Elizebeth Friedman (1892-1980)

One hundred and thirty years before the publication of this weblog post, Elizebeth Friedman née Smith (1892–08-26 – 1980-10-31) was born. She was known in later life for her expertise in cryptanalysis.

Cryptanalysis, popularly called code breaking, is actually an important branch of computer science. All practitioners are expected to have some basic understanding of it, at both practical and conceptual levels. It is actually a broader topic than many realize. It involves the analysis of information systems to understand what lies hidden. As expected, Wikipedia has an article on the topic. People often describe some (often their own) cryptanalytic efforts as reverse engineering. Other people may actually think they know what this term implies, but it is vague, often deliberately used to cover up the specific techniques involved in ferreting out system information.

American Cryptanalysis begins at Riverside, Illinois, where a number of documents on the subject were published, some of which are available for download. This was mainly the work of one woman, Elizebeth Friedman (1892-1980), sometimes assisted by her husband, William (1891-1961), who was working at Riverside, starting in 1915, then went on to lead the research division of the Army’s Signal Intelligence Service (SIS) in the 1930s, and some follow-on services into the 1950s. William’s one major contribution was inventing the term cryptanalysis!

Unfortunately for the world, some scientific practices are shameful. It is not so much the individual facts that are either stumbled upon or ignored that constitute a major problem, but rather how some practitioners (typically male) take credit for work performed by others (typically female). In addition, large numbers of women have been actively discouraged in pursuing scientific careers, simply on the basis of their gender. In the twentieth century, when they were permitted to participate, they were shunted into inferior positions/ roles, and their activities were depreciated. Hopefully, in the twenty-first century, this will come to an end.

Elizebeth Friedman was the foremost cryptanalyst in USA, exceeding in ability, the talents of her husband. This is mentioned because, while they worked together, only William Friedman’s name appears on published documents, although many knew that they were sometimes written jointly, but often by Elizebeth alone. It is difficult (if not impossible) for me, a male, born more than half a century after her, to understand her situation, let alone her motivation for allowing her husband to receive full credit.

Yet, the most outrageous appropriation of her work did not involve her husband, but another American man who should have been regarded as Public Enemy #1, John Edgar Hoover (1895 – 1972). who took credit for much of Elizebeth’s cryptanalysis. As Wikipedia states, “Later in life and after his death, Hoover became a controversial figure as evidence of his secretive abuses of power began to surface. He was found to have exceeded the jurisdiction of the FBI, and to have used the FBI to harass political dissenters and activists, to amass secret files on political leaders, and to collect evidence using illegal methods. Hoover consequently amassed a great deal of power and was in a position to intimidate and threaten others, including multiple sitting presidents of the United States.”

Fake Science and its consequences

Originally, this post ended with the previous paragraph. Then, on 2022-07-22, some allegations emerged that part of a key 2006 study of Alzheimer’s disease may have been fabricated. Matthew Schrag (1971 – )found serious problems with underlying research led by Sylvain Lesné (1974 – ) on a specific protein. Science has now issued a statement about it. Images accompanying and supporting the research, seem to have been altered.

One problem with fake research is that it often results in fakers getting undeserved research grants. More importantly, real researchers get denied these grants, which can mean that medical breakthroughs get delayed. This can result in unnecessary suffering, or even premature death. The amount of money involved can reach hundreds of millions of dollars. The wrong papers get cited. In this particular case, one published in Nature, has been cited 2 300 times.

Schrag told Science, “You can cheat to get a paper. You can cheat to get a degree. You can cheat to get a grant. You can’t cheat to cure a disease.” This is the real essence of the problem. Fake research leads society down a cul-de-sac that leads nowhere.

Much of the world is already treating science with contempt. In particular, there are climate deniers, who use falsified science to justify their own claims. There are oil companies that have knowingly publicly denied the climatic impact of the carbon dioxide produced from the combustion of petroleum products, despite knowing about its consequences for about six decades. This is having a negative impact on billions of people, while some few others are provided an unwarranted life of luxury.

