May 23, 2023

Are the Large Alberta Fires the Result of Climate Change?

During the last few weeks, large fires have initiated and grown over northern Alberta, resulting in massive smoke plumes (see the image below from one week ago).   Here in Washington State, we experienced a few days of smoke aloft from these fires last week.

I have received a number of emails asking whether such Alberta fires are unusual for this time of the year and whether global warming (climate change) could be the cause.

In addition, several media outlets have published headline articles about the topic, suggesting that human emissions of greenhouse gases were the main cause.

It turns out that reality is more complicated.   

May is typically the biggest month for Alberta wildfires, there is little upward trend in Canadian wildfires, and anthropogenic greenhouse gas emissions are a very small part of the story.

Canadian Wildfire Statistics

Based on an official Canadian government wildfire database, here is a map of Canadian wildfires from 1980-2020.  Alberta wildfires are generally found over the northern half of the province, which includes large areas of boreal forest and grassland.

What is the long-term trend of Canadian wildfires?  Increasing due to global warming?  

Perhaps surprising to some, the answer is no (see below).

For all of Canada, the number of fires is DECREASING, and there is no obvious trend in the area burned.

What about Alberta, where the current batch of wildfires are burning?

Lots of variability but little upward trend (see below).  The biggest fire was in the early 1980s.

The lack of a long-term trend in wildfires is important:  one WOULD expect an upward trend if global warming/climate change was a significant contributor.

Some folks have argued that having big Alberta fires in May points to global warming.  They suggest that it is warming so fast that wildfires are occurring early!  

But folks making such claims need to look at the data.  Historically, May is the month of the most frequent wildfires in Alberta.  (a graphic from a paper on trends in Alberta wildfire below).

Furthermore, many of Alberta's great wildfires occurred in May, such as the huge Fort McMurray fire in early May 2016 and 2011 Great Slave Lake fire of 2011.

But why is May such a big month for northern Alberta wildfires?

It has to do with surface fuels.  After a long, cool/wet winter, there are a lot of dead fuels (e.g., dried grass, annuals) from the previous year that are on the ground after the snow has melted.  Such light fuels dry very quickly during the first warm weather and are ready to burn in early May.

But the optimal burn season is limited in time.  Only a few weeks later, there is a greening of the surface vegetation (grasses start to grow, annuals sprout leave) and such greening REDUCES the flammability of the surface fuels.  Which side would you expect to burn in the picture below?

There is a short favorable May window for large Alberta fires before the greening.    But to take "advantage" of it you need favorable drying conditions, which are associated with a strong, upper-level ridge of high pressure over the region.  And strong winds and lightning are favorable as well.

Furthermore, rainfall peaks during the summer (see monthly precipitation in Edmonton below).

The setup for the fires earlier this month was nearly perfect. In early May, an intense ridge of high pressure developed over southern Canada (see a plot of the difference from normal heights at 500 hPa pressure below for 1-15 May). Red and orange indicate MUCH higher than normal pressure in the lower atmosphere (around 18,000 ft).

Such high pressure resulted in intense drying and warming that helped dry the surface vegetation before greening occurred.  There is no evidence that such a pattern is the result of climate change.
There were periods of strong, dry winds in early May due to the large pressure gradient at the edge of the high pressure at lower elevations (see example below on May 6).  Strong wind is a primo accelerator of fire.

You can understand the situation by looking at the observed weather at Edmonton Airport from late April to early May (below).   Rainy and around 60F in late April, then rapid warming and wind on April 30th with a jump to 85F on May 1, followed by 86 and 88 on May 3-4.   

Perfect weather to dry out the surface fuels, followed by lightning at the high pressure shifted eastward.  Human ignitions are also distinct possibilities.

In summary, there is little evidence that the Alberta wildfires represent a climate event.  

Intense drying weather occurred exactly when the surface fuels were most vulnerable before greening.  May is typically the month of the biggest Alberta fires for a reason and the smoke that reached the Northwest aloft from the fires was simply the result of a favorable wind pattern aloft (easterly flow), not the results of a slowly warming planet.


