From Dr. Roy Spencer’s Global Warming Blog
NOTE: This is the Tmin (daily minimum temperature) version of the Canada temperature trend results I posted yesterday , which were for Tmax (daily maximum temperatures). These results are quite different: whereas the high temperatures have seen essentially no warming trends across southern Canada since 1900, the nighttime temperatures have warmed in each one of the 6 provinces. In the next few days I will post just how much these observed Canadian temperature trends depart from the CMIP6 climate model simulations, which are the primary tool being used to change energy policy.
SUMMARY
- Over the period 1900-2023, the average summer (JJA) daily low temperatures across the six southernmost large provinces of Canada (British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, and Quebec) show warming trends, averaging +0.14 C/decade.
- The strongest warming (+0.18 C/decade) occurred for the coolest summer nights (coolest 3 days per summer month), while the warmest summer nights warmed at +0.10 C/decade.
- Whereas 7 of the 10 warmest summer daytime (high) temperatures occurred in the 1930s, 8 of 10 of the warmest nighttime (low) temperatures have occurred since 2003.
- Results for the 6 provinces separately are also presented.
Introduction
Below I present analyses of summertime daily low temperature (Tmin) trends from all available stations in the 6 southernmost large provinces, based upon the daily Global Historical Climate Network (GHCNd) dataset. These are the 6 provinces that border the Lower 48, and contain 86% of Canada’s population. (The results for daily high temperatures [Tmax] were posted yesterday.)
I simply averaged together the relevant statistics (monthly average Tmin, average of the warmest 3 days’ Tmin in each month, and average of the coolest 3 days’ Tmin in each month) from all available stations. Each station had to have at least 90% of the days in a month reporting data for that month to be included in the analysis.
Since stations come and go over the years, and since there are some large terrain elevation variations in western Canada, I performed an elevation correction to these Tmin metrics, in all provinces, using the departure of each year’s station-average elevation from the all-year (1900-2023) station average elevation, using a lapse rate of 6.5 deg. C per km. Corrections for average changes in station-average latitude were not done, which might be necessary in the winter since there are large North-South gradients in air temperature then. Such corrections in the summer would likely be small, but I can revisit that nuance at a later time.
Results
I’ll start with the 6-province average Tmin temperature time series, along with the total number of stations available in each year. In all plots that follow, I list the linear temperature trends, but plot a 3rd order polynomial fit to the data to help capture any multi-decadal variations not well reflected in simple linear trends. In all provinces the number of stations increases from 1900 to the 1970s, then decreases substantially in recent years.
As can be seen in the first plot (averages for all 6 major provinces), there has been an average summertime warming trend of +0.14 C/decade
I have also annotated 2021, which experienced the extreme heatwave in late June in western Canada. That event helped to push the warmest 3-day average Tmin metric (red curve) to the highest average temperature of any year since 1900. (Just to be clear, this is the warmest 3 days in each month in *minimum* daily temperature [Tmin]).
Notably, 8 of the 10 warmest summers in the all-days average Tmin have occurred since 2003. But, as I will show in the next few days, numbers matter: these warming trends are well below what the CMIP6 climate models produce for the same region of Canada.
Individual Provinces
The results for the individual provinces follow. I present them without comment; my Canadian friends can peruse the results for their home province if they wish. These are presented from West to East:
Oh no!. It’s -35 in Norman Wells this morning. That’s up from -34.86 just a decade ago in 2015. The Mackenzie is boiling!
Ugh, another denier pointing to local weather to dismiss global warming, like that’s a new move.
If the warming really was “global”, there wouldn’t be any declines in temperatures anywhere.
So maybe you should re-designate the description to “scattered warming”?
Ugh, another believer labeling someone a “denier” like a parrot with only one memorized line.
Ugh, another wokie cheaping out without a humor detector.
Actually it is another skeptic whose maths skills are so bad that the they think -35 is hotter than -34.86.
And despite that, the reply still managed to get 11 upvotes.
Relax, eClang; maybe 12 people have a Saturday sense of humour.
Eclang, votes? You might as well believe that adding CO2 to air makes thermometers hotter if enough ignorant and gullible people agree that reality can be overturned by “voting”!
As to 11 upvotes, that just shows that up to 11 people demonstrated their ignorance and gullibility.
Facts can’t be changed by popular acclaim.
And two mindless climate hysterics missed the joke. 😉
“It’s all about the decimal places.”
Izaak, AI can suffer from a similar problem, and thought dry ice was warmer than gaseous CO2! Bigger number = hotter!
Maybe Kelvin should be used by all scientists, except in particular circumstances? I think the SI temperature standard is Kelvin.
Thanks for noting that it actually GOT COLDER.
You are not your cause, Izzy ! 😉
Typo. 2nd line was meant to be…
You are not helping your cause, Izzy !
And your attempts at insulting me are somewhat contradictory. First you claim that I missed the joke which implies that Len Werner was claiming that the temperature was increasing and then you claim that I am harming my cause (whatever that might be) by pointing out that Len claimed it was getting colder.
A cheap sneer word from you in response to a smart-a remark.
Again, would you prefer global cooling since 1900? Would that be better for all life on Earth?
Probably even colder to the south in southern Yukon.
Decades ago a B737 crew asked everyone to expedite boarding as temperature was dropping toward limit allowed by flight manual for aircraft ground operation.
(Dawson City or Whitehorse.
In the 1950s I experienced -40F for two weeks straight, more than once, in the Peace area of NE BC.. (But sky clear, no wind.)
Uh, isn’t warming winter nights a signal of UHI?
Or CO2. It would suggest it isn’t the sun.
But in any event, these are summer temperatures, not winter.
