Climate change is not responsible for every heat wave. But it made a heat spell that spanned Europe in June 2019 five times more likely than normal. That’s the new finding of an international team of scientists.
Extreme heat broke records in parts of Germany, Switzerland, Italy, Spain, the Netherlands and the Czech Republic. And it set an all-time high in France of 45.9° Celsius (114.6° Fahrenheit)!
Attribution science is a fairly new field of science. It seeks to tackle the tricky question of whether and how much a given weather event might have been linked to global warming. And an international group has just weighed in on that.
Current climate conditions made the June heat wave in France up to 100 times more likely than it would have been in 1901, the team found. It couldn’t say precisely how much climate change increased the risk. (Among the reasons: Temperature records have only been available there since 1947.) But the researchers are “very confident” that climate change increased the probability by at least a factor of five.
The study’s authors are part of an international network of climate scientists. Their group is known as World Weather Attribution, or WWA. They use the latest research techniques to investigate the likelihood that any particular event has been caused by — or made worse by — global warming. And on July 2, they shared their rapid-response findings on the WWA website.
Karsten Haustein is a member of the network. He’s a climate scientist at the University of Oxford in England. In June, he told Science News that this group formed so that it could “look at any given extreme events while they’re happening and try to scientifically attribute the climate-change factor.” For example, has global warming made such an event more likely to occur?
Heat waves aren’t just about isolated high temperatures. Other factors also help define these events. That might include where they are, when they develop and how long they last.
In their new analysis, the network’s scientists examined three-day averages of the daily temperatures for France throughout the heat wave. Then they compared those to previous temperatures. They also compared the June extremes to what computer models would have predicted, based on when and where the events showed up.
And the intensity of heat waves has increased, the new analysis found. One hundred years ago, the three-day average temperature during a heat wave would have been cooler by about 4 degrees Celsius (7.2 degrees Fahrenheit).
When heat waves show up early in summer, schools may still be in session or people working. That can make it harder for people to escape the heat. It will leave more of them vulnerable to the high temps than during heat spells that occur later in the summer.
For now, it is too soon to know how much the European heat wave in June may have increased local death rates. Figuring that out requires looking at longer-term statistical averages.
attribution See attribution science (if it's related to weather or climate).
attribution science A field of research, largely used in climate studies. It seeks to test whether — and by how much — climate change may be responsible for certain extreme weather events, such as droughts, extreme flooding, hurricanes, excessive heat or odd storm trajectories.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
climate The weather conditions that typically exist in one area, in general, or over a long period.
climate change Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
computer model A program that runs on a computer that creates a model, or simulation, of a real-world feature, phenomenon or event.
death rates The share of people in a particular, defined group that die per year. Those rates can change if the group is affected by disease or other deadly conditions (such as accidents, natural disasters, extreme heat or war and other sources of violence).
develop To emerge or come into being, either naturally or through human intervention, such as by manufacturing.
factor Something that plays a role in a particular condition or event; a contributor.
field An area of study, as in: Her field of research was biology. Also a term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.
global warming The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.
network A group of interconnected people or things. (v.) The act of connecting with other people who work in a given area or do similar thing (such as artists, business leaders or medical-support groups), often by going to gatherings where such people would be expected, and then chatting them up. (n. networking)
probability A mathematical calculation or assessment (essentially the chance) of how likely something is to occur.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
weather Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.
Report: G.J. van Oldenborgh et al. Human contribution to record-breaking June 2019 heatwave in France. Posted online at the World Weather Attribution Network, June 2, 2019.
News report: C. Gramling. Is climate change causing Europe’s intense heat? A scientist weighs in. Science News. June 28, 2019.