Guest post by David Archibald
News has come from the Duluth office of the National Weather Service that both International Falls & Hibbing broke their records for low temperatures on the morning of September 17. The Falls got to 23°, breaking the old record of 24° set in 1959, and Hibbing to 24°. We shouldn’t be surprised because the Canadian prairies have been cooling for decades now. Also, President Trump, while in California on September 14, had predicted cooling, saying “It’ll start getting cooler. You just watch.” Three days later a new cold record is set at the iconic International Falls weather station. Either President Trump actually has some control of the weather or he is getting very good advice.
The paper on the Canadian prairies by Garnett, Khandekar and Kauer notes that “During the grain growing months of May-July, the mean temperature on the Canadian prairies has cooled down by 2ºC in the last 30 years. The cooling appears to be most certainly linked to diminishing solar activity” and “This cooling has led to a reduction in Growing Degree Days (GDDs) and has also impacted the precipitation pattern.” The paper includes this figure showing the multi-decadal decline in GDDs:
The Canadian prairies grow about 75 million tonnes per year of grains and pulses so the temperature downtrend evident is concerning with respect to the ability of the world to feed itself. The fact that the reduction of solar activity over that period is likely to have been the cause of the cooling is supported by the following figure, produced from data in Table 4 of the paper:
Over the period 1985 to 2019, the figure above shows the correlation between sunspot activity and GDDs on the Canadian prairies. The blue line is the line of best fit.
While the Canadian prairies have been cooling for decades, the Modern Warm Period only ended 14 years ago as shown by the following graph of the cumulative aa Index against the long term average:
While sunspots are visual manifestations of solar activity, it has been suggested that the Sun’s magnetic activity is the biggest factor in controlling climate on Earth. The figure above suggests that trends in solar activity are about 70 years long. If so, the Earth has just started into a long term cooling trend.
David Archibald is the author of The Anticancer Garden in Australia