Mass extinctions and temperature

By April 22, 2023Environment, Science

I missed a paper from a couple of years ago; but it is a bit disturbing nonetheless. It deals with the relationship between extinctions and the past heating of the planet1.

French anatomist and naturalist Georges Cuvier (1769-1832) established the concept of extinction as a fact, whereas it had been considered very speculative previously2. Indeed, some had suggested the organisms considered to be extinct still existed in a remote part of the world where they awaited discovery3. In his Essay on the Theory of the Earth (1813), Cuvier proposed that now-extinct species had been wiped out by periodic catastrophic flooding events2.

Most of the organisms that have ever existed on this planet are extinct, and a proportion of them became extinct in what are termed mass extinction events. Scientists have known for decades that these extinction events wiped out a fairly large proportion of the species on the planet at the time. There have been five large extinction events (the ‘big 5’) in the last 450 million years. They are:

  • End Ordovician event
  • Late Devonian event (aka the Frasnian-Famennian event)
  • End Permian event
  • End Triassic event
  • End Cretaceous event4

Numerous mechanisms have been suggested to account for these mass extinctions, and several of these have recently received an enormous amount of supporting evidence as to their ultimate cause. However, one of the factors which has been difficult to measure is the temperature rises and falls in the past. This is usually done by using what is termed a palaeothermometer and they range from isotopic ratios, elemental ratios, all the way to leaf physiognomy. However, the most commonly used technique in deep time is the oxygen isotope ratio (i.e. the ratio of 18O to 16O). High values for this ratio (i.e. more than the standard 2005 parts per million) means low temperatures. In ancient rocks this is quite commonly measured in the biomineralized parts of marine fossils (foraminifera, conodonts, brachiopods, belemnites etc.) because these shells have been deposited in isotopic equilibrium with the surrounding water5. Hence, it is a way of determining the temperature of that marine water.

Although it may not be the ultimate cause of the extinctions, we do know that climate change has been the proximal cause of mass extinctions in the past. However, calibrating this relationship has been difficult. The paper I missed was by geoscientists from the China University of Geosciences in Wuhan; they have attempted to do that by using oxygen isotopes to show this relationship. To attempt to do so, they looked at the magnitude as well as the rate of temperature change and compared that with the extinction rates of marine animals as portrayed by the fossil record through the past 450 million years (Myr). The results showed that both the magnitude and the rate of temperature change are significantly positively correlated with the extinction rate of marine animals1.

They also found that the major mass extinctions in the last 450 Myr can be linked to thresholds in climate change (warming or cooling) that equate to magnitudes of greater than 5.2°C increase (or decrease), and rates of increase (or decrease) of greater than 10°C/Myr1.To make sure that the five large mass extinctions had not skewed their results, they excluded those from a second analysis and found that the relationship between temperature change and  extinction still applied1. Their findings have the corollary that a temperature increase of 5.2°C above the pre-industrial level and at the present rate of sea surface temperature increase (0.078°C per decade6, which equates to a rate of increase of over 7,000°C/Myr!), we are in line for an extinction event similar to those listed above as the ‘big 5’ extinctions.

Indeed, the 6th mass extinction is probably already under way, this time caused entirely by humans. Considerable evidence indicates that there is a biodiversity crisis of increasing extinctions and plummeting abundances, but some people deny this is happening, arguing that the rate of species loss does not differ from the background rate. In this, they rely on the International Union for the Conservation of Nature’s ‘Red List’ which lists species threatened with extinction. However, the Red List is heavily biased towards birds and mammals and only lists a minute fraction of invertebrates that have been evaluated against conservation criteria. Incorporating estimates of the true number of invertebrate extinctions leads to the conclusion that the current extinction rate vastly exceeds the background rate. For example, molluscs are the second largest phylum in numbers of known species, and it is estimated that since about 1500, as many as 7.5–13% (150,000–260,000) of the 2 million known species have already become extinct, orders of magnitude greater than the 882 (0.04%) on the Red List7.

