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21st century warming trend change may not be due to greenhouse gasses, leading climate scientists say

December 16, 2022

By Paul Homewood

 

 

A new study by a team of leading climate scientists suggests that the effect of carbon dioxide this century might be small when compared to natural climate variability.

Global surface temperature is, and always has been, the key climate parameter. Whatever is happening to the Earth’s climate balance, it must, sooner or later, be reflected in the global annual average temperature, and not just in regional variations. But therein lies what is to some an inconvenience as the changes in the global temperature this century is open to differing interpretations including the suggestion that increases in anthropogenic greenhouse gas emissions are not needed to explain the changes we have seen in the last 20 years or so.

It’s a conclusion that many would dismiss as coming from climate “sceptics,” or downright deniers. But what if it’s the view of scientists from two of the world’s leading institutes researching climate change; the University of Oxford and the US National Center for Atmospheric Research. Then it must be taken seriously and not dismissed offhand.
It is important research because it is the trend in the increase of global temperature caused by anthropogenic greenhouse gas emissions that is most important variable for policymakers considering the scale and timescale of action in the coming decades. However, this vital parameter is uncertain because recent decades have shown that were are living through a period of considerable natural climate variability.

A new study by a team of leading climate scientists suggests that the effect of carbon dioxide this century might be small when compared to natural climate variability.

Global surface temperature is, and always has been, the key climate parameter. Whatever is happening to the Earth’s climate balance, it must, sooner or later, be reflected in the global annual average temperature, and not just in regional variations. But therein lies what is to some an inconvenience as the changes in the global temperature this century is open to differing interpretations including the suggestion that increases in anthropogenic greenhouse gas emissions are not needed to explain the changes we have seen in the last 20 years or so.

It’s a conclusion that many would dismiss as coming from climate “sceptics,” or downright deniers. But what if it’s the view of scientists from two of the world’s leading institutes researching climate change; the University of Oxford and the US National Center for Atmospheric Research. Then it must be taken seriously and not dismissed offhand.
It is important research because it is the trend in the increase of global temperature caused by anthropogenic greenhouse gas emissions that is most important variable for policymakers considering the scale and timescale of action in the coming decades. However, this vital parameter is uncertain because recent decades have shown that were are living through a period of considerable natural climate variability.


Aerosol Emissions, the real culprit?

 

Thus, a new study published in the Journal of Climate suggests the effect of carbon dioxide this century might be small when compared to natural climate variability. The researchers contend that recent temperature trends might indicate that there is no significant increase in global temperature due to greenhouse gas emissions.

 

While this suggestion is interesting it must be said that the researcher’s get themselves in a muddle when estimating temperature trends this century. On the one hand they acknowledge the existence of the global temperature hiatus between 2000 – 2014, but on the other hand they do not properly distinguish the effects of the natural El Nino events that have taken place in the past seven years. This is why they conclude there might have been an acceleration in global temperature increase over this period.

 
They say that most of change in trend is not due to greenhouse gasses but to aerosol emission reductions. The combustion of fossil fuels releases greenhouse gasses but it also causes pollution that cools the Earth, offsetting most of the warming. This is good news for public health as airborne particles kills several million people a year, but it also accelerates global warming.

 
Their assessment is that aerosol emissions have contributed to an increase in the rate of anthropogenic warming since 2000 although they have a large uncertainty. When considering estimates of the amount of warming due to aerosol reduction along with natural climate variability they find a solution with all the post-2000 temperature trend change being due to natural variability alone. They say (p 4283) it’s a credible hypothesis that global temperature trend changes since 2000 could be “arising largely from internal variability.”

https://www.netzerowatch.com/21st-century-warming-may-not-be-due-to-greenhouse-gasses-leading-climate-scientists-say/

37 Comments
  1. ThinkingScientist permalink
    December 16, 2022 9:24 pm

    Chickens coming home to roost….climate models warming too fast and outrunning predictions, maybe?

    Hedging your bets….

    First one to blink….

    Covering your arse….

    Just in case the warming is way less than exepcted, have an explanation for the new pause….

    All keeps the grants rolling in, hey?

