Scientists can now reveal how human-caused climate change influenced an extreme weather event within a few days of its occurrence.
Remember that June heat wave that had us sweating before spring was even officially over?
“Climate change is not just something in the vague future,” said Gregory Flato, director of climate research at ECCC. “It is something that we are experiencing right now. And what the rapid event attribution system allows us to do is to quantify, right now, how extreme events, in this case extreme heat waves, are already being changed by human-caused climate change.
“By demonstrating and calculating the increased likelihood we are already experiencing for events like this, it, I hope, provides more compelling information for Canadians to understand the role of climate change, how it effects our lives and environment, and how it will continue to affect us. … The more the climate warms, the more likely these kinds of extreme temperature events will occur. By providing this information immediately after an event, our hope is that it drives home the message that climate change is already affecting us right now and will continue to affect us in the future.”
From June 17 to 20, maximum daily temperatures were much higher than normal at that time of year, with more than 200 daily heat records set across Ontario, Quebec and the Atlantic provinces. The heat wave was accompanied by very high humidity, and nightly temperatures that did not do much to relieve the heat.
“It’s rare to have conditions like this as early as June and our attribution analysis has shown that a heat wave like this has become much more likely because of the influence of human-caused climate change,” Flato said.
The prototype system, developed as part of Canada’s recently-funded National Adaptation Strategy, has been up and running since April. Canada is among the first countries in the world to use this type of system and June’s heat wave is the first significant event for which results are being shared.
Extreme weather event attribution is done using two sets of computer simulations of the global climate system, one representing the climate of the 1800s, before human activities had substantially altered the climate, and a second using today’s conditions with the greenhouse gas amounts and other changes that are affecting the climate, Flato said.
“By carefully analyzing the difference between these simulated climates, we can calculate how much the likelihood of an observed event has been altered by human-caused climate change.”
The system allows researchers to describe to what extent extreme weather events are becoming more frequent and more intense as a consequence of climate change. While this has been possible in the past, these analyses used to take months to perform. With the new system, it takes only a few days.
- “far more likely” (meaning at least 10 times more likely);
- “much more likely” (at least two to 10 times more likely);
- “more likely” (at least one to two times more likely);
- “No evidence of an attributable change in likelihood”;
- “less likely” (at least one to two times less likely);
- “much less likely” (at least two to 10 times less likely); and
- “far less likely” (at least 10 times less likely).
Over time, ECCC researchers will assemble a catalogue of these extreme weather events, which will provide valuable information regarding the extent to which heat waves, and other extreme weather events, are becoming more frequent and more intense.
“This information will help with adaptation planning and decision making to ensure that we are prepared to cope with the climate of the future,” said Flato.
By next winter, ECCC will be using the system to analyze the likelihood that extreme cold snaps, or unseasonably warm winter weather, is due to human-caused climate change, and by next year they expect to be able to use the system to include analysis of precipitation extremes.
As evidence mounts about the frequency and intensity of these events and the causes, decision-makers can take informed steps to protect the public and the environment, Flato said, whether through new building code requirements to protect against flooding and fires or stronger policies on carbon emissions.