What COVID-19 Taught Us About Observed Data vs. Model Projections: They Are Different - Let's Remember That When Interpreting Climate Models

COVID-19 - observed data on ICU cases and projected capacity

"All models are wrong, some are useful".  Predicting COVID-19 conditions has taught us that models come with a great deal of uncertainty, and are based on a lot of assumptions.  Furthermore, models have to be constantly updated over time with real observed baseline data to represent the starting point for future predictions. At least we recognize the difference between theoretical model projections and the past observations on COVID-19 conditions.  More attention should be given to the difference between theoretical models of climate effects and observed changes in extreme weather.

In early April, COVID-19 ICU cases were projected to increase to 1200 in a best case to about 1500 in a worst case in Ontario, increasing considerably from actual data counts in late March.  The chart at right shows that ICU beds peaked at under 300 cases by mid April, a fraction of the best case model prediction, and has declined since.  So model projections should be viewed with some caution, and the reliability of the projections should be questioned and validated where possible with real data.

Predicting future weather extremes due to climate change effects has a great deal of uncertainty as well.  The recurrence time of extreme rainfall is predicted to decrease due to climate change effects, meaning that the "return period" of storms would become smaller.  For example, a rainfall event that had a return period of 35 years today (meaning a probability of occurring in any year of 1/35, or 1 in 35) has been predicted to occur every 12 years in the future (i.e., a higher probability of happening each year of 1/12 or 1 in 12 ... that a greater chance than today's 1/35).  That is what is projected to occur in Canada from now to 2100.

The above example on decreasing recurrence times is from a simulation presented in Canada's Changing Climate Report by Environment Canada (link: https://changingclimate.ca/CCCR2019/).  It is for a future scenario with several assumptions about growth and emissions called the RCP8.5 scenario, representing a Representative Concentration Pathway of just one of several future scenarios.  The shift in 24-hour precipitation recurrence times are presented on Figure 4.20 b shown below:

Canada's Changing Climate Report Figures 4.20 b), Projected Extreme Precipitation Recurrence Time / Return Periods for Past, Present and Future Time Periods, RCP8.5 Model Simulation Scenario

As annotated above, today's recurrence time is noted as 35 years, the future recurrence time is 12 years and the past time was 50 years. So the model predicts these shifts in recurrence time (return period) and annual probability:

   Period         Recurrence Time       Probability Each Year
1986-2005             50 years                       2.0 %   (1/50)
2016-2035             35 years                       2.9 %   (1/35)
2081-2100             12 years                       8.3 %   (1/12)

Some have misinterpreted the theoretical, simulation model changes from past to present as 'actual' observed changes in extreme precipitation when in fact the Environment Canada report clearly notes these are 'projected changes' and are 'simulated by Earth system models' for the scenario RCP8.5.  A different scenario's simulated results, with different assumed emissions and growth, and different recurrence time shifts are presented in Figure 4.20 a) as well.

CBC News In Our Backyard - Flooding

CBC's In Our Backyard interactive notes "Climate change is no longer theoretical. It’s in our backyard" - unfortunately it presents theoretical past model trends as real changes that are "In Our Backyard" now.  Here is the online report link: https://www.cbc.ca/news2/interactives/inourbackyard/

CBC News report: "Climate change is making extreme rainfall a more frequent occurrence. Storms that historically happened only once every 50 years are now coming every 35 years or less. By the end of the century, they could happen once every 12 years on average, according to a recent climate report from Environment Canada. All this increases the potential for urban flooding."

CBC News In Out Backyard Extreme Rainfall Frequency - Past, Present, and Future Recurrence Times Confuses Simulation Model Projections With Observed, Historical Trends

So while predicted changes are only theoretical, CBC News mistakenly reports that changes have already occurred and are 'now coming' at smaller recurrence intervals (i.e., higher frequency and higher probability each year).

The CBC Ombudsman has indicated that the CBC should be careful to distinguish between past, present and future extreme rainfall trends, as noted in a recent post: https://www.cityfloodmap.com/2020/05/past-present-or-future-cbc-ombudsman.html

We agree.

A review of historical extreme rainfall trends in one region of Canada affected by may flooding events has shown no decrease in the recurrence time, or return period, of extreme precipitation.  A previous post showed that today's 35 year storms are actually occurring less frequently than in the past. In southern Ontario, long term climate station observations show that the average 25 to 50 year rainfall intensities today are actually slightly smaller than they were considering observations up to 1990. See previous post: https://www.cityfloodmap.com/2020/05/southern-ontario-extreme-rainfall.html

Analysis of the Version 3.10 Engineering Climate Datasets IDF Files updated in March 2020 show that southern Ontario long term rainfall intensities have decreased slightly since 1990, on average by 0.1%.  The 50 year return period rainfall intensities are on average unchanged.

