Water management will become more important for Prairie farmers as the climate warms.
Speaking at the recent online Saskatchewan Agriculture Agronomy Update, Dave Sauchyn, research coordinator at the Prairie Adaptation Research Collaborative, gave a synopsis of climate models and observations to help producers understand what their farms will face.
He recently compiled average world temperatures in month-long increments from January 1880 to the end of last month.
“Ever since the mid-1970s, every single month, this is thousands of months, have had a warmer than average temperature with one tiny exception. There’s a small blue bar. I think that’s December 1984,” Sauchyn said.
“Which means without doubt, which is pretty strong language for a bunch of scientists. Scientists are never absolutely certain about anything,” said Sauchyn.
“They went on to say that the observed warming of the world can be fully explained by human factors with little contribution from nature.”
The IPCC also concluded it is likely that human influence contributed to the pattern of precipitation changes since the mid-20th century, noting an increase in the intensity and frequency of hot extremes.
The committee said it is confident that a warmer climate is leading to greater moisture transport into weather systems, and that a warmer climate over land increases drought severity.
“In other words, with warmer temperatures, more evaporation from land and ocean, and that warmer air has the capacity to hold more moisture and therefore if the moisture doesn’t precipitate in rain, in the absence of rain is an increase in the severity of drought,” Sauchyn said.
He has graphed Canadian prairie precipitation over the past 30 years and projected it for the next 30. In a warmer climate the Prairies will receive more precipitation but it will likely increase in winter and spring with only a small increase in summer.
The increase will not be enough to offset losses from the increase in atmospheric evaporation in a warmer climate.
“There’s an increased probability of both lower precipitation and higher precipitation. So even though the models project slightly more precipitation, there’s a higher probability of dry events,” Sauchyn said.
He noted it can be difficult to tie individual extreme weather events to climate change, but some are difficult to explain without the contribution of a warmer globe.
For instance, the heat wave that hit parts of B.C. earlier this year spurred scientists to attribute it to global warming.
“They concluded that this heat wave would have been virtually impossible without human-caused climate change,” said Sauchyn. “After all, Lytton, B.C., temperatures approached 50 C, which smashed the existing all-time record for Canada.”
Of relevance to the Prairies is the tendency for the hottest periods to occur during dry times. In the absence of soil moisture, solar radiation is converted into heat rather than used to evaporate moisture.
“The cooling effect of evaporation is very much reduced in dry years, and we tend to get the highest temperatures, nearly always we get the highest temperatures, in the driest years.”
Weather stations at Swift Current and Indian Head, Sask., show a dramatic rise in winter temperatures since the 1880s. Sauchyn said cold winters help keep pests and disease at bay and are also important for holding moisture.
However, the Prairies are losing the advantage of cold winters, as the average winter temperature rises and the number of frost-free days increases.
“Most of our soil moisture is derived from melting snow and the nice thing about snow is it accumulates, it’s natural storage of water. As winter gets warmer and shorter, we can expect more of our precipitation to arrive in the form of rain as opposed to snow, and then we can expect snow to melt within various times in winter,” Sauchyn said.
He presented a winter precipitation model for the agricultural zone in Saskatchewan using data from 1951 and projected precipitation to 2100. It shows wetter winter conditions.
However, the range in the projection is getting larger, indicating there will be years that are drier and years that are wetter than in the past.
“So, this is the kind of climate that, if you’re sensitive to weather, which of course the ag industry is very much, you have to be prepared to take advantage of more winter moisture,” said Sauchyn.
“You have to be prepared to take advantage of years that are drier than we’ve experienced and wetter than we’ve experienced.”
There are three main sources of uncertainty in climate modelling: natural variability; different climate models; and different greenhouse gas scenarios. Natural variability dominates the differences in projected outcomes.
“If you use different models, it doesn’t make a lot of difference. The greenhouse gas emission scenario doesn’t become important until later in the century, and it’s hardly important at all in summer,” Sauchyn said.
“Now don’t misconstrue this information. It’s extremely important that we limit greenhouse gas emissions into the atmosphere because they are changing our climate. But, in terms of predicting future precipitation, it’s largely the variability that is arising from the natural variability, which is being amplified within a warmer climate.”
The Canadian Prairies have the most variable climate on earth, a distinction shared with Kazakhstan, Mongolia, Southern Siberia and Western China. They are all in the centre of a large continent far from oceans.
Paleoclimate climate records can be used to understand extreme weather patterns.
Sauchyn said the decades in which water levels were extremely low and persisted for a decade or two are important to note.
“The worst-case scenario for the Canadian Prairies is when we will get a decadal drought but in a much warmer climate.”
Much of Earth’s excess heat is now stored in the Pacific Ocean, which is the source of Prairie precipitation. This will likely cause more overall precipitation during wet times and less than expected in dry times because natural oscillation of the atmosphere and ocean is occurring in a warmer climate.
Sauchyn’s full presentation will be available at www.saskatchewan.ca/ He also contributed to a chapter on the Prairies for a Government of Canada report called Changing Climate: Regional Perspectives Report. It is available at bit.ly/323pB4Q.