The world needs to prevent the publication of falsified reports, such as those by Lesné. Currently, the peer review system lacks a mechanism to prevent the publication of doubtful works. I remember my wife, Trish’s cousin, Terry Heaps (1941 – 2017), discussing a paper he had peer reviewed as a resource economist. He had rejected it, because it contained some bad data that produced incorrect conclusions. He had been alerted to this situation by an illustration. He notified the publication of this fact. The publication then notified the author. Despite this, the paper showed up in another publication, complete with the bad data and incorrect conclusions, but minus the illustration.

In addition to developing a system to prevent inappropriate works from being published, science needs to ensure that people who make valuable contributions, such as Elizebeth Friedman, are fully acknowledged.

Addendum

Once again, this post ended with the previous paragraph. Then, on 2022-08-21, X-ray evidence emerged that Wyndham Lewis (1882 – 1957) had deliberately destroyed Helen Saunder’s (1885 – 1963) missing artwork, Atlantic City (ca. 1915), by painting Praxitella (1921) on top of it. Students Rebecca Chipkin and Helen Kohn, used X-ray and other imaging technology to investigate Praxitella, because of its “uneven texture and glimpses of bright red through cracks in the surface paint.”

Vorticism was an artistic movement, heavily influenced by cubism and futurism, whose artworks typically used bold colours, harsh lines and sharp angles. It originated with the Rebel Art Centre, started in 1914 by Wyndham Lewis and Kate Lechmere (1887 – 1976), who financed it. Helen Saunders and Jessica Dismorr (1885 – 1939) were associated with the movement as practicing painters. The movement also had literary supporters that included Ford Madox Ford (1873 – 1939), Ezra Pound (1885 – 1972), T S Eliot (1888 – 1965) and Rebecca West (1892 – 1983).

The Courtauld Gallery is an art museum in central London, established in 1932. It houses the collection of the Courtauld Institute of Art, a self-governing college of the University of London, specializing in art history. Barnaby Wright, deputy head of the Courtauld Gallery and a 20th-century art specialist, is quoted several times in the Guardian article.

“Saunders was a really interesting figure, but she was largely overshadowed by her male contemporaries. She and Jessica Dismorr were the backbone of the group,”

“In the prewar years, [Saunders] was one of the most radical painters and draughtspeople around. There were only a handful of people in Europe producing that type of hard-edged abstract painting and drawing.”

Atlantic City depicts a fragmented modern metropolis, almost certainly in the vibrant colours associated with the Vorticists. A black and white image of the painting appeared in Blast, the avant garde Vorticist journal.

Starting on 2022-10-14, Courtauld Gallery will open Helen Saunders: Modernist Rebel, an exhibition of 18 of Saunders’ drawings and watercolours, tracing her artistic development. It will also show Praxitella, loaned from Leeds Art Gallery, alongside the X-ray and partial colour reconstruction of Atlantic City.

Finally, one has to ask why men deliberately destroy the work of women? From my perspective, social justice demands that the layers of paint constituting Praxitella must be removed, to allow Atlantic City to reemerge. Criminal actions cannot be allowed to triumph over legitimate actions.

Back to Elizebeth Friedman.

This post originally started at some forgotten point in 2020, It was based on one simple question. Why is Alan Turing (1912-1954) remembered as a cryptanalyst, but not Elizebeth Friedman? Of course, Elizebeth was not the first cryptanalyst. The first known recorded explanation of cryptanalysis was given over 1 100 years earlier by Al-Kindi (c. 801–873).

Other important women cryptanalysts include Aggie Mayer Driscoll (1889-1971) and Joan Clarke (1917-1996).

Extreme Heat Belt

The counties marked in red are expected to experience temperatures of 125 °F = 51.67 °C at least one day a year, by 2053. This area is referred to by some as the Extreme Heat Belt. Screenshot of an Axios map, without the underlying data provided at the county level by the First Street Foundation.

