Temperature and Weather
=== by Bob Sutherland ===
Having named my website after a very cold temperature it only seems fitting that I should devote a section of my website to information about thermometers, temperature, weather, climate, wind chill, frostnip, frostbite, meteorology, climatology, global warming and -40 degrees.
Some basic knowledge
The only temperature reading on a thermometer where the number is the same on both the Celsius scale and the Fahrenheit scale is -40°.
-40 °C = -40 °F
To convert temperatures between degrees Celsius and degrees Fahrenheit use the following formula:
C ÷ 5 = ( F - 32 ) ÷ 9
Where:
C = temperature in degrees Celsius
F = temperature in degrees Fahrenheit
If you are a high school student you should be able to plot the above equation on graph paper. Pretend F = x and C = y. Use the equation to calculate and plot a bunch of (x,y) or (F,C) points on your graph paper. Or if you know how rearrange the equation so you can plot it directly on the graph paper. Either way when you connect the points you should have a straight line graph that does not go through the point (0,0).
You can use your graph to find equivalent temperatures between the Fahrenheit and Celsius scales. Select any point on your straight line graph. Go straight down from your point to find its measurement in degrees Fahrenheit along the x-axis. Go straight across from from your point to find its measurement in degrees Celsius along the y-axis. The Fahrenheit and Celsius measurements for any point along your straight line graph are equivalent temperatures.
The following table lists some equivalent temperatures. Many of them are temperatures you should memorize when you are a student because you will find them useful throughout your lifetime.
| °C | °F | Notes |
|---|---|---|
| 100 | 212 | Boiling point of water |
| 40 | 104 | |
| 38 | 100.4 | A doctor or nurse will say you have a fever if your body temperature rises above this point |
| 36.7 or 37 | 98.1 or 98.6 | Normal body temperature of humans |
| 30 | 86 | A hot summer day in Canada |
| 20 | 68 | Ideal room temperature for desktop computers and people |
| about 14-15 | about 57-59 | Average surface temperature for planet Earth |
| 10 | 50 | Wear a jacket or sweater |
| 0 | 32 | Freezing point of water = Melting point of ice |
| -10 | 14 | |
| -20 | -4 | |
| -30 | -22 | A cold winter day in northern Canada |
| -40 | -40 | Exposed human skin freezes (frostbite) in 5 to 10 minutes |
| -273.15 | -459.67 | Absolute Zero, no molecular movement, 0 Kelvin |
A few quick notes related to the above temperature conversion table
If you are a high school student working in a science laboratory do not be surprised if your real life measurements with a thermometer are off by a few degrees from the textbook numbers in the above table. Record and use your own measurements in your experiment.
In real life my students in northern Canadian high school classrooms found the boiling point of tap water or distilled water measured with red alcohol thermometers averaged about 97 °C ±10 °C.
The Fahrenheit temperature scale is a good scale for mild climates where the temperature remains between 0 °F and 100 °F. It would be much easier to teach young students about temperature if the weather outside was always a positive number.
A room temperature of 20 °C and 68 °F is perfect for desktop computers and quite pleasant for humans.
Historically Canadians were inclined to set the thermostat controlling the furnace a bit higher around 22 °C and 72 °F in a drafty building on a cold winter day. If Canadians could afford air conditioning during very hot summer days they might set the thermostat temperature as low as 19 °C or 66 °F. In recent years Canadians have been constantly bombarded with messages from energy conservation campaigns telling them to set the temperature of their furnace cooler and the temperature of their air conditioner warmer to reduce the amount of energy consumed.
Style Manuals
I have consulted a few generally authoritative style manuals to see how I should be typing out temperatures and found there is no agreement among them. Some style manuals will suggest that I keep everything together without a space, e.g. -40°C . Other style manuals will suggest that there should be a space before the letter, e.g. -40° C . A third group of style manuals will suggest that there should be a space after the number, e.g. -40 °C . Most of the style manuals seemed to agree that in the absence of a letter there should be no space, e.g. -40° .
Body Temperature
The normal body temperature of humans of 37 °C or 98.6 °F that is listed in the above table is a widely published historical number. I read somewhere that more recent surveys are finding the average body temperature of the world population tends to be about half a degree Fahrenheit cooler at about 98.1 °F or 36.7 °C. It is quite possible the historical value was simply rounded off to the nearest degree Celsius by the doctors who first collected and published data about the average body temperature of their patients.
Your own body temperature varies over the course of the day with people typically being coolest at night between 3 a.m. to 6 a.m. and warmest in the afternoon between 3 p.m. to 6 p.m..
You can measure a person's body temperature with a thermometer placed in the mouth under the tongue, in the ear, under the armpit or in the anus. The temperature reading at each of these locations will probably be slightly different. I am not suggesting you try placing a thermometer in any of these locations to measure a person's body temperature unless you have received instructions from a doctor, nurse or pharmacist as to how to do it safely.
