When we see records being broken and unprecedented events such as this, the onus is on those who deny any connection to climate change to prove their case. Global warming has fundamentally altered the background conditions that give rise to all weather. In the strictest sense, all weather is now connected to climate change. Kevin Trenberth
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Michael Mann, climate scientist at Pennsylvania State University, along with colleagues, has published a new study that connects these disruptive weather extremes with a fundamental change in how the jet stream is behaving during the summer. Linked to the warming climate, the study suggests this change in the atmosphere’s steering current is making these extremes occur more frequently, with greater intensity, and for longer periods of time.
The study projects this erratic jet-stream behavior will increase in the future, leading to more severe heat waves, droughts, fires and floods.
The jet stream is changing not only because the planet is warming up but also because the Arctic is warming faster than the mid-latitudes, the study says. The jet stream is driven by temperature contrasts, and these contrasts are shrinking. The result is a slower jet stream with more wavy peaks and troughs that Mann and his study co-authors ascribe to a process known as “quasi-resonant amplification.”
The altered jet-stream behavior is important because when it takes deep excursions to the south in the summer, it sets up a collision between cool air from the north and the summer’s torrid heat, often spurring excessive rain. But when the jet stream retreats to the north, bulging heat domes form underneath it, leading to record heat and dry spells.
If the excursions in the jet stream endure long enough, it can then set the stage for floods where the jet dips, and wildfires and drought where it ascends.
“What made these events [in the summer of 2018] so devastating was not just the extreme nature of the meteorological episodes but their persistence,” Mann said in a blog post discussing the implications of the new study.
The study, published Wednesday in Science Advances, finds that these quasi-resonant amplification events — in which the jet stream exhibits this extreme behavior during the summer — are predicted to increase by 50 percent this century if emissions of carbon dioxide and other greenhouse gases continue unchecked.
Whereas previous work conducted by Mann and others had identified a signal for an increase in these events, this study for the first time examined how they may change in the future using climate model simulations.
“Looking at a large number of different computer models, we found interesting differences,” said Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research and a co-author of the study, in a news release. “Distinct climate models provide quite diverging forecasts for future climate resonance events. However, on average they show a clear increase in such events.”
In an email, Mann said climate models aren’t fully capturing the phenomenon, and, for this reason, we should expect weather extremes “beyond what is typically projected” into the future.
Mann added the existing analyses that attempt to uncover the role of climate change in recent extreme events “are under-attributing the role that climate change is having … because they are not capturing the key mechanism responsible.”
Mann said in his blog commentary that he was particularly struck by the jet-stream behavior in the summer. “In summer 2018, I would argue, that signal was no longer subtle,” he said. “It played out in real time on our television screens and newspaper headlines in the form of an unprecedented hemisphere-wide pattern of extreme floods, droughts, heat waves and wildfires.”
Although model projections suggest these extreme jet-stream patterns will increase as the climate warms, the study concluded that their increase can be slowed if greenhouse gas emissions are reduced along with particulate pollution in developing countries. “[T]he future is still very much in our hands when it comes to dangerous and damaging summer weather extremes,” Mann said. “It’s simply a matter of our willpower to transition quickly from fossil fuels to renewable energy.”
Dr. Jennifer Francis, a climate researcher at Rutgers University who has published work exhibiting changing jet-stream behavior because of climate change, found the results of this new study compelling. “This work takes a big step toward understanding the spate of deadly extreme weather events during recent summers — heat waves, floods and droughts,” she said in an email.
A group of British scientists and their supporters is willing to risk a prison term to press governments to tackle climate change and environmental crisis.
by Alex Kirby, Climate News Network, October 31, 2018
LONDON − A growing number of British academics, writers and activists say they are ready to go to prison in support of their demands for action on the environment.
Scientists are not normally renowned for their political activism, and the UK is hardly a hotbed of determined and risky protest against its rulers. But, if this group of nearly 100 British scientists and their backers is right, all that may be on the brink of changing.
Today sees the launch of ExtinctionRebellion, which describes itself as an international movement using mass civil disobedience to force governments to enter World War Two−level mobilization mode, in response to climate breakdown and ecological crisis.
The group is launching a Declaration of Rebellion against the UK government “for criminal inaction in the face of climate change catastrophe and ecological collapse” at the Houses of Parliament in central London.
“We need ExtinctionRebellion as part of the mosaic of responses to the extremely precarious situation we now find ourselves in”
From today it promises “repeated acts of disruptive, non-violent civil disobedience” if the government does not respond seriously to its demands, and says “there will be mass arrests.”
“Now is the time because we are out of time. There is nothing left to lose.”
The group’s demands include the declaration by the UK government of a state of emergency, action to create a zero carbon economy by 2025, and the establishment of a national assembly of “ordinary people” to decide what the zero carbon future will look like.
“Children alive today in the UK will face unimaginable horrors as a result of floods, wildfires, extreme weather, crop failures and the inevitable breakdown of society when the pressures are so great. We are unprepared for the danger our future holds.”
Its members say they are willing to make personal sacrifices, to be arrested and to go to prison. They hope to inspire similar actions around the world and believe this global effort must begin in the UK, today, where the industrial revolution began.
Another supporter is Andrew Simms of the New Weather Institute. He told the Climate News Network: “This is almost a cry of desperation. People are bewildered. But almost every profound change in British society, from the abolition of slavery to the improvement of shipping safety, has involved people risking arrest.
“The signs I am getting from the UK government now are that it is a reckless administration putting its own people and others at risk by putting climate change virtually nowhere.
“The Declaration alone won’t bring about change: we’ll need people working practically to make change happen on the ground. But we need ExtinctionRebellion as part of the mosaic of responses to the extremely precarious situation we now find ourselves in.”
Simms, convinced that an entirely new potential for rapid societal change now exists, says: “We know what’s needed, and the resources to do it are there. ExtinctionRebellion is one example of how new ideas can spread quickly and rapid shift − and radical action − can come closer.”
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