Blazing Hot!

An extraordinary weather event occurred in the Pacific Northwest (NW) on June 26-28, 2021.  An Omega Block High set up over the British Columbia (BC) and the NW creating a heat wave.  There is nothing extraordinary about that, except for the fact this one was extremely strong.  What surprised me was the extremely high temperatures that it created. Portland, Oregon now has a higher record high temperature (116°F) than all of Colorado (115°F), and almost as high as Las Vegas, Nevada’s record (117°F).  The old records were exceeded by several degrees. Portland’s prior record was 107°F so the record was broken by 9 degrees!  It was broken for each of the three days with 116°F happening on the last day (June 28).  Seattle, Washington had only reached 100°F or more on three separate days in the past, but under this heat wave Seattle also broke 100°F for 3 days in a row (June 26-28).  But the biggest record breaker was Lytton, BC which had a record high temperature of 121.3°F. That shattered the Canadian record and it is higher than or equal to all but 4 state records in the USA.  Unfortunately for Lytton, soon after the record, a wildfire started and destroyed much of the town. For a retired meteorologist like me this heat wave was exciting, but also kind of scary.  (Note the heat in the West continues in July.)

So was this heat wave a rare event? And will it still be that rare in the future? Yes, I believe it was a very rare event.  But the second question is much harder to answer.  It depends how much climate change/global warming affects the weather in the NW.  I believe in human-caused global warming, so I am not a denier, but I am not an alarmist either.  I believe the world is warming and I believe it is at least partially due to humankind.

The earth is warming.  The image below shows the change in 30 year normals.

Professor Cliff Mass, University of Washington says that the heat wave was natural variability and was not really affected by climate change.  (Note Cliff Mass believes in climate change.)  However the Oregon State Climatologist is quoted saying,

High-pressure systems like the one driving the Pacific Northwest heat wave are “something like three times more likely to occur when we have a tropical cyclone out in the Pacific,” he [Larry O’Neill, Oregon’s state climatologist] said. “So climate change is impacting tropical cyclone activity through modulation of sea surface temperatures, and also things like wind shear.”

And there was a tropical cyclone that could have been indirectly strengthening the high pressure ridge. Similarly there is the climate change weak lazy jet stream theory which allows for big ridges of high pressure.  That theory is still being debated with pros and cons.  And there is World Weather Attribution, which is a European effort that calculates probabilities, and they have said this heat wave “was virtually impossible without human-caused climate change” for the extreme temperatures to have occurred. 

What do I think? If I had to make a choice, I think, except for the 2°F warming from climate change that has already occurred, the heat wave was not directly affected by climate change and it was mostly just a very extreme case of natural variability (like what Professor Cliff Mass said), but I am not certain.  Indirectly, it is possible that the tropical cyclone in the Pacific could have strengthened the Omega Block High with that tropical cyclone being more likely to form in warmer ocean temperatures due to climate change.  And is it “virtually impossible without human-caused climate change” as stated by the World Weather Attribution people?  Maybe, but I would need to better understand more how they determined the probabilities. 

Does that mean that events like this will be more common?  Maybe, I really do not know.  I personally would rather not label individual events as “caused by climate change”, though it is possible they may be strongly influenced by climate change.  Global warming is a long term happening, and it does affect individual weather events, but I believe the effects tend to be indirect (e.g. warmer temperatures, increased available energy, etc.), so therefore I would not like to declare a weather event to be caused by global warming rather I would say individual weather events are influenced by climate change.  It may just be wording, but I like the word “influenced” better.  

However note that I believe climate change does make a difference.  I do not feel confident in saying how much, but this is how I see it.  Today it is like jumping off a 6 foot high diving board.  50 years ago the diving board was 1 foot high and 50 years from now it may be a 20 foot diving board.  Jumping off (the weather event), is the same no matter what the height of the board is but the splash will be bigger jumping off the higher board.  The height does influence the splash.  Climate change does make a difference.  To sum up where I stand, I do believe that the earth is warming and human-caused climate change is real.  We need to be concerned, because doing nothing will make it harder on future generations. 

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