Note:  I will do a special online Zoom session this Saturday (May 27th for my Patreon supporters).  Will talk about wildfire meteorology and answer your questions.


  1. "But folks making such claims need to look at the data." Data, we don't need no stinkin' data! All of you science - haters just need to step up and give us more trillions from your hard - earned incomes to support our ever - expanding onshore/offshore windmill farms and massive solar fields! And don't forget to keep shutting down the evil nuclear plants and outlaw every and any gas - fueled vehicle and appliance!

  2. Thanks for explaining why May is prime fire season. I would have thought late summer would be prime season... like it is here. Summer must be their wet season, though I expect Alberta is too far north to benefit from the southwest monsoon.

  3. I wonder how long it's going to take society to move beyond the climate change hysteria thing. Another 5 years? 10 maybe? It's already completely worn out.

    1. The most staunch/militant deniers, mainly the Fox News set, will be dying off soon enough. They might even go into their graves truthfully claiming that climate change had no impact on their quality of life. That's fine. Over the long haul, it's going to warm up. Not sure if asking if the ending of the "hysteria" is welcoming grounded discussion or outright denial in reference to the viewpoints of some. Ending the hysteria would certainly make the fossil fuel tycoons happy for a while. Still, eventually those fuels will become economically unfeasible. There is only so much that is easy to extract, along with an exponential increase in the population of potential human consumers every year.....yah. Weening off the fossil teet has to happen eventually. The whole manner of how society works has to fundamentally change. Again, luckily for the typical diehard Fox News's not your problem to solve. It's in that briefcase left for the young generations along with all the other IOU's

    2. The issue of climate change has been co-opted by non science people into a religious cult. If you read the U.N. IPCC reports and look at how they define probabilities, it becomes clear that mainstream media picks and chooses what to share. "Green" energy will not support modern society and until the climate change believers accept nuclear power as a reasonable energy source, it is difficult to accept their position.

    3. The media is not in the truth business. Their job is to get eyeballs on advertising so as the owners of those eyeballs jump in their cars and buy stuff they don't need. Ultimately, even if the media claims to be "helping", they are a huge part of the problem by driving rampant consumerism. Save the climate! And now, an ad for a 3 ton SUV that gets 15mpg....
      Should nuclear be in the mix? Definitely. Something has to power all those EV's doing their 3 hours of daily commuting to some sprawling single use zoned burg to another sprawling single use zoned burg. Lots of stuff the greenies get axle wrapped about really doesn't cover overpopulation, the consumerism, the poor use of land resources, and how hard that will be to challenge. Climate change really is a by product of several issues that no one really wants to talk about, namely too many people wasting our limited resources just to make a select few very wealthy.

  4. I was young in 1950 (western Pennsylvania) on a day when we went into Church while the sky was pretty blue with a few clouds. A bit later when we came out the sky was gray and the sun red -- slowly all went black. The end of the world!
    Actually, this was caused by fire, see:
    Started on June 2nd
    Location map here:

  5. Seems to be some disagreement about the data: Government of Canada National Risk Profile: "Driven by periods of intense drought and record-breaking high temperatures, recent wildland fire seasons have been longer and more intense than usual.

    The 2021 wildland fire season saw well above average fire activity with over 6,500 fires burning over 4 million hectares of land. For comparison, the 10-year average was approximately 5,200 fires and 2.5 million hectares burned. There were 5 fatalities resulting from wildland fire or suppression activity in 2021, the most in Canada since 1986.

    The area burned annually by wildland fires has more than doubled since the 1970s. It is predicted that, by 2100, the area burned could double again."

  6. Unfortunately, as recently pointed out by Todd Myers, Washington state is now explicitly teaching students to IGNORE the data and consider only their emotions with regard to climate change.

  7. Gosh, you guys are right, all this stupid climate change hysteria is so overblown.
    Daily CO2
    May. 22, 2023 = 424.02 ppm
    May. 22, 2022 = 420.82 ppm
    How silly to think that elevated CO2 levels higher than any in recorded human history could ever have any meaningful effect on the climate.

