Extreme precipitation events have always occurred, but are they changing?

A woman wades into flood waters in Calgary, Alta., on June 14, 2020, after a major hail storm damaged homes and flooded streets. THE CANADIAN PRESS/Jeff McIntosh

Francis Zwiers, University of Victoria and Ronald Stewart, University of Manitoba

Extreme weather and climate events causing extensive damage are a fact of the Canadian climate, and this year is no exception.

On June 13, a mammoth hailstorm pounded Calgary with damage in excess of $1 billion dollars, the most expensive hailstorm in Canadian history. In early July, eastern Canada was subjected to both persistent extreme heat coupled with high humidity and major flooding.

As we cope with these events, questions invariably arise about what role climate change may have played. Has a particular extreme been made worse because of our changing climate? How will these extremes change in the future?

Water cycle accelerating

Many of these questions are linked with the hydrologic cycle — the evaporation of water from the Earth’s surface and its vegetation, the transport of water vapour in the atmosphere from one place to another and the ultimate return of the water to the surface as precipitation.

The water cycle speeds up when the climate warms. A warmer atmosphere holds more water vapour, creating the potential for more intense precipitation events. The evidence that human activity has warmed the global climate over the past century is incontrovertible. Satellite data available since 1988 indicate that the atmosphere has moistened, and that this is primarily due to the human-induced warming of the climate.

Individual extreme events are, however, influenced by many other factors. A storm can leave behind moisture at the surface that can re-evaporate and strengthen subsequent events.

The collision between a cold front and a lake breeze can lead to heavy precipitation. A delayed lake freeze-up during a warm winter can enhance lake-effect snowfall. Or a drought could limit local evapo-transpiration — evaporation from the land surface and transpiration from plants — eliminating the rainfall that comes from local moisture recycling and further intensifying hot, dry conditions.

Heavy rainfall

Many studies have examined precipitation-related change, usually focusing on average conditions rather than extremes. This is understandable because individual events, like a tornado or hail storm, are complex, and sparse ground observations and evolving techniques mean there aren’t yet long-term records that allow scientists to reliably estimate trends.

In contrast, numerous rainfall records beginning in the 1950s or earlier exist across the globe. Statistical analyses of data from these rain gauges confirm that rainfall extremes have grown more intense at the global and continental levels, in agreement with climate models.

A man stands in shin-deep water in an apartment.
A man surveys the damage to his basement apartment after a severe thunderstorm caused localized flooding in Toronto on July 8, 2020. THE CANADIAN PRESS/Carlos Osorio

There are broad indications that these changes in rainfall extremes are due to human influence on the climate at global and continental scales. Extreme one-day rainfall events that occurred about once every 20 years in the past are now occurring about once every 15 years.

Even so, scientists still struggle to confidently say that a particular extreme rainfall event is the result of climate change. This is because there is naturally a large amount of variation in precipitation in one place, and the signal from climate change can get hidden within the natural noise.

Future extremes

Not all places have seen one-day rainfall extremes grow more intense over the past several decades, but that doesn’t mean it won’t happen in the future. The science indicates, with considerable confidence, that as the climate continues to warm, precipitation extremes will become substantially more intense in the mid-latitudes and northern land areas, including Canada.

Although details are uncertain, heavy snowfall, freezing rain and hail will all change with continued warming. For example, a recent study suggests that large hail could become more likely in Alberta by mid-century, but less likely in some other parts of Canada.

There is no doubt that human-induced greenhouse gas emissions have changed the climate. Nevertheless, the human imprint is often difficult to see in local meteorological observations. Despite that lack of direct “in your backyard” evidence, we should prepare for a future in which many precipitation-related extremes will become more intense.

Francis Zwiers, Director, Pacific Climate Impacts Consortium, University of Victoria and Ronald Stewart, Professor, Environment and Geography, University of Manitoba

This article is republished from The Conversation under a Creative Commons license. Read the original article.

133 thoughts on “Extreme precipitation events have always occurred, but are they changing?

  1. “The evidence that human activity has warmed the global climate over the past century is incontrovertible”

    Except that there is no evidence for human cause. That the observed rise in atmospheric CO2 is caused by fossil fuel emissions is the essential relationship needed for human cause but no empirical evidence has been provided for this critical relationship.

    Pls see





    • Chaamjamal
      You have to understand that it was an opinion piece in The Conversation. They only publish things that support the official party line. And, they delete comments that disagree with the conclusion(s) of the author(s).

    • I live in Calgary and to say a storm pounded the city is a huge exaggeration. I would guess that about 80% of the city was spared the large damaging hail. For me on the west side of town the storm was almost entirely a rain event with only a brief period of small hail near the end of the storm. The part of town with the damage is all in the northern part of the northeast quadrant …. ie only a portion of the northeast.
      I would guess the dollar amount of the damage is an over estimate too but a friend that did get damage has severe damage to her siding and some windows …. her car was spared as it was at the Honda dealership and got no hail damage but Honda’s loaner car had the rear window taken out and lots of hail dimples.
      Griff as usual is full of u know what 😉

      • Hail storms with golf ball sized hail are common summer months event in South-Central Alberta. The path of destruction is typically half a mile wide and 2 to 3 miles long. Fortunately the land area is mostly agricultural. Farm building and vehicle window damage doesn’t make the news like city damage does. Every farmer likely accepts that he is going to get a field wiped out by hail once or twice a decade.

      • The reason for the high cost of damage is NOT due to more damage, it is due to the escalating costs of repair and replacement. All you need is a few dents today and they write the car off. My house insurance went up significantly a number of years ago as “replacement” became removal and rebuilding of the whole building.

    • Anthony and his team simply repost articles that are relevant and of interest… I guess he leaves the interpretation up to us… I am certain he is not claiming the validity of the claims.. in fact quite the contrary.

    • AC totally agree.
      The link between Global warming and flooding has not been established.
      What happens is
      A. Alarmist scientists make broad claim About increase or decrease in rainfall in a given region
      B. Alarmist scientists then drill down to major catchments within regions and find out that broad claim not valid
      C. Ignore catchment study and go back to broad claim soundbite

  2. Contiguous US Climate Extremes Index for extreme one day precip events has this going up by ~0.6 days/year, post 1980, with a standard deviation of that trend of ~0.2 days/year. I.e., about a 1/10,000 chance that this is not an actual trend. I’m not defending their methodology, or making a larger point about AGW. Just looking at the NOAA data….

