Two new climate models predict that global warming due to climate change will be faster and more severe than previously thought, meaning humanity will have to work even harder to curb its emissions and meet the warming goals set out in the Paris agreement.
If we continue to use fossil fuels to drive rapid economic growth, the new models say, mean global temperature could rise as much as 7 degrees Celsius by 2100, which is 1 degree higher than previous estimates. In terms of climate change, that’s a lot.
“It is difficult to imagine the impacts of that level of warming,” Olivier Boucher, head of the Climate Modeling Center at the Institut Pierre Simon Laplace in Paris, said in an email. “But there would be dramatic for many natural and human systems. As a comparison, the difference between an ice age and interglacial period is 5 [degrees Celsius].”
These models came out of the Coupled Model Intercomparison Project, part of the World Climate Research Program, and were unveiled at a press conference on Tuesday. The models will be factored in to future Intergovernmental Panel on Climate Change (IPCC) reports in 2021. Currently, the Paris Agreement—which is based on older climate models—wants to cap warming at 2 degrees Celsius.
French scientists from multiple research institutions sorted through a massive amount of data, racking up around 500 million computing hours. The models they came up with predict that the climate will respond faster and more easily to our greenhouse gas emissions than previously assumed. This increase in expected climate response, called “equilibrium climate sensitivity,” means that humanity will need to curb its emissions even more drastically to satisfy the Paris agreement
This research is the latest in a series of new models being created worldwide to better understand our changing climate. The work wasn’t done exclusively by climate scientists. Nearly 100 scientists from numerous disciplines participated in the work, including climatologists, oceanographers, glaciologists, and other specialists.
In addition to global climate patterns, the new research zeroes in on some more local phenomenon (such as heat waves and tropical storms), simulating them more realistically than ever before.
The impacts of the worst-case scenario under the new models (a 7 degree Celsius warming by 2100) are severe, and will likely require more research to accurately predict. But it is estimated that, at about half of that warming, most species would not survive and all summer Arctic ice would disappear.
The countries who signed the Paris agreement pledged to limit global warming to 2 degrees Celsius, a far cry from the worst-case scenario. Even 2 degrees warming above pre-industrial levels will have severe consequences for sea level rise, heat waves, ice melt, and extreme weather events. We haven’t even hit one degree of warming yet, and are already facing record heat waves, intense wildfires, and rapidly melting ice.
In these new models, there is only one socio-economic scenario that limits warming to 2 degrees, and it requires strong international cooperation and investment in sustainable development. Even then, the scenario calls for extreme mitigation efforts, and we will still likely exceed the target at some point in the next century, warming over 2 degrees before cooling down only if drastic geoengineering measures are taken.
"We have to do both adaptation for the warming to be expected, and as much mitigation as possible to be on the best possible path," Boucher said.
In a time when international cooperation is paramount to fighting climate change, Trump is still attempting to pull out of the Paris agreement as soon as he’s able (in November 2020), despite pushback from Congress.
The Paris agreement, which already lacks real regulatory teeth, will need to be strengthened and redefined if we want to avoid more extreme warming scenarios. And then, we actually have to follow through.