The mission statement of the First Street Foundation reads: Make climate risk accessible, easy to understand and actionable for individuals, governments, and industry. A changing climate is impacting the risks facing American properties, communities, and businesses as perils like flood, fire, heat, and drought become more common, and more severe…. First Street Foundation is a non-profit research and technology group dedicated to quantifying and communicating those risks by incorporating world class modeling techniques and analysis with the most up to date science available in order to simply, and effectively, inform Americans of their risk today and into the future from all environmental changes.

Extreme heat refers to a maximum heat index greater than 125°F. This refers to a temperature reached at least one day a year. Currently (that is, in 2022) 8 million Americans are exposed to it. By 2030, some additional coastal areas in the Southeast and Mid-Atlantic may also experience a heat index at or above 125°F. By 2053, the number of people exposed to extreme temperatures, is expected to increase to 107 million people.

Dangerous days have a heat index greater than 100 °F = 37.78 °C. The Gulf Coast and Southeast will see the highest chances and longest duration of exposure to these. While many place experience more than 20 consecutive days with heat indices above 100°F, by 2053, these streaks could involve up to 74 consecutive days.

Local hot days are days that exceed the temperatures typically experienced for a particular area. The West will have the highest chance of long durations of these.

Future cooling-driven increases in carbon emissions could aggravate warming further. Texas, Florida, California, Ohio and Missouri are the top 5 states with the greatest cooling demand expected increase in CO2 emissions between 2022 and 2053.

As a missionary for SI, the international system of units, temperature always presents a quandary. In this official system, temperature is measured in kelvin, with symbol K. Both the kelvin and celsius systems use a 100 K/ °C difference between the freezing and boiling point of water, at a standard/ sea-level air pressure reading.

0 K is set to absolute zero, which is -273.15 °C, while 0 °C, in the celsius system, is set to the freezing point of water. In the Fahrenheit system, water freezes at 32 °F = 0 °C and boils at 212 °F = 100 °C, resulting in a 180 °F difference between these two points.. Thus, 125 °F = 324.8167 K.

SI clergy undoubtedly use many nights, sleeplessly pondering if the extreme heat value should be increased to 325 K = 125.33 °F, or if 50 °C = 122 °F, should be used. Those prioritizing as little change as possible will support the former. Those wanting to use rounder values, ending in 0, will opt for the latter. The reason for this proposal is that the world needs a mechanism to compare extreme heat locations, which will require heat to be expressed in degrees celsius. This is why, personally, 50 °C holds greater appeal, even if more locations in the world will fall into that category.

Those wishing to be further perplexed by this topic, are invited to read the Wikipedia article on thermodynamic temperature. In an imperfect world, every gram of improved understanding is worth the effort.

Analogue Electric Vehicles

A Woodpecker skateboard, to encourage young experimenters to investigate battery electric vehicles. Photo: Woodpeck.org

Part 1

On 2021-07-07 Robert N. Charette wrote an article in IEEE Spectrum, How Software Is Eating the Car, The trend toward self-driving and electric vehicles will add hundreds of millions of lines of code to cars. Can the auto industry cope?

As usual, an article in Slash Dot ( /.) is my main source of biased opinions about a serious technological issue, with one typical comment given a score of 4: interesting. It read: “If you get something pre-1978 then the most sophisticated electronics in the vehicle will probably be the radio kit.” This was then followed by numerous comments about 1976 (and later) Chrysler Cordobas. This type of reasoning reaches its zenith with, “What was the last car without this nonsense? Makes me want to buy a classic car or motorcycle, just for the simplicity.”

Yes, for a long time the trend has been towards increasing [Engine Control Units =] ECUs, based on the design philosophy of, “If you want a new feature, you buy a box from a Tier 1 [top-level component suppliers, such as Bosch] that provides the feature, and wire it in. As a general rule, automakers love outsourcing work; for most of them, their dream scenario is that everyone else does all the work for them and they just slap a badge on it and take a cut.