    • bigoilbob,
      If the temperature has gone up 1 degree over the industrial age….say from 14C to 15C, that is 7% more water vapor in the air (at saturation temp). So has precipitation gone up 7% ? It would be very hard to tell since annual rainfall variation can be 50% or more. Are there 7% more extreme events? Again, very hard to tell since one has to rely on early newspaper accounts of extreme weather as a starting point.
      So a degree of global warming SHOULD cause some more precipitation, and should as a result cause a few “normal” weather events to become “extreme” events.
      But if it was a significant effect, we should see desserts blooming, and they aren’t.

      • “So has precipitation gone up 7% ”

        If you do the arithmetic, the expected value of extreme one day contiguous US extreme precip events is ~60% higher than in 1980. Yes, the standard error of that trend is such that you might expect 1 in 10 samplings, 40 years apart, to have the latest number lower than the older one.

        No matter how you spin it, expecting 24 more days of an extreme pricp event/ year than that of 40 years ago is a BFD…

          • “I think the “events” have gone up proportional to media coverage, 60% more with the invention of television.”

            Not too thoughtful. I evaluated the statistically bullet proof trend in post 1980 single day extreme precip events. I think even way back in 1980, they both knew what they were, and how to record them. Television was not part of the process.

            This trend was coincident with unprecedented increases in man made GHG emissions. Feel free to “bbbuuuttt, bbbuuutt” to your hearts content…

      • Whenever climate induced rainfall increase is discussed, the logic is that a warmer atmosphere holds more water vapor. However, the key word is “holds”. For it to rain more, there has to be more instances of warm, moisture laden air encountering cold air masses. This could conceivably happen with orographic lifting – making it rain more in areas upwind of a mountain range as in (already) wet areas west of the Cascade Mountains. I have not seen any evidence of that. Rainfall is more complicated than that; it’s MUCH warmer in the summer than in the winter yet in many places (like west of the Cascades) it rains far less in the summer.

        Absent orographic lifting, one would expect less mixing of warm and cold air masses as the temperature difference between the tropics and the poles has decreased (Arctic temperature amplification). I suspect claims that Global Warming is causing dramatic precipation increases are all wet.

        • In the ‘holds’ idea… warm air ‘can hold’ more water vapor… but it does not have to. That is what the relative humidity tells us… how much below saturation the air at the current temperature is.

      • The comments about water vapor are cherry picked. They made the statement, but there are studies that show the actual moisture content in the atmosphere has NOT increased.
        Warmer temperatures only mean the air CAN hold more moisture and that is only at the saturation level.

    • There are other factors besides temperature that can affect water holding capacity and rainfall intensities – studies show the Clausius-Clapeyron relationship (1 degree = 7% more) does not hold up: https://www.cityfloodmap.com/2017/06/does-higher-temperature-increase-rain.html

      So its a theory. It also assumes saturation – is that reasonable in Alberta? Perhaps not. Seeing what happens with real data and observed rainfall intensity trends (to check the theory) shows little change in trends in Alberta: https://www.cityfloodmap.com/2020/07/can-we-use-daily-rainfall-models-to.html – in fact the 24 hour rainfall intensities have been decreasing per the Environment Canada v2.3 to v3.1 Engineering Climate Datasets.

  3. Re, my last comment, I was X eyed when I looked at the data. The trend is not durable ~99.99% of the time, but “only” for 99.9% of the time. I regret the error.

  4. Absolutely yes in the UK, which since 2000 has seen 18 years with severe flooding (1 in 100 or worse flood levels), flash flooding in summer, severe and damaging storms. Infrastructure like reservoirs and rail embankments which has stood since Victorian times has been damaged. Newly built flood defences are overcome just years later.

    And no it isn’t building on flood plains or some imaginary lack of or banning of dredging.

    climate change is a reality in th eUK.

    • So, are you implying that if the UK continues on the path to “Net Zero” carbon [sic] then when [if] achieved, the weather will be better and that it will have been worth it to fix “climate change”.

      If not, what is the point of the statement you make?

      Have you looked at the design basis documents for these flood defence projects? I’ve seen a few and I was surprised at their naivety, with respect.

    • Show us the data bullsh!tter

      Then show us your maths on how this is related to temperature.

      Then show us your maths on how this is linked to carbon dioxide.

      (first hurdles beware)

    • I’m always confused about the one in a hundred year claim. How many places are there in the UK. How many places should have 1/100 occurrences in a year? It’s not that hard. Sure, UK is having a rainey time, there is a cold area occurring the Atlantic for a bit. Climates changes a bit all the time all over the planet, even for decades, sometimes for centuries.

      • Good comment. Here in Colorado, the forecasts for tomorrow calls for record precipitation in the form of snow to be set going back to the late 1800’s. The record low temperatures and record low highs for the dates for the next couple of days are likely to be set also.

        Our records are shorter here, so more records are likely to be set on either extreme. In general, most people don’t have good sense about statistics and probability. I know for sure the house rules, especially in gambling towns.

        • Scissor… yea, saw that rolling Ventusky forward to see when the cold front will get to Dallas.

          Per NOAA at


          …i n the ‘reliable’ records (since 1948) Earliest snowfall for Boulder, CO month/day/year was Sep 12, 1974. That record will fall in the morning, if the forecast is correct.

      • If you have 100 measuring stations, it is statistically likely that one of them will see a once in a century event every year.

        • Statistics agree with you Mark. The proliferation of rain gauges in urban areas (in Canada to support operational aspects of the wastewater systems and calibration of models for inflow and infiltration (extraneous flow) management) means we have over 170 gauges in the Greater Toronto Area for example. Statistics show it is not uncommon to get many 100 year events over a short period with so many observations: https://www.cityfloodmap.com/2019/03/are-six-100-year-storms-across-gta-rare.html

          More observations = more extreme events just by casting a finer net. The local rain trends may still be down at an individual station: https://www.cityfloodmap.com/2020/05/southern-ontario-extreme-rainfall.html

        • Since regions are coupled, meaning that stations within a region experience more or less similar patterns, records will tend to cluster.