ZERO evidence that CO2 has any effect on the climate whatsoever.
MASSIVE amounts of evidence of UHI effect.
Definitely the Sun and Earth’s relationship with it.
Now that POTUS Trump has stopped funding the the war against carbon dioxide and declared peace, we can all get back to looking at what causes climate change. The Sun is #1 culprit but Earth is not innocent either.
Yes it isn’t the sun. It’s the lack of sun or more precisely, more cloud cover = warmer nights.
. . . cloud cover over Canada has been increasing over the past half-century . . .
I wonder if that might be connected to both waste heat causing increased convection, along with an increase in cloud condensation nuclei – maybe resulting in increased cloud formation. I haven’t seen anything particularly useful about either speculation.
Huh? Waste heat causing convection? There’s not enough of it. Warmer temp by sunlight and water vapor by evaporation cause convection.
During the daytime….Sunlight Increases surface temp > increases evaporation over most of our water wet planet> increases cloud cover rate of formation, depth and extent > decreases surface temp under the shade of the clouds. At night cloud bottoms are relatively warm compared to the warmer surface’s view of cold outer space, so result in less heat loss from the surface than does a clear sky.
I’m an expert from Boy Scout wilderness survival camp…maybe the heat transfer classes in later years helped, but didn’t have much to do with choosing a spot for your sleeping bag in cold weather.
If you had the courtesy to quote me, you might have realised I wrote –
“I wonder” indicates that I am not sure, and “increased” means increased – not previously existing.
Your attempt to be gratuitously offensive falls a bit flat, and seems to be the product of a discourteous person who suffers a severe comprehension deficit. Should I value the opinion of such a person? I think not.
Better luck next time.<g>
“At night cloud bottoms are relatively warm compared to the warmer surface’s view of cold outer space, so result in less heat loss from the surface than does a clear sky.”
Wat a minute. The radiation emitted by the earth is based on its own temperature, not on the temperature of the clouds. What changes is the heat transfer from the lower atmosphere to the upper atmosphere because of a lower gradient between the lower and upper atmosphere. What warms is the lower atmosphere.
You might get less conduction loss from the earth to the lower atmosphere but climate scientists always pooh-pooh that conduction as being a very small part of the heat loss from the surface. Thus a change in a small component remains a small component.
Her work is interesting has there been any follow up to it over the last 20 years?
Can’t give details with phone but a quick AI search says yes, her findings have been confirmed with later studies
I looked at the daily high & daily low separately twenty years ago. I discovered most of the rise is in the overnight low temperature. Essays from Willis provide plenty of explanation that daily highs are moderated by the action of latent heat in water vapor. And that green house gasses being the moderator of night time lows. Evidence of this is seen as in today’s (6Dec25) foggy/cloudy weather in Northern California, with overnight lows in the lower 40s, and daily highs in the lower 50s—a 10° spread. Contrast that to typical dry July temperatures with overnight lows in the lower 60s and daily highs sometimes over 110°F, for a 50°spread.
Daily maxima are also moderated by the fact that daytime heat loss is based on T^4. As daytime temps go up heat loss goes up faster.
Looks like an URBAN WARMING signature due to the massive population increase.
More good work. Thanks
Has anyone ever established what the interglacial accounts for as background?
It certainly accounts for the fact that the area in question isn’t covered in ice right now, as it was some dozen thousand years ago, or so. Your point is well taken. Too often commentators don’t consider that our present interglacial will be coming to an end shortly (in geological time frames). Those who believe in catastrophic anthropomorphic global warming, should sell their oceanfront property on Hudson Bay now, while they have a chance.
Not just covered with ice but thousands of feet thick ice!
We have the Met Office and they can magic up any old climate reality. They don’t even require weather stations to do it.
They have AI
“They have AI”
They have the “A” part.. most of their data falls in that category…
… but they remain totally lacking in the “I” department.
Al Gore works for the Met Office?
The disturbing thing for me is why are they using fewer stations?
It is a real concern that the measured cold temperatures in Canada are getting a tiny bit warmer.
How will they cope ????? 😉
The nighttime temperatures may be slightly increasing due to increasing amounts of ambient water vapor from increasing irrigation use. Spraying millions of acres of fields with water, which causes damp soils and local humidity that sticks around at night, means that more of the heat is trapped near the surface, and the latent heat converts to sensible heat as the dew forms.
Certainly a factor. As Tyndall pointed out, water vapour reduces the rate at which energy escapes to space, even more than CO2 (and the rest of the atmosphere). What many people don’t realise is that no matter how much energy the atmosphere “blocks” or “absorbs”, at night the surface cools anyway. And so does the atmosphere, in case the ignorant and gullible haven’t noticed.
Arid desert nighttime temperatures drop faster and further than humid areas.
No warming (increasing of temperature), but less extremes of cold – which “climate scientists” redefine as “warming”.
And that’s exactly what is expected due to increased man-made heat. No influence of the sun at night to overwhelm the comparatively small man-made contribution, compared with the Sun’s input.
it should be obvious to everyone that whatever the du jour mechanism of global warming, it should be most pronounced at night, when there is no significant energy input from the sun.
or sumptin
It appears the climate is becoming more benign. Less extreme
I am somewhat concerned that the numbers of stations used in the system have decreased dramatically since 1990. Does this mean that fewer rural stations are being used, and wouldn’t this increase the % of UHIE resulting in warmer averages since then?
If the averages can be calculated to 1/1000th C then what precision is the actual data?
Climate scientists assume sll measurement uncertainty is random, Gaussian, and cancels. Therefore the averages have infinite resolution. The only limit is how many digits your calculator has.
Ha anyone looked at the dew point and factors which affect that such as heating your home?