Then Rei adds a score 5: informative, but long, comment: “This article actually has it backwards. The first company to break with this philosophy was Tesla, which has from the beginning had a strong philosophy of in-house software design, and built basically a ‘car OS’ that offloads most vehicle software functionality into a handful of computers (with redundancy on safety-critical functionality). … Eventually everyone is going to have to either make their own ‘car OS’ stack or lease one from someone else. The benefits are just too significant[:] Lower hardware costs, lower assembly costs, lower power consumption, simpler cheaper lighter wiring harness, faster iteration time on new functionality, closer integration between different subsystems, you name it. This trend throws into reverse the notion of ever-increasing numbers of ECUs (which quite simply was an unsustainable trend).”

Who could possibly disagree?

Part 2

What is the minimal vehicle a person needs? Of course, there will be as many answers as there are people, and it will all be dependent on what they are doing. There are a lot of vehicles available, but I will not refer to them as choices. Some places lack trams or other forms of public transit. They may exist in other places, but run at inappropriate frequencies. Some communities lack bike lanes, forcing cyclists to compete for space with cars. Some streets are perpetually gridlocked.

Some people need to work, outside of their residences! Does one have to take children to kindergartens or schools? What distance does one have to travel to attain basic health and nutritional needs? Can this be done as part of a commute, or is a separate trip necessary? What about specialty shops? What is the distance to the nearest bus station/ train station/ airport/ international airport? Is there a need for a social life? Is one dependent on driving a car? Could a bicycle do for some items? Are trains or buses an option? So many questions, so few obvious answers.

Perhaps my own situations could be used as an example. Compared to most people, my life is simple: no job is calling me, and I am no longer responsible for looking after young children. Yesterday, I used a vehicle with a mass of about 1.5 Megagrams (where 1 Mg = 1 000 kg), to drive 40 km. Admittedly, there are vehicles that weigh less than a car. A bicycle is probably the most efficient device for conveying people, and it can have a mass of from about 5 to about 20 kg. Yet, I would not feel safe driving one of these on the roads of rural Norway. There are no buses, but if I plan in advance and contact the appropriate office a day in advance, I might be able to use public transit, essentially a taxi charging bus rates, as long as I am willing to wait up to several hours, for a return trip.

The most basic foods, as well as building supplies, can be purchased with a 14 km return trip across Skarnsund bridge in Mosvik, where there is even a coffee bar, with better than acceptable lattes. Basic health care (doctor, dentist, pharmacy, optometrist) and a larger selection of food and basic necessities are met by driving 26 km for a return trip in the opposite direction, into Straumen. More specialty shops are available in Steinkjer involving a 70 km round trip. This all involves driving. However, there is also a train station at Røra, 40 km round trip by car, that will allow one to connect with an international airport (TRD), and the fourth largest city in Norway, Trondheim, about 120 km away – 240 km round trip, with an even larger selection of shops and activities.

Part 3

I am in agreement with Rei, that more software (and less hardware) is needed in vehicles. Yet, I am reading this week that General Motors is charging purchasers of many GMC, Buick, and Cadillac vehicles, that are shipped with OnStar and Connected Services Premium Plan by default, $1 500 for the three-year plan that was once optional, but is now required. Other companies are doing the same sort of thing. It is estimated that this revenue stream could give GM an additional $20 to 25 billion per year by 2030. BMW has come out with similar claims, giving them an additional revenue of about $5 billion per year by 2030. I do not want to ensure that a wealthy elite continues to take more of an income pie that is already unfairly divided.

