Natural climate change remains a mystery

Covid has proven that even large reduction in emissions do not affect global climate. Are we certain that carbon is really the driver? Do we at least understand preindustrial climate change?

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Mgr. Vítězslav Kremlík, web: Climateapocalypse.eu , author of "A Guide to the Climate Apocalypse: Our Journey from the Age of Prosperity to the Era of Environmental Grief" (Identity Publications, 2021), contact: kremlik@seznam.cz  

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Although it seems plausible that the increase in greenhouse emissions has somewhat contributed to the observed warming, we do not understand climate well enough to identify the main driver of the climate change. Climate has been changing many times in the past for reasons unknown and the very same natural factors may be at play now.

Let us look at some examples. In 2008 an article by Mauree Raymo and Peter Huybers in Nature summed up concisely how little we know about what causes the ice ages. True, Milankowitz theory sounds reasonable. A 100,000 year oscillation in the elipticity of the Earth's orbit around the sun means that sometimes in winter Earth is in greater distance from the Sun which makes the winters more severe. However the resulting changes in insolation are seemingly too small to matter. "Perhaps the longest-standing puzzle in the Earth sciences is what caused the Northern Hemisphere ice sheets to come and go… Scientists still do not understand how the subtle shifts in insolation at the top of the atmosphere are converted into massive changes in the ice volume on the ground." [1]

Last Glacial Maximum was about 6°C colder in global average than now. And sea level was about 125 m lower than today. This is a large change of climate. And we cannot exactly explain that. Some research also suggest that the change was quite rapid. "At the end of the last Ice Age ice shelves surrounding Antarctica's coastline retreated at speeds of up to 50 metres a day — much faster than any observed rates today. " These are conclusions of researchers who examined Weddell Sea in 2019.[2]

Another example of Rapid Climate Change are Heinrich Events - recurrent rapid warming events during the last ice age associated with massive ice melting. These events were named after the German researcher Hartmut Heinrich who discovered them in 1988 [3]. These events are thought to have peaked at about 16,800 (H1), 24,000 (H2), 31,000 (H3), 38,000 (H4), 45,000 (H5), and 60,000 (H6) years ago. They occurred in roughly 8,000–9,000-year cycles. Each Heinrich event seems to have occurred abruptly and lasted between about 200 and 2,300 years.

It is not widely known or acknowledged, but Heinrich Events seem to be closely related to the timing of Upper Palaeolithic cultures in Europe. Modern people, that is Homo Sapiens Sapiens, colonised Western Europe around 50 – 40 thousand years ago. The first large culture of these people was Aurignacian whose start corresponds to Heinrich Event 4. The start of Gravettian culture corresponds to Heinrich Event 3. The start of Solutrean corresponds to Heinrich Event 2 and Magdalenian to Heinrich Event 1. This impact of HE on Late Pleistocene cultures has been postulated by multiple authors such as Bradtmöller et al. (2012) or Schmidt et al (2012).

"The North Atlantic Heinrich Events clearly coincide with periods of strong aridity on the Iberian Peninsula… Such rapid climatic switches, associated with HE all around the Mediterranean, must have had tremendous impact on settlement patterns for hunter-gatherers all over Europe, including Turkey and the Near East." [5]

We do not really know what mechanism triggers the HE. Melting of ice sheets has been proposed as the trigger of Heinrich Events, however it does not explain why the sheets started melting in the first place. "To this day, the underlying mechanisms interlinking Dansgaard-Oeschger cycles and Heinrich events remain poorly understood." [6]

Natural drivers of recent climate change are also poorly understood. It has frequently been claimed that changes in solar activity are too small to explain either the cooling in Maunder Minimum or the 20th century warming.

In 1893, English astronomer Edward Maunder noted that between 1645 and 1715 there were almost no sunspots on the Sun, making its activity very weak. In 1976, American solar physicist John Eddy proposed a link between this solar minimum and the cold temperatures of the Little Ice Age down on Earth. Yet there are authors (Schrijver et al., 2011) who claim that the change in Total Solar Irradiance was too small to explain the energy flows associated with extensive cooling of climate. [7]

If the same thing happened today, anthropogenic activity would be blamed because we cannot explain the occurrency by natural drivers. 

During the worldwide pandemic of Covid-19 the production in 2020 decreased by 22 percent compared to year 2019. [8] It had no impact on the concentration of CO2 in the atmosphere. Because human production represents only 5% of annual emissions, the rest being from natural sources.[9] This is not meant to dispute that humans are replenishing the carbon cycle with something new that hasn't been in the atmosphere since the Mesozoic. However it does mean that even if China and other BRIC countries join the decarbonisation effort the results will be almost impossible to see for decades.

We do not understand how climate works yet, but we have already seen how tiny we are compared to the forces of nature.

SOURCES:

[1] Maureen Raymo & Peter Huybers, Unlocking the mysteries of the ice ages. Nature, Vol 451, 17 Jan 2008.

[2] J. A. Dowdeswell et al. Delicate seafloor landforms reveal past Antarctic grounding-line retreat of kilometers per year.Science368,1020-1024(2020).DOI:10.1126/science.aaz3059

[3] Heinrich, Hartmut, 1988. Origin and consequences of cyclic ice rafting in the northeast Atlantic Ocean during the past 130,000 years. Quaternary Res., 29, 142–152.

[4] Heinrich Events. Geomar.de (retrieved on 25 Feb 2025) https://www.geomar.de/en/research/fb1/fb1-p-oz/research-topics/low-to-high-latitude-climate-linkages/heinrich-events

[5] Marcel Bradtmöller et al. The repeated replacement model - Rapid climate change and population dynamics in Late Pleistocene Europe .Quaternary International, Volume 247, 9.  January 2012, Pages 38-49. https://www.sciencedirect.com/science/article/abs/pii/S1040618210004039?via%3Dihub

[6] Schannwell, C., Mikolajewicz, U., Kapsch, ML. et al. A mechanism for reconciling the synchronisation of Heinrich events and Dansgaard-Oeschger cycles. Nat Commun 15, 2961 (2024). https://www.nature.com/articles/s41467-024-47141-7

[7] Feulner, G. (2011): Are the most recent estimates for Maunder Minimum solar irradiance in agreement with temperature reconstructions?. - Geophysical Research Letters, 38, L16706

[8] Robert Monroe. Why COVID Didn't Have a Bigger Effect on CO2 Emissions. Scripps Institution of Oceanography. 3 May 2021. https://keelingcurve.ucsd.edu/2021/05/03/why-covid-didnt-have-a-bigger-effect-on-co2-emissions/

[9] Edwin X. Berry. Human CO2 Emissions Have Little Effect on Atmospheric CO2. International Journal of Atmospheric and Oceanic Sciences (Volume 3, Issue 1, 4 July 2019)