  2. Douglas Dragonfly permalink
    December 16, 2022 9:28 pm

    An interesting and informative article. I actually enjoyed reading it as well, what a bonus. Nor does it try to have all the answers as after all, the topic is immense and constantly changing. Maybe the editors and other writers at the Daily Telegraph could take note after this week’s aberrations laughing called news reports.

  3. GeoffB permalink
    December 16, 2022 9:35 pm

    So the warming is just down to less aerosols (soot) in the air, due to clean air acts in the 60’s and 70’s. That’s a relief no more Net Zero then, planet saved, end of crisis. As if!

    • It doesn't add up... permalink
      December 16, 2022 10:30 pm

      Isn’t the solution to burn more coal?

    • John Hultquist permalink
      December 17, 2022 1:54 am

      In the USA the 1948 Donora smog and in the UK, the 1952 Great Smog of London led to clean air regulations soon after each. It took a long time for the results to be seen. I’m old enough to remember the brown haze hanging over American cities as one approached from miles away.
      Entering that dome of polluted air, I would get runny eyes and soon a headache. Unlike many folks, I’ve never had a warm and fuzzy feeling about large metro areas.

      • catweazle666 permalink
        December 17, 2022 5:26 pm

        I experienced the last big smog in Eccles in Manchester in the 1965 winter, just come out of the pub, bit misty, saw the front of it coming down a long straight road progressively extinguishing the orange street lights, couldn’t understand what it was until it reached us, quite disturbing.

        Then it got to the one we were standing under, put that out too, literally couldn’t see your hand in front of your face, had a right job finding my way home some of which entailed going along the bank of a canal!

        Closed Manchester down completely for three days, and Khant in London witters about pollution, there aren’t literally tens of thousands of Lancashire boilers burning coal of dubious quality firing up at 4AM every Monday morning these days!

        This was during the Great Ice Age scare, of course.

    • Stuart Hamish permalink
      December 17, 2022 4:44 am

      My computer was ‘redirected ‘ and my comments erased as I first attempted to post this contribution so I will try again.

      No Geoff , cloud cover variation probably in tandem with legislated industrial aerosol pollution reductions, provides a more plausible explanation for the resurgent warming from the 1980’s to 2000 following the 60’s and 70s cooling trend and the temperature “pause’ that persisted for over [ 2000 – 2014 ] a decade afterward . Although the 2013 IPCC WRG report mentioned vulcanism and solar irradiance as
      warming hiatus factors , cloud cover changes can account for most of the internal variability in temperatures this century . Even the IPCC has conceded clouds which act as a shading parasol at certain latitudes , are the largest source of uncertainty in climate models so essentially the climate models are bunkum . This is an excerpt from Joanne Novas blog article discussing the Pokrovsky study As one can see from Pokrovskys plotted cloud cover time series , the recovery after 2000 mirrors ‘the pause ‘ rather neatly :

      “cloud cover changes over three decades during the period of global warming can explain not only the linear trend of global temperature but also a certain interannual variability ………….A 0.07C warming effect for each means a fall of 4% in [global ] cloud cover would lead to a 0.3C [rise in ] warming . This is just 1986 – 2000 AD and is roughly the same amount of warming …seen in Hadley ” https://joannenova.com.au/2019/11/new-study-settles-it-global-warming-and-the-pause-was-driven-by-changes-in-cloud-cover-not-co2/

      • Stuart Hamish permalink
        December 17, 2022 4:49 am

        typo : ” A 0.07C warming effect for each 1% decrease in cloud cover means a fall of 4% in [ global ] cloud cover would lead to a 0. 3C in warming …..”

      • December 17, 2022 9:04 am

        Aerosols cause more cloud cover.
        https://earthobservatory.nasa.gov/images/5724/aerosol-cloud-interactions

      • December 17, 2022 10:09 am

        Cosmic radiation can also seed clouds as the work of Friis-Christenson & Svensmark and the CERN Cloud project have shown. Cosmic radiation is increasing steadily as we progress through this solar minimum.

      • dave permalink
        December 18, 2022 9:35 am

        “Cosmic radiation is increasing steadily as we progress through this solar minimum.”

        Or, more precisely, the dips during the active periods of succeeding 11- year solar cycles are smaller. Even today,
        the Oulu numbers are in positive territory and described
        officially as “Elevated.”

