Scientists had long predicted extreme weather events were more likely with global warming. But now many are surprised by so many happening so fast – with the global atmosphere just 1.2 degrees Celsius warmer than the preindustrial average. The Paris Agreement on climate change calls for keeping warming to within 1.5 degrees.
"It's not so much that climate change itself is proceeding faster than expected -- the warming is right in line with model predictions from decades ago," said climate scientist Michael Mann of Pennsylvania State University. "Rather, it's the fact that some of the impacts are greater than scientists predicted."
"Global warming was well projected, but now you see it with your own eyes," said Corinne Le Quere, a climate scientist at the University of East Anglia. Countries need to realize that extreme events are here to stay, even if the world can rapidly reduce emissions, scientists say. "There's almost no strategy for adapting to a changing climate," Le Quere said. "Governments are not prepared."
This suggests that climate modelling may have been underestimating the "the potential for the dramatic rise in persistent weather extremes," Mann said.
While climate modelling has evolved over decades to where scientists have high confidence in their projections, there are still uncertainties in how climate change will manifest -- particularly at a local scale. Answering these questions could take many more years.
The June heat wave that killed hundreds in Canada would have been "virtually impossible" without human-caused climate change, scientists from the World Weather Attribution network determined. But those temperatures -- as much as 4.6 degrees Celsius higher than the previous record in some places -- might also have resulted from new atmospheric changes that are not yet captured by climate models. One area of mystery is how the Earth's four main jet streams respond to shifting temperatures. The jet streams are fast-flowing air currents that circle the globe -- near the poles and the tropics -- driving many weather patterns. They are fueled by temperature variations. Some studies have suggested climate change may be slowing down parts of the northern polar jet stream, especially during the summer. That can cause heatwaves by trapping heat under high-pressure air, as seen in Canada in June, or it can stall storms for longer in one place, potentially causing flooding. A key research challenge is the fact that extreme events are, by definition, rare events so there are less data.
There is "tantalizing evidence" that the warming has introduced new, unexpected factors that have amplified climate change impacts even further than previously understood, but more research is needed, said Ken Caldeira, an atmospheric scientist at the Carnegie Institution for Science's Department of Global Ecology.
"From my perspective, the jury is still out on that," he said. "Whichever the answer is, the policy prescription is the same. We need to get ourselves off of CO2 emissions as soon as is practical."
"In the climate models, this does look like a freak event," said the study's co-author Friederike Otto, a climate scientist at the University of Oxford. "The climate models do simulate such rare events and don't suggest there is something else going on, but of course that could mean the models are just not correct. This is really something we and the scientific community need to look into."
"It is clear that extreme weather is the new normal. From Germany to China to Canada or the United States: wildfires, floods, extreme heatwaves. It is an ever-growing tragic list," said Joyce Msuya, Deputy Executive Director of the U.N. Environment Programme. "2021 must mark the beginning of the era of action, and it must be the year where science reigns supreme," she said.
This blog does not share her confidence that climate scientists will have their advice heeded. It is corporate accountants who have the ear of governments.
Ahead of science report, wild weather puts focus on climate change (trust.org)
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| COP26 WILL BE THE SAME FAILURE |
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