Storms show climate change is here, now

Environment Canada’s weather service tells us the devastating rainstorm that struck the Rural Municipality of Minitonas-Bowsman two weekends ago was a “one-in-200-year” event. Approximately 150 mm of rain fell in a few hours.

This probability estimate is almost certainly — although understandably — wrong, because we have lost something called “hydrologic stationarity.”

Our estimates of the probability of occurrence of floods has been based on a couple of centuries of records during a period of variable weather but stable climate. The latter condition, driven by global warming, no longer applies and although it hasn’t for some time, the phenomenon is accelerating.

In Manitoba, we began to comprehend what was happening when, in the late 1990s through the early 21st century, we were hit with several spring floods in the Red River Valley — all “low probability” events — and we were forced to use the floodway to deal with summer rainstorm runoff for the first time. It caused a rethink of past estimates and hastened the expansion of the Red River Floodway in the wake of the 1997 “Flood of the Century.”

The global average temperature increase over the previous long-term norm has now exceeded 1.5 degrees Celsius and is well on the way to 2.0. For every one degree rise in air temperature, atmospheric capacity to contain moisture increases by seven percent. So, 14 per cent is just around the corner. In volumetric terms, this is an enormous volume of water. In fact we now encounter “atmospheric rivers”, a term recently adopted by news media although long used by climate scientists.

Not only is there much more water up there to feed more intense rainfall, but increased global temperature has altered circulatory patterns increasing the likelihood of “stalling” — storms affecting an area for longer periods of time. More intense heat events provide the energy to breed more powerful storms.

Climate science has been warning for several decades of the effects to be expected as the global temperature increase approaches two degrees.

Well, guess what? We’re there now, and shockingly unprepared for the consequences. Massive wildfires were a predicted consequence, yet when they occurred we were apparently and inexcusably taken aback, and are just now coming to grips with the new reality.

The same can now be said about our preparedness to deal with extreme weather events.

The Minitonas-Bowman area was warned of an approaching storm system that might produce 80 mm or so of precipitation; in the event, about twice as much rain fell. Even if an accurate warning had been given, it’s unlikely the physical outcome would have been different, although certainly the locals would have been much better prepared to assure their own safety. It seems that our ability to accurately evaluate in a timely manner these increasingly frequent “super storms” needs to be addressed.

It is now also apparent — as it should have been some time ago — that outside Winnipeg the infrastructure to deal with hydrologic extremes is woefully inadequate. This includes the opposite extreme for which we will find ourselves equally unprepared — when a prolonged drought settles over southern Manitoba.

Unfortunately, having experienced one of these “rare” events, a community cannot relax with the notion that it need not worry for another 200 years. Each event is an independent occurrence, and the probability — whatever it now is — remains the same, so there is a finite chance that a similar storm will arrive next year or even next month. Be prepared.

The global backsliding on climate-change action, led by the U.S., ought to tell us that it will be some time before global warming and its effects can be substantially slowed, let alone stabilized. Our best response as a nation and a province is to adapt our systems to these now-inevitable effects.

The most effective and critical adaptation is to our water management systems.

A first small step is understanding the existing inadequacies. A team should already be in the Minitonas area, surveying and measuring; where did the runoff go, how rapidly, where did it pool and so forth — providing one small component of the eventual mosaic that will be the basis for a whole-system redesign.

In the meanwhile, the local community, both residential and agricultural, requires the full support of the province to recover. Hopefully their voices will be added to a growing chorus directed at our provincial and federal governments to get on with building resilient systems to accommodate climate change rather than reacting to each perfectly predictable event, with astonished surprise.

Norman Brandson is the former deputy minister of the Manitoba departments of environment, conservation and water stewardship.