Let’s look at what using climate scenarios in planning might look like in practice. Say we want to plan for the effects of extreme heat across Canada and in Montreal in particular. Understanding how extreme heat will change is important for public health planning, managing outdoor workers, and energy planning, since air conditioning is a growing draw on electricity supplies.
We might start by looking at how the number of days above 32°C has changed and what the effects have been. This map shows that historically, temperatures rarely, if ever, exceeded 32°C across most of Canada. However, in some locations, this number has risen in recent years as the world has warmed. In Montreal, for example, there are now about 4 days per year above 32°C.
Now let’s look at the graph of how many such days we can expect in Montreal under a high emissions scenario, say RCP 8.5. We see that 34 to 86 days are projected to be above 32°C by 2100 under this scenario. So while days over 32°C are currently rare, we could expect to have about two months of such days by 2100 under a high emissions scenario.
But this doesn’t have to happen. As this graph shows, if global emissions are reigned in, consistent with the RCP 2.6 scenario, the number of days above 32°C by 2100 would be similar to the current number. This comparison shows us how much the future lies in our hands. This difference could potentially mean life or death, especially for vulnerable communities.