(ORDO NEWS) — For many years it has been argued that human intervention will soon lead to a sharp “deoxygenation” of the Earth’s seas and the subsequent death of many species. An unenviable prospect, given that extinctions on land are clearly unavoidable.
New scientific work shows that, on the contrary, it is human intervention that can lead to an increase in the oxygen content in the world’s oceans. Why did the minus suddenly change to a plus?
If we take a bottle of mineral water out of the refrigerator and leave it in a warm room, then the next time we open the bottle, gas will begin to rapidly escape from it (sometimes taking some of the liquid along with it). This is banal physics: the warmer, the less the solubility of gases in a liquid and the more they “rush” out of it.
Exactly the same thing should happen (and is happening) in the modern ocean. In tropical latitudes, much less oxygen and carbon dioxide are dissolved in sea water than in subpolar latitudes. Meanwhile, the fish must breathe something: if there is little oxygen in the water, it will become much more difficult for them to live.
Not surprisingly, in 2022, Science published a high-profile article: anthropogenic CO 2 emissions will lead to the extinction of marine species, and a colossal one, not seen since the extinction of the toothy dinosaurs.
Everything is very logical: carbon dioxide leads to a heating of the planet – from average +14 to +15 for 1970-2020, and heating leads to a decrease in the solubility of oxygen in the ocean.
“Aggressive and rapid reduction of greenhouse gas emissions is critically needed to avoid a large, mass extinction of ocean species,” said Curtis Deutsch, senior author of that sensational work, in no uncertain terms. Simply put, they are waiting for mass death by suffocation.
Why is it important? For two reasons. Here is the first: in the real world, greenhouse gas emissions are not only not decreasing, but also growing rapidly (following fuel combustion).
In the 1960s, CO 2 in the atmosphere was added by 0.8 parts per million per year, in the 1980s – by 1.4, in the zero years – by 2.0, and now by 2.4 parts per year. Simply put, a large and massive extinction of oceanic species looks absolutely inevitable. For the chances of Deutsche’s demanded cuts are, frankly, nil.
And the second reason is that a mass extinction at sea automatically means a major extinction on land. In the history of the Earth, there have simply not yet been cases where one happened without the other. This is an alarming sign: people in the event of a mass extinction will have a hard time.
We don’t see the elephant in the small room?
A clear and understandable picture, however, caused a number of scientists to question. Anthropogenic emissions promise 2-3 degrees of warming – at most 5 (but only in the most daring models). That is, not higher than the average planetary +19.
However, only tens of millions of years ago, the typical average temperature on Earth was +20 … +26. Much higher than promised from anthropogenic emissions. So, if the conclusions of the authors of the article in Science are correct, in that era there should have been a huge, mass extinction of marine species.
It’s just that he wasn’t there. From 56 million years ago to 35 million years ago, by modern standards, it was unthinkably warm: on the shores of the Northern (then non-icy) ocean, the average annual temperature was +12, about the same now in Yalta or Paris. One of two things: either there was an extinction then, or we do not see something very, very important.
The authors of a new, just published paper in Nature were among the scientists who noticed this apparent discrepancy. And they decided to find out directly how things were with oxygen in the ancient ocean of the warm part of the Cenozoic era.
To understand whether the inhabitants of the ocean will suffocate from the current warming, they took the middle Miocene and early Eocene climatic optimums (14-18 and ~54-56 million years ago). As you can easily guess from the names, these eras were named so for the extremely warm climate.
The average annual temperature then reached +26, 11 degrees higher than today, and obviously above the ceiling of anthropogenic warming (earthlings simply do not have enough fossil fuels to reproduce this).
Scientists took the ratio of various nitrogen isotopes in sedimentary ocean rocks during these periods and compared with modern ones.
Normally, the remains of marine organisms undergo denitrification – nitrogen is extracted from them by biogeochemical processes and then transferred to the surface waters of the continental shelf.
The speed of this process is directly related to the amount of oxygen dissolved in sea water: where there is little of it, the process is very weak.
However, it turned out that in both very warm periods studied in the Pacific tropics, denitrification proceeded better – significantly better than in the colder periods before and after. The researchers conclude.
“Contrary to popular belief…our data indicate a decrease in oxygen-poor zones during the warmest parts of the Cenozoic.”
It turns out that instead of “suffocation”, warming has led marine inhabitants to breathe easier.
Why physics didn’t work
A legitimate question arises: how is this physically possible? The same laws of physics applied then as they do today. And from this it follows that there should have been less oxygen in the ocean than in colder epochs.
The authors of the work are also concerned about this issue. They offer two possible explanations. First, with the warming, for some reason, sea creatures stopped consuming oxygen in large quantities. Less people – more oxygen.
What could have caused this? For example, researchers believe, a violation of the circulation of water in the depths of the ocean, which led to a reduction in the amount of trace elements needed by the inhabitants of the ocean. True, there is an important nuance, and the authors themselves honestly write about it:
“However, evidence of [related] changes…. in the periods studied] are few and contradictory.”
To clarify the situation, scientists have tried to find mechanisms that can increase the solubility of gases in ocean water even as temperatures rise.
They soon discovered that the saturation of gases for the oceans could increase very seriously if the mixing of waters in the Southern Ocean surrounding Antarctica is activated. And, characteristically, many models show that the mixing of water there becomes much more intense with warming.
Ultimately, the paper concludes, this mechanism appears to be the most likely explanation for how the record-breaking warm ocean and the ocean depths then warmed up 18 degrees warmer than today could have had more oxygen than it does today.
What does all this give us?
It seems that the work is a simple calming of agitated nerves. Mass extinction from suffocation in the seas is canceled, which means that it will be easier for us, people, to live. Let’s face it: it’s not that simple.
The fact is that the absence of marine extinctions in the warm epochs of the past was not a secret for paleontologists long before this work. As well as the fact that bioproductivity and species diversity during warm epochs – the same early Eocene and so on – do not actually fall, but increase.
Or the fact that warming does not lead to an increase in droughts (as well as floods ), and even reduces human mortality.
The problem was and remains that all this information does not affect the mood of the scientific world as a whole, and therefore, in the end, does not affect our lives. Although it would be worth it: a fierce fight against global warming under the slogan “prevent mass extinction” has been going on for more than a decade.
And there are quite some achievements there: as we already wrote , the current crisis with high prices for fuel and everything else began in 2021 and precisely because of such a struggle.
It is precisely because of the alleged (but not yet confirmed by the experience of past eras) fatality of greenhouse gases that the West blocked investments in fossil fuels, as well as long-term contracts for its purchase, which led to the accelerated inflation observed around the world.
Of course, such achievements cannot stop the growth of anthropogenic emissions. This is impossible, mainly because, within the framework of modern Western energy, a full-fledged transition to renewable energy sources with the rejection of carbon fuel is simply unrealistic.
But the struggle itself – and its ambiguous consequences for humanity – did not become less fierce because of this.
The fact that it is completely isolated from the latest scientific data that refutes the death of corals or mass suffocation of fish from CO 2 emissions is extremely disturbing. It turns out that we humans make decisions of epochal significance, stubbornly ignoring scientific research.
And for this reason, the era of expensive fuel and the same prices for other goods can be seriously delayed. Or not end at all until people in their political and economic decisions stop ignoring well-known scientific discoveries.
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