At issue is the right of consumers to direct access to vehicle data, which historically has been obtained from an on-board diagnostic (OBD-2) port (North America) or European on-board diagnostic (EOBD) port, since 1996 and 2001, respectively.  These allowed vehicle owners and technicians access to vehicle data to assist with maintenance and repair. This situation is threatened by vehicle manufacturers, who want to use telematics = the sending of data wirelessly and directly, restricting vehicle data to manufacturers. In 2021, 50% of new cars have these connected capabilities, but no country has more than 20% of its vehicle fleet equipped. USA has the most. By 2030, it is estimated that about 95% of new vehicles sold globally will have this connectivity, according to a study by McKinsey. ​

While this data could provide economic and other benefits to car owners, vehicle manufacturer want to act as gatekeeper, determining who can access it, and at what cost. This is a detriment to consumers, which could result in: Increased consumer costs; restrictions on consumer choices for maintenance and repair;  safety and security issues involving the use of non-standard data types and formats; privacy concerns. Automotive mechanics, and other aftermarket providers can also be affected. 

This has resulted in a consumer backlash, which I associate with the right-to-repair movement. There are already open-source groups working to ensure that consumers retain their rights. In addition, Automotive Grade Linux (AGL) is an open source project hosted by The Linux Foundation that is building an open operating system and framework for automotive applications. It was started in 2012, and currently has 146 corporate members.

I imagine that automotive manufacturers will try to add just enough proprietary software to their vehicles, to profit maximally from their investment. On the other hand, I see that there will be an incentive for ordinary consumers to demand right-to-repair legislation, and for guerilla activists to produce generic software substitutes where this is useful.

In Europe, repair is increasingly regarded as an essential consumer right and an environmental necessity. The main objective of the European Green Deal, is to be climate neutral by 2050. The European Commission’s Circular Economy Action Plan (CEAP), published 2020-03, details how this goal is to be reached. To reduce waste, products have to be designed to last. If they don’t last, they shouldn’t be sold. To encourage the development of products that are longer-lasting, there could be lifespan labels, service manuals, and an EU-wide repairability index. This would encourage the market to compete on repairable and durability.

In 2020-11, the European Parliament voted overwhelmingly in favor of a right-to-repair, and insisted that the more conservative European Commission administrative arm, implement it. It also included repairability labeling.

In 2020-11, voters in Massachusetts approved Question 1, involving a right-to-repair Law, with almost 75 percent in favour. The law requires automakers to provide a way for car owners and their chosen repair shops to access vehicle data, including that sent wirelessly to the manufacturer. The intent of this law is to prevent manufacturers and dealerships from having exclusive access to data.

Massachusetts is the state where the first automotive right-to-repair law was passed in 2012. That law made car makers open up the data inside the car. Rather than create a state by state solution, automakers reached a nationwide agreement with car parts makers/ suppliers and repair shops on how to share the data. This agreement opened the OBD-II port. With this new and improved right-to-repair law, similar transformative actions are required.

There are an increasing number of underpaid programmers and other software and hardware specialists, unable to fully live the American (and Scandinavian) dream. Many of these would undoubtedly be willing to work as guerilla technologists to develop the tools needed for retrofitting vehicles with more consumer friendly components, especially after warranties have ended. There are an increasing number of inexpensive microprocessors and systems on a chip that can be used for these purposes.

Part 4

To put electric vehicles in perspective, one needs to return to 1965-11-05, when President Lynden Johnson was given a copy of Restoring the Quality of Our Environment, a report by the Environmental Pollution Panel, President’s Science Advisory Committee. On publication of this blog, people have had 20 735 days or 56 years, 9 months, 8 days to confront this challenge, but have failed miserably at this task.

One fundamental question is, where can younger people learn more about the construction of appropriate vehicles for the 21st century? Currently the most interesting project is Woodpecker, that describes itself as an: “Open source based Carbon negative Electric Vehicle Platform. Woodpecker is a game changing micromobility vehicle to decrease CO2. Electrical propulsion allows to use solar and renewable power. Production of Wooden frame even decreasing CO2 because it is encapsulated by [wood] while growing. Vehicle built on Circular Economy concept – most parts are recyclable.” It appears to have originated in Latvia, and includes partnerships with many higher-educational institutions in the country. One problem with Woodpecker, is that it as an organization is too closely bound to commercial enterprises. For example, a good starting point for most open-source projects is to become acquainted with their documentation. In this case it requires people interested in downloading their technical drawings to have a Trimble account, in order to use Sketchup.

