Dozens of rapid warming and cooling periods episodically occurred throughout the last glacial. However, they have often been dismissed as local-only events. A 2020 study published in Science robustly affirms steeper-than-today warming periods spanned both hemispheres and 23 of 25 were “globally synchronous.”
Geologists have long recognized that Greenland abruptly warmed up by 5 to 16°C “within a few decades to centuries” about 25 times in the last ~100,000 years (Capron et al., 2021).
These past abrupt climate changes do not even require a clear external trigger to explain their provenance. They can simply be “unforced or noise-induced oscillations” internal to the climate system (Capron et al., 2021, Li and Born, 2019).
Image Source: Capron et al., 2021
The magnitude and rapidity of the temperature changes occurring during the last glacial were many times greater than what has been observed in the modern era.
In the last 100 years , for example, 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.
Globally, the average warming rate is just 0.05°C per decade since 1860 (Zhu et al., 2018).
Image Source: Zhu et al., 2018
When it’s pointed out that there were about 25 unforced, naturally-occurring abrupt climate changes (called interstadials) much faster and of much greater magnitude than the last few centuries, those wishing to advance the claim that modern warming is human-induced and unprecedented typically suggest these past warming episodes were just local changes specific to Greenland.
But a growing body of evidence from 63 independently published records has led scientists to conclude there was “synchronous timing” (within a few decades) spanning the entire globe – from Greenland to Antarctica to the tropics and mid-latitudes – for 23 of these 25 warming episodes (Corrick et al., 2020).
In other words, modern global warming is no more “special” in its magnitude or speed than the much larger unforced global climate changes internal to the climate system pervading the last glacial period.
“… those wishing to advance the claim that modern warming is human-induced and unprecedented …”.
It is certainly not unprecedented even in the instrumental record (such as it is); the warming rate 1910 – 1945 was faster than that post 1980 and could not have been caused by human emissions.
https://www.woodfortrees.org/plot/hadcrut3gl/from:1900/plot/hadcrut3gl/from:1910/to:1945/trend/plot/hadcrut3gl/from:1980/trend
Nonetheless, logically, historical natural climate fluctuations can have no bearing on to what extent the presumed post-1945 (as per IPCC) warming was induced by human emissions, nor whether that warming was good, bad or indifferent.
The warmists’ last argument is that the speed of the ongoing warming is unprecedented: About 1°C within one century.
Now we know that there were faster and greater warmings by the end of last glacial.
[…] There Were 23 Global Warming Jolts Many Times Faster And Greater Than Modern During The Last Glacial […]
[…] Malgré ses 14 000 références, ce nouveau rapport du GIEC est incomplet et ne mentionne pas les publications que nous pourrions qualifier de gênantes. Voici un exemple : le 21 août 2020, il y a presque un an, paraissait dans le journal Science un article de Corrick et collaborateurs[2] concernant les évènements de Dansgaard-Oeschger (DO). Cet article, non cité par l’AR6 (comme le montre une recherche informatique rapide par mot-clé), démontre que les évènements DO se sont déroulés sur la planète entière, et qu’il ne s’agit pas d’évènements confinés à certaines zones comme les alarmistes du CO2 tendent à vous le faire croire. […]
[…] Malgré ses 14 000 références, ce nouveau rapport du GIEC est incomplet et ne mentionne pas les publications que nous pourrions qualifier de gênantes. Voici un exemple : le 21 août 2020, il y a presque un an, paraissait dans le journal Science un article de Corrick et collaborateurs[2] concernant les évènements de Dansgaard-Oeschger (DO). Cet article, non cité par l’AR6 (comme le montre une recherche informatique rapide par mot-clé), démontre que les évènements DO se sont déroulés sur la planète entière, et qu’il ne s’agit pas d’évènements confinés à certaines zones comme les alarmistes du CO2 tendent à vous le faire croire. […]