February 29, 2024

The Climate #6: Blowing through 1.5

What can prior mass extinctions tell us about where we are taking the global Life fleet?

Humanity sailing over edge of world with all life not far behind

A key point about the five stages of grief is that we can experience them in any order. I oscillated between all five stages: denial, anger, bargaining, depression & acceptance as another six-day February heatwave, with daily minima as high as 30°C (86°F) and maxima topping out at 47°C (117°F), rolled across South-West WA last week.

Fire risk: extreme. Too dangerous to stay in the tinder-dry Nannup bush in this weather. A comfortable time of day for outdoor exercise? None… but best prior to dawn. Energy use powering air conditioners day and night in Perth - our State capital city (pop 2.1 million) - through the roof! I recall a conversation with local Bureau of Meteorology staff in the mid-1990s. We used to average only 2 days above 100°F (37.8°C) during February - the South-West’s hottest month of year for most of the 20th century.

This is, of course, but a taste of summers to come. The multiple heat waves this summer have been brought forward by record warm ocean temperatures and a ‘mild’ El Nino. To quote the Bureau:

“Australia's climate has warmed by 1.50 ± 0.23°C between 1910 and 2023, leading to an increase in the frequency of extreme heat events.”

World ocean map splattered red with patches of anomalously hot seas
Ocean temperatures are breaking records. Source

So it’s official. We are blowing through 1.5°C as we speak. And we are not stopping. Global greenhouse emissions continue to increase at just over 1% per annum. CO2 emissions alone topped 37 Gigatons in 2023 - a new global record. Atmospheric CO2 levels, at 422ppm are at their highest level for 14 million years - an increase of 50% above pre-industrial levels in less than three centuries.

These levels could double by 2100. Children born today will be living with CO2 levels similar to those when Dinosaurs roamed the South Pole, over 60 million years ago. A key question that runs through my mind is: what will be the consequences? Not just for us, but for all life on earth, given the rapidity of these climatic changes.

Atmospheric greenhouse gas concentrations have been both higher and lower than now in the Earth’s past. There have also been several periods during the Earth’s 4.5 billion years existence where life has experienced devastating extinction events. Five mass extinction events where likely 75% or more of all species of life disappeared in less than a couple of million years have occurred over the last half a billion years. All were associated with extremes in atmospheric greenhouse gases. So what can we glean from these events about the relationship between rapid changes in greenhouse gases and the survival of life?


What can we learn from the extinction of the dinosaurs? Source

The Oxygen Catastrophe: 'Hell' freezes over
A good place to start is the earliest event thought to have nearly wiped out all life: the Oxygen Catastrophe (aka Great Oxidation Event). This extinction commenced about 3 Billion years ago and demonstrates that our atmosphere always needs some greenhouse gases - sort of in a goldilocks range - for life to thrive. Too little CO2 and methane - the dominant two greenhouse gases - and the Earth pretty much freezes over.

The catalyst was primitive blue-green algae (aka cyanobacteria) evolving chlorophyll-based photosynthesis. That is, harnessing sunlight to convert CO2 into carbon-based life molecules (eg proteins) and pumping out pure oxygen as waste.

During these hellish times, the earth’s atmosphere was unbreathable, with almost no oxygen and high levels of CO2 and methane. Over millions of years, the cyanobacteria sucked most of the CO2 from the atmosphere and gradually pushed up oxygen levels from near zilch to about a tenth of today’s atmospheric oxygen concentration. The free oxygen rusted a lot of stuff, particularly iron dissolved in the world’s oceans. The oxidised iron fell to the bottom of shallow seas, depositing the banded iron formations we mine for iron ore across the world today, including in WA’s Pilbara region.

Stromatolites on edge of Shark Bay Western Australia
Stromatolites - rare, isolated survivors of the Oxygen Catastrophe- still living at Shark Bay, WA.

The oxygen also reacted with atmospheric methane - a much more potent greenhouse gas than CO2. Atmospheric methane levels plummeted, which together with the falling CO2 levels created an ‘icehouse’ effect. The climate became colder and colder - resulting in glaciers likely making their way all the way from the Poles to the Equator.

It was probably the rise in atmospheric oxygen more than glacial smothering that wiped out so much life. Most life at the time were humble bacteria adapted to living in low oxygen environments (aka anaerobic bacteria). Surviving descendants cause bad breath if you don’t floss properly and make compost stink if you don’t aerate it enough. However, some can still be found living as they did billions of years ago, in rare stromatolite colonies, in an uneasy harmony with oxygen belching bacteria, on the edges of warm shallow seas.

The Great Dying
The poster child of what happens when atmospheric CO2 levels rise ‘rapidly’ is the Great Dying (aka End Permian extinction event), which occurred about 250 million years ago. Less than a quarter of all known species of life, across land and sea, survived this event. Previously abundant corals, trilobites, early fish species and many terrestrial tree, insect and early reptile species were wiped out.

The likely ‘culprit’ was volcanic activity creating the Siberian Traps. This, incomprehensibly massive, million-year, episode of volcanism in Siberia extruded enough lava to cover the entire USA landmass a kilometre deep in fresh rock. Volcanic gas emissions and associated widespread fire on land and underground carbon fossil beds caused about a 4 fold rise in atmospheric CO2 and other greenhouse gases from levels roughly similar to today. Global temperatures rose about 8-10°C. Sea levels rose as warming oceans expanded, ice melted and the Earth became essentially glacier free. The oceans became anoxic and experienced widespread algal blooms as ocean temperatures rose.

