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The heat wave baking the American Pacific Northwest and British Columbia, Canada, is of an intensity never recorded by modern humans. By one measure, it’s much rarer than it occurs once in every 1,000 years – which means that if you could live in that particular place for 1,000 years, you’d likely only encounter a thermal dome like this once, if at all.
Portland, Oregon, already broke its all-time record high of 108 degrees on Saturday and the heatwave peak has yet to be reached. Canada is expected to record its highest temperature ever in the country before the event ends. These are very serious numbers, especially in an area that is not used to heating like this, where many people don’t have air conditioning.
By Monday, some – if not all – of the all-time records shown below are expected to break, with many other cities not listed here expected to achieve the same feat.
These are permanent temperature records for selected cities. Portland has already broken its previous record of 107. CBS News
The heat is caused by the combination of a large atmospheric masking pattern over a man-made climate change world where core temperatures are already a few degrees higher than naturally.
The core of the thermal dome, as measured by the thickness of the air column over British Columbia and the North Pacific Ocean, is -statistically speaking – equivalent to one event in every 1,000 years or even one event in every 10,000 years. CBS News
This heat wave comes on the heels of another historic heatwave less than two weeks ago, which ravaged hundreds of record highs in the western United States, the desert southwest, and California.
Meanwhile, the eastern United States is also heating up, with temperatures rising to 100 degrees by Monday and Tuesday in major cities with the I-95 corridor. Back-to-back and fencing heat waves are more likely to occur due to highly undulating jet streams and an abnormal heating climate.
Heat wave in the Pacific Northwest
Sunday and Monday are expected to be the hottest days of the heat wave along the Northwest Coast from Portland to Seattle. Even before peak heat was reached on Saturday, several records had already been broken, with temperatures rising ahead.
It has never been hotter in Portland than it was yesterday; Every part of an ongoing, historic, and dangerous heat wave in the Northwest; Many homes do not have air conditioning. WeatherProf helps explain how we know this is so historical https://t.co/AJT1oU0TLt #WAwx #ORwx #MNwx pic.twitter.com/nC2mGtRUwm
– Mike Augustyniak (@MikeAugustyniak) June 27, 2021
As construction of the thermal dome continues, cities like Portland will likely break their all-time thermal record again, on consecutive days. Sunday’s thermometer is expected to reach 112 degrees – five degrees higher than the record-high 107 degrees, ahead of 108 degrees on Saturday.
CBS News
After a record high of 102 on Saturday, the thermometer is likely to break an all-time high of 103 degrees in Seattle on Monday, with an expected high of 108. In its history, Seattle has reached 100 degrees just three times. Remarkably, in this heat wave, highs in the city easily exceed 100 degrees 3 days in a row.
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Some inland cities in eastern Washington and Oregon are likely to have maximums in the 115-120 degree range. And while heat will erupt along the coast of Washington and Oregon by midweek, record heat will persist over the interior of Washington, Oregon, Idaho and Montana into late week.
CBS News
Over the past week, while computer models have consistently predicted seemingly incredible numbers, meteorologists have struggled to understand how a heat wave of this size might be possible, given that this region had never experienced anything of this magnitude before. Were the models wrong? Or, given climate change, should we now expect the unexpected — is this now just becoming a routine?
The expected temperatures in Sun-Mon via PacNW are so extreme that I think people are having a hard time putting it into context. There is still some uncertainty, but places along the I-5 corridor from Medford to Seattle have the potential to *smash* all records. # Orabi_habibi pic.twitter.com/W9yr7XXxLF
– Daniel Swain (@Weather_West) June 23, 2021
The models turned out to be correct and we should expect extreme heat waves, even unprecedented ones like this, to become more routine. says Dr. Michael Mann, Distinguished Professor of Atmospheric Sciences at Penn State and author of the new book The New Climate War.
But calling it the new normal isn’t enough, says Mann, “some people have called this ‘the new normal’.” But it’s worse,” Mann explained. “We will continue to see more and more extreme heat waves, droughts, wildfires, and floods as long as we continue to warm the planet through burning fossil fuels and carbon emissions.”
As shown in the infographic below from the Oregon Climate Assessment, this is only the beginning of the expected warming if humanity continues to burn fossil fuels. By 2100, temperatures are expected to be 7 to 10 degrees above what they should normally be, meaning a significant increase in extreme heat waves.