If 50 year rainfall intensities actually occurred more frequently and now occur at a 35 year return period, as CBC mistakenly reported, then the magnitude of the 50 year intensities would have had to increase by about 6%.  This considers the example long term climate station at Toronto's Pearson International Airport - the 35 year 24-hour rainfall intensity of 99.7 mm at the airport would have to increase to the 50 year intensity of 105.7 mm.  Back in 1990, the 50 year 24-hour rainfall intensity at the airport was 109.3 mm, meaning the 50 year rainfall has decreased by several percentage points.  Here are the 1990 data (copied from my top desk drawer):

Toronto Pearson International Airport IDF Table With Data Up to 1990 - 50 year design rainfall intensity of 109.3 mm  (shown here) was higher than today's version 3.10 Engineering Climate Datasets intensity of 105.7 mm (see table below to 2017).  

Here are the recently updated IDF values from Environment Canada considering data up to 2017:

Toronto Pearson International Airport IDF Table With Data Up to 2017 - 50 year design rainfall intensity of 109.3 mm (see previous table to 1990) shown is lower than today's version 3.10 Engineering Climate Datasets intensity of 105.7 mm (shown here).

Climate models that predict more frequent future rainfall intensities, characterized by shorter recurrence times (i.e., lower return periods = higher probabilities of occurrence) are not necessarily in step with observations (see Toronto airport example above and previous post on southern Ontario long term stations).  Here is a comparison of past trends in 100-year rainfall intensity based on observed data and projections from various studies - the actual data curve is already 'flat', so the need to flatten the curve can only be made based on projections and not past data.

Extreme Rainfall IDF Trends - Toronto 24-Hour 100-Year Rainfall Volumes per Environment Canada Engineering Climate Datasets - Past Data and Linearly Projected Trends Shown in Black.  Various Studies and Models Project Significant Increases That Have Not Shown Up In The Data Observed Data Statistics

Just like COVID-19 models have considerable uncertainty and must rely on observational data to calibrate and validate them - so they they are more reliable and useful in making projections of the future - climate models require checks on accuracy and usefulness.  Media like CBC News may not discern between model predictions and actual trend data which can mischaracterize trends in extreme weather.  Since models predicting extreme rainfall do not appear to match past observations over the recent past few decades, the accuracy and reliability to project conditions over the next 80 years should be closely scutinized.

While in the case of COVID-19, the need for "flattening the curve" is clear given the close scrutiny of observed data that has shown rising counts of infections, hospitalizations or deaths - that gives clear direction on actions to be taken to mitigate observed phenomena.  In the case of COVID-19, these values may even increase at an exponential rate.  In contrast, the IDF curve trends are largely flat if not already declining based on observed data in some regions.  Any change in extreme rainfall trends has been explained by natural variations (i.e., trends can go up).

***

There is a long-standing gap in the media mixing up predictions of extreme weather and actual Environment Canada observed data trends - sometimes a single report can start a narrative that can go unchecked for some time.  The "Telling the Weather Story" report is one such example where a theoretical shift in extreme weather has been reported, and repeated endlessly in the media as actual data when it is clearly not:

Storm intensity not increasing - factual review of engineering data - Canada and Ontario from Robert Muir

Vaccines and Rainfall Extremes

What do vaccines and rainfall extremes have in common? Both have been victims of bad science when it comes to public education and media reports. And this can lead to bad policies and misguided actions that fail to address real problems.

Recently the outbreak of measles has led the media and medical professionals 'call out' those falsely linking increased autism to vaccines through their anecdotes, beliefs and unscientific arguments. Similarly, increased flood damages have been linked to more extreme weather - more intense storms - due to climate change.  But what do the statistics of extreme rainfall show? How does the scientific data compare to the media hype? Data in Canada (see links at the bottom of this post to maps, charts, tables, etc.) show no increasing trend in extreme rainfall.

But its hard to argue with pictures like a stranded GO Train in the Don River Valley, and suggest that flooding isn't increasing.  That is unless you realize that the river outlet - the Keating Channel - was designed with a low capacity and was the subject of a flood inquiry in the early 1980's.  Keating Channel flood inquiry report.  If it is not dredged it gets clogged with sediment and backs up.  Its not news, its fluviogeomorphology and hydraulics.  TRCA has a nice summary of the century-old problem:

"Since its construction between 1914 and 1922, the Keating Channel has been subject to heavy sediment loads, requiring regular dredging to maintain sufficient depths to allow for and maintain shipping activities at the mouth of the Don River. Between 1950 and 1970, widespread development throughout the Don Watershed and the construction of the Don Valley Parkway increased sedimentation rates by up to four times that of the pre-was era. After 1970, decreases in the number of new watershed disturbances and improved sediment control structures likely contributed to the decline in sedimentation in the Keating Channel to levels similar to the pre-war era. A reduction in shipping activities within the Keating Channel, combined with restrictions on the open water disposal of dredgate imposed by the International Joint Commission (IJC) in 1974, resulted in a cessation of dredging in the Keating Channel. In the following five to six years, the Keating channel filled with sediment and debris to the point where it became visible under all but high lake levels, resulting in increased flood risk along the lower Don."




