Extreme weather takes climate change models “off the scale”

    01 Aug 2021

    Fires, floods, heatwaves, and droughts. The deadly weather that has unfolded in the summer, 2021 has left climate scientists “shocked” and concerned that extreme events are arriving even faster than models predicted, The Finance Info states.

    In southern Oregon, a fire over an area 25 times the size of Manhattan has raged for weeks, aided by a record-shattering heat wave. In China, floods left 51 dead after a year’s worth of rain fell in a single day in the central city of Zhengzhou, causing more than $10bn in damages.

    And in Russia, a state of emergency has been declared in Yakutia in the Far East, where authorities are creating artificial rain by seeding clouds with silver iodine in an attempt to put out more than 200 fires.

    Climate scientists say the severity of these events is simply “off-scale” compared with what atmospheric models forecast – even when global warming is fully considered.

    “I think I would be speaking for many climate scientists to say that we are a bit shocked at what we are seeing,” said Chris Rapley, professor of climate science at University College London. “There is a dramatic change in the frequency with which extreme [weather] events occur.” 

    From the deadly flooding in Germany last week to scorching heat in Canada and a deluge in the Black Sea region, the pace, and scale of catastrophic damage have been almost unimaginable, even for experts who have spent their lives studying it.

    One driver behind many of these events is the shifting pattern of the jet stream, a fast-flowing band of air that governs weather in the Northern hemisphere. It is becoming slower and wavier, particularly in the summer months.

    When the jet stream becomes slow and wobbly, high-pressure systems and low-pressure systems grow in magnitude and get stuck in place, explains Michael Mann, director of the Earth System Science Center at Pennsylvania State University.

    This means heatwaves and drought (linked to high-pressure systems) and flooding (linked to low-pressure systems) both become more persistent.

    The phenomenon, known as “planetary wave resonance,” is behind the recent heatwave in North America, for example, where temperatures in Western Canada hit a scorching 49C.

    It also contributed to the extreme heat in the Russian Arctic region, where extensive wildfires are producing toxic smoke that has blanketed the city of Yakutsk, a port city in Siberia, more well known as one of the coldest winter cities on the planet. The fires have caused one of the world’s worst air pollution events, generating dangerous levels of particulate matter.

    Mann is worried that current models do not reproduce the jet stream behavior accurately. “This means they are underestimating the magnitude of the impact of climate change on extreme weather events,” he says.

    “While the overall warming of the planet is pretty much in line with climate model predictions from decades ago, the rise in extreme weather events is exceeding the predictions,” Mann notes.

    The world has warmed about 1.2° C on average since pre-industrial times. Still, that warming is unevenly distributed, with the Arctic region warming about three times faster than the rest of the world primarily because of the loss of reflective snow and ice.

    This Arctic heating has a significant impact on the jet stream, which is governed in part by the temperature difference between the cool polar air and warm tropical air.

    In Germany and Belgium, the slower jet stream is one factor that contributed to the flooding this month that led to the death of more than 120 people and destroyed towns and villages.

    “We had a low-pressure field over central Europe which did not move; it was persistent and long-lasting. Normally our weather patterns moved from west to east,” said Fred Hattermann, a researcher at the Potsdam Institute for Climate Impact Research.

    “The engine for our West wind is the temperature gradient from the equator to the Arctic,” he explains. Warming in the Arctic means that “this engine that we have is weakened.”

    Not all extreme weather events are solely related to the jet stream.

    Global warming also directly impacts precipitation and rainfall because warmer air can hold more moisture – about 7% more water for each 1C of warming.

    This is part of the reason why the recent floods in India and China were so devastating, involving monsoonal cycles rather than jet stream behavior.

    In the torrential rain that drenched central China’s Henan province last week, its capital Zhengzhou saw 20 cm of water fall in a single hour. The widespread flooding that swamped its subways drowned 12 passengers.

    By July 24 the floods had caused 51 deaths and Rmb65.5bn ($10bn) worth of direct damages in Zhengzhou alone. Unusually large volumes of water vapor were pushed inland by typhoons on China’s southern coasts. They became rain after being blown over mountain ranges in Henan, according to the China Meteorological administration.

    Consistent high-pressure over the Sea of Japan and Northwest China meant that the rain clouds stagnated in a vortex of low pressure over Henan, becoming a slow-moving series of intense and successive storms known as the “train effect,” the administration told Chinese state media.

    Chinese authorities said the volumes had exceeded anything on record for the past 5,000 years, extending to the official start date of Chinese civilization.

    Meanwhile, in northeastern Russia, firefighting teams continue to battle more than 200 blazes. The Yakutia region has regularly experienced lows of minus 50C in some places but has recently set several new records for the highest temperatures inside the Arctic Circle.

    The governor, 49-year-old Aysen Nikolayev, has long been raising the alarm over the impact of global warming in his region.

    “Undoubtedly, there is only one reason – global climate change,” he told local television. “It is happening; we see Yakutia get hotter every year.”

    Extreme weather renews focus on climate change as scientists update forecasts

    As scientists gather online to finalize a long-awaited update on global climate research, recent extreme weather events across the globe highlight the need for more research on how it will play out, especially locally, Reuters states.

    The list of extremes in just the last few weeks has been startling: unprecedented rains followed by deadly flooding in central China and Europe. Temperatures of 49° C in Canada and tropical heat in Finland and Ireland. The Siberian tundra ablaze. Monstrous U.S. wildfires, along with record drought across the U.S. West and parts of Brazil.

    “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.

    Scientists had long predicted such extremes were likely. But many are surprised by so many happening so fast – with the global atmosphere 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.”

    That suggests that climate modeling may have been underestimating “the potential for the dramatic rise in persistent weather extremes,” Mann said.

    Over the next two weeks, top scientists with the Intergovernmental Panel on Climate Change (IPCC) will finalize the first installment of its sixth Assessment Report, which will update the established science around greenhouse gas emissions and projections for future warming and its impacts. Government representatives are also taking part in the virtual two-week meeting.

    The report will expand on the last such IPCC report in 2013 by focusing more on extreme weather and regional impacts.

    “As I speak, 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, during the event’s opening ceremony on Monday.

    “2021 must mark the beginning of the era of action, and it must be the year where science reigns supreme,” she said.

    When released on Aug. 9, the report will likely guide governments in crafting policies around the environment, greenhouse gas emissions, infrastructure, and public services. The report’s release was postponed several months due to the coronavirus pandemic.

    While climate modeling 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° C higher than the previous record in some places – might also have resulted from new atmospheric changes that climate models do not yet capture.

    “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 the scientific community, and we need to look into.”

    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. Temperature variations fuel them. 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 occasions, 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. Still, 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.”

    More immediately, though, 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.”

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