          Wouldn’t it be funny if all of this climate change alarm is due to bad statistical analysis? Time will tell. Certainly over periods of several lifetimes, extremes are pretty common.

          • Scissor
            There is no proof of increased flooding due to climate change.

            They only have broad sound bites at a regional level.
            Every catchment has unique topography and properties.
            Any catchment level analysis fails to show any link

    • Your flooding is due to the fact that drainage canals and flood basin are no longer maintained because EU regulations don’t allow putting the dredge spoils on the banks (thus making them higher). So the idiots on your local Councils just stopped dredging. Gee, I wonder what that might lead to? griff, you are the true definition of an oxygen thief.

    • So stuff gets old, nothing like the deaths from storms we had in 1928, 1952, 1953 where a total of 355 folk died. We seem to have been pretty good at responding to such weather events since. Mitigation, that’s the solution not a return to pre-industrial times.

    • Griff,
      Every time there are claims in the Gutter Press (I include the BBC in that group) of more extreme weather Paul Holmewood goes to the source data at the Met Office. There is never any statistical trend where the records are more than a couple of decades long.

      The last one I remember was the Stonehaven rail crash.


      I would suggest that this should be your first port of call before repeating unsubstantiated wild claims of impending doom.

    • Of course climate change is a reality in the UK. Most of the UK was composed of permafrost for the last 100,000 years, it only thawed out about 10,000 years ago.

      I hope and pray that warming continues for another 10,000 years.

      You wouldn’t want to go back to glaciers nd permafrost again, would you?

    • not convinced… has dredging been curtailed for whatever reason and has it had an impact on river flow??
      building on flood plains or indeed anywhere will affect the runoff and hence flow downstream and change the flow.. and so overwhelm previous structures (ie victorian).. so yes while humans have affected the outcomes of heavy rainfall where is your evidence that humans have caused more of it??

      So as usual.. I cal BS griff

    • griff you are a hoot with your after the fact….facts
      if it had gone the other way….severe droughts….you and they would still be blaming global warming

    • Love how griff knows the answer and thinks he can refute it up front by simply asserting that it’s not true.

    • Absolute rubbish from a fellow UK citizen.
      The only cause of the flooding in the UK is the lack of maintenance of the waterways and strict adherence to EU rules that put nature before people and their property.

      • I had this discussion on another site a few years ago with a bloke from Southampton who, incredibly, worked in water management. I knew absolutely f-all about water management but it was more than he knew, so I posted the data for him for his education. It was like this one:


        He skulked off and came back two years later posting that philincalifornia is tiresome as if the previous interchange didn’t exist and hello, yes it was one click away.

        I actually think that you can fix stupid, but you can’t fix libtard.

        • Phil
          Thanks for the graph
          But flooding is both regional and local
          Flooding of a individual location is also dependent on storm length.

          Here in Melbourne the most common flood the causes damage is a 40mm +event in about 30 minutes.
          But this year we have had many rain days with more than 40mm. It’s just that the 40mms occurred over several hours So no flood damage.
          When looking at historical rain data for a given town such as on BOM website you can not distinguish whether the 40mm fell in 30 minutes or 24 hours.
          This is what makes the “more floods” claim baseless

          • Yeah, that was kinda my point, but trying to teach this to people with the brain power of talking parrots is pretty much a non-starter.

    • griff
      Any idea how much the percentage of impervious surfaces has increased in the UK since Victorian times? You are like the person who thinks all problems are ‘nails,’ and therefore only owns a hammer.

      • Exactly. Urban areas, because of impervious surfaces, flood alot faster than otherwise. Then all of that runoff is channeled down storm-drains & affects less urbanized areas downstream. And the cultural marxists/greenies want to pack everyone into crowded urban constructions….

    • I live in southern Ontario and I can’t recall any 1 in a hundred year flooding, as you describe, in the last 18 years. So, by your logic Griff, Climate Change isn’t a reality!
      I believe the original term was “Global Warming”, not Regional Warming.

    • Griff,

      NO DATA, so you have no evidence, or is it that your compulsion born of the belief in man-made climate change forces you to lie.
      During the LIA storms and flooding across the British Isles and Europe were much worse than now. Reacquaint yourself with history (e.g. read http://www.breadandbutterscience.com/A_Chronological_Listing_of_Early_Weather_Events.pdf ) and understand this period of time is NOT unusual, it is all part of the great chaotic cycles of weather.

    • Is that the same UK that used to grow grapes in Roman times, but then had ice fairs on the frozen Thames during the Little Ice Age?

      So yes Griff, climate change IS a reality in the UK.
      (And astonishingly, in other parts of the world as well)

      I say – let’s stop these climates changing RIGHT NOW!

    • Once again, griff equates flooding with rain and only with rain.
      Completely ignoring how the flood control projects that have been built over centuries have been allowed to decay, if not actively been removed by his fellow believers.

    • I have trouble with defining climate change based on 1/4 of a person’s lifetime and an area the size of the UK.

      And it seems to me rail embankments and reservoirs withstanding the ravages of time and weather might succumb to 100+ year floods that are within the parameters of normal climate fluctuations without being a harbinger of world ending climate catastrophe.

    • Griff

      Here are the met office figures


      Heaviest rainfall was in 1876 and 1912 . There are far more data points in wet upland areas these days as no one wanted to live there in the past. I have a thousand years of weather records for the UK and some of the rainfall events in the past would make your hair curl, including nearly 3 Years of virtually continuous rain in the 1315 period which caused great famine.

      Things often look worse because these days we have 65 million people in the country many of them living on flood plains, yes that is a big factor , I was on the environment agency flood defence committee and we would tear our hair out at the local councils approving them as we would then have to build flood defence structures. Lack of dredging was also a huge problem because of an EU directive on wildlife, especially on the Somerset levels


    • Yet another griff post based on NOTHING but “feelings”

      NO DATA,


      Just the usual empty mess.

