Let’s continue from where I left in previous post about a Newsweek fact check of the claim that “humanity would end by 2023”. This claim was made in 2018 and attributed to James Anderson in a gritpost article. The fact checker made the argument that the gritpost article didn’t correctly report on Anderson’s claim and that the claim was in fact about the polar ice caps, more specifically, that “unless the world stopped using fossil fuels by 2023, the effect on the polar ice caps would be irreversible“.
That seems rather vague, especially after having read the articles that were used by the fact checker. I think he pretty much understated the actual claim that was reported in those articles:
The chance that there will be any permanent ice left in the Arctic after 2022 is essentially zero.
It was also reported that Anderson believed that it would not be possible to recover just by reducing emissions. It would take a WW2-style transformation of industry, starting to remove carbon dioxide from the atmosphere and making an effort to reflect sunlight away from the earth’s poles. This all had to be done within five years, otherwise no permanent ice would be left after 2022. By the way, we didn’t do any of these in the last five years.
Because of the statement that an effort to reflect sunlight away from the earth’s poles would be necessary, I initially assumed that the albedo effect would be important in Anderson’s reasoning and therefor Arctic sea ice extent would be the dataset to look at in order to figure out how Anderson envisaged the Arctic sea ice plunging towards zero in those five years.
But then, I played around with Arctic sea ice extent data at the end of last year and couldn’t remember seeing anything that would point to this.
The claim was attributed to a speech that Anderson gave in January 2018, so the latest known minimum extent data point back then was of September 2017. Trying some trends from 1979 until 2017 that eventually go to zero gives this:
The quadratic trend went to zero by 2040 and the linear trend by 2070. Other trends didn’t even go to zero. This made me wonder which trajectory Anderson anticipated back in 2018. That must have been a pretty steep decline in order to get to zero in just five years…
Then I found an AP fact check in which Anderson was asked whether he actually made the claim in 2018 that “humanity would end by 2023” (my emphasis):
He said that during the seminar, he was displaying the most recent observations of Arctic sea ice volume – specifically the ice floating on the Arctic Ocean – and made the statement that “the current observed rate of floating ice loss volume, there will be no floating ice remaining by 2022.”
The focus of the statement was on the floating ice volume and the observed rate of disappearance at that time, he said.
If that quote is accurate, then this learns me two things. First, it confirms that Anderson actually made the claim that there would not be Arctic sea ice left by 2022. Second, Anderson’s prediction was in fact a projection of the Arctic sea ice volume trend using the observations that were available at the beginning of 2018.
Could that be the case? Trying some trends from the minimum volume data until 2017 indeed shows that the quadratic trend crosses the x-axis at 2023:
So yes, it is entirely possible to arrive at a sea ice free Arctic in 2023, by looking at volume instead of extent.
It is a bit underwhelming though. Anderson was presented in the gritpost article as a “top climate scientist”, a title that gave much more weight to what he was saying and this resulted in people taking his claim at face value. His dire prediction was however not based on knowledge about the Arctic sea ice, but was just a simple projection of a trend that seems to have changed trajectory in the meanwhile.
via Trust, yet verify
April 14, 2023 at 04:34PM