  8. Thanks again Cliff for your data driven insights....

  9. Looking at your graph of hectares burned in Alberta, there may not seem to be any trend. However if you divide this time period into two parts (1959 to 1991, 1992 to 2023) and include the latest years up to this year, there is a little different story. A rough approximation from the graph gives about twice the number of hectares burned from 1992 up to this year so far than was burned in the earlier period. Also, only one year equaled or exceeded 500,000 hectares between 1959 and 1991 while that amount was exceeded in about 7 years in the more recent period.

    1. I also noticed that the total area under the curve for the latter half of the graph appears greater than for the former half - especially if the most recent years, including 2023, are taken into account.

    2. Is there any statistical trend in the long term Alberta areas burned time series, Cliff? Seems like eyeballing it is producing mixed results and perhaps the more scientific thing to do would be to see if anything significant is actually there. I personally "see" what these two commenters note (looks like increase over time), which is opposite of what you say about it in the text (no increase over time). But squinting at graphs might not be the best way for any of us to examine the question?

    3. with the variability, the trend would not be statistically significant

    4. Cliff, maybe you could elaborate a bit more on your above comment about the statistical significance of this. There is a lot of variability from year to year or over shorter time periods, but I was comparing two longer 30-year periods, and the recent 30-year period seems to have significantly more area burned than the earlier period.

  10. sidulin: ".......... How silly to think that elevated CO2 levels higher than any in recorded human history could ever have any meaningful effect on the climate."

    I've been playing with ChatGPT lately asking it a number of climate related questions, just to see how it responds. And so I asked ChatGPT a question related to the assertion made above. My question reads as follows:

    "What was the concentration of carbon dioxide in the earth's atmosphere during the Roman Warm Period?"

    ChatGPT's response:

    "The Roman Warm Period, also known as the Roman Climatic Optimum, is a term used to describe a relatively warm period that occurred in Europe and the North Atlantic region roughly between 250 BC and 400 AD. However, direct measurements of carbon dioxide (CO2) concentrations in the Earth's atmosphere were not available during that time as the technology for such measurements did not exist.

    Scientific methods to directly measure atmospheric CO2 concentrations became available in the late 1950s with the establishment of the Mauna Loa Observatory in Hawaii. The continuous monitoring of CO2 concentrations at Mauna Loa and other locations around the world has provided a detailed record of atmospheric CO2 levels since then.

    Based on ice core data and other proxy records, scientists have reconstructed past CO2 concentrations for periods before direct measurements were available. However, these reconstructions are associated with uncertainties and limitations. According to available scientific research, the pre-industrial CO2 levels during the Roman Warm Period were likely around 280 parts per million (ppm) or slightly lower. It's important to note that this estimate is subject to some degree of uncertainty.

    By comparison, prior to the Industrial Revolution, CO2 concentrations remained relatively stable for thousands of years, fluctuating between approximately 260 and 280 ppm. Since the Industrial Revolution, human activities, particularly the burning of fossil fuels, have significantly increased CO2 emissions, leading to the current concentration of CO2 in the atmosphere being over 410 ppm as of 2021.

    Keep in mind that the Roman Warm Period was driven by various factors, including natural climate variability, solar radiation, and regional factors, and the CO2 concentration alone does not provide a complete picture of the climatic conditions during that time."

    I find ChaGPT's response quite interesting. In this modern age of directed artificial intelligence which relies upon the prior writings of today's mainstream climate scientists for its analysis of climate issues, how could anyone -- let alone a pseudo-human A.I. chatbot such as ChatGPT -- believe that various factors including natural climate variability, solar radiation, and regional factors can affect climate; and further, that the CO2 concentration alone does not provide a complete picture of the climatic conditions occurring in any time period whatsoever, let alone the Roman Warm Period.