      • Fred is right. The plural of anecdote is not data. Try this out – when you read an article with no data about extreme rainfall and flooding trends, list the cognitive biases that are at play that Daniel Kahneman describes in Thinking Fast and Slow: https://www.chijournal.org/C449

        It’s amazing all the mental short-cuts that are taken just to tell stories, when there should be an evidence-based focus on data.

  5. There is no doubt that human-induced greenhouse gas emissions have changed the climate.

    There is considerable doubt that is the case.
    Water is cooled by low level infrared in the CO2 wavelengths as the infrared increases the evaporation from the surface. Taking plant cover into account water covers close to 90% of the Earth’s surface.

    Then a set of houses built in 1930-1950’s are shown and the damage to them us used to assess increase is storms? in 1920 that would just be prairie and a heavy storm would go unnoticed. At the same time covering what was open land with concrete leads inevitably to flash flooding. The flooding of a basement in what was open prairie would obviously be more expensive but that does not mean there are more storms or more damaging storms.

    • Of course there is doubt. This is something the poster knows very well. They try to bolster the argument with reference to empirical observation, such as:

      From the post: “Satellite data available since 1988 indicate that the atmosphere has moistened, and that this is primarily due to the human-induced warming of the climate.”

      The poster has linked to a scientific paper for the second assertion (the human induced bit) – the second sentence of which is:
      “Results from current climate models indicate that water vapor increases of this magnitude cannot be explained by climate noise alone.”

      WTF! Climate noise in models that have been shown to be inaccurate and of no predictive use. A busted hypothesis – yet these same models and be used to make assertions about ‘climate noise’.

      So you don’t have to go to the trouble of explaining how the system actually works – just look for the patently false arguments they present.

  6. The water cycle is a strong negative feedback mechanism. It takes heat to evaporate water from the Earth’s surface. Later, that heat is released higher in the atmosphere when the water vapour condenses and falls as rain. That heat is then radiated to space.

    If the water cycle is indeed accelerating, that means more heat is being removed from the planet. That puts the brakes on global warming.

    Scientists sometimes present work they think supports the CAGW narrative. When you examine the implications of their work, you very often find that it actually supports the skeptical viewpoint. 🙂

    • With no disrespect to commiebob I post the following as a general commentary:

      All this arguing about angels by pinheads gets frustrating….. Water vapor is THE dominant “greenhouse” gas. While I abhor that term, it gets the point across. (not a greenhouse but rather a blanket, reducing the outgoing radiation somewhat)

      I’ve been doing my own experiment – measuring the ground temperature (grass, away from buildings), and vertical air column temperature with a decent IR instrument every morning at dawn since January. The data are very instructive. (cross checks verify the IR instrument vertically, against clear sky measures up to 30,000 feet ASL accurately)

      At the same time, I have the air temperature at 6 ft elevation and derive the absolute humidity. Relative humidity is a useless metric and hides the fact that water vapor dominates thermal processes.

      The absolute humidity in my locale (South Florida), ranges from about 5,000 ppm in winter to 35,000 ppm in late summer. The mean is 22,800 ppm.

      I also then plot the outgoing radiative energy flux via Stefan-Boltzman and plot it against absolute humidity. I can predict the absolute humidity given the ground and air column temperature, or can predict either the air column (vertically against clear sky) or ground temp given the other two measurements.

      The R^2 of these plot trends is above 96%.

      Average outgoing radiative flux is ~180 W/m² against clear sky. Now the IPCC says outgoing radiative flux from CO2 is just about 2 w/m².

      Ergo carbon dioxide as the “blanket” is 90 times on average less effective at “warming” the planet as is water vapor!!!

      The argument that CO2 is causing catastrophic global warming is as stupid as saying the heat generated by the alternator in your car’s engine bay, is causing your engine to overheat! The Alternator produces on average about 500 watts of electrical power, and maybe 50 watts of waste heat. Your engine produces from 5,000 to 30,000 watts of waste heat.

      To say with a straight face that your alternator is causing your engine to overheat ignores the elephant in the room of the capacity of the engine’s water cooling system!

      CO2 caused global warming as crisis is nonsense and a false narrative not based on any real physics. (does it warm things – yes a teensy bit compared to water vapor)

      • Indeed. My point was that even papers that try to support the CAGW narrative often end up contradicting it when closely examined. The only reason CAGW is still a thing is that it can be used to further a political agenda.

  7. BEFORE:

    There is no doubt that human-induced greenhouse gas emissions have changed the climate. Nevertheless, the human imprint is often difficult to see in local meteorological observations. Despite that lack of direct “in your backyard” evidence, we should prepare for a future in which many precipitation-related extremes will become more intense.


    The human imprint is often difficult to see in local meteorological observations. Despite that lack of direct “in your backyard” evidence, we should prepare for a future in which many precipitation-related extremes will become more intense. Nevertheless, there is no doubt that human-induced greenhouse gas emissions have changed the climate.

  8. From “Climate Change in Prehistory” by Burroughs, starting at the bottom of page 47 and talking about 6,000 years ago when the post-glacial warming reached it’s peak, “On the evidence of tree cover the average summer temperature in mid-latitudes of the northern hemisphere was 2 to 3 degrees warmer than it is today. Not only had trees spread farther north than now but they also extended higher into upland areas: . . .”

    So the big questions are, what caused that terrible warming back then? Why has it been so cold now? Is the next big ice age approaching? How are we going to stop all of this unacceptable climate change?

  9. Looks like Bob and Doug Mackenzie are writing under the pseudonyms Francis Zwiers and Ronald Stewart. It’s a beauty way to go, eh? My apologies to the few sane Canadians holding out against the woke nonsense.

    • Ron
      We are here, fighting the tide of idiocy
      We had a big flood in Calgary in 2013 and the talking heads of course said climate change and used sciency terms like 500 year floods.
      Then later that year the U of C published a study that this was only the 5th worst flooding level in the previous 130 years

      • Re Calgary flood of 2013.
        There were 3 floods in the late 1800’s and early 1900’s that had higher water flow. However that was long ago so the fools went and built in the valley and got flooded. Suzuki tried to blame climate change and was told where to go by some Albertans.