Meteorology, Climatology and related Sciences
Meteorology is the science of studying and predicting changes in our atmosphere and daily weather. The person who makes the weather predictions you hear and see on radio, television, newspapers and the internet is a meteorologist. You probably grew up calling a meteorologist a weatherman, weather-woman or weather forecaster.
Climatology is the science of studying and predicting our weather patterns over long periods of time such as seasons, years, decades and centuries. A climatologist is often a weatherman or weather-woman who after studying the long term weather trends may attempt to predict what our climate will be like this coming summer compared to previous summers.
Many other scientists including astronomers, oceanographers, archaeologists and geologists may become involved in studying and making discoveries about our current and historical atmosphere, weather and climate as it relates to their work. What is happening in our atmosphere and how to see through it is a very important consideration for astronomers when trying to peer through their telescopes at distant stars in the universe. Oceanographers study the oceans. It has been discovered that changes in the direction and temperature of ocean currents have a major impact on seasonal changes in our climate. Archaeologists often discover clues about what the climate was like long ago as they excavate the ruins of ancient civilizations. Many major geological events that geologists study such as ice ages, volcanoes, earthquakes and floods can have a major impact on our planet, climate and weather.
Years ago I was a member of a geological field party mapping the soils and rocks of an area of northern Canada as part of a much larger scientific research project on acid precipitation and climate change.
Mercury, Alcohol and Bimetal Thermometers
Mercury is a silver coloured liquid metal that can rise up a thin glass capillary tube in a thermometer. Meteorologists prefer to use a mercury thermometer for taking weather temperature readings because of its accuracy.
Unfortunately a mercury thermometer cannot be used to measure outside temperatures in cold climates. The liquid mercury in a thermometer will freeze to a solid at about -39° Celsius or -38° Fahrenheit. If the mercury is frozen the thermometer will never display a temperature of -40° as the mercury has stopped moving in the thin glass capillary tube before it gets that cold.
A mercury thermometer must be taken inside and kept warm whenever there is a risk of the outside temperature dropping low enough for the mercury to freeze. If mercury freezes then as it thaws air bubbles are likely to form in the thin capillary tube of the thermometer. The presence of air bubbles would destroy the calibration of the thermometer.
Mercury is now considered an environmental health hazard. If the thermometer glass breaks spilling the mercury then it can be absorbed and accumulate in our bodies poisoning humans, fish, animals and plants. Because of the health risk mercury thermomters are no longer used in schools and most hospital applications.
An alternative to the mercury thermometer is an alcohol thermometer. In this case alcohol is just a generic term. The actual thermometer may or may not contain alcohol. There are a number of clear liquids that the manufacturer may use depending on what they have available in stock. The liquid is usually dyed red, but it can be dyed blue or some other colour to make it more visible in the thin capillary tube rising up from the bulb of the thermometer.
The temperature scale on the side of an alcohol thermometer will change depending on what liquid is used to make the thermometer. Different liquids each have their own range of temperatures that they are effective at measuring.
Bimetal thermometers are widely available in hardware stores in Canada. They are made by bonding two different metals together, one layered above the other, in a thin flat sheet. The bimetal sheet is then cut up into thin metal strips and coiled up like a spring. As the temperature changes one metal will expand or contract more than the other metal causing the coil to partially unwind or curl up tighter. A needle attached to the end of the coil points at the temperature scale on a circular dial.
Environment Canada Weather Office
Environment Canada is a department of the federal government in Canada that is primarily involved in scientific research. The Weather Office is part of Environment Canada. The primary collection sites for weather data in Canada are the airports scattered across the country. Weather data is also collected from other sources such as the weather offices of other countries, satellites orbitting the earth, and weather measurement buoys floating in lakes and oceans.
As far back as I can remember Environment Canada has always owned one of the biggest, most powerful, supercomputers in the country. As a Computer teacher I am jealous. Apparently Environment Canada needs the supercomputer to process all of the weather data it collects. There is a tremendous amount of calculations that must be done with the data collected before the meteorologists can forecast our weather.
The meteorologists at the Environment Canada Weather Offices make weather forecasts for communities, airports, large lakes and regions all across the nation. Other organizations also use Environment Canada's weather data or analysis to make their own weather forecasts for specific markets.
Here is a link to the Environment Canada Weather Office website.
Weather Office changes from Fahrenheit to Celsius
Historically the weather offices in Canada used degrees Fahrenheit (abbreviated °F) to measure temperatures. Then about half a century ago the weather offices in Canada switched over to using degrees Celsius (abbreviated °C). At the time of the switch students in Canadian schools were using the Centigrade temperature scale for Science experiments. The whole Canadian population had to be taught that the Centigrade temperature scale was being renamed the Celsius temperature scale and would be used for weather forecasts.
