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Whither The Prairie Climate?

“The evidence is pretty clear to my mind that global warming is underway, and greenhouse gas emissions are causing some changes in the climate.”

– BRUCE BURNETT, CWB

Adapting to climate change will be tough, that’s for sure.

It might be easier if Prairie farmers knew exactly what to plan for, but one thing is certain, nobody really knows what to expect.

Dave Sauchyn, a senior research scientist at the Prairie Adaptation Research Collaboration (PARC), is perhaps best known for his pioneering work documenting the climate of the Prairies over the past 2,000 years based on the salinity levels of mud core samples taken from an Alberta lake and tree rings in the Cypress Hills area.

In a research paper published in 2002, he found that the Prairie climate’s most benign period has occurred since the time of settlement in the 1890s to the present.

Before that, it was a wild ride, and decades-long droughts were not uncommon. Tree rings show that the Medicine Hat area saw punishing droughts in the 1790s and the 1850s, and sediments at Chauvin Lake, Alta., indicate that the modern era has been the wettest since the mid-1300s.

It’s easy to make a living on the Prairies when it rains, as everyone knows. But if climate change brings a return to the bad old days, adaptation strategies will have to include plans for surviving extended periods of severe drought.

In a recent interview, Sauchyn noted the latest data seems to show Prairie weather is strongly linked to Pacific Ocean weather phenomena such as La Nińa and El Nińo. Those short-term cycles are fairly well understood, but lately a better picture of longer-term cycles – 25 to 50 years or more – is emerging.

DRY DECADES

“The weather on the Prairies depends a lot on the status of the ocean. The ocean covers three-quarters of the Earth, and that water stores a lot of heat,” he said.

“When you think about it, the 1930s were dry and the ’80s were dry. So, we have these really dry decades about every 50 years. Then halfway in between, we have decades that are dry as well. People have long speculated about that, but now we have scientific evidence that it is all related to the circulation of the oceans.”

Unusually cold weather this year in the Northern Hemisphere – beginning, ironically, during the Copenhagen climate summit – has many climate skeptics grinning. But whether that’s the result of “climate chaos,” the arrival of a new solar minimum, or a reduction in the Atlantic thermohaline circulation that saves northern Europe from the frozen fate of Canada’s Arctic, is still largely the stuff of idle speculation.

“All of these things interact. Sometimes they reinforce each other, sometimes they oppose each other. It makes things pretty hard to figure out,” said Sauchyn.

“Then on top of that, you have human-caused climate change which is superimposed on all of these natural cycles. The big question is, as we heat up, how will that affect these ocean cycles?”

Canadian Wheat Board weather and crop surveillance analyst Bruce Burnett gave his take on the possible implications of climate change on Prairie farmers at the recent conservation districts AGM.

Mark Twain once said the “Climate is what we expect; weather is what we get.” That, in a nutshell, is the difference between the two, he said.

The smallest slices of weather trends that climatologists look at are 30-year chunks. For the average person, they can only hope to experience at most three of those – if they live to be 90.

“So you’re not going to be able to feel the climate warming or even prove it conclusively within your lifetime,” he said, adding that it’s natural for humans to question the science if they haven’t taken the time to research it in depth.

“The evidence is pretty clear to my mind that global warming is underway, and greenhouse gas emissions are causing some changes in the climate.”

The latest climate models for the Prairies show a general warming trend and a longer growing season, but the jury is still out on whether it will be wetter or drier, but increased variability either way is expected, said Burnett.

Prairie weather is notoriously erratic and always has been, he added. That may put farmers in a better position to adapt than others to violent changes, but it still means that they’ll have to be more nimble than ever before.

Already, no till and chemfallow have shown benefits in cases of drought, while future improvements in water use efficiency could give farmers

an extra edge. New crops might be adopted, he added, noting that even a few decades ago, few thought soybeans would ever be a significant crop in Manitoba.

Ron Stewart, head of the department of environment and geography at the University of Manitoba, who also spoke at the MCDA conference, said that there is evidence that more extreme weather events might result if global average temperatures rise as predicted by climate scientists.

Because climate is basically driven by energy from the sun, it stands to reason that if more solar radiation is absorbed and trapped within the atmosphere, the more horsepower there will be available to drive weather systems and hydrological cycles.

Not only has mankind altered the composition of the gases in the atmosphere by burning fossil fuels, but we have also altered Earth’s surface through tillage, clearing forests, building roads and cities – all of which interferes with normal evaporation rates in the global water cycle.

One thing is certain, warmer air is better able to hold water vapour than cold air. In the past couple of decades, the global average temperature has risen by nearly 1.

CARRYING CAPACITY

If, by the end of the century, the global average temperature rises by 2 to 4 or even 5C, there will be a “very significant” impact on the overall water-holding capacity of the atmosphere.

“So, then we can expect to have a change in the water cycle, which should lead to a change in the extremes,” said Stewart.

With warmer oceans, not only can the air hold more water, but the process of evaporation happens at faster rates. That means more water vapour will be available to fall out of the sky as rain, and precipitation events will be more extreme.

But on the other hand, there is still a lot of disagreement on whether the future on the Prairies will be wet or dry, he noted.

Already, as sea ice in the extreme north melts, exposing more ocean to warmth and therefore evaporation, there are signs that increased precipitation in the Arctic is occurring.

Then again, some say that higher average temperatures will lead to overall drier conditions as evaporation rates over land increase. In the interior of Australia, where a decade-long drought and catastrophic bush fires have stoked fears in some quarters that climate change is a real and present danger, this view has become more widely accepted.

“But we could look at any of the other 10 or so credible climate models in the world, and they could show you ones where we have an increase, and ones where we have a decrease,” said Stewart. [email protected]

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