        • Development in floodplains was noted by Auditor General of Alberta as a factor in 2013 flooding: https://calgaryherald.com/news/politics/province-failed-to-control-floodplain-development-auditor-general-says

          An attribution study for the 2013 flooding suggested there may be a chance of more rain but that is offset by less snow, resulting in no change flood flows: https://commons.erau.edu/publication/906/

          “Event attribution analysis suggests that greenhouse gas increases may have increased 1-day and 3-day return levels of May–June precipitation with respect to pre-industrial climate conditions. However, no anthropogenic influence can be detected for 1-day and 3-day surface runoff, as increases in extreme precipitation in the present-day climate are offset by decreased snow cover and lower frozen water content in soils during the May–June transition months, compared to pre-industrial climate.”

  10. “Extreme weather and climate events…”

    What is a “Climate Event” and how does it differ from a “Weather Event”?

  11. A good pair of questions is “What is the optimum level of water vapor in the atmosphere? Are we presently on the moist or dry side?”

    Yesterday morning the official NWS forecast for our town was -3F Wednesday morning. In late summer! By last night the forecast changed to 19F entirely because an overcast sky and a bit of snow would prevail over the area until Wednesday sunrise, we hope. Dry air behind a storm can lead to extreme and rapid cooling, with attendent damage to water pipes, crops, gardens, etc…

    • icisil,
      Looks like it was that sheet particle board garbage that is highly prone to damage and leaking if not painted and maintained regularly. Old time wood siding would have lost some paint but it would not have come off in chunks like what we see in the photograph!
      I did a little remodel recently where some of the stuff had suffered quite a bit of water damage. In New Mexico! We don’t get much rain in New Mexico unless you’re talking about the Great Taos Flood mentioned in Tony Hillerman’s classic ‘The Great Taos Bank Robbery.’ Well worth the read if you’re not familiar with it!

  12. Oh yes the UK…… terrible place for flooding….just look at these accounts…..

    October 1767 “They have had the greatest flood at Manchester ever known.”

    February 1767 “. . .in Wales, no man living ever saw such floods.”

    July 1760 “So violent a storm of rain, attended with thunder and lightning, fell near Fordingbridge and Ringwood in Hampshire, that the water of the brooks running from the New Forest into the river Avon, were in less than hour’s time raised to the height of ten or twelve feet perpendicular.”

    September 1772 “A most astonishing rain fell at Inverary, in Scotland, by which the rivers rose to such a height, as to carry everything along with the current that stood in the way; even trees that had braved the floods for more than 100 years, were torn up by the roots, and carried down the stream.”

    September 1890 “The greatest flood in Langdale that has been known for 20, or some say 40 years. Skelwith bridge was washed away about 2 a.m. on October 1st.”

    June 1903 “……. a total amount of nearly 1.200,000 million gallons, or 5,348 million tons of water precipitated on the land in three days: enough water if it could all be stored to supply the whole population of England and Wales with 25 gallons per head for more than three years.”

    January 1903 “On the morning of 27th the Lune overflowed its banks and flooded the country to a greater extent than had been known for 12 years.”

    February 1903 “The heavy rain almost all over Scotland on February 7th and 8th was attended with disastrous consequences in the lower reaches of the Clyde…. the river burst its banks in four places in spite of vigorous efforts to strengthen the banks. Thousands of acres of land were submerged, and the low-lying districts were under water for nearly two miles to an average depth of 10 feet. About Dalmarnock Bridge many factories and mills were completely flooded out, and between 5000 and 6000 persons were thrown out of employment temporarily. The present flood, however, far surpassed both 1832 and 1886 floods in amount of damage, owing to the enormous increase in recent years of buildings for industrial purposes along the river.”

    ….you get the picture, I guess it must have been all that CO² in the atmosphere….

  13. We take many more measurements now than in the past and we have satellite views through darkness and clouds, so we are aware of everything that is happening 24/7 in very fine detail. Plus we have 10x more housing, development and infrastructure all exposed to the elements than 50-75 years ago, which will take a normal beating, including UHI making cities much warmer than the surrounding country side. As compared to 50-75 years ago when not as much measuring going on, and less people and infrastructure affected.

    Having said that, with increased warming for whatever reason, the atmosphere holds more water, so there will more precipitation. Which is probably net beneficial in the scheme of things. Even those floods in Calgary and Alberta that cost a billion $$ led to filling all the dams on the Saskatchewan River drainage, so there is increased electricity production and more water for irrigation. The dams were all spilling this year downstream of Calgary/Edmonton on both forks of the Saskatchewan River and the main stem that winds up in Lake Winnipeg and downstream for Manitoba Hydro on the Nelson River to Hudson bay. We hear about the immediate damages from weather, but they never balance that with what happens with the benefits on the other side of the total balance sheet ledger. Calgary has always had weather extremes, such as the warm winds of a normal Chinook that Leonardo DiCaprio mistook for radical climate change. Just like the coolish wintery weather coming to Denver and area tomorrow after being 100 F in the shade yesterday. I am sure that to will be blamed on ‘climate change’.

  14. Flooding happens in flood plains- don’t build here and you won’t get flooded. Poorly implemented land use also contributes to more flooding in those flood plains. To blame flooding on carbon emissions is without merit.

    “There is no doubt that human-induced greenhouse gas emissions have changed the climate.”
    No doubt? I should have stopped reading at that point.

  15. “A man surveys the damage to his basement apartment after a severe thunderstorm caused localized flooding…”
    Flooding in basements is often caused by poor drainage around the building and lack of well designed gutters and downspouts to get the water off the property.

    And as I noted in a previous post- if the building isn’t in a flood plain- and the building and its lot are well designed to get rid of water- then no severe thunderstorm can cause the building any damage. Blaming flooding on rain is simple minded.

  16. Climate change is a reality in the UK, says Griff. Well that,s true, but then climate is always changing, and historical records show extreme weather was was much ,much worse in the past. But in my lifetime the floods in the July 1968 were worst I can remember 7 inches of rain in as many hours, the worst for 200 years. and the hurricane force winds in 1987/88
    As I have said before, rainfall amounts have been about average for 90% of the time, in the last 10 years.
    As for the climate getting warmer, well that is just not true, if anything it is getting colder. The winters of 2009 to 2011 were the coldest since 1961/63. Spring 2013 was one of the coldest since 1659, and Christmas day 2010 was the coldest on record. and the period from 25th November to 25th December 2010 was also the coldest on record.
    The next three winters could be even colder. Whats your prediction Griff ?