The Americans are always a bit slow at learning new things so the weather offices in the United States are still using degrees Fahrenheit (abbreviated °F) to measure temperature. The students in American schools have probably been using degrees Centigrade and then degrees Celsius to measure temperature in Science class for just about as long as the Canadian students. Since the students know how to measure in degrees Celsius therefore it must be the American adults who are to blame for the United States weather offices being so slow about switching temperature scales.
Frostnip and Frostbite
At -40° removing your mittens to fumble with small things such as keys to unlock a door is risky. As your fingers, hands and face quickly react to the cold first you will suffer frostnip, which is a mild form of frostbite. Your skin will still feel soft to the touch as it freezes. Some books and websites write that you will feel a very painful tingling or burning sensation.
After frostnip the more serious frostbite condition occurs as the tissues under your skin including fat, muscle, bone and tendons freeze. The skin will become hard to the touch and there will be no sensation. Your hands, face or other exposed body parts will go numb.
The historical medical treatment for frostbite often involves amputation of toes and fingers after doctors try to thaw and restore life to the frozen body part.
A main purpose of our toes is to help us keep our balance when standing and walking. If your toes are amputated the sensory touch input our toes provide to your brain when they are touching the ground will not be there. The unconscious part of your brain needs that sensory touch input from your toes to assist in determining the slope of the ground relative to the slope of your feet.
Based on my personal experience I would describe frostnip of the hands and face as being very painful. More like an overall burning of the whole hand rather than the pinpoint burning of just one spot that you might accidentally get around a stove. You can still move your fingers although it rapidly becomes increasingly more difficult to hold, feel and manipulate small objects such as keys, locks, screws, nuts, bolts and wires.
As temperatures drop down toward -40 °C trying to remove the small cap to put air into a single deflated truck tire requires a major amount of willpower to overcome the frostnip pain and keep working at it. Your mind will be going numb in the cold so you will no longer be thinking about the three other tires plus the spare tire that also need air put into them as the cold temperature will have deflated those tires as well.
You might experience frostnip and frostbite right through your clothing if you do not have enough insulation and body warmth to protect you from the wind chill and cold temperatures. That is why so many people suffer frostnip and frostbite of the ears, toes, fingers, feet and legs while wearing winter clothing.
Based on my personal experience I would describe frostnip of the legs where the cold is penetrating through clothing such as jeans or poorly insulated overalls as initially being a mild pain with a tingling feeling as your blood circulation decreases in response to the cold. The pain intensifies on the front of your thighs and down your leg. The skin on the front of your thighs thickens to feel stiff like a piece of plastic sports armour as it begins to freeze solid. The tingling sensation gradually goes away indicating that there is very little or no blood left flowing near the skin. You can slap or punch the front of your thigh and your leg will barely feel the pain of the impact while your hand will feel like it just hit a wall if it is not frozen as well. For some reason you feel a need to hit your thigh every once in a while just to test if you still have any sensation of feeling there. Your knees, lower legs and feet just get extremely painful. If your feet are not well insulated then the pain will start in your toes and migrate back through your feet and up your legs. If your feet are well insulated but not your legs then the pain will be travelling down your legs to your ankles. Your feet will start going stiff as you lose the bounce to your step. You will begin having difficulty just trying to move your legs to walk as they will feel stiff and clumsy. It becomes increasingly more difficult to keep your balance while standing. The pain in your knees, lower legs and feet will become very intense as if you were standing in a large fire with flames up to your waist.
Splitting of the skin around the fingernails, finger tips and lips of the mouth are common problems among the population living in northern Canada during the winter season. Possibly the skin is contracting in size and becoming stiffer so it tends to split rather than bend. I found teachers up north were experimenting with all sorts of different skin moisturizers and lip care products to try to prevent or treat the problem.
Living in Canada's northern communities I found my resistance to frostnip decreased over the years. Age may be a factor but I am just past middle age. Repeated short term exposure to extremely cold temperatures definitely took its toll on the ability of my hands and body to withstand freezing temperatures.
Wind Chill
Wind chill is a measure of how cold the wind feels as it blows on the bare skin of your face. In Canada the wind chill is measured in temperature like units equivalent to degrees Celsius but without saying "degrees Celsius". For example, the temperature outside is -10 °C but a wind speed of 30 kilometres per hour makes the wind chill feel like -20. This means that your face feels just as cold as it would on a day with no wind and a temperature of -20 °C.
The United States cooperated with Canada in developing the wind chill scale but their temperature like units are equivalent to degrees Fahrenheit. The Canadian example above would be expressed in the United States as an outside temperature of 14 °F with a wind speed of 19 miles per hour making the wind chill feel like -4.
