Extreme weather event attribution

Extreme weather event attribution explores how weather events like heat waves, floods, and wildfires are linked to human-caused climate change.

About extreme weather event attribution

The science of calculating how much human-caused climate change has influenced extreme weather events is called extreme weather event attribution.

Extreme weather events

An extreme weather event is when we get unusual or unseasonal extremes compared to historical data. Extreme weather events include:

Human-caused climate change

Human activities, mainly greenhouse gas emissions, are causing the global climate to change. This leads to:

The warming environment influences the strength, number, and risks of extreme weather events.

Why we calculate the effects of climate change on extreme weather

When we calculate how much human-caused climate change affects extreme weather events, we can better prepare for and adapt to the changing weather. This information helps us plan for, respond to, and rebuild from weather emergencies. Our research is meant to give Canadians more information to use when deciding how to prepare for and adapt to the risks and effects of a changing climate.

The science of extreme weather event attribution

Climate scientists study how human-caused climate change is linked to the frequency and severity of extreme weather events. This work brings together meteorology, weather observation, and climate science.

Research on past extreme weather event attribution

As part of our mandate, we conduct and share the results of extensive climate science research in Canada and internationally.

Our research helps decision-makers, leaders, and professionals to make science-based, informed decisions.

Canada’s National Adaptation Strategy is the long-term vision to reduce the damaging effects and risks of climate-related disasters. Our goal is to help prepare our communities for climate change impacts and empower them to protect their health, well-being, and livelihoods.

The Rapid Extreme Weather Event Attribution system

The new Rapid Extreme Weather Event Attribution pilot system can explain how human-caused climate change increases the risk of heat waves.

A pilot system for rapid heat wave attribution

The new pilot system can quickly reveal the relationship between a recent heat wave in Canada and human-caused climate change.  In the future, the system will be extended to include extreme cold weather events and extreme precipitation.

How it works: simulating two different climates

The Rapid Extreme Weather Event Attribution pilot system uses various climate models to simulate:

Within several days of a heat wave, scientists can compare the number of heat waves in the simulated climates to calculate how much human activity has changed the chances of such a heat wave occurring.

Plans for the pilot stage

During this pilot stage, scientists will examine heat waves in 17 regions across Canada that are experiencing far higher temperatures than usual.

Regions
  • Alberta
  • Atlantic Canada
  • Eastern Ontario
  • Fort Smith
  • Inuvik
  • Kitikmeot
  • Kivalliq
  • Manitoba
  • Northern British Columbia
  • Northern Qikiqtaaluk
  • Northern Quebec
  • Saskatchewan
  • Southern British Columbia
  • Southern Qikiqtaaluk
  • Southern Quebec
  • Western Ontario
  • Yukon

Importance of the new pilot system

When we can understand the causes and calculate the risks of extreme events such as heat waves, wildfires, drought, and floods, we can better support the health and safety of Canadians. The new pilot system will help us plan for, respond to, and rebuild from weather emergencies and support informed decisions to protect property, health, and safety.

Pilot stage results

During the pilot stage, analysis will be conducted when temperatures in a region of Canada are warmer than usual.

We have three ways to share our results:

Statement of likelihood

We use seven set statements to describe how much more likely an extreme weather event happened because of human influence on the climate.

On one end of the scale, the extreme weather event was:

  • far less likely because of human influence on the climate
  • much less likely because of human influence on the climate
  • less likely because of human influence on the climate

In the middle:

  • no evidence of an attributable change in likelihood for this event

On the other end of the scale, the extreme weather event was:

  • more likely because of human influence on the climate
  • much more likely because of human influence on the climate
  • far more likely because of human influence on the climate
Probability/risk range

The probability/risk range is a scale that describe how much more likely an extreme weather event happened because of human influence on the climate.

On one end of the scale, if the event was:

  • far less likely: at least 10X less likely to have happened
  • much less likely: at least 2X to 10X less likely to have happened
  • less likely: at least 1X to 2X less likely to have happened due to human influence on the climate

In the middle, if there was:

  • no evidence: no change due to human influence on the climate identified

On the other end of the scale, if the event was:

  • more likely: at least 1X to 2X more likely to have happened
  • much more likely: at least 2X to 10X more likely to have happened
  • far more likely: at least 10X more likely to have happened due to human influence on the climate

Heat wave attribution analyses

For the month of June 2024, we have analysis results for the heat waves in:

Attribution analysis for June 2024

Eastern Ontario

Southern Quebec

Northern Quebec

Atlantic Canada

Related resources

See related news releases. Find local, national, and global weather forecasts. Learn how to keep safe during severe weather events. Explore Canada’s plan to adapt to climate change. Discover additional climate-related research.

Related resources

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