  17. Um, nothing new about hail in Calgary, it’s in a belt from IIRC Red Deer to Lethbridge. The recent case is worst in a long time. Insurance companies were paying for cloud seeding to reduce the size of hailstones.

    Keep in mind that extreme events are improbable, for example the earlier flooding in Calgary and in Cedar Rapids IA were the worst in 75 years.

  18. My own simplistic unscientific observation about climate, temperature, water temps, CO2 from observations this weekend at the lake in Saskatchewan

    The alarmist position is that CO2 increases temps which in turn heats oceans.

    In the prairies this year it was a cold wet spring right through end of July , despite this the lake temp rose to its usual 73F by end of July, comfortable swimming

    Then we had a gorgeous August, sunny, Many stretches of 30C weather, best August in recent memory, no rain
    And yet by this weekend the lake has dropped to 62F

    All that hot atmosphere and the lake still cooled
    Because the sun is getting lower, and is up less time

    So no matter how hot it is the lake got significantly colder, because it’s the sun

  19. So,
    “Cool, Canadian air will filter and settle into the Rockies and Plains as surface high pressure
    slides south in the wake of the cold front. A significant cool down is
    expected to parts of the Northern/Central Rockies and the surrounding
    areas. Snow will be possible at higher elevations for this area with this
    early season cold blast. Winter Weather Advisories and Winter Storm
    Watches are in effect for portions of the Northern/Central Rockies Monday
    evening into Tuesday. Freeze Watches are in effect across most of North
    Freeze this time in the grow cycle is not good.

  20. The IPCC attributes the increase in temps to 50% natural and 50% human. How then can increased severity of storms etc, if true, be caused primarily by human involvement.

  21. Satellite data available since 1988 indicate that the atmosphere has moistened, and that this is primarily due to the human-induced warming of the climate.

    If I look at the data of the rel. humidity at 300 mb lever or the
    data of the spec. humidity at the same level, I can’t see an increase….

  22. Well, is it extreme climate change when the last snow of the season has been April 30 consistently for four years now? Yeah, I have photos that date these events, otherwise I wouldn’t bother posing the question. Ditto, first snow of “winter”: if it’s October 31 for four years in a row (yes, dated photos, too) does that mean that “winter is coming earlier?

    I don’t know, don’t have an answer, but also don’t have a weather station that provides humidity levels and barometric pressure readings, and where I live, early and late snows aren’t all that odd. And since these things happen in my area, then it’s local weather, NOT climate change.

    There’s snow in the western states (WY, MT,etc.) so does that mean anything, especially when snow this “early” in Colorado at high elevations is a frequent occurrences? No, it does not. It is NOT unusual for snow to fall in those areas in July, either.

    It is nothing but cotton-pickin’ weather, and as with real climate change, we have no control over it, never will. An indicator of REAL climate change is substantial growth in glacier thickness and their subsequent flow toward the equator in both hemispheres. And some day, it will happen but it will take real time to occur.

    Such things do not happen overnight. If it comes early and stays late and never melts, period, what does that mean? The only direction the planet can take is toward the return of the ice sheets, not the other direction.

  23. Probably dinosaur ph#rts wot done it.
    Meanwhile few people have large enough brains to encompass your concepts.

  24. Citizens dislike taxes and to minimize pain, the first thing to go is civil maintenance (like clear storm-water drains); add relentless pressure to build over drainages installed over the countless millennia by Mother Nature; couple this with a potent communication technology that didn’t exist three decades ago; factor in the large number of children born since then, not forgetting their questionable education. And be cognizant of the plethora of industries whose very survival is synonymous with click-baiting … and hey presto: welcome to our Brave New World.

    • But what ever will those children do if — suddenly, no warning, just BINK! – all their commlinks go dead?

      The horror!!!! Oh, noes!!! The hysterics! The pain and suffering! They will be witless and wandering in a desert empty of “other”.

      The horror…. or something….

  25. For Canada overall extreme intensities have decreased for 24 hour intensities (per the most recent Environment and Climate Change Canada’s Engineering Climate Datasets v3.10): https://www.cityfloodmap.com/2020/07/how-have-rainfall-intensities-changed.html

    The 24 hour trends may not match what is happening at a shorter temporal scale and that it critical to urban flooding – different regions in Canada have short duration intensities going in different directions: https://www.cityfloodmap.com/2020/07/can-we-use-daily-rainfall-models-to.html

    That means one should be cautious about extrapolating the models (1 day resolution) to shorter durations. “Heavy precipitation” in a climate model is not the same as extreme rainfall from a civil engineering, municipal drainage perspective, but these are often conflated.

    In Alberta the observed trends in annual maximum rainfall series are more downward for 24 hour periods:
    significant decrease – 2 stations
    decrease – 22 stations
    no change – 1 station
    increase – 17 stations
    significant increase – no stations

    For shorter periods there are more increases but no significant increases:
    significant decrease – 1 station
    decrease – 14 stations
    no change – 5 stations
    increase – 20 stations
    significant increase – no stations

    Despite these overall non-trends in observed data, models consistently overpredict higher frequency rainfall in that region. A recent paper in PNAS (https://www.pnas.org/content/pnas/early/2020/05/26/1921628117.full.pdf) notes: “In the west and central west, HadEX2 shows a decrease in extreme precipitation over this period, while all three models show increases of varying magnitude.”

    • Robert
      Thanks for the excellent comment.
      The alarmist must come up with a hypothesis why a region will have more or less rain.
      Prove their hypothesis in say Calgary
      And then prove it in Edmonton.
      It is my understanding that they haven’t been able to do this anywhere.
      But really when you are talking about the civil engineering aspects of flood control you will need to prove it for at least individual suburbs of Calgary and Edmonton

      • Thanks. The observed data trends don’t lie – this shows Edmonton and Calgary trends in annual maximum series: https://www.cityfloodmap.com/2019/03/environment-and-climate-change-canada.html

        100 years of Edmonton data and no real change. Saskatoon just reviewed 126 years of data and found no overall change: “Historical weather station data from 1892 to 2018 was examined to determine rainfall changes. Results show a mix of increasing and decreasing rainfall trends that are mostly statistically insignificant and vary depending on rain gauge location, duration of rainfall, time period, and methodology to assess (e.g. linear trend or moving average trend).”

