When will the planet really start to heal?
The coronavirus crisis has helped the planet heal, according to the meme-makers on the internet - but we’ve just been given an indication of how long that process could actually take.
Climate Change
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From coyotes roaming the streets of San Francisco, to NASA satellite imagery showing massive drops in air pollution, the coronavirus crisis has spawned some good news stories for the planet.
The worldwide lockdowns and slowdowns have also led to a significant cut in greenhouse gas emissions, although new modelling shows it could take decades for these declines to have any actual impact on temperature trends.
Scientists including Dr Pep Canadell at the CSIRO recently found that daily global CO2 emissions had decreased 17 per cent from average 2019 levels by early April 2020. That research estimated global emissions would drop by somewhere between 4 and 7 per cent in 2020, depending on how long COVID-19 curtailed normal human activity.
But modelling by Norwegian scientists published today in Nature Communications suggests it could take decades before even significant emissions reductions led to detectable changes in global surface temperatures.
The team found that a zero emissions goal for carbon dioxide would make a difference on its own of just over one degree (1.05 celsius) to global temperatures by the year 2100.
If global carbon dioxide emissions dropped to zero in 2020 (which is not going to happen), the effect on the planet’s temperatures would start to be noticeable by 2033, while a progressive annual reduction of 5 per cent would start to be noticeable in 2044, the researchers found.
The researchers, led by Bjorn Samset at the Centre for International Climate and Environmental Research, said the modelling showed mitigation efforts were not a quick fix.
“These are expectations that need to be clearly explained and communicated to policy makers, and to the public, if we wish to avoid a backlash against perceived ineffective mitigation policies,” the researchers said in the paper.
Professor Mark Howden, the Director of the ANU Climate Change Institute, said the lag between action and effect was a huge challenge.
“It’s much easier to make decisions where you’ve got a fast cycle time between your response and the reaction, because then you can adjust your responses accordingly. But when you’ve got a big lag then it makes that decision making much more problematic. That’s when you need to rely on models and projections, and some people have a view that they’re inadequate for that particular purpose.”
Prof Howden said he expected Australia’s greenhouse gas emissions for 2020 to be “largely similar” to the global trend.
The lockdown had produced emissions reductions at enormous cost, he said, but there were smart ways to achieve a similar or better result that did not wreck the economy.
“What the coronavirus has shown us is that expertise really matters, that early and informed action really matters and that uncertainty and cost shouldn’t get in the way of making good decisions,” Prof Howden said.