The small Canadian town of Lytton sits about 100 kilometers to the northeast of the city of Vancouver in British Columbia. Situated at a latitude of 50º North of the equator Lytton is hardly the place that you would expect to be competing for the honour of being one of the world’s hottest places. In fact the daily high temperature in Lytton during the hottest times of the year rarely reached above 30ºC. Or at least it did before global warming.
(Before I go any further I just want to state again that in my opinion the green house gasses we are dumping into the atmosphere are causing Earth’s average temperature to rise, that’s global warming. But that rise in temperature can cause many different localized changes to the environment, that’s climate change. Nevertheless, I don’t care about whether you call it global warming or climate change I just want something done about it!)
Over the past week however Lytton has suffered under a once rare weather phenomenon called a heat dome. Simply put a heat dome is a very strong high pressure system that gets cut off from the high altitude jet stream and therefore can remain in the same location for several days or more. Now remember that in the northern hemisphere the wind blows clockwise around a high pressure system so where I live in Philadelphia the hottest days occur when there is a Bermuda high off the Atlantic coast. The clockwise flow around the Bermuda high brings warm, moist air from the Gulf of Mexico over the southern states, where it warms even further, right into the Mid-Atlantic region. Bermuda highs are generated by the warming of the waters in the western Atlantic during the summer and thanks to global warming they have been getting stronger over the last decade.
On the west coast the high pressure systems that generate heat domes are caused by a difference in temperature, technically known as a gradient in the Pacific Ocean with the temperature rising as you go from west to east. In other words the ocean waters near Japan are relatively cool but get progressively warmer as you go east towards the North American west coast. Recalling that the air above warm water rises means that the northern Pacific can become a kind of wind tunnel pointing towards North America. These prevailing winds bring warm air onto land and sometimes during the winter those winds can become trapped against a jet stream pushing down from the Artic forming a massive high pressure system, which as the summer begins forms a heat dome.
These heat domes have appeared several times in the past few years over the US pacific northwest states leading to record high temperatures in cities like Portland Oregon and Seattle Washington. This year’s heat dome has been the largest and strongest ever seen reaching all the way from Portland, which set it’s all time record high of 46º on June28th, to the Canadian Yukon and Northwest Territories.
Little Lytton sat right in the middle of the high pressure system which meant that for several days there was virtually no wind or clouds in the town. Nothing but Sunlight lasting for nearly twenty hours a day. Remember Lytton is at 50º north latitude so the days there in summer are very long. After days of baking in the Sun on June 27th Lytton broke Canada’s all time high temperature record of 45ºC with a temperature of 46.7ºC. That record was only the start however for on June 28th the high temperature in Lytton reached 47.8ºC before finally on June 29th reaching an astounding 49.4ºC, hotter than it’s even been recorded in the city of Las Vegas, Nevada. That temperature is in fact the hottest ever recorded at any latitude above 45º, north or south on the entire planet!
Of course it wasn’t just Lytton that sweltered in oppressive heat, almost the entire western part of Canada and the United States have been subjected to an unprecedented heat wave in regions where it rarely gets hot, regions where air conditioning is virtually unknown. While the consequences to public health will take some time to fully determine an initial heat related death toll of 380 has been announced for Canada and at least several hundred for the US states of Washington and Oregon.
So is this the new normal, it certainly does seem as if we’ve reached a tipping point where massive changes to large areas of the globe are happening right before our eyes. And the evidence has become so overwhelming that it seems as if even the worst climate change deniers have become silent. Still there’s so much we have to do if we’re to prevent even worse climate disasters, and so little time left.
Post Script: As I was writing this post the BBC broadcast a story about a wildfire that was ravaging the Canadian province of British Columbia. Caused by the excessive heat and drought conditions generated inside the heat dome the wildfire had virtually wiped out the small town of Lytton!