        Nothing-burger in some regions.

  26. There are always questions having driven through river valleys where it always seem to rain more. So could this be like the heat island effect? Well they only use experts–“We work only with recognized experts – epidemiologists, immunologists, public health scholars and others – to bring you information that is fact-based, accurate and 100% independent. ” These are their experts for their claim.

    “The first was a Mann–Kendall nonparametric trend test, and it was used to evaluate the existence of monotonic trends. The second was a nonstationary generalized extreme value analysis, and it was used to determine the strength of association between the precipitation extremes and globally averaged near-surface temperature. ”

    “Australian data dataset is based on a historical rainfall dataset first documented in Lavery et al. (1992),that has been quality controlled by identifying and removing problematic records using statistical techniques, visual checks and station history information……Another caveat is that while we have attempted to use data that have been systematically quality controlled, the data quality remains a concern.”

    Seems like there are still questions?

  27. Looking at the picture at the top of the article. I’m willing to bet that the main cause of the street flooding was the hail (and possibly debris) clogging the drains.

    • Plus the fact that city is half paved over with all the roads and houses/buildings taking up such a footprint that there is not much natural drainage to begin with now. Throw in a few plugged storm drains, and you practically get a flood event in the city with every little downpour, where there would have been none 75 years ago in that same exact location with the exact same storm/precipitation event. But this gets the press now, because climate change. Oh, and when they search for the perfect flood picture, they go to the lowest spot in the neighborhood where it is guaranteed to pond until it slowly drains away. 3 blocks over, it is high and dry.

      • You are right. Calgary design standards allow for ‘trap lows’ or sags in the roadway profile where ponding can and should occur. In some regions with low grades (south west Ontario) this ‘saw tooth’ roadway profile is commonplace. When I was a municipal engineer we would get complaints about ‘roadway flooding’ during extreme rainfall events when in fact the system was design that way. Same thing for overland flow easements – residents call about flooding because they have not seen the drainage system at work as intended before.

  28. NOAA’s Atlas-14 was what we typically use in the US for rainfall events in engineering design.

    Volume 11 covering Houston was updated in 2018. The 100-yr, 24-hr rainfall total is 17.1 inches. The 90% confidence interval is 12.0 – 24.1 inches! Quite a range.

    The nearest US locations to Calgary have not been updated since 1973.

  29. Worst floods in World History/US +rain records

    From a meteorological point of view, if we increase the amount of moisture in the warmer atmosphere(in this case by something like 6% but that varies-more in the higher latitudes) we WILL get more precipitation.

    That includes high end, excessive rain/flooding events. To deny this, is to deny the physical laws and reality.

    With regards to more extreme events, that’s not always the case. The warming has been greatest in the higher latitudes(coldest places warming the most, especially during the coldest times of year). Nights are warming more than days.

    This has decreased the meridional temperature gradient. As a result there is less energy available for mid latitude cyclones/weaker jet streams and there has been a significant decrease in violent tornadoes.
    Also, less extreme cold days.

    But more extreme rain and extreme heat days from climate change.

    Cold kills 16 times more humans than heat and cold kills hundreds of times more non human life than heat.

    So life prefers it this way.

    • “So life prefers it this way”

      That is, the beneficial warming(along with the heavier rains).

      Otherwise known as a climate optimum using authentic scientific (not political) verbiage.

    • Mike
      “That includes high end, excessive rain/flooding events. To deny this, is to deny the physical laws and reality.“

      The physical reality is that excessive rain is NOT guaranteed to be linked to excessive flooding events.
      In the civil engineering of flood mitigation and hydrology in general the key concept is the IDF ( intensity/ duration/ frequency) for each catchment.
      Each catchment has it’s own unique topography and is impacted by its own unique storm event.

      The Yarra river flows through the Melbourne CBD
      Flooding from the river will only occur at high tide after days of rain across the region ( 100to 1000sq km plus)
      But Elizabeth Street in the heart of the city floods from
      A short 30minute storm ( catchment 3sq km)

      Any alarmist claim for more intense storm and subsequent flooding will have to be specific about intEnsity duration and frequency

  30. Data shows trends in annual maximum rainfall observations (official Environment Canada data, updated in March 2020): https://www.cityfloodmap.com/2020/05/annual-maximum-rainfall-trends-in.html

    Some provinces have more overall decreasing trends or no trend (Alberta, Manitoba, Quebec, Prince Edward Island). Some regions like southern Ontario (where 1/3 of Canada’s population is and where high flood damage occur regularly) have decreasing annual maximum series trends and IDF (intensity) trends.

    Meanwhile growth and hydrological effects have been significant for decades and can explain higher local flood risks: https://www.cityfloodmap.com/2019/04/is-wild-weather-and-new-normal-for.html

    • Those trends are only from 1940 or 1950. They used 1948 as a starting point to show temperature increase. they ignored the warm 1940’s which would have almost negated the trend increase.

  31. …and on the west coast of the United States, the great floods of 1861-1862 were preciptated by global warming? Look it up. And all because of CO2 emitted by the SUV trains that were bringing settlers across the great plains. There was was a lake in the Central Valley of California almost 500 miles long and up to 50 miles wide because…global warming?

    My contempt knows no bounds for those who refuse to look at evidence that didn’t come from satellite guesses and electronic instruments. Photographs of flood don’t mean anything. Rain gauges dumped by hand are suspect. High water marks can’t be right unless we used a laser for measuring.

    And guess what what, Griff (and all your over educated under thinking ilk), it is going to happen again. So called Arkstorms are going to hit us again, and again, and again. Get over it. It is called weather.

  32. Most precipitation falls on the oceans. Oceans cover 71% of the surface area of the planet, Antarctica is about another 9%, so there’s 80% of the earth practically untouched by humans. Of the remaining 20% of semi-habitable land mass, I would say at least 80% is mostly uninhabited. Vast chunks of northern Africa, most of Russia, eastern China, much of Canada and the western US, much of South America, the bulk of Australia: nobody in sight. Humans maybe impact on 5% of the planet by area. And that tiny chunk has good croplands, grazing lands, parks, forests, and gardens.