Notes:

1. This post follows up some aspects of Vehicle Devices, published 2020-11-03. The division between parts is not based on content, but time. Part 1 of this weblog post was originally written 2021-06-18 and saved at 10:49. It had been patiently waiting to be published. On 2022-08-12, outdated content was removed, and Part 2, was added, starting at 20:43. Parts 3 was started on 2022-08-13 at about 07:40, while part 4 was started on the same date at 08:48.

2. Trondheim claims to be the third largest city in Norway, but I would give that title to Stavanger. The challenge with Stavanger, is that its metropolitan area is divided between multiple municipalities. Yes, I am aware that I have offended some of my Norwegian readers, because of their origins in Trøndelag. However, Stavanger is the only place in Norway where I have ever been able to find/ buy root beer! This is probably due to Americans working in the oil industry, and living in the Stavanger area.

WBT

WBT = wet-bulb temperature. Yes, I appreciate short, cryptic post titles. That said, there is a serious point to this post, with life-saving potential, related to heatwaves.

A digital psychrometer (combined dry and wet-bulb thermometer).
The functions available with a modern psychrometer.

When a wet cloth/ wick covers the bulb of a thermometer, evaporation of the water cools the thermometer. This results in a WBT, which is equal to or below the dry temperature, measured on a thermometer without a wet cloth. The WBT reading reflects the humidity in the atmosphere. Humidity refers to the relative saturation of air with water. Low humidity means there is not much water in the air; high humidity means lots of water in the air. When the air can hold no more water, it is totally saturated. It is referred to as 100% relative humidity (RH). Air at a higher temperature is able to hold more water vapour, than air at a lower temperature.

A related concept is that of dew point = the temperature to which air must be cooled to become saturated with water vapor, at the current relative humidity. At, and below this temperature, water vapor condenses to form dew, a liquid state of water.

WBT is important because it can measure heat-stress conditions, that affect many people. In fact, a high WBT can kill them. This happened mainly from 2021-06-24 to 2021-07-01 in British Columbia. At 100% RH, the WBT will equal the dry temperature.

A combined dry and wet-bulb thermometer is referred to as a psychrometer. While analogue models are available, they require either calculations or the reading of graphs to determine values. One should not overestimate the ability of a person to perform even simple calculations, when they are potentially dying of heat stroke. Digital models can be purchased at relatively low cost that do all of the calculations automatically. The model illustrated above costs NOK 255 = US$ 26.38 = CA$ 33.72, including taxes and delivery charges to Norway (as of 2022-08-01). The quality of this particular model has not been evaluated.

At Cliff Cottage, we have recently received temperature and humidity sensors that will be part of our weather station, a subsystem of our home automation system. These components are considerably cheaper than the Habotest model, but require electrical and mechanical work, as well as programming, to implement as a system. Thus, the first iteration does not produce a cost effective system, may be frustrating to make, but will give satisfaction when completed.

From 2021-06-20 to 2021-07-29, the British Columbia Coroners Service, reported the following heat related deaths, in the table below. There are some who feel the number of deaths were under reported. Note that 445 of the 569 deaths (78%) occurred during the transition week, between June and July.

Age Group# of Deaths 
<40 2
40-49 13
50-59 42
60-69127
70-79160
80-89149
90+ 76
Total 569
Heat related deaths during the summer of 2021. Source: British Columbia Coroners Service.

British Columbia, was only one of many jurisdictions, that faced heat challenges in 2021. Temperature records are being broken regularly, throughout the world. In the United States, every state and territory had a maximum temperature that exceeded 37 °C. Of these 46 entities, only six had recorded maximum temperatures below 40 °C. Four states, had maximum temperatures at or exceeding 50 °C: New Mexico, 50 °C; Nevada, 52 °C; Arizona, 53 °C; and, the highest, California, 57 °C. In Canada, Lytton, British Columbia, distinguished itself with 49.6 °C, on 2021-06-29, the maximum ever recorded in the country. The next day, a wildfire destroyed most of the town. In Norway, the highest temperature recorded is 35.6 °C, at Nesbyen, on 1970-06-20.

