seems to be not as huge as Hansen argues. I have no idea who is right on the issue. Both very clever people.

    Zeke seems to be arguing the temperature spike this year is caused by "bit of everything" including the el nino, the volcano, reduction in industrial aerosols, but  that the el nino is the big factor. I tracked down his commentary and here it is for anyone interested:

    heatmap.news/climate/september-2023-hottest-heat-zeke-hauffather

    He could be right, although I think MAR has made a good case that the volcano is the main factor. The study you quoted did suggest that the water vapour is not enough to explain the temperature spike, but perhaps that study is underestimating it. Water vapour ejected  so high up has a strong warming effect.

    That leaves the possibility of the el nino plus the volcano being the two main  factors and about equal, and a little bit from industrial aerosols reductions. That would be a good explanation.

    Blaming it all on a combination of factors is a fairly safe approach but I admit its not entirely satisfying.

     

    I'm retired now. For me its an interesting puzzle. I respect your views. I think MS is right that we just dont have enough data and we dont have a definitive understanding of effects of aerosol's so cant be very certain at this point. But its fun and stimulating to speculate a bit.

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33. Just Dean at 22:59 PM on 15 November, 2023

    nigelj,

    I appreciate your kind words. It is fun to speculate. I probably spend too much time consuming climate change science and solutions online. It has  become a passion for me in retirement. I suspect commenting at sites like this help me replace the interactions I used to have at work. I do appreciate knowledgable communities. Some of my favorite sites are The Climate Brink, Sustainability by the Numbers, And then theres physics and CarbonBrief.

    I must admit I am biased when it comes to Zeke. If I have a question about a climate change issue, I always start by finding out what Zeke thinks, e.g. WDZT.

    cheers,

    Dean

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34. nigelj at 05:08 AM on 16 November, 2023

    Just Dean, 

    "I probably spend too much time consuming climate change science and solutions online. It has become a passion for me in retirement. I suspect commenting at sites like this help me replace the interactions I used to have at work."

    I'm retired and I spend a couple of hours a day sometimes more reading websites on environmental, political, current affairs and economic issues and often participating in discussions. Particularly on the climate issue.  I think its a replacement for work interractions like with you, and it keeps the mind active and I like to share information and discuss issues. 

    I like light entertainment and fiction novels as  as well, but I would go crazy if that was the only thing in my life, and I find 90% of reality TV is awful. Not really into social media gossip.

    I don't think you should feel guilty for being passionate about the climate issue and spending time on it. Unless it was the ONLY issue you spent time on. That might be a warning sign. As  long as we retired folk aren't somehow hurting other people or neglecting something important whats the problem? People can do what they want in retirement. We all have different tastes.

    Thanks for the tips on the list of climate websites. I read some of those but I dont normally contribute to discussions. Might do so a bit more.

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35. Andrew741 at 03:30 AM on 17 November, 2023

    Dear Dean,

    Your passion for climate issues post-retirement is truly inspiring. It's wonderful to see how you balance staying informed on critical topics with a touch of light entertainment. Your commitment to meaningful content and discussions showcases the richness of your retirement pursuits. Thanks for your positive feedback on the climate websites, and feel free to share your insights anytime,

    Best,
    Andrew John 

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36. Just Dean at 22:49 PM on 17 November, 2023

    Andrew,

    Thanks for your kind words and invitation. It is appreciated.

    I try to walk the talk when it comes to fighting climate change and share what I learn. I have written a couple op-eds that have made it into the local papers but there you are limited by the whims of the editor.

    I sometimes wonder what difference it will make. It is hard to change people's minds. I just hope one day my granddaughter will appreciate my efforts.

    Best,

    Dean

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37. michael sweet at 11:28 AM on 12 December, 2023

    Just Dean,

    Andrew Dessler, a renowned climate scientist, has a post on Climate Brink about this years heat.  He discusses the items we have covered.  He thinks it is not the volcano.  Climate change, El Nino and aerosols are not enough to explain the extreme heat this year.  He seems to suggest random shifts in climate for most of the heat.  He expects it will be explained in a few years.

    The Climate Brief is always informed and easy to read.

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38. michael sweet at 11:31 AM on 12 December, 2023

    This is the correct link to the climate brink

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39. scaddenp at 14:35 PM on 12 December, 2023

    My 2c. Very roughly, Ocean heat content increases in La Nina, decreases in El Nino (transfer heat to atmosphere). 3 La nina's in a row means more than usual heat in ocean (look at the marine heat waves). I'd say with transition to El Nino, more than usual heat is coming out of ocean to atmosphere, so higher than the value calculated from regression. It would imply that other triple La Nina's should have had above average impact on temp during following El Nino too. If I had time, I would check. On other hand, if it was that clear cut, I am sure Dessler would spotted it.

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40. MA Rodger at 19:54 PM on 12 December, 2023

    Dessler's post does rather hedge its bets by suggesting it might be "due to natural variability persisting over an extended period" which will at some point come to an end (so as per the 2007-12 slowdown but in reverse). But he also points to the recent deep La Niña which may be amplifying the impact of the less-than-massive El Niño.

    The ENSO indices do show the build-up to present weak El Niño conditions were unusually preceded by strong La Niña cinditions which had been, if anything, strengthening through the period rather than, as is usual, weakening as El Niño conditions approach. (The MEI perhaps shows this situation best.) Yet the big 1997-98 El Niño also strengthened quite suddenly and showed nothing like this 2023 bananas situation.

    

    The bananas (sudden appearance of an additional +0.2ºC in the global average temperatures) won't be some sudden forcing as there is no sign of anything (or things) approaching the required force. That means we have a natural wobble.

    But is that wobble reversing something that has been shielding the impacts of AGW and so it won't reverse? Or is going to abate in coming months/years? Dessler looks to the climate models as suggesting it is the latter. But the question is still an open one!!

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