By Paul Homewood

h/t Ian Magness

There have been several stories developing while I was away, so I will be picking up on some of them in the next few days.

The first concerns the Pacific Northwest heatwave:

The heatwave has quite frankly generated a hysterical reaction. Roger Harrabin says it scared him, while Matt McGrath repeats the lie that the heatwave would have been “virtually impossible” without global warming. And it’s not just the BBC; the media seems to have a collective nervous breakdown and lost its ability for rational thought.

The idea that global warming is responsible for the heatwave is patently absurd. According to HADCRUT, global temperatures have only risen by half a degree since the 1940s, so its impact on last month’s heatwave would have been tiny at the most.

Nobody is denying that the temperatures in the Pacific Northwest and Canada were extraordinarily high, but there is a perfectly rational explanation why.

Cliff Mass is one of the leading American meteorologists. As Professor of Atmospheric Sciences at the University of Washington, he has devoted most of his career to studying meteorology and climate modelling in the region.

On July 5th, he wrote a long, factual essay on the heatwave:

It is worth reading in full, but this is how he explains the actual event:

A number of factors came together simultaneously to produce the extreme high temperatures over the Northwest observed last week. 

The key factor in this and previous regional heatwaves is the development of an unusually strong and persistent area of high pressure over the Northwest.

The figure below illustrates what the ridge looked like at 11 AM  last Sunday around 18,000 feet above the surface (500 hPa pressure).  At this level, the ridge was the most intense ever observed over the region (will prove that later).

High-pressure areas/ridges are associated with warm temperatures during the summer.  First, high-pressure areas possess strong sinking, and sinking causes powerful warming as air is compressed as it descends to the higher pressure that exists at low levels (pressure decreases with height).  Your air pump, very warm after inflating a tire, is a good illustration of this mechanism. 

Ridges also possess southerly (from the south) flow on their western sides (apparent above), bringing subtropical warmth northwards.

But there is more!

The sinking air in high-pressure areas prevents clouds, thus allowing maximum solar heating (and the sun is near maximum strength now).  And on the southern side of upper-level ridges there is often easterly (from the east) wind, which can move down the western slopes of terrain barriers, producing even MORE compressional heating as the air descends the slopes.

It is no accident that every major summer heatwave in our region is associated with a ridge of high pressure. Ridges are veritable heating machines during summer and sometimes are colloquially referred to as heat domes.  The media loves this term. 

The origin of the intense ridge of high pressure of last week is fascinating.

Our ridge appears to have originated in the far western Pacific, where a tropical disturbance rammed into the Pacific jet stream, causing high-amplitude waviness in the jet stream thousands of miles downstream to the east.  The result was a strong ridge over the Northwest, with the waviness also producing a deep trough over the central Pacific (see upper-level map on Wednesday, June 23rd, 500 hPa pressure–about 18,000 ft).


The Atmospheric Heat Supercharger

In our heatwave, there was a feature that supercharged the warming west of the Cascade crest and the coastal mountains (e.g., the Olympics):   an approaching upper-atmospheric low-pressure area (or trough) that was west of northern California in Map A above.

Between the offshore trough and the ridge over the Pacific Northwest, there were strong southeasterly (from the southeast) winds that pulled up air from the warm desert Southwest.  This air subsequently descended the western slopes of the Cascades, where the air was further compressed and warmed. 

You can see this “supercharger” in action on Monday afternoon in a forecast map valid for around 5000 ft (850 hPa pressure level).  The colors indicate temperatures (darker red is warmer) and winds are also shown.  You can think of the solid lines as representing the pressure at that level. Note the low offshore and the high to the northeast.  The white arrow shows the warm southeasterly flow that descended the Cascade’s western slopes.


Everything had to come together just “right” to give us this extreme event.

Record amplitude of a ridge/high pressure over our region, forced by a tropical disturbance in the western Pacific, that produced a downstream “wave train”.   An environment that allowed the resulting wave to amplify.  The ridge had to be in exactly the right position relative to our terrain.  An upper-level trough had to develop in just the right location offshore and move in the optimal direction to cause strong southeasterly flow, fostering the supercharger noted above.  We needed a period when the sun was very strong.    And a summer stretch without smoke, which has a profound cooling effect.

The meteorological dice had to come up all sixes.  And they did.

In other words, it was a natural weather event, albeit an extremely rare one, something you might term a Black Swan event.

Mass goes on to address what influence global warming may have had. He makes the point that there has actually been no trend whatsoever to heatwaves growing hotter in the region, something you would have thought should be occurring if global warming was a factor.

He also deals with claims that global warming has led to more intense high pressure episodes and more drought. Again he finds that the actual data shows nothing of the sort. Indeed there is solid evidence that the reverse is true.

He concludes:

Politicization and Miscommunication of Science

The inaccurate information being distributed about the origins of this heatwave is very disturbing.

Some of this is being done out of ignorance or laziness, but a few individuals are deceiving the public deliberately.   Science journalism is only a shadow of what it was decades past, and a number of scientists now see social activism as more important than the determination and communication of truth.

Our nation has made costly mistakes when the truth was twisted for political reasons, such as for the Iraq war, when our nation spent trillions of dollars and initiated a war that killed hundreds of thousands of people based on misinformation about non-existent weapons of mass destruction.

We are now making similar mistakes with global warming, with politically inspired misinformation slowing realistic and life-saving steps, such as thinning our forests and restoring natural fire, or proceeding rapidly with nuclear energy.  Hyping global warming puts unrealistic and unnecessary fear into the hearts of our fellow citizens.  Unconscionable.  Global warming is an issue we can deal with, but only if truthful, factual, and science-based information is provided to decision-makers and the nation’s citizens.

I have spent my life trying to understand the weather and climate of our region and it is so frustrating that the media (e.g., KNKX public radio, the Seattle Times, the Seattle Stranger) and local politicians (such as our governor) have placed such a low priority on providing accurate information regarding climate change and other environmental challenges. 

All of this information is out there, so why have the BBC and the rest of out gullible media totally ignored it?

It is not even as if freak heatwaves like this have not happened before. The heatwaves of the 1930s were far more severe and affected large swathes of the US and Canada.

In Kansas, for instance, temperatures peaked in 1936 several degrees above anything seen in recent decades. And it was not just a one off event, as similar heatwaves were commonplace throughout the 1930s.

But apparently the BBC’s Environment and Science Department are no longer interested in facts!


July 18, 2021