>>The world is now dangerously close to tipping points that will set in motion unstoppable ecosystem collapses. This is a climate emergency.
That’s the message from scientists writing in Nature on Thursday, who say that for some systems, the window to act may have already closed.
A decade ago, it was widely thought that most tipping points wouldn’t be reached until around 5 degrees Celsius of warming, but now evidence is mounting that they’re more likely to happen at between 1C and 2C above pre-industrial levels, according to Will Steffen from ANU’s Climate Change Institute, one of the authors of the paper.
“Models suggest that the Greenland ice sheet could be doomed at 1.5C of warming, which could happen as soon as 2030,” they wrote.
All the evidence from the geological record shows that the earth doesn’t make smooth, slow transitions during times of climate change, according to Katrin Meissner from UNSW’s Climate Change Research Centre, who wasn’t an author on the paper.
Although these systems will take between hundreds to more than 1,000 years to fully melt, even a small proportion of that melting over the coming decades will have catastrophic consequences.
The IPCC predicts that seas could rise by up to 60 centimetres by 2100, even if warming is limited to below 2C.
If the world sticks to its current pledges to reduce emissions, we’re on track to hit 3C of warming, the authors say.
Other tipping points that we’re fast approaching include the collapse of coral ecosystems, which are likely to contract in diversity by more than 90 per cent as warming approaches 2C.
That in turn is likely to trigger a massive collapse in sea life including fish stocks which depend on those systems.
Melting in Greenland is causing an influx of freshwater into the North Atlantic, which has already slowed circulation in an Atlantic ocean current that feeds rainfall to the Amazon.
If Amazon rainfall decreases, converting it to a drier system, up to 90 gigatonnes of CO2 will be released into the atmosphere.
“The intervention time left to prevent tipping could already have shrunk towards zero, whereas the reaction time to achieve net-zero emissions is 30 years at best,” they wrote.
It’s time to listen to the kids, Professor Steffen said.<<
https://www.abc.net.au/news/science/2019-11-28/climate-emergency-kids-are-right/11735942