The challenge with these high temperature values, is that they do not take into consideration humidity, which determines how people experience heat. Some locations on planet Earth may be approaching values that prevent human survivability. The countries most affected are Saudi Arabia and other Arabian Gulf states, Pakistan, India and Australia. What is not fully appreciated, is that indoor climates in temperate zones, can also create conditions that kill people during heat waves.

The difference between WBT and dry temperature, measures how effective people can cool themselves by sweating. Admittedly, this is a simplification because, in addition to humidity and temperature, solar radiation and wind speed are other factors that affect survivability. Yet, WBT is especially important in indoor environments, where deaths often occur in heatwaves.

Sweating above WBT will no longer cool down a person, but lead to a steady rise in body temperature. This is the limit of human adaptability to extreme heat. If a person cannot escape these conditions, their body’s core temperature will rise beyond the survivable range, and organs will start to fail.

The critical WBT value for humans was usually considered to be 35 °C, indicating a situation where a healthy person could survive for six hours. One representation of this is an air temperature of 40 °C, and a relative humidity of 75%. This value comes from a 2010 theoretical study. However, research by Vecellio et al., found that this value only applied to young healthy people. Real-world data indicates that the critical WBT value is closer to 31.5 °C.

This means that the numbers of people exposed to potentially deadly combinations of heat and humidity across the world would be vastly higher than previously thought. Many older and compromised people will experience dangerous conditions far below the threshold WBT.

In Canada, the humidex = humidity index has been used since 1965 to describe how hot the weather feels to the average person. It is a nominally dimensionless quantity, calculated from °C and the dew point. Values of: 20 to 29: little to no discomfort; 30 to 39: some discomfort; 40 to 45: great discomfort, avoid exertion; above 45: dangerous; heat stroke possible/ probable.

Humidex plot (Source: Morn, using Matplotlib code)

The American Heat Index (HI) was developed from the Humidex in 1979. It is calculated using °F or °C and relative humidity. It makes assumptions about: human body mass, height, clothing, level of physical activity, individual heat tolerance, sunlight exposure, ultraviolet radiation exposure, and wind speed. Significant deviations from these will result in heat index values which do not accurately reflect the perceived temperature.

Heat Index plot (Source: Morn, using Matplotlib code)

In many situations, building construction results in indoor temperatures exceeding outdoor temperatures. Construction methods may prohibit water saturated air from leaving a building. In climates with high humidity, such as along the Gulf of Mexico coast and even on the Atlantic coast of Florida, in the United States, it is often common to use a vapour barrier close to the outer wall, with negative consequences during heatwaves. Sometimes the best solution is to omit a vapour barrier. This is the opposite of the approach used in cold climates, such as Canada, Norway and northern United States where the vapour barrier is located on the inside of the outer wall.

Heatwave Precautions

Since many of the readers of this weblog are older, it is important for them to know what to do when temperatures rise.

A first step is to realize that an indoor environment can be particularly deadly, in part because there is no wind to increase evaporation rates, needed for effective sweating/ perspiration.

A second step is to track indoor temperatures. Even without a psychrometer or wet-bulb thermometer, one knows that the WBT will be below this dry temperature. This means that temperatures should probably not be allowed to rise above, say, 30 °C, without taking some action. Thus, moving to a shady, outdoor location, may reduce risk, compared with staying indoors.

Air conditioning units are another solution, but not everyone can afford them. Their acquisition typically has to be planned well in advance of a heatwave. Fans can be effective at increasing the quantity of air available for evaporation, but they usually should be used with an open window.

In some places, special shelters have been built/ commissioned, that people can visit without charge to find heat relief. While many people will search for information online about shelters located near them, there are other sources of information available. Public libraries are a great place to find this sort of information.