Francis Zwiers: Climate change is real but other human behaviour make the damage worse

If putting the phrase “climate change” in front of as many Canadians as possible were enough to prepare citizens for a changing future, we’d be set after media coverage of the summer wildfire season, this fall’s hurricanes and the recent “1.5°C” report from the UN Intergovernmental Panel on Climate Change.

But blaming climate change for every wildfire and extreme weather event is neither accurate nor helpful. It does not address the multiple roots of such problems or help us to mitigate the risk.

Yes, climate change is real. Research increasingly indicates that extreme weather events are intensifying and becoming more frequent because of climate change. But many other factors also affect their occurrence and their impacts.

Scientists studying the world’s climate observe that the regional climates that help to characterize our sense of place are changing in ways that intensify most types of extreme events (extreme cold being an exception). Warming is not a good thing, even for a cold, northern country like Canada.

Ironically, climate change increases both the risk of intense, damaging and extreme rainfall and, consequently, some types of flooding and wildfire risks.

In Canada, the area burned by wildfire has doubled since the 1970s and is projected to double again by the end of this century. Natural Resources Canada anticipates a longer wildfire season across Canada in coming decades. By 2100, it may last a full month longer in high-risk areas such as B.C.’s north.

An area about the size of Connecticut was burned in B.C. in the unprecedented 2017 wildfire season — 1.2 million hectares, with an even bigger loss of 1.35 million hectares in 2018. Climate change played a role by increasing the odds of the hot summer conditions conducive to wildfire but it wasn’t the only factor.

Historic wildfire and forestry management practices have inadvertently primed the pump for larger wildfires through decades of fire suppression. Practices are changing but development in rural-urban interface zones adds to the challenge.

In the U.S. alone, the number of people living and vacationing in such zones has increased to more than 140 million from 25 million in 1960. Not surprisingly, the number of homes destroyed each year by wildfire in the U.S. has increased 10-fold in that same period, to more than 4,000 annually.

Extreme rainfall will also intensify with warming. As the climate warms, the atmosphere’s moisture content increases, with about seven per cent more atmospheric moisture per degree of warming.

While the annual total precipitation will likely increase at a substantially slower rate, it’s a good bet that extreme rainfall events will intensify at somewhere near the seven per cent rate — something we’re already seeing in worldwide rainfall data.

More intense extreme rainfall will inevitably lead to more flash flooding and damage. Limiting development in flood-prone areas is more important than ever.

The 2013 Alberta flood that caused more than $6 billion in damages — arguably the costliest natural disaster in Canadian history — is a case in point. While my colleagues and I found little to suggest that human-caused climate change played much of a role in that case, the damage to developed areas was extensive and expensive. Even when climate change is a factor in extreme events, it’s not what necessarily creates the devastation. Humans collectively create that vulnerability by putting infrastructure and housing in harm’s way.

There is more than ample evidence that global warming does threaten us and that we urgently need to reduce greenhouse gas emissions to limit warming. But equally we must mitigate the increased vulnerability resulting from our development and land-use practices. Each of us bear responsibility on both sides of the risk equation as users of fossil fuels, natural resources and land.

It’s our responsibility to act accordingly and folly to focus on only one aspect.

Francis Zwiers is a climatologist and the director and CEO of the Pacific Climate Impacts Consortium at the University of Victoria.


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