How science proves whether humans are the cause of extreme weather events

Field emerging from climatology Who analyzes Extreme weather events Behind the statement that Heat waves The unprecedented events that struck the world are the result Human-induced climate change.

Extreme event attribution checks Human footprint on climate-related disasters by comparing our current world (and its increasing number of climate anomalies) with an ideal world, where there is no human impact on the climate at all.

To do this, researchers are running Programming Known as climate models that Simulate weather patterns Over time, similar to models used for seven-day local forecasts. but this Recreating the climate over decades or centuries, Instead of hours or days.

“The really interesting thing about climate models is that you have a scientist on a computer and you can run experiments on it,” he said. Andrew Pershingvice president of science at the nonprofit research organization Central climate. “And you can literally do the experiment What would this world be like if there was global warming? “It would never have happened.”

The link between a changing climate and human activity goes back to the work of two Nobel Prize Winners in Physics, Syokuro Manabe and Klaus Hasselmann, Who were pioneers in developing climate models starting in the 1960s, and climate models help us understand How the climate changed in the past and how it might change in the future. They solve mathematical equations that describe how energy and matter interact in different parts of the ocean, atmosphere, and land.

Attribution scientists use climate models to Replaying the past few hundred years on Earth, Eliminate everything Gas emissions Greenhouse gases produced by humans. By comparing this fantasy world to our own, you can find out whether you like the extreme events or not Floods, droughts or cold waves Different and what impact these emissions have on our climate.

For example, an attribution study conducted in July found that Heat waves In North America and Europe they would have been “Virtually impossible” in a world without climate change.

If humans didn’t warm the planet burning fossil fuels, Such heat waves will remain rare. But in reality, we can expect them to appear every 15 years in North America and every 10 years in Europe, according to attribution scientists.

They also warn that if humans continue to produce emissions at the current rate, Heat waves will accelerate Until it became every two or five years, starting in the mid-nineties. 2030.

“This is really important information for water resource managers, urban planners and policy makers in terms of climate adaptation and resilience,” he said. Kevin A. Reed, Professor of Marine and Atmospheric Sciences, College of Science Stony Brook University.

Until recently, scientists have largely avoided linking any single event to climate change, believing it to be primarily caused by climate change. Time is inherently unpredictable It does not have a single cause. But in 2004, what was considered the first study of extreme events found that… Climate change has at least “doubled the risk” of a heatwave than the previous year in Europe, which More than 70 thousand people were killed.

Almost any climate phenomenon can occur by chance, but the authors argue that climate models can be used to achieve this Reveal the role played by humanity By making such extreme heat more bearable. They simulated the climate with and without human emissions thousands of times, counting the number of times an extreme heatwave like the one in 2003 occurred. Although the event was rare in both cases, It happened twice as often In the world with human emissions.

Since that first study, scientists have investigated more than… 500 disaster Related to climate around the world, it has been discovered that 71% of them are more likely or more dangerous due to climate change Caused by humans. With the help of faster computers and more accurate climate models, researchers can now perform these analyzes in days rather than months.

The initiative Global climate attribution (WWA), which was formed in 2015 by an international team of climate scientists, has conducted more than 50 attribution studies, most of them after the events or during them. WWA was responsible for Analysis of the extreme temperatures of July around the world, Analyze it It took only five days to assemble.

Many researchers see attribution of extreme events as a communication tool that has the potential to link climate change to people’s everyday experiences. “Doing real-time attribution is what will be very useful in keeping people informed, focusing attention on an extreme event,” said Robert Vautar, a member of the WWA team and director of the Pierre-Simon Laplace Institute.

WWA has cited global warming as the main driver of climate change Drought in East Africa since 2020 a Heat wave in 2022 in South America And the 2022 floods in Pakistan. But in the case of A Drought in Madagascar 2019 WWA found that the decrease in precipitation is mainly due to natural climate change, Despite the United Nations declaring otherwise.

Climate Central has adapted methods developed by WWA to create Climate change index (CSI), a measure that reveals the extent to which daily weather conditions have changed due to climate change. Pershing and his colleagues calculated the results of 22 climate models, calculating the probability of daily local temperatures with and without historical greenhouse gas emissions.

His latest analysis caused by climate change July was warmer for more than 6.5 billion people, Or 81% of the Earth’s population, they analyzed data from 4700 cities and 200 countries. “Almost no place on Earth has escaped the impact of climate change” in July, Pershing said.

The Reed Lab specializes in event attribution studies that specifically look at affect Tornadoes. In each study, he ran 40 simulations over the past 150 years, with sea surface, temperature and air humidity varying slightly to add an element of chance in influencing climate conditions. Also includes a “The race for pre-industrial control” Which depicts the climate of 1850, or the time before human emissions increased.

After approaching a specific time and area to capture the target tornado, Reed publishes a seven-day weather forecast. To determine the human footprint, they compared characteristics of hurricanes during that week, such as rainfall rate, amount of accumulation, intensity and size.

His study north atlantic hurricane season 2020, One of the most active people ever discovered that Climate change has increased rainfall rates By 11 percent and rainfall amounts of 8 percent.

*Merry Kim (c) 2023, The Washington Post