        The idea of cloud-seeding from cosmic radiation is interesting, but there is a theoretical problem that the cosmic ray cascades induce nuclei that are too small to do the job. Some sort of amplifying ‘trigger’ must be postulated.

        For what it is worth, Piers Corbyn, who strongly supports the idea of natural variability from solar and lunar influences, does not agree with the seeding concept.

        There are multiple hypotheses about the Sun’s workings and about the dynamics of the solar system as a whole, which is healthy from a purely scientific point of view but frustrating for anyone desiring
        clear predictions.

  4. William Morgan permalink
    December 16, 2022 9:51 pm

    What we hear little of is how little of this Mauna Loa CO2 data on climbing levels, can be blamed on Mankind. The ethical science suggests that historically, CO2 follows warming, not the other way around. Also, CO2 warming is logarithmic, and already saturated. Termites emit more CO2 than man, etc. Our effect on CO2 is around 3%.
    Look towards sources such as Murray Salby, Ian Plimer and Piers Corbyn.

    • Stuart Hamish permalink
      December 17, 2022 11:19 am

      Termites emit more methane than human activity William …..Decaying wood and the role of insect symbiosis in the decomposition process releases more carbon dioxide into the atmosphere each year than humans …Not a lot of people know that

      • Harry Passfield permalink
        December 17, 2022 7:25 pm

        And how long have termites been doing that, Hamish? Certainly not only since 1850.

      • Stuart Hamish permalink
        December 18, 2022 12:48 am

        Since time immemorial Harry ….The study William may have had in mind was this one that conjectured 10.9 billion tonnes of carbon is emitted annually from forest deadwood while termites and other wood matter foraging insects are responsible for 30% of that huge carbon release …..And in their environmentally conscious wisdom the project researchers who co authored this paper : https://science.anu.edu.au/news-events/news/decaying-forest-wood-releases-whopping-109-billion-tonnes-carbon-each-year

        ” recommend deadwood is left in place – in the forest . Removing deadwood may not only be destructive for biodiversity and the ability of forests to regenerate , but it could actually substantially increase atmospheric carbon ”

        Has the the thought ever passed their minds that leaving masses of dead wood in situ – fuel loads by another name – in fire prone ecosystems such as Australia , California and the Mediterranean will inevitably exacerbate future megafires that ” may not only be destructive for biodiversity ” and endanger human lives and property ” but …could actually …increase atmospheric carbon ” ?

        Can we get Justin Rowlatt and the BBC climate unit onto this story ?

      • ThinkingScientist permalink
        December 20, 2022 1:55 pm

        Its a bit longer than “Time Immemorial” Stuart.

        ‘Time Immemorial’ is a legal phrase defined as common law existing before the start of Richard I’s reign in 1189

  5. catweazle666 permalink
    December 16, 2022 10:08 pm

    So we’re back to aerosols…

    ATMOSPHERIC CARBON DIOXIDE AND AEROSOLS:
    Effects of Large Increases on Global Climate.

    Abstract.

    Effects on the global temperature of large increases in carbon dioxide and aerosol densities in the atmosphere of Earth have been computed. It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere. For aerosols, however, the net effect of increase in density is to reduce the surface temperature of Earth. Because of the exponential dependence of the backscattering, the rate of temperature decrease is augmented with increasing aerosol content. An increase by only a factor of 4 in global aerosol background concentration may be sufficient to reduce the surface temperature by as much as 3.5 deg.K. If sustained over a period of several years, such a temperature decrease over the whole globe is believed to be sufficient to trigger an ice age.

    The rate at which human activities may be inadvertently modifying the climate of Earth has become a problem of serious concern . In the last few decades the concentration of CO2 in the atmosphere appears to have increased by 7 percent . During the same period, the aerosol content of the lower atmosphere may have been augmented by as much as 100 percent .

    How have these changes in the composition of the atmosphere affected the climate of the globe? More importantly, is it possible that a continued increase in the CO2 and dust content of the atmosphere at the present rate will produce such large-scale effects on the global temperature that the process may run away, with the planet Earth eventually becoming as hot as Venus (700 deg. K.) or as cold as Mars (230 deg. K.)?

    We report here on the first results of a calculation in which separate estimates were made of the effects on global temperature of large increases in the amount of CO2 and dust in the atmosphere. It is found that even an increase by a factor of 8 in the amount of CO2, which is highly unlikely in the next several thousand years, will produce an increase in the surface temperature of less than 2 deg. K.