Volcano spewing lava beside Dr Spok from Star Trek
Volcanism (not Vulcanism) likely caused the Great Dying

Most extinctions occurred during the ‘rapid’ rise in atmospheric greenhouse gases and temperatures. By rapid, we are talking temperature increases of no more than a degree or two every two to three hundred thousand years. This is rapid when looked at from a geological timescales perspective.

But 'rapid' compared to our fossil-fuel emitting climate recklessness? We have doubled atmospheric greenhouse gases and increased global temperatures 1.5°C in only 250 years. This is three orders of magnitude - a 1000 times faster - than during the Great Dying! Given what we know about the relationship between greenhouse emissions and the Great Dying, the sheer velocity of change we are wreaking upon our atmosphere and ecosystems is breathtaking - meaning - likely to take the breath away permanently from many, many species of life.

Trouble in Mexico
There was perhaps only one mass extinction event which had a more abrupt precipitant than our 250 years of burning fossil fuels. That is, when a 10-15 km (6-9 mile) wide asteroid smashed into the Yucatan peninsula about 66 million years ago, bringing the age of the dinosaurs to an end (aka the Cretaceous-Tertiary extinction).

Most animals larger than 25 Kg were wiped out as the chain of life across the planet was disrupted by ‘sudden’ ocean acidification and dramatic atmospheric greenhouse gas and climate changes. Ocean pH dropped about 0.2-0.3 units due to acid rain over as short a timescale as a few hundred years (lower pH = more acid). This was caused by the asteroid blasting vast quantities of sulphur rich rocks into the atmosphere. The sulphur combined with oxygen to form sulphur dioxide - which acidified the rain.

World ocean map showing severe acidification is likely by 2100
We are on track, by 2100, to acidify the oceans more than the dinosaur-killing asteroid. Source

Many shell-building plankton (aka foraminifera), ammonites, marine and freshwater snails and mussels could no longer build their acid-soluble calcium carbonate shells and were immediately wiped out. A complex cascading chain of ecological collapse ensued; which took several hundred thousand years to restabilise. Ocean acidification and anoxia, greenhouse emissions from volcanism and post impact atmospheric dust and haze may have all played a role in various stages of the collapse and restabilisation.

Shell-building plankton: ocean acidification ‘coalmine canaries’
Today’s ocean pH has dropped by 0.1 units in only a couple of hundred years as the ocean has absorbed our fossil-fueled CO2 emissions. That is, we are acidifying the world’s oceans at least as rapidly as after the asteroid impact.

Modern shell-building plankton are already struggling to synthesise their shells. And we are on a path that will acidify the oceans more than when the dinosaurs went extinct if CO2 emissions are not rapidly reduced. That is, we are on track to wreak catastrophic damage to the world’s largest ecosystems - our oceans - before the end of the century.

The Earth will heal...eventually
The ‘good news’ is other mass extinctions teach us that, on geological timescales, the Earth has mechanisms to moderate high greenhouse gas levels.

For example, algal blooms spawned by hot oceans die and sink, burying carbon under the sea floor. As mountain ranges rise as a consequence of, say, the Indian subcontinent slamming into Eurasia - the Himalayas are still growing - newly exposed mountain range rock absorbs CO2 as it weathers, lowering atmospheric CO2 levels and cooling the planet.

The problem for Life on Earth today is that it takes thousands of years, not decades, for these mechanisms to appreciably lower atmospheric CO2. And our ecosystems need action now.

Atmospheric CO2 and methane graphs showing ongoing straightline increases through end 2023
Atmospheric carbon dioxide (CO2 and methane (CH4) concentrations continue to track higher. Source

Despite all our political masters huffing and puffing, has anyone seen a realistic plan to lower global emissions at all? The measurements at Mauna Loa show there isn't one in action yet. Atmospheric greenhouse gas concentrations are tracking relentlessly higher.

The Anthropocene Extinction - our dangerous experiment
Anyone who thinks that the rate at which we are emitting greenhouse gases and acidifying our oceans is ‘OK’ is kidding themselves. As we continue to heat the planet, acidify the oceans and destroy wilderness, we are losing species at least a hundred times and perhaps as rapidly as a thousand times faster than before industrialisation. A human-induced sixth mass extinction is underway. In the absence of genuine climate action, we risk annihilating most life on earth more rapidly than any prior Mass Extinction.

Vanilla Ice meme - cooking planet like a pound of bacon
We are cooking the planet a thousand times faster than during The Great Dying.

It is impossible to overstate how risky it is continuing our ‘business as usual’ fossil fueled ecocide. When billionaires start to spend less on bunkers and more on global cooling experiments we should take notice. Even they are working out that there is no point having a bunker if there is no food or folk, that is, an ecosystem, to service it.

Apologies... This has ended up a much darker post than I intended when I started researching it. But rather than return to the five stages of grief I began with, perhaps I can scratch out a note of optimism in ..... Chernobyl!

Chernobyl, where humans don’t go much anymore, gives a hint at Gaia’s powers of recovery - even when we make catastrophic mistakes - if we just leave an area alone for a while to recover from our vandalism. Until next time…


Thirty years after the Chernobyl nuclear accident, fewer humans allows nature to thrive. Source


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