Worst-Case Climate Change Scenario Is Even Worse Than We Thought

New Scientist - Michael Le Page

These lignite-fired power plants are among the largest in Europe. Thomas Corzelius / iStock / Getty Images Plus

The phrase “worse than we thought” is a cliché when it comes to climate change. There are lots of studies suggesting we’re in for more warming and worse consequences than thought, and few saying it won’t be as bad. But guess what: it’s worse than we thought.
A study of the future global economy has concluded that the standard worst-case scenario used by climate scientists is actually not the worst case.
How much the climate will change depends on how much greenhouse gas we emit, which in turn depends on the choices we make as a society – including how the global economy behaves.
To handle this, climatologists use four scenarios called RCPs, each of which describes a different possible future.
The RCP8.5 scenario is the worst for the climate. It assumes rapid, unfettered economic growth and rampant burning of fossil fuels.
It now seems RCP8.5 may have underestimated the emissions that would result if we follow the economic path it describes.

More money, more emissions
“Our estimates indicate that, due to higher than assumed economic growth rates, there is a greater than 35 per cent probability that year 2100 emissions concentrations will exceed those given by RCP8.5,” says Peter Christensen of the University of Illinois, Urbana-Champaign.
In one sense, it is not quite that bad. RCP8.5 assumes no action is taken to limit warming, which is unlikely.
“We’ve already locked in a certain amount of climate policy,” says Glen Peters of the Center for International Climate Research in Norway.
But the worrying implication is that emissions could be much higher than expected even if climate action continues and is ramped up.
“The results will also affect estimates of emissions pathways under a variety of policy scenarios,” says Christensen.
While some claim the link between economic growth and greenhouse emissions has been broken – or “decoupled” – it’s only been weakened.
 Carbon emissions have risen in the European Union over the past four years as economic growth has picked up, Peters points out. In 2017, EU emissions rose 1.8 per cent.

Links

• Climate downgrade: Arctic warming
• Climate downgrade: Extreme weather
• Climate downgrade: Food production hit
• Climate downgrade: Sea level rise
• Climate downgrade: Planetary feedbacks
• Climate downgrade: Human emissions
• Climate downgrade: Heat stress
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