The sea surface temperature is now on average about 0.9°C warmer than the pre-industrial average (1880-1900), with the temperature increasing 0.6°C over the last four decades alone8. While, the atmosphere heats up faster than the ocean as the latter has a greater heat capacity9, the heat in the atmosphere will eventually heat the oceans up, and the rate of heating of the atmosphere is increasing faster than predicted. The aim of the Paris agreement, which entered into force in November 2016 was to hold the increase in the global average atmospheric temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels10.

Given that the world’s temperature has already increased by 1.2°C, keeping the temperature increase below 1.5°C seems a forlorn hope. 1.5°C was expected to be reached by about 2040 according to the Intergovernmental Panel on Climate Change report from 202111. At COP27, which was held in Egypt in 2022 it was suggested that 1.5°C might be reached by 203012. Now it is predicted by the World Meteorological Organisation that 1.5°C could be exceeded as early as 202613.

We are in deep, deep trouble, but the problem might be worse than is indicated by global averages increasing as they are. This is because averaging hides the differential heating of parts of the planet and the parts that are heating the fastest have some of the most dangerous feedbacks.




  • Arthur Baker says:

    About three weeks ago, a “mate” of mine, a long-term so-called “Liberal” voter, with whom I argue frequently, referred to “these Nutjob Greenies who think they can transition to Net Zero by 2030 and get rid of all fossil fuel generation, totally impossible.would be lucky to do it by 2050”.

    Here’s an edited, much shortened, version of my reply. (The original included a number of expletives, deleted in what follows).

    Begin quote:

    In the 26-year period between 1996 and 2022, the Fraudulently-Named “Liberals” (FNL) were in what they laughably called “government” for 20 years, During that time, they not only COMPLETELY FAILED to make even the most basic plans to counteract the climate catastrophe predicted by 97% of the world’s most eminent climate scientists, but also MUDDLE-HEADEDLY ACCUSED the same climate scientists of participating in a ludicrously impossible worldwide conspiracy, OPENLY MOCKED those who intelligently and justifiably advocated urgent action, SHAMELESSLY DENIED that there was even a hint of a potential problem, MASSIVELY FAVOURED their rich fossil-fuel-producing political donors, and SIGNALLY FAILED to take the opportunity to convert Australia from one of the world’s largest exporters of climate-destroying materials into a world-leading supplier of environmentally-friendly renewable technology – which Australia easily could have been, with a government which even remotely cared about the future of its own grandchildren.

    For the remaining six years (2007-2013), they made not one skerrick of positive contribution to Australia’s national prosperity, wellbeing or international reputation, instead preferring to embark on a six-year campaign of relentless negativity in an attempt to sink and demonise and misrepresent and destroy any darn thing that the Rudd/Gillard/Rudd interregnum proposed, not on the basis that the RGR initiatives were intrinsically inadvisable, but simply on the basis that they (the FNL) were The Opposition, and therefore their job was to bull-headedly OPPOSE every darn thing the Labor Party put forward.

    The Albanese government which came to power after the May 2022 election was therefore the inheritor of more than a quarter of a century of stubbornly obstructive anti-environmental tactics whose only purpose was to prolong or maximise the FNL’s grip on power, with NO THOUGHT WHATEVER about any long-term prospects for a liveable planet for Australia’s (or indeed any country’s) younger people. The FNL, for a period of 26 years, didn’t give a flying fart about the obviously oncoming climate disaster, and arguably some of their principal representatives should be facing a court somewhere, charged with crimes against humanity, criminal negligence risking the destruction of human society as we know it, and disregard even for the conditions in which their own grandchildren and further descendants might be condemned to battle to survive.

    TWENTY-SIX UTTERLY WASTED YEARS – during which no progress was made in the blatantly necessary struggle to combat climate change in Australia, and during which time, for the most part, you voted robotically for the FNL dingbats.

    That’s the sickening mess that Labor is now having to try to clean up, and because the ALP is politically cowed into caution owing to the relentless negative attacks by the FNL, the Greens are attempting valiantly to make their climate mitigation efforts worth the trouble of even writing down.

