Tuesday, April 27, 2010

Weather and climate

This morning I awoke to find an intermittent cover of wet snow on the ground and a temperature of 1C (34F). Yesterday, I got a little sunburned on the golf course with temperatures reaching 20C. Today's snow was the first recorded in Ottawa for over two months. The last snow was sometime in February. March, for the first time on record, saw no snow at all.

When the snow absence record was recorded in March, a local climatologist laid down $100 in a bet that there would be snow recorded in April. I guess he has won that bet with this snowfall dated April 28th. What he was betting on was the difference between weather ( what happens on a day to day basis) and climate ( what happens on the the long-term average.)

On a long-term average, there have been few if any April's in Ottawa that have not seen snow. A climatologist would know that the chances of a particular April departing form that pattern would be very small. So the chances of winning such a bet would be large.

It reminds me of the bets I would have with students in my Grade 11 Physical Geography class each year. I would bet that in Red Lake there would be a "January Thaw." My students would find this notion ridiculous. January, in Red Lake was famous for its -40 temperatures. And the climate average temperatures were always well below zero C. Almost every year, I would win my bet since at least for a few minutes or an hour or so, there would be at least one day in Red Lake where the day's high temperature went above zero. A thaw indeed. And such "Thaws" had been recorded in almost every January since record keeping began.

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