    The doomsters, as usual, are full of bull.

  33. From the Met Office annual climate report for the UK for 2019:

    2019 rainfall for the UK overall was 107% of the 1981–2010 average and 112% of the 1961–1990 average.

    England and Wales had its fifth wettest autumn in a series from 1766, although much less wet overall than autumn 2000 (the wettest autumn in the series).

    Six of the 10 wettest years for the UK in a series from 1862 have occurred since 1998.

    The most recent decade (2010–2019) has been on average 1% wetter than 1981–2010 and 5% wetter than 1961–1990 for the UK overall.

    For the most recent decade (2010–2019) UK summers have been on average 11% wetter than 1981–2010 and 13% wetter than 1961–1990. UK winters have been 4% wetter than 1981–2010 and 12% wetter than 1961–1990.

    You might like to look at the detail here:

    Noting such information as:
    019 was the 12th warmest year for the UK in a series from 1884, and 24th warmest for Central England in a series from 1659.

    Four national UK high temperature records were set in 2019: a new all‐time record (38.7°C), a new winter record (21.2°C), a new December record (18.7°C) and a new February minimum temperature record (13.9°C). No national low temperature records were set.

    February 2019 was the second warmest February in the series from 1884 and the warmest February for daily maximum temperature.

    All the top 10 warmest years for the UK in the series from 1884 have occurred since 2002.

    • Griff
      You still don’t get it.

      Alarmists must use physical phenomena to hypothesise what impacts extra warming will have on regional rainfall.
      They then must use the rainfall statistics of towns within the region to confirm their hypothesis.

      You can’t use averages of locations
      You can’t use averages of time scales

      All alarmist attempts to do this fail.

    • Oh Griff, you do so want to pull up statistics without significance. You use a later start date rainfall set for UK, but reference CEP without talking about rainfall in that set. You are cherry picking your datasets to get the answers you want.

      Lets look at the longest precipitation record in the world – the Central England Precipitation (CEP) record.

      Using your period averages of 1981-2010 and 1961-1990 as the two baselines, lets just look at the high annual results in the series. I am not even going to go down to 107%/112% that you quoted:

      Year 1981-2010 1961-1990
      1768 132% 136%
      1770 114% 118%
      1782 117% 121%
      1789 117% 121%
      1792 118% 122%
      1797 115% 119%
      1799 114% 118%
      1821 110% 113%
      1828 113% 117%
      1839 114% 118%
      1841 112% 116%
      1848 119% 124%
      1852 128% 133%
      1860 114% 118%
      1866 111% 115%
      1872 136% 140%
      1876 112% 116%
      1877 121% 125%
      1882 121% 125%
      1886 111% 115%
      1903 122% 127%
      1912 116% 120%
      1924 114% 118%
      1927 117% 121%
      1946 111% 115%
      1951 116% 120%
      1954 115% 119%
      1960 126% 131%
      1966 112% 116%
      1994 111% 115%
      1998 112% 116%
      2000 130% 135%
      2002 118% 122%
      2008 115% 119%
      2012 131% 136%
      2014 117% 121%
      2019 116% 120%

      Top 30 Annual Rainfall list from CEP:

      Place YEAR ANN
      1 1872 1284.9
      2 1768 1247.3
      3 2012 1244.4
      4 2000 1232.5
      5 1852 1213
      6 1960 1195
      7 1903 1160.3
      8 1882 1146.2
      9 1877 1144.1
      10 1848 1130.1
      11 2002 1117.8
      12 1792 1116.8
      13 1782 1109.3
      14 1789 1109.3
      15 1927 1108.2
      16 2014 1105.6
      17 1912 1098.6
      18 2019 1095
      19 1951 1094.6
      20 1954 1092.7
      21 1797 1090.4
      22 2008 1089.6
      23 1860 1083.2
      24 1924 1082.7
      25 1770 1079.4
      26 1799 1079
      27 1839 1076.2
      28 1828 1073.2
      29 1841 1064.4
      30 1998 1062.6

      The average year for the period 1766 – 2019 is 1892.5. The average year of the Top 30 is 1892.7. The average year for the Top 10 placings is 1897.4, for the Top 15 placings its 1884.4. So they are pretty much random.

      If we divide the period 1766 – 2019 into three periods of 85 years each, the number of top 30 placings in each 85 year period is

      1766 – 1849 11 years
      1850 – 1934 9 years
      1935 – 2019 10 years

      That looks pretty random too.

  34. An excellent and very pertinent statement by Demetris Koutsoyiannis in a recent paper discussed here at WUWT was:

    Extremes are connected to disasters. A shortage of disasters has never been the case, but our perception of them is driven less by disasters per se and more by the communication thereof. In this respect, one may notice increasing trends, both in reporting disasters to the general public and in the production of research articles on disasters. Such articles typically focus on particular areas recently hit by disasters. California is a popular example but not the only one. Evidently, if we choose at random, say, 12 000 sites on Earth, then every month we will have, on the average, one catastrophic event of a 1000-year return period in one of the sites.

    (Koutsoyiannis, D., 2020, Revisiting the global hydrological cycle: is it intensifying?, https://doi.org/10.5194/hess-24-3899-2020)

  35. Climate change is a constant of global geological history, there is no doubt the climate is changing, indeed I would be very surprised and not a little worried if it were not. Mans contribution to that change is insignificant in terms of flooding when compared to the changes caused by development of flood plain land . In particular the development of huge industrial parks where there are acres of hard standing and more importantly run off from hundreds of acres of factory and warehouse roofing. Simple planning and design can reduce this flow by 80% by the introduction of ponds and sinks within the development areas to catch the water and slow the rising limb of the hydrograph smoothing out the flood curve of rivers affected. Perfect case in point is in NW England where the floods in the Whalley area earlier this year and last are exacerbated by the development of large industrial estates on the Calder River Drainage basin, no planning to intercept the water led to severe flooding in a rain event that was not despite media reports exceptional, Flooding is occurring in rainfall events that in previous years were not causing problems and this will no doubt continue and be blamed on climate change.

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