By Julian Cribb AM
Fifty-five million years ago, the Earth took a fever. Somehow, 12,000 billion tonnes of carbon escaped into the atmosphere – and global temperatures soared by 5-8 degrees Celsius over the next few thousand years.
What caused this event [i] is still subject to scientific debate, but a vast release of methane from the deep oceans and burning peat swamps and jungles in the tropics are favoured theories. The key lesson is that it only takes a relatively small push for the Earth to generate catastrophic shifts in heating or cooling on its own.
Underlying all the rhetoric and posturing, the genuine promises and the veiled insincerities at COP26 in Glasgow lies one enormous, utterly risky, assumption: that humans can actually stop the climate machine from cooking the planet. Growing evidence suggests we may no longer be in control of our own fate.
Most people have by now heard of ‘tipping points’ – where the Earth system flips rapidly from one state to another, without possibility of a return. Where a small change in a system makes a vast difference. In the end, humanity’s fate will most probably depend, not on our own actions, but on what happens with nine key tipping points.
- West Antarctic Ice Sheet: currently melting three times faster than it was in the 1990s. If it goes it will lift the oceans by 3.3 metres, and add to global warming by losing the ice that reflects the Earth’s excess heat into space.
- Greenland Ice Sheet: is currently on track to disintegrate completely, raising sea levels by 7.7 metres and adding to global warming by loss of its reflectance.
- Amazon dieback: the world’s largest rainforest is shrinking rapidly before human destruction and fire. Scientists think that once 25% is lost, the rest will rapidly convert to dry savannah and desert, changing the climate both locally and globally. From soaking up carbon, the Amazon has now begun pouring out a billion tonnes a year, adding to human-caused global warming.
- Boreal forest dieback: the northern forests hold one third of all terrestrial carbon. But they are now shrinking rapidly due to logging, forest fires and climate change, removing one of the key ‘brakes’ on global warming. Like the Amazon, they will begin to emit billions of tonnes of carbon instead of absorbing it.
- Frozen methane in tundra and on the seabed is one of the largest carbon banks on the planet, totalling an estimated 3-5 trillion tonnes. The melting of the tundra could yield 240 billion tonnes of carbon, and the seabed far more. Peat fires in former tundra will add to the carbon emitted. Neither process can be halted by human action.
- Monsoon shifts over India, Southeast Asia, China and West Africa are expected to result in increasingly erratic weather, sharper droughts and larger and more frequent floods. So far flood intensity has increased by about a third since the mid-1990s.
- Changing Ocean Circulation: ocean currents are the Earths’ main heat distribution system and their changes presage major climatic disruption over land. The Atlantic Gulf Stream[ii] is already showing signs of breaking down, with serious consequences for Western Europe and Eastern North America in the form of harsher winters and stronger storms. Similar concerns apply to the Southern Ocean current, the largest natural influence on global warming.
- Global Wildfires. The number and intensity of wildfires in forests, tundra, peat swamps, grasslands and semi-arid regions is climbing rapidly. On any day from 10-30,000 blazes rage globally. As fire intensity grows, it will release vast amounts of new carbon into the atmosphere, accelerating global warming, and destroying the very systems that lock it up.
- Changes in Cloud Cover: anxiety is growing over how the Earth’s cloud cover will respond to global heating. As the planet warms, more water vapour enters the atmosphere and clouds form: in theory this should have a cooling effect. However, recent research indicates that in a hotter world, clouds may actually thin out or disperse – admitting more heat.
There are numerous other tipping points and feedbacks, including the loss of the world’s corals, destabilization of the El Nino/Southern Oscillation, spreading deserts and loss of sea-ice which all add smaller or larger impacts to the effects of the major ones.
These tipping points reinforce one another, forming what scientists call a ‘cascade’, which will will add another 1.5 degrees or more to the +3-4 degrees already unleashed by human activity. This will lead to the condition known as Hothouse Earth, in which much of the planet becomes basically unliveable for humans and large animals. Summer heatwave temperatures of 50, 60 and even 70 degrees will become common in the world’s hot regions such as the Middle East, SubSaharan Africa, Australia, southwest USA, the Gobi and Andean South America.
The reason for the urgency at COP26 is that this cascade of self-reinforcing, irreversible changes was once thought to set in once the Earth warms to +2 degrees. However new observational science tells us that most of these effects are already under way at +1.2 degrees and are proceeding faster, some much faster, than expected. Also, there is little we can do about any of them: the Earth is now warming itself.
Humans lit the match. Our home is afire. The dwindling possibility of saving ourselves from immolation requires not only a complete cessation of all human carbon emissions within the current decade, but also heroic measures to remove carbon from the atmosphere, such as replanting half the world with trees. Even then there must be serious doubt whether tinkering with the intricate machinery of the climate will yield anything other than fresh, unanticipated disasters.
It is time to put aside the juvenilia of nationalistic chest-thumping and disputation, and for all peoples together to throw all our energies into a plan for human survival. Otherwise, we embrace the unthinkable.
[i] Known as the Paleocene–Eocene Thermal Maximum
[ii] Known as the Atlantic Meridional Overturning Circulation