By Paul Homewood
The Pacific Northwest heatwave now seems to have broken, with Portland maxing out at 116F. This is well above the old record of 107F, set in 1965.
We know that the heatwave this week has been the direct result of extremely rare meteorological conditions, which have driven hot desert air west over the Cascades and into what is usually a much milder region. Temperatures have been simultaneously boosted by the Fohn effect, with air masses sinking as they cross the mountains.
But is there any evidence that global warming has turbo charged the heatwave?
For that, we need to check out temperature data at Forest Grove, a small town of 10,000 just 25 miles from Portland, Oregon. The weather station there is on the Pacific University Campus in relatively unurbanised conditions.
We can see from the chart below that there has been no upward trend in the highest daily temperatures set each year (chart is only up to 2019 – no data available yet for this month).
Quite clearly if climate change was having any effect on heatwaves there, we would expect to see these trends rising.
We can also look at duration of heatwaves. The chart below shows number of days 100F and over each year. These peaked in the 1990s, since when heatwave days have returned to “normal”:
In short, what Oregon has had this week has been a freak weather event, and not a product of global warming.
All data is from CLIMOD
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June 30, 2021