  11. The sad thing is that this "cry wolf" tactic being used where EVERYTHING that happens is directly tied to climate change (and break out the labels to be used against anyone who dares to ask any questions about it). That actually harms that agenda because some people are now getting tried of it all and I think before long people will stop believing in it at all, even in cases where it might REALLY be from climate change. Weather data is out there to check for most of these things, and in many cases (especially where Cliff breaks it down), climate change can be empirically proven as not a root cause for some of the things the cultists of climate change say they are.

    1. What they don't seem to get is, when an issue like this is turned into a religious cause, all credibility is lost and levelheaded people realize it's just BS. I wonder.. how long will it take before the light goes on for these folks?

  12. Thanks for keeping it real Cliff! I enjoy seeing the comments from some people who when you show them the real data, they go completely into name calling and finger pointing.

  13. I'm normally one to agree with Cliff's take on these matters, but I grew up in Calgary. There is no way you can try to tell me or anyone from southern Alberta that fire behaviour hasn't changed. Objectively and subjectively Calgary has gone from being a city that would get a couple mildly smoky days every few years to a city the spends entire months with barely breathable air every single year. The drastic, radical change in smoke patterns was a major contributing reason to us moving to the west coast. If this data is showing there's been no change in fire patterns then either the data is wrong, it's not being interpreted correctly, or something fundamental is missing in the analysis to explain why the number of smoke hours Calgary sees every year has skyrocketed by hundreds of percent in the last decade.

    I am telling you as a person who has lived there for nearly their entire life - something drastic has changed that is massively affecting people's health and quality of life in a way that it simply never did before. It wasn't like this in the early 2000s, it wasn't like this in the 90s, it wasn't like this in 80's. It's unbearable now. For weeks and weeks on end. Every single year.

    1. I am talking about wildfires...not smoke. And particularly wildfires in Alberta in May. Smoke has increased the last few years over the Northwest and SW Canada in recent years....for a number of reasons.

    2. It would seem as though an unstable, warming climate is the determinant in the increase in Alberta wildfire activity over the past 30 or so years that the above data shows. Since the wilderness of western Canada does not have the history of fire suppression that the western U.S. does, a human-induced buildup of fuels as a factor in said increase is off the table. In fact, the graph of area burned vs. time for Alberta and Manitoba came from a study published by the Fraser Institute that concludes wildfire activity in western Canada is increasing and is, in fact, "unprecedented".

  14. Cliff, I am not sure whether you have adequately made your case. First, I am a long time reader of your weather blog and have a huge respect for your weather analysis and the data driven approach you take. I also have a lot of respect for calling out unsupported claims.

    With this said, it seems there are a few hypotheses on the table:

    (1) fires are starting earlier than is usual

    (2) fires are burning more intensely than usual

    (3) number of fires have increased

    I do not currently think either hypothesis is actually refuted in this analysis. Knowing that fires usually burn in May in Alberta is a very useful piece of information. To really confirm hypothesis (1), I think we need to look at the number of fire starts by week of the year, and not at total acreage burned by month. For example, if there are dozens of small fires that are easily suppressed, we could have hypothesis (1) being true with a similar observable total acreage burned over the entire month.

    Hypothesis (2) similarly needs data that shows acreage burned per fire per rate of time. Seemingly quantity of smoke is a proxy for fire intensity, yet smoke is not part of the analysis of this blog post (for better or worse). To another extent, we are missing lots of data; many of the questions we are asking will not have a conclusive answer until many more decades have passed.

    Though, the large variable I think left out is fire suppression activity. The budget for fire suppression has tripled since 1970 [1]. If we have similar areas burned per year and have tripled the amount of fire suppression activity, it would seem that fire activity has increased.

    What is more, any change over (mere) decades is (IMHO) significant when discussing climate. AFAIK, the human lifetimes is relatively short when compared to climate. Changes in climate generally should therefore play out over centuries if not thousands of years. Observable changes within a human lifetime, even if small, are seemingly quite significant. Thus a statement like "there is little upward trend in Canadian wildfires", as observed over the course of just a few decades is perhaps evidence supporting the notion that significant changes are occurring.



Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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