As all-time record heat approaches the Pacific Northwest, a look at future climate change projections – Graph shows mean annual temperature in Oregon 📈
+ Oregon Climate Assessment (see Figure 10): https://t.co/CYo3H4u8nk+ National Climate Assessment: https://t.co/TXvHgQu5lj pic.twitter.com/IUZqlhg7r0
– ZLabe (@ZLabe) Jun 26, 2021
In the case of this specific thermal dome, a mountain of hot air stacked vertically through the atmosphere, it happened once in 1,000 or even 10,000 years for this particular region. How do we know? In fact, it is easy to explain.
The intensity of a heat dome is measured by how “thick” the atmosphere is in a particular place. The hotter the air in that column, the thicker the air in that column, because heat expands. In our historical record of the Pacific Northwest in North America, this heat dome registers a statistical standard deviation from the mean of greater than 4.
In normal terms, this means that it lies more than 4 deviations to the right of the center of a typical bell curve (shown below) and this equates to values with a 99.99% lower probability.
This is called a temperature distribution, similar to a bell curve. It shows the normal distribution of temperatures that we should expect given the historical record. However, as the animation shows, as the globe warms up and the mean shifts towards the right – the warmer side. As a result, the extremes shift further resulting in more intense and frequent heat waves. central climate
In other words, statistically speaking, there is a 1 in 10,000 chance of experiencing this value. So, if you can live in this place for 10,000 years, you will likely experience this type of thermal dome only once, if at all.
To put climate extremes into perspective, we measure against the mean. Sigma is the standard deviation of the normal distribution of expected values. In this case, the maximum heat dome is 4.4 – this means that it is outside 99.99% of the expected values or a 1/10,000 + (1/2) chance pic.twitter.com/8raIMAngkg
– Jeff Berardelli (@WeatherProf) June 27, 2021
It should be noted that our historical record is limited and such statistics are very sensitive to small changes. But if it sounds like an exaggeration to say there’s a 1 in 10,000 chance of having such a thermal dome, it’s certainly not an exaggeration to say that this is the kind of event you’d expect to experience once every 1,000 years.
But we’ll know the exact value soon, as some of the best extreme weather reference scientists will likely be working hard to do rapid attribution – a new kind of cutting-edge science – this week to determine the actual values and to what degree climate change has contributed.
What that means for the northern Pacific is that there will be a very high rate of climate change for the upcoming event and the exact numbers will depend on how hot the weather is. The hotter it is, the higher the attribution ratio.
No matter the reason, stay safe!
— Gavin Schmidt (@ClimateOfGavin) June 25, 2021
So what is causing this heat wave? Like any heat wave, it is caused by a highly amplified jet stream pattern. These extreme disturbances in the jet stream are a normal and normal part of the atmosphere. But the climate science community is divided over whether extreme jet stream disturbances are made more likely by climate change — a phenomenon known as the ripple jet stream.
CBS News
Along with a more undulating, twisting and slow jet stream comes a phenomenon called “blocking”. This occurs when the waves in the jet stream become so elongated that they separate, sit and rotate. In this case, there is a type of textbook called an omega block over the Pacific Northwest because it resembles the Greek letter omega. Inside this omega, heat gathers and intensifies.
There is a faction of climate scientists who believe that a warming climate – specifically the Arctic – results in a wandering jet stream at certain times of the year. But there is heated debate – there is an equal amount of research that does not reach this conclusion.
Mann and colleagues took part in some of this research, finding that a certain type of obscuration in the northern hemisphere – what he calls quasi-resonance amplification – will increase by 50% this century under typical human-caused warming. “I do believe that the phenomenon we describe in our work played a very important role in the record heat wave,” Mann said.
As for the lack of consensus in climate research about undulating jet streams and blocking, Mann thinks it has more to do with the current state of climate modeling “This is an area where current generation models do not capture a real-world climate connection,” Mann explained.
Whatever the cause, the result of the extreme jet stream pattern is extreme in many parts of the nation and the world. Over the past few days, the central United States has seen heavy rain on its feet with flash floods along a stalled front. Starting Sunday and continuing through most of the next week, major East Coast cities will also be sweating through a heatwave—though not nearly as intense—with temperatures feeling like near 100 degrees from Washington, D.C. to Philadelphia and New York City.
CBS News
While the natural fluctuations between hot and cold patterns will continue, the trend is clear – extreme heat waves are bound to become more common, more intense and deadly in the coming years. In practice, solving the exacerbation of extreme weather is a formidable challenge for humanity, but in theory it is simple: “We can prevent things from getting worse if we quickly decarbonize our civilization,” Mann said.
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