Scientists Again Affirm Natural Warmings Of 5–16 °C In ‘A Few Decades’ Can Be ‘Entirely Unforced’

A new study asserts that when Greenland naturally warms by multiple degrees per decade, this “abrupt climate variability can result entirely from unforced or noise-induced oscillations of the coupled atmosphere-ice-ocean system.” This means the recent modest climate changes for Greenland may easily fall within the scope of an unforced natural variability pattern.

In the last 100 years Greenland has not experienced any obvious net warming. In fact, not only was the “1919–32 warming trend […] 33% greater in magnitude than the 1994–2007 warming” (Box et al., 2009), but the Greenland ice sheet has not warmed (net) since the early 2000s.

Now a new study (Capron et al., 2021) has shown Greenland only needs a few decades to warm up by anywhere from 5 to 16°C. These abrupt warmings have occurred rather routinely in the past – perhaps every few millennia.

And even though these past climate changes are many times larger both in magnitude and rapidity than those witnessed in the last century, they do not even require a clear external trigger to explain their provenance. They can simply be noisy oscillations internal to the climate system.

Image Source: Capron et al., 2021

Another recent study determined Iceland was ~2°C warmer and the Arctic region had much less sea ice as recently as ~1400 to 1000 years ago (Miles et al., 2020). In the last 1400 years the Arctic experienced marked climate changes (~1.5°C in decades) that may have occurred “spontaneously,” or without requiring “an external trigger”. So, again, abrupt warming (and cooling) events may arise largely as a consequence of unforced natural variability.

Image Source: Miles et al., 2020

If climate changes of these magnitudes can and do occur without an external forcing mechanism, there is little reason to assume that the much more modest changes in the last century fall outside the range of internal variability either.

7 responses to “Scientists Again Affirm Natural Warmings Of 5–16 °C In ‘A Few Decades’ Can Be ‘Entirely Unforced’”

  1. ArndB

    The clear naming of the period 1919-1932 as a warming at the East coast of Greenland, which was part of the Early Arctic Warming from end of 1918 to 1939 is appreciated. A discussion at (published as book 2009)links the change to external forcing, namely the naval war during the First World War from 1914-1918. Book pages 106.

  2. James H. Shanley

    I agree that “abrupt climate variability” is likely to have had an impact on
    Greenland ice cap. We should keep in mind however that the ice cap is reputed
    to be over 9,000 feet thick. If that is the case, the ice cap will loose mass
    from the bottom. When the ice cap that covered Canada and northern US reached it’s maximum about 50,000 to 20,000 years ago New York’s Hodson River carried a lot of water, and cut a channel below it’s present outlet to a point which is 300 feet below todays sea level. Experts claim that the ocean was maximum 400 feet below present level. That represents a lot of water that had to be evaporated from the ocean and it follows that a lot of heat was required. Perhaps we should consider the possibility that the ice age was caused by global warming.

  3. RoHa

    “the recent modest climate changes for Greenland may easily fall within the scope of an unforced natural variability pattern.”

    It *may*, but we know that it is *actually* caused by Man Made CO2. It said so in the Sunday paper.

    1. The Indomitable Snowman, Ph.D.

      Natural statistical variability is a strangely-understudied aspect of climate and weather. It is facial obvious that natural variability in this particular system is enormous, but this never gets the attention it deserves.

      For example, the idea of a “normal temperature” is based on averaging 30 years of data for, say, the measured high temperature on that particular date; this average is a “mean” not a “normal” – as “normal” implies that the same number is generated in lockstop year after year (it isn’t). When one rolls a pair of dice, the “average” result is a 7, but this is not a “normal” result as the word is interpreted.

      More importantly, the concept of a mean value (i.e., average over the data in question) is basically meaningless unless it is accompanied by an accompanying number for the standard deviation. If you bother to go compute them, the standard deviations in this system are enormous – which indicates that the system is going to be dominated in its behavior (particularly in the short-term) but statistical variability in what is otherwise a stable underlying system. And the enormous standard deviations also imply difficult limits to the know-ability of a variety of things.

      And this is on top of the simple fact that this system is a driven/dissipative system, and will show all sorts of bizarre organizing phenomena. Things like the Madden-Julian oscillation are one of my favorites on that count…

  4. CO2isLife

    I’ve updated the graphics to include CO2 and the Trend in Temperatures.

    In my opinion, this data set is undeniable proof that if you isolate the impact of CO2 on Temperature by controlling for the Urban Heat Island Effect and Water Vapor you can demonstrate that CO2 does not impact temperatures in the lower Troposphere.

    These graphics also highlight how any causative relationship between CO2 and Temperature is basically non-existent, and if you place CO2 and Temperature in a Multi-Variable Linear Regression Modeling Program such as R, SAS, or even Excel you will get a non-significant R-Squared and coefficient on CO2.

    Lastly, I put a regression line on Temperature. You can see that:
    1) Some Months are (+) some months are (-)
    2) The high volatility of the data make the slope basically meaningless
    3) Climate Alarmists have no answers for the evidence I’ve provided with these graphics. Even their nonsensical slope arguments are debunked with those charts. I have more (-) slopes than they have (+), but the fact that the same location has both (+) and (-) Slopes depending on the month pretty much proves regression slopes are useless in this analysis.

    Here is the Evidence:

  5. Phil Salmon

    The AMOC is key to this – the chaotically excitable feedback driven Atlantic Meridional Overturning Circulation – gives chaotic variability to the whole northern hemisphere, especially the North Atlantic. In contrast to the Southern Hemisphere which has no corresponding system and whose climate is much more stable and slow-changing.

    AMOC driven variation in the strength of the Gulf Stream should be the null hypothesis explanation for climate changes on a decadal scale in the NH. But with the myopic focus on recent warming as “unprecedented”, this obvious source of climate variability has been overlooked.

  6. Phil Salmon

    This n a nutshell here’s the positive feedback that drives the chaotic oscillations of the AMOC and with it, the whole northern hemisphere climate.

    Tropical water carried toward Europe on the Gulf Stream is more saline than North Atlantic water. But eventually this water flows north all the way to the region between Norway and Greenland where it gets cooled down – but it still hasn’t lost its elevated salinity. This combination of near freezing temperature and still higher salinity gives this water very high density – enough to make it sink right down to the ocean floor. This downwelling is the “propeller” that drives the global system of 3-dimensional ocean circulation that is for that reason called the “Thermohaline circulation” or THC. The downwelling such as in the Norwegian Sea is also called “deep water formation”.

    The reason why it’s a positive feedback is that the downwelled cold water has to go somewhere and it flows south along the ocean floor. (It’s not uncommon in the THC for currents at different depths to be flowing in different directions.) For conservation of mass and to prevent an embarrassing slope developing on the ocean surface, water at the surface has to flow north to compensate; in this way the flow circuit of the Gulf Stream – called the AMOC or Atlantic Meridional Overturning Circulation, self-reinforces in a positive feedback.

    This positive feedback is intermittent and not continuous – otherwise the North Atlantic would end up spinning like a washing machine or the scene at the end of Pirates of the Caribbean – at world’s end. Accelerated Gulf Stream circulation warms the Arctic by carrying warm water northward. However this warmth melts Arctic and Greenland ice eventually releasing into the North Atlantic enough fresh water to choke off the Norwegian Sea downwelling. Then we’re back to square one and the cycle begins again. It’s chaotically intermittent with a time period varying between 30-70 years, and is sometimes called the AMO (Atlantic Multidecadal Oscillation).

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