    However, the effect on surface temperature of an increase in the aerosol content of the atmosphere is found to be quite significant. An increase by a factor of 4 in the equilibrium dust concentration in the global atmosphere, which cannot be ruled out as a possibility within the next century, could decrease the mean surface temperature by as much as 3.5 deg. K. If sustained over a period of several years, such a temperature decrease could be sufficient to trigger an ice age!

    Schneider S. & Rasool S., “Atmospheric Carbon Dioxide and Aerosols – Effects of Large Increases on Global Climate”, Science, vol.173, 9 July 1971, p.138-141

  6. Stuart Hamish permalink
    December 17, 2022 1:02 am

    This may be of interest to you Paul : the Mike Mann of Medicine who once argued AIDS was transmissable via routine human interaction has published a climate plague jeremiad to coincide with his swansong replete with more of the same pseudoscientific nonsense . How convenient that Dr Fauci who was deeply implicated in the NIH’s gain of function collaborative research with the Wuhan laboratory suspected to be the source of the Covid 19 pathogen is now pushing this quackery . We are way beyond the dawn of Medical Lysenkoism with a nod to James Lindsays brilliant troubling podcast

    ” As I prepare to step down from my dual positions at the National Institute of Allergy and Infectious Diseases [ NIAID ] …….a bit of reflection is inevitable ………The emergence of new infections and the reemergence of old ones are largely the result of human interactions with and encroachment on nature . As human societies expand in a progressively interconnected world and the human – animal interface is perturbed , opportunities are created , often aided by climate changes , for unstable infectious agents to emerge , jump species , and in some cases adapt to spread among humans ”

    ” Anthony Fauci merges COVID & Climate : Infectious diseases ‘ largely the result ” of human encroachment on nature & often aided by climate changes – Published in New England Journal of Medicine ‘ , WUWT , Dec 12 , 2022 .

    There is no evidence whatsoever that infectious diseases have proliferated as a consequence of global warming …Malaria and dengue fever have both receded from the cool climate zones of the Little Ice Age when the contagions were endemic in North America and nothern Europe . The three most virulent and lethal pandemics in human history – the Justinian Plague ; the 14th century Black Death and the 1918 -2o
    “Spanish Influenza ” – all emerged in times of reduced temperature

  7. Broadlands permalink
    December 17, 2022 1:56 am

    Last we heard the atmospheric level of CO2 had made another new record at Mauna Loa. The net result? According to NOAA, as of 2021 the global mean temperature anomaly was up by plus 0.84 °C. And that was lower than it was in 2016. Meanwhile, the equatorial Pacific ENSO remains in the cold La-Nina mode. And it has been seven years since the last warm El-Nino. None of that provides support for any 21st century global warming trend to be due to greenhouse gases.

    • catweazle666 permalink
      December 17, 2022 4:59 pm

      It is interesting that despite there being a claimed reduction in anthropogenic CO2 emission during the CV19 affair – I have seen 17% claimed – there was speculation that this would reduce the overall concentration and “prove” man’s contribution to the ongoing increase, there is as far as I can see no evidence of this on the Mauna Loa graph.

  8. Julian Flood permalink
    December 17, 2022 7:26 am

    1. To lower global albedo. Take 5ml of olive oil. Find a lake. Pour olive oil on the lake. The oil will spread into a one molecule thick layer which will supress the formation of ripples, lowering albedo. See classic experiment by Ben Franklin on Mount Pound, Clapham Common.

    2. To warm a body of water. Repeat 1. The oil layer will reduce evaporative cooling by spreading into a one molecule thick layer. See classic experiments by Lord Rayleigh.

    3. To increase the coverage of a water body with natural lipids. Feed a body of water with dissolved silica, (farming run-off), artificial fertiliser (ditto) and sewage. This feeds oleaginous plankton which bloom. When the bloom peaks and dies (aided by spilt mineral oil from minor spills, see data from SeaWifs satellites which also reduces stirring thereby limiting nutrients being brought from below the dark zone) the resultant smooth warms by 1 and 2.

