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Policy
| 03/01/17

Will global warming turn Vancouver into San Diego? Not so much

TCE

Climate change is set to give Vancouver balmy, southern California-style weather by 2050, with warmer summers and longer growing seasons—at least according to reports by regional media outlets this past week. This idyllic picture was accompanied by warnings of wildfires and torrential rains.

However these stories give audiences an impression that is simultaneously too rosy a picture while exaggerating the dangers.

In September 2016, the Metro Vancouver published a 74-page document delivering medium and long-term projections for the region up to 2050 and 2080, but the media have only now picked up on the publication. The paper was based on what is called ‘statistical downscaling’ by the Pacific Climate Impacts Consortium (PCIC), PICS’ sister institute.

Downscaling involves taking global climate models, which have very coarse-grained descriptions of what happens at a regional level, and developing methods to use that information to supply a more fine-grained assessment.

The projections in the report built upon years of work by PCIC on downscaling, taking a roughly 100 km resolution down to just 10 km, and also accounting for local climate differences at a scale of 800 m.

Under a global emissions “business-as-usual” scenario, PCIC’s downscaling work found that the region can expect the length of the growing season to increase by a fifth, a 60 percent decrease in the number of frost days, heating demand to fall by almost a third, and an upswing in demand for air conditioning.

The projection also envisages more than a doubling in the number of hot days per year on average by 2050.

Media outlets jumped on the projection that average summer daytime high temperatures would likely be warmer than present-day San Diego and even warmer by the 2080s. Many readers were left with the impression that Vancouver’s climate would in effect become like that of the southern Californian city, and drove home this message with contrasting images of shovelling snow and heading to the beach.

However there are important things to keep in mind to avoid being misled by these interpretations, say the scientists. First, while summer will be warmer and winter less cold, the sharp difference between summer and winter will not go away. This is due to our northerly latitude. San Diego, in comparison, experiences much less seasonal differences.

In addition, reports of forest fires and summer droughts being followed by torrential downpours were also off base. Instead, the document said such extreme conditions would possibly be more common and should be planned for. This may appear to be a subtle distinction, but exaggeration of the dangers of climate change is as much of a problem as dismissing the dangers.

The report also includes projections based on lower greenhouse gas emissions scenarios. For example, by the 2080s, the number of hot days projected under a BAU scenario would be four times the historical norm, but if the world is able to cut emissions in half, then there would be two and a half times the number of hot days, and if the world gets down to net zero emissions within a decade, there would be just twice the number of hot days.

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Media have reported that climate change will turn Vancouver into San Diego. But how accurate is this?

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