Today, weather in southern Manitoba is smashing historical norms. Environment Canada predicts seven degrees this afternoon for Winnipeg, which is unheard of in early January. But how unusual is it?
The previous record for this day is 4.3 degrees, while the average maximum temperature for this time of year is minus 13 degrees. It is 20 degrees above normal. Such an extreme anomaly is highly unlikely to arise by chance. According to Environment Canada data for Winnipeg weather 1970-2000, the standard deviation for January 5 (a measure of the distribution of probable temperatures) is 8 degrees. Today’s temperature is fully 2.5 standard deviations from normal.
Events of such as this have a probability of 6/1000 of occurring by chance.
NASA’s climate scientist James Hansen writes how with global warming, it’s like loading the dice for our typical weather. Winnipeg keeps rolling snake eyes.
*This blog post includes a correction of a statistical error spotted by a Green Action Centre member.