    And now? This very week, the UN’s Independent Panel on Climate Change has issued its final plea to the world that if urgent action isn’t taken RIGHT NOW, the 1.5 degree barrier will be exceeded, with appalling potential consequences.

    Now, you have the exquisite effrontery to sit there and (seriously!?) type out a message accusing the Greens of being “Nutjobs”? When you’re ready to talk politics with even a modicum of reason and accountability, be sure to let me know.

    End quote

    • admin says:

      A superb reply. Because of people like your ‘mate’ and the people he votes for, it is likely that much of the planet will become uninhabitable. I’d be interested to hear if he does reply.

      • Arthur Baker says:

        Thanks. He won’t reply now, because a couple of weeks have elapsed, and if he has anything even half-intelligent or half-coherent to write, he’s usually shooting back within 24 hours. Silence from his end for anything more than about 48 hours means he’s given up trying to think of any way to justify what he wrote or refute what I wrote, and he doesn’t want to make himself look even more idiotic (there are a few others in our informal discussion group).

  • Arthur Baker says:

    And he didn’t reply. Which is always a sure sign that the message got through and he can’t think of anything credible to say about it.

    • admin says:

      I saw something online a day or so ago which seems pretty true. These people abuse greenies etc. because they do not have any cogent arguments to counter the science. In addition, something I have said for quite some time is that RWNJs tend to accuse others of the crimes they commit themselves.

  • Mark Dougall says:

    Thank you Arthur and thank you admin. Great posts. Now I’ll let off some steam.

    I got into an argument on the Guardian comments yesterday with an atrocious idiot who stated that not only was climate change fairly unimportant but that it would actually help reduce the number of deaths worldwide. He was jumped on immediately by a number of posters one of whom called him a swivel eyed loon, which I really think was all that needed to be said. Unfortunately I responded saying he was promoting a lie. He then claimed that it was in the Lancet and that was his proof. I went to last years Lancet state of the climate report which said, as you imagine, no such thing. I copied some of the report and attached a link to it. The hidiot (hideous idiot) then stated that I was wrong. That he had read all about it on EurekAlert (which I had not heard of). It’s apparently some science type news alert thing which has a disclaimer that it cannot verify the authenticity of all the items it publishes. So I read several EurekAlert Lancet Climate Change related news drops and they all were warning of the adverse consequences. The bloke was stark staring mad. It just makes me so angry that these appalling fools lie, lie again and then defend their lies, and even pretend that there is science backing them up. They feed this garbage to naive people they and it gets believed because it is what they want. They do not want it to be real but if it is real it is good. I wish these particular turds would go extinct very quickly. If only they would it would spare all the rest of the lifeforms on this poor old world from having to put up with their utterly pointless and vilely harmful bullshit.

    • admin says:

      I have noticed that sort of thing a few times: Vegetables taking something that someone said on a blog/site/video with reference to some scientific journal/article/book, as gospel when, in fact, it takes the gist of said journal/article/book and turns it around to say the opposite. The bastards that do this do so out of malice, while the vegetables who believe it, simply do not have the knowledge to understand what they are regurgitating. If I was The Lancet, I’d go after the malicious bastards and take them to the cleaners.

    • Arthur Baker says:

      “it gets believed because it is what they want.”

      Thanks Mark. And isn’t that just the most succinct summary of the recent Dominion v Fox News imbroglio? The Fox News people realised that if they spoke the truth (which in that case they knew to be the truth), their audience would switch to another channel, Fox would lose advertisers and sponsors, and Fox might go broke. They knew that their audience (coached into accepting falsehoods by, you guessed it, Fox) were now so utterly brainwashed that the only thing they wanted to hear was the bullshit they wanted to hear. So the Fox people had painted themselves into a corner from which they couldn’t possibly speak the truth because if they did, they’d be out of a job.

      I love stuff like that. Not that their admission of fault will do anything much to stem the tide of bullshit which vomits out of right wing media, more’s the pity.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.