Why are we seeing so many record-shattering weather events right now?
The speed at which we are changing Earth's climate may be the fuel driving record-smashing extreme weather events.
New research reveals how looking only at past weather events is no longer enough when preparing for the extreme weather to come. Instead, with rapid warming fueling recent "record-shattering" events, and even more expected in the years to come, we need to plan for extremes we have never experienced before to reduce the risk of being taken by surprise.
The news so far this summer has been inundated with stories of record-breaking weather. The extreme heat wave that spread across the Pacific Northwest and the severe wildfires that followed, the "terrifying" rainfall and flooding across central Europe, the once-in-1,000-years flooding that impacted parts of China — all these events have piled up onto one another over the last two months.
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A wildfire burns near the town of Vernon, B.C, on July 9, 2021. Credit: Gavin Phillips/Instagram
In the past, it was difficult to directly attribute specific severe and extreme weather events to global warming and climate change. More recently, by putting these events into context with the past, researchers have revealed clearer connections. This has allowed us to get a better sense of just how much more severe any particular weather event was due to the rise in global temperatures.
"Weather, climate and water-related hazards are increasing in frequency and intensity as a result of climate change," Prof. Petteri Taalas, the Secretary-General of the World Meteorological Organization (WMO), said in a statement. "The human and economic toll was highlighted with tragic effect by the torrential rainfall and devastating flooding and loss of life in central Europe and China in the past week."
The village of Rhineland-Palatinate, Kordel, Germany, is flooded by the high water of the Kyll on July 15, 2021. Credit: Sebastian Schmitt/picture alliance via Getty Images
"Recent record-breaking heat waves in North America are clearly linked to global warming," Prof. Taalas explained. As the WMO reported in early July, climate change due to greenhouse gas emissions made this heat wave at least 150 times more likely to happen.
"What we are seeing is unprecedented. You're not supposed to break records by four or five degrees Celsius," Friederike Otto, of the Environmental Change Institute at the University of Oxford, said of the extreme Pacific Northwest heat wave. "This is such an exceptional event that we can't rule out the possibility that we're experiencing heat extremes today that we only expected to come at higher levels of global warming."
The WMO says that the Pacific Northwest heat wave in June of 2021 was virtually impossible without the influence of climate change. Credit: NOAA Climate.gov
"But, increasingly, heavy rainfall episodes also bear the footprint of climate change. As the atmosphere gets warmer it holds more moisture which means it will rain more during storms, increasing the risk of floods," Taalas added.
According to the WMO, droughts, storms, floods, and extreme temperatures top the list of hazards that have caused the greatest number of human deaths over the past 50 years. Floods and storms are also among the top 10 with respect to economic losses.
In their upcoming publication WMO Atlas of Mortality and Economic Losses from Weather, Climate and Water Extremes (1970-2019), they show that weather, climate, and water hazards accounted for half of all disasters, nearly half of all reported deaths, and almost three-quarters of all reported economic losses over the 50-year period.
This photo taken on June 12, 2017, shows submerged cars in a flooded street in Guiyang, in China's southwest Guizhou province. Sudden heavy rains flooded a number of streets in the city. Credit: STR/AFP via Getty Images
So, what's behind these unprecedented and record-shattering weather events?
The science is clear. A warmer atmosphere holds more water vapour, which makes severe rainfall and flooding events more likely to occur. A weakened jet stream (potentially caused by rapid warming of the Arctic) results in weather systems more easily stalling in place. Thus, some regions can see persistent rainfall and storms, while others are trapped under intense heat domes, causing prolonged heat waves and droughts.
Still, a new study published in Nature Climate Change has delved deeper into exactly why weather and climate records are not just being broken in recent years, but are being shattered by wide margins.
The sun sets behind Joshua Trees in Lancaster, California where temperatures reached 41.6 degrees Celsius on July 12, 2021. Wildfires were burning across more than one million acres of the western United States and Canada at the time, as scorching temperatures held their grip on areas reeling from a brutal weekend heat wave. Credit: Robyn Beck/AFP via Getty Images
Based on their findings, the researchers determined that the strongest influence on the likelihood of any event shattering a previous record was the rate of warming — how quickly temperatures were rising, rather than the precise degree of temperature rise. Based on their simulations, this was especially true when there was a surge in temperatures following a period of little to no warming.
"Thus, primarily due to the accelerating warming rate the probability of record-shattering extremes rapidly increases in high-emission scenarios from low values in the twentieth century to high values by the second-half of the twenty-first century," they wrote, referring to the 'business as usual' trajectory the world is currently on for greenhouse gas emissions.
As emissions continue to rise, causing global warming to further accelerate, the likelihood and severity of these events is expected to increase.
From their models, they found that there was less than a five per cent chance per year of a record-shattering event occurring during the past 30 years (from 1992-2020). Under the 'business as usual' emissions scenario, that likelihood jumps to over 22 per cent per year between 2021-2050, and to over 50 per cent per year from 2051-2080. The chances that we will see events far beyond just 'record-shattering' also increased, from less than one per cent per year over the past 30 years, to over 17 per cent per year between 2051-2080.
This map plots out the probability that different parts of the world will experience at least one record-shattering climate extreme event, per year, between the years 2051-2080. Credit: Fischer, et al./Nature Climate Change (2021)
If emissions were reduced, they said, the frequency and intensity of events suck as heat waves would still be higher than they were in the past, but the chances of record-shattering extremes would rapidly decrease.
"Recent climate extremes have broken long-standing records by large margins. Such extremes unprecedented in the observational period often have substantial impacts due to a tendency to adapt to the highest intensities, and no higher, experienced during a lifetime," the researchers wrote.
This tendency will have even greater impacts on society in the future, as these events worsen. Thus, the researchers emphasize that any infrastructure plans we make to adapt to worsening climate impacts need to take into account the potential for these record-shattering events.
"We show that taking into account the warming rate is vital for adaptation decisions," they concluded.