Environment Canada has charts and information about wind chill and cold weather exposure on their web page Canada's Wind Chill Index.
Something that Environment Canada highlights on their website is that the risk of frostbite increases rapidly when wind chill values go below -27.
As the air temperature decreases or the wind speed increases the wind chill will decrease down toward the danger zone.
The following numbers are taken from Environment Canada's wind chill chart:
| Air Temperature (°C) | Wind Speed (km/h) | Wind Chill |
|---|---|---|
| -15 | 30 | -26 |
| -20 | 10 | -27 |
| -25 | 30 | -39 |
| -30 | 10 | -39 |
| -35 | 10 | -45 |
| -40 | 10 | -51 |
The meteorologists at Environment Canada generally only include wind speed predictions in their weather forecast if the mean wind speed will be 20 kilometers per hour or greater.
Feeling any wind on your face or seeing a weather vane begin to move is an indication that the wind speed is 10 kilometers or greater.
Seeing small tree branches move, large flags flap and loose paper rise up is an indication that the wind speed is 30 kilometers or greater.
Unfortunately in Canada's northern aboriginal communities there is unlikely to be any weather vanes, large flags and the Inuit do not have any trees up in the arctic. So these wind speed prediction guidelines are of very limited value to them. All they are left with is the possibility of looking for some paper litter blowing around on the ground or trying to feel the wind with a face that can become weather-beaten through prolonged time spent outdoors.
Today's weather forecast: High 40 °Celsius, Low -40 ° Celsius
Human beings are a very adaptable species. We have wandered all over our planet setting up communities almost everywhere but temperature does play a role in limiting where we can live. All communities with a permanent population of inhabitants must experience a climate where temperatures normally stay between 40 °C and -40 °C.
In places like northern Canada and Siberia our species can survive the occasional cold spell when temperatures drop below -40 °C for anywhere from a few hours up to about ten days. We just stay indoors and hope our buildings, plumbing, heating and electrical systems can withstand the cold.
In parts of the world closer to the equator some communities survive temperatures that rise to or above 40 °C for short periods of time.
There are military and scientific research stations on the continent of Antarctica and near the North Pole where the temperature drops below -40 °C for longer periods of time. A complete turn over of staff occurs at these military and scientific research stations every few months as people do not stay there very long.
Average surface temperature of our planet
The average temperature of the air at the height of someone's neck above the surface of the earth is about 14 °C or 57 °F. Do not quibble with me over the fact that some people are tall and others are short so their necks are not always the same height above the ground. There is already enough fudge factor in this average temperature of our planet statistic. Neck height is about how high the scientists and students would be holding their thermometers when they read the temperature. It was fairly easy to find volunteers to take measurements in all of the big cities of the world but it was very difficult to get anyone to wander out across the surface of the oceans and the polar ice caps to take temperature readings on the day we did the survey.
So you do not believe my last paragraph, eh? Well the temperature of about 14 °C or 57.2 °F is approximately correct although it may have risen to 15 °C or 59 °F by now. The amount of fudge factor involved in trying to measure and calculate the average temperature of our planet is approximately correct. A large part of the Earth's surface is covered by oceans and ice caps where there are relatively few thermometers. The large land mass of northern Canada also has relatively few thermometers. There have been disagreements over whether the scientists should try to determine the average temperature of the top few centimetres of the dirt and water on the earth's surface or the temperature of the air we walk through just above the earth's surface. A few different groups of scientist have probably tried various ways of measuring, calculating and estimating a value for the average surface temperature of the Earth. The actual methods that scientists have used is something that you can research. (Hint: Check to see if NASA has tried to do any measurements from up in space then search around for alternative groups of scientists who may have tried to measure the earth's surface temperature while staying closer to the ground.)
While the temperature of our daily weather can change quite drastically the temperature of our planet remains relatively constant. When one place on our planet gets hot another place cools off keeping everything in equilibrium. We get our energy from the sun. Our atmosphere acts like a protective blanket around the Earth controlling how much energy reaches the planet's surface and how much escapes back into space. Climatologists tend to record one average surface temperature per decade for our planet and their records go back to 1880.
To start a new ice age would only require an average surface temperature drop of 2 degrees Celsius for our planet. Geologists have found evidence that our planet has experienced a number of ice ages. Since 1880 the average surface temperature of our planet has increased by about 0.8 degree Celsius or 1.4 degree Fahrenheit. That is why scientists are getting everyone concerned about global warming. The rate of temperature increase has not been steady but rather it has been accelerating over the past few decades.
The average surface temperature of different regions of our planet tends to fluctuate more than our whole planet.
Here is a link to a NASA related web page on this topic. There is an interesting world map at the top of their page showing which regions of the world have been hotter or cooler compared to the same region in prior decades. NASA Earth Observatory