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

Posted: December 16, 2022 by oldbrew in aerosols, climate, Emissions, Natural Variation, research, Temperature
Tags: , ,

It’s ‘study suggests’ time again. NZW: They say (p 4283) it’s a credible hypothesis that global temperature trend changes since 2000 could be “arising largely from internal variability.”
— These results definitely won’t please the climate obsessive tendency.

– – –
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, says Net Zero Watch.

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 we are living through a period of considerable natural climate variability.

Full article here.

  1. catweazle666 says:

    “They say that most of change in trend is not due to greenhouse gasses but to aerosol emission reductions”


    Effects of Large Increases on Global Climate.


    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

    Those results were based on a climate model developed by none other than James Hansen, incidentally.

  2. JB says:

    Hard to extend any credibility to these barnyard prognosticators when they can’t get their basic units correct. There are no degrees in Kelvin temps.
    Beklagelig, there is no Atoz (STOS) to send them back in time to join the dinos with their higher CO2/O2/temps. Blame them.

  3. Graeme No.3 says:

    CatW… yes, I remember when increasing aerosols (polution) were going bring on the next ice age. So are all those stories about Chinese, Indian and all other countries whose cities have high smog levels actually decreasing the risk of Global Warming©?
    That must be it! After all the only other explanation is that the effect of rising CO2 has been much exaggerated.
    JB: Just because (warm blooded) dinosaurs survived for over 200 million years at CO2 levels way higher (1000 – 2700 p.p.m.) than the current ‘danger level’ of 550 p.p.m. doesn’t mean anything tothose who think the world started in 1979.

  4. dodgy geezer says:

    What they are saying is not new – diminishing impact as CO2 increases has been discussed for 20 years to my knowledge. But perhaps the Overton Window is opening..

  5. oldbrew says:

    The Asian Brown Cloud aka Atmospheric Brown Cloud @ Wikipedia

    Global warming and dimming
    The 2008 report also addressed the global concern of warming and concluded that the brown clouds have masked 20 to 80 percent of greenhouse gas forcing in the past century. The report suggested that air pollution regulations can have large amplifying effects on global warming.
    . . .
    Black carbon in snow causes about three times the temperature change as carbon dioxide in the atmosphere. On snow—even at concentrations below five parts per billion–dark carbon triggers melting, and may be responsible for as much as 94 percent of Arctic warming.

    – – –
    Pick the bones out of that 🤔 (‘masked’?)

    NASA says (c. 2007):
    This study shows that unless they take into account the greater area covered by clouds when aerosols are present, scientists may be seriously underestimating the climate-forcing potential of aerosols. [bold added]


  6. Phoenix44 says:

    The reason we should all be sceptical is because we do not know. We don’t know whether it’s natural variability, we don’t know the ECS of CO2, we don’t know about feedbacks, we don’t know about the various climate cycles, we don’t know about aerosols, we don’t know about obliquity, we don’t know about clouds and cosmic rays and we don’t know whether there’s other stuff we don’t know about.

    Climate science is a vast preponderance of ignorance, yet climate scientists are so absurdly certain.

  7. Chaswarnertoo says:

    ‘Teh Skiense’ isn’t settled? Oh no!

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