    4. To quantify the area of the oceans smoothed by 1, 2 and 3. Use the paper by Ruf and Evans who when trying to detect ocean smoothing by microplastic found their Cygnss satellite data was actually revealing lipid/oil smoothed surfaces. Extend their research.

    5. To see how bad pollution smoothing can get, look at the temperature profile of the Sea of Marmara. See 3.

    JF

    • catweazle666 permalink
      December 17, 2022 5:05 pm

      Interesting Julian.

      I wonder if there was any evidence of such smoothing during the Battle of the Atlantic during WWII when huge quantities of petroleum were released in both the Atlantic, Pacific and Mediterranean due to the sinking of oil tankers.

      Also interesting would be to see if anyone was keeping track of atmospheric CO2 concentrations, there were a large number of substantial conflagrations due to bombing of cities and large armoured battles on a number of fronts.

      • Julian Flood permalink
        December 17, 2022 5:57 pm

        “I wonder if there was any evidence of such smoothing during the Battle of the Atlantic ”

        Funny you should say that. If you look up the arguments which blew up over the corrections to sea surface temperatures made by Prof. Tom Wigley you will see the way that corrected temperatures tended to smooth the 1940 to 1945/6 uptick. Prof Wrigley emailed about this and how he reduced it but asked (I paraphrase) “Why the blip?”

        Somewhere on the internet is a Facebook post with a simplified exposition of my argument: some global warming is caused by pollution of the marine/atmosphere interface, don’t know how much but it should be looked at.

        There’s a post about smoothing on TCW Defending Freedom with an image of a truly huge smooth..

        JF

  9. Julian Flood permalink
    December 17, 2022 7:31 am

    If my long and laborious post detailing
    extra warming causes has really disappeared I will sulk for a week. I forgot to mention, suppressed wave breaking causing reduced cloud cover.

    JF

    • Gamecock permalink
      December 17, 2022 11:41 am

      Hint: any post you’ve put significant effort in, save a copy to notepad before submitting.

      Ask me how I know.

      • Julian Flood permalink
        December 17, 2022 9:59 pm

        //laughs//

        I never learn. Besides, two finger typing on phone in bed makes saving awkward.

        JF

  10. Micky R permalink
    December 17, 2022 9:29 am

    Re: climate, the only certainty is that it changes. There is no certainty re: the causes of the changes.

  11. December 17, 2022 10:02 am

    We certainly should not be getting excited by this. The study is 100 per cent model based and giving it credit is still a vote in favour of the aberrant “attribution science”. Basically claims that model runs have the same evidential status as the real world with the implication that the difference between two model runs can tell us the difference between two actual real worlds.

  12. Chaswarnertoo permalink
    December 17, 2022 10:07 am

    So ‘ Teh Sciense’ isn’t settled?….
    No sh1t, Sherlock.

  13. Dung permalink
    December 17, 2022 12:53 pm

    This paper is worthless, light on facts/knowledge but heavy on assumptions. I do not support papers that get to the same results that I get but by junk science methods.

    • catweazle666 permalink
      December 17, 2022 5:09 pm

      IMO it takes us little further than the 1971 Schneider and Rasool paper I quote from above in fact.

      Going round in circles basically.

  14. ancientpopeye permalink
    December 17, 2022 1:12 pm

    I think its hot air generated by politico’s greens and anyone that can make money on promoting lies.

  15. lordelate permalink
    December 17, 2022 5:33 pm

    Well, I am suprised!
    Not.

  16. December 18, 2022 8:47 am

    They say (p 4283) it’s a credible hypothesis that global temperature trend changes since 2000 could be “arising largely from internal variability.”

    People like Roy Spencer have said that for years. But what might be causing the internal variability are they talking about? The Earth has an external power source – the Sun.

    • December 18, 2022 10:27 am

      Nothing “causes” internal variability. It just happens when certain entirely deterministic processes of sufficient complexity play out through time they exhibit a vacillating behaviour. The processes don’t have to be particularly complex either as has been shown with many predator-prey interactions which can be coded up very simply.

      • December 18, 2022 10:31 am

        The essential ingredients appear to negative feedbacks or interacting positive feedbacks and the so-called climate system contains many such within itself and at its contact points with other elements of the broader Earth System.

  17. December 23, 2022 4:06 am

    Reblogged this on Climate Collections.

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