<
https://theconversation.com/antarctic-tipping-points-the-irreversible-changes-to-come-if-we-fail-to-keep-warming-below-2-207410>
"The slow-down of the Southern Ocean circulation, a dramatic drop in the extent
of sea ice and unprecedented heatwaves are all raising concerns that Antarctica
may be approaching tipping points.
The world has now warmed by 1.2℃ above pre-industrial levels (defined as the
average temperature between 1805 and 1900) and has experienced 20cm of global
sea-level rise.
Significantly higher sea-level rise and more frequent extreme climate events
will happen if we overshoot the Paris Agreement target to keep warming well
below 2℃. Currently, we are on track to average global warming of 3-4℃ by 2100.
While the recent Antarctic extremes are not necessarily tipping points, ongoing
warming will accelerate ice loss and ocean warming, pushing Antarctica towards
thresholds which, once crossed, would lead to irreversible changes – with
global long-term, multi-generational repercussions and major consequences for
people and the environment.
The Earth system is designed to reach equilibrium (come into balance) in
response to climate heating, but the last time atmospheric levels of carbon
dioxide (CO₂) were as high as they are today (423ppm) was three million years
ago.
It took a millennium for the world’s climate to adjust to this. When it did,
Earth’s surface was 2℃ warmer and global sea-levels were 20m higher due to
Antarctic ice-sheet melting. Back then, even our earliest human ancestors were
yet to evolve.
The evolution of humankind could only begin after CO₂ levels dropped below
300ppm, about 2.7 million years ago. Since then, Earth’s average temperature
has fluctuated between 10℃ during ice ages and 14℃ during warmer inter-glacial
periods.
During the past 10,000 years of our present inter-glacial period, Earth’s
greenhouse gas thermostat has been set at 300ppm of CO₂, maintaining a pleasant
average temperature of 14℃. A goldilocks climate – not too hot, not too cold –
but just right for human civilisation to flourish."
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
