Canada: Virtually No Change in July/August Highs Since 1939

Ross McKitrick analyzed Canadian weather records. Summers aren’t any hotter.

Since 1939 there has been virtually no change in the median July and August daytime highs across Canada, and October has cooled
slightly

If people knew that summers won’t get an hotter and winters would get a little warmer, would anyone mind?

 

SUMMARY
Here are a few points that you might notice in the graphs and tables that follow.
1. There is a tradeoff between the number of available stations and the length of record. There are 30 stations with data back to 1888
and 267 stations with data back to 1978.
2. Over the past 130 years the median warming rate in the average daytime high is about 0.1 degrees per decade or 1 degree per
century.
3. Over long samples there is little polar amplification (increased warming with latitude) but it does appear in fall and winter months
in more recent subsamples.
4. Over the past 100 years, warming has been stronger in winter than summer or fall. October has cooled slightly. The Annual
average daytime high has increased by about 0.1 degrees per decade. 72 percent of stations did not exhibit statistically significant
warming or cooling.
5. Since 1939 there has been virtually no change in the median July and August daytime highs across Canada, and October has cooled
slightly.
6. There are 247 stations with data back to 1958. However as the time span decreases the range of observed trends greatly expands.
All months exhibit median warming but with much wider variability.
7. Post-1958 Arctic coverage is much better than earlier. There is little indication of polar amplification.
8. Post-1978 the range of trends grows dramatically. The median trend in March and April is slightly negative.
9. Some polar amplification is observed in the post-1978 annual trend, mainly due to the late fall and early winter months.

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