Because of the low capacity, engineering solutions have been built or proposed like the Lower Don Flood Berm, or the Don Mouth Naturalization Project (DMNP) that just received provincial EA approval (see file EA 03 03 02). Of the DMNP TRCA: "This project will transform the existing mouth of the Don River (the “Don Mouth”) including the Keating Channel, into a healthier, more naturalized river outlet to the Toronto Inner Harbour and Lake Ontario, while at the same time removing the risk of flooding to over 290 hectares of urban land to the east and south of the river." To see how the Keating Channel system was designed to spill all over with limited capacity, check out the hydraulic simulation video above that shows - this is the widespread flooding based on today's design and climate conditions.

In a separate post we explain that the GO Train flood was an operational mishap and not an extreme event - record rainfall at Pearson Airport in the Etobicoke Creek Watershed on July 8, 2013 did not hit the Don River Watershed where the GO Train was stranded, and where the river peaked at a measly 80.7 m, lower than the May 29, 2013 weeks earlier, and lower than the river's one-in-five-year design flow.

Back to rainfall extremes.  Environment Canada's Adaptation and Impacts Research Climate Research Division recently reviewed Southern Ontario rainfall statistics to see if there have been any measurable trends in rainfall patterns and intensities.  These guys are no dummies. A brief summary for those without time to read all 176 pages:

• Significant increases, as well as decreases, were detected at some stations in a number of the extreme precipitation indicators.  However, the majority of station trends were determined to be non-significant and no consistent geographical patterns for increases or decreases were observed across Canada.  In most cases, the magnitude of the observed changes was also very small.
• On sub-daily or short duration rainfall intensities of less than 24 hours (this is the data / or trends municipalities would use for planning, design and management of most drainage and stormwater systems that respond to flashy storms):  The majority of the trends were determined to be non-significant with no simple patterns or uniform rates of change evident in the short duration rainfall.  Trends were determined to vary with duration and regional location. 

Temperatures have gone up in recent years - here's a graph at right showing global temperatures increasing.  The internet is full of these, and it is undeniable that temperatures are increasing.

And insurance losses have been increasing in Canada.  You'll have no problem finding graphs and statistics showing the number and size of weather related claims increasing (see below).

But are there any statistics of increasing rainfall intensities?  Apparently Environment Canada does not have any.

But this has not stopped the media from reporting increases as facts.  This may be because the media confounds future predictions with historical trends.

The CBC's Weather Gone Wild documentary
was written by Helen Slinger and Melanie Wood.  To carry on the vaccine science analogy, they are the Jenny McCarthy's of meteorology.  They cite that every degree of temperature rise means 7% more moisture in the air, implying this means more extreme weather (more rain?).  If this linkage is true, how come the rainfall intensities are not increasing like the temperature graph does?  In other words, why does Environment Canada not have a parallel graph showing rainfall intensities increasing too? Jenny McCarthy should consider autism rates were increasing while MMR vaccination rates were decreasing - no correlation.  Helen Slinger and Melanie Wood should consider temperatures were increasing but but rainfall intensities were not - no correlation.

Linking insurance losses to climate change rainfall impacts can cause a province like Ontario to focus on distractions instead of solutions; for example cause it to embark on an expensive green energy program that hurts the economy and consumers.  But what if there have been no increases in extreme rainfall statistics - just extreme weather reporting?  Would the push for green energy be so strong? Would there be as strong a support for GHG reductions?  Yes, there are legitimate reasons to mitigate temperature increases and the effects on our environment, but so far, increased rainfall intensities is not one of those effects (not scientifically measurable). Insurance industry claims have been dismissed based on CBC's consultations with Environment Canada.

Do images of flooded GO Trains support the need for carbon taxes / carbon pricing so that we can tackle supposed rainfall increases?   Maybe we should have a carbon tax, but please use the money to dredge the Keating Channel instead of subsidizing solar panels, and maybe improve some other 100 year old infrastructure that still can't handle today's weather.

Models vs Data - WHat has COVID-19 taught us?: https://www.cityfloodmap.com/2020/05/what-covid-19-taught-us-about-observed.html

More on the 1981 flood inquiry:
go-train-flooding-not-new-1981-inquiry.html

More on why the GO Train flood on July 8, 2013 was completely avoidable:
http://www.cityfloodmap.com/2015/12/stranded-metrolinx-go-train-avoidable.html:

More on why cognitive biases that hamper rational though on flood causes:
http://www.cityfloodmap.com/2015/11/thinking-fast-and-slow-about-extreme.html

Extreme rainfall trends in Canada (Environment Canada Engineering Climate Datasets):

Static Maps: http://www.cityfloodmap.com/2015/12/severe-storm-trends-canada-rainfall.html

Interactive Map: http://www.cityfloodmap.com/2015/12/canadian-extreme-rainfall-map-climate.html

Table Summaries: http://www.cityfloodmap.com/2015/12/canadian-extreme-rainfall-summary-by.html

Chart and Table: http://www.cityfloodmap.com/2015/12/top-weather-story-in-canada-2015-less.html

Long-term Station Table: http://www.cityfloodmap.com/2015/12/long-term-climate-change-short-term.html

Environment Canada Denies Changes: http://www.cityfloodmap.com/2015/10/bogus-statements-on-storms-in-cbcnewsca.html

Contradicting Insurance Industry Claims: http://www.cityfloodmap.com/2015/12/trends-in-canadian-shortduration.html