Here is your short essay on Climate and Human Comfort

Of all elements of our physical environment, climate affects human health and comfort most. Changes in the weather affect the physiological functions of the human body. However, personal reactions to the weather or climate differ greatly according to the following variables: (i) health, (ii) age, (iii) sex, (iv) clothing, (v) occupation, and (vi) acclimatization.

Personal comfort depends on the maintenance of a body temperature at about 37°C (98.6°F) without any demand to increase heating by shivering or by exercise, or to increase cooling by evaporation.

This was how human comfort was defined by two eminent meteorologists, namely Linacre and Hobbs. Because of human variations, definition of discomfort criteria is not easy.

It is interesting to note that of all the living creatures, man is the most adaptable to changing atmospheric conditions. Climate is unquestionably a factor in human efficiency.

Any serious study of weather and physical comfort must take into account several other meteorological factors such as, sequences of hot days, persistence of a weather type, and the possible relationship between weather and insects or air pollution.

At this point it would be more appropriate to bring to light the fact that insects such as mosquitoes affect comfort, and the life cycles of these insects depend on the climatic conditions.

Among the weather elements affecting the human body are air temperature, sunshine and humidity. Wind is also an important climatic element that exerts an influence through its direct effects on skin temperature, and body moisture.

Atmospheric pressure, cloudiness, visibility and storm induce physiological discomfort. Thus, the entire climatic environment has direct influence on human comfort.

In order to appreciate the physical comfort of human beings, we must have information about the thermal conductivity of clothing, vapour pressure of the skin, and the metabolic heat rate due to activity of the human body.

Clothing exerts great influence on comfort. Its influence on the radiation balance through its colour and insulating properties is worth consideration.

Besides, exchange of sensible temperature between the human body and the atmosphere is influenced by conduction and convection, whereas the former is not so effective in adding heat to the body, but its importance in reducing heat loss because of the low thermal conductivity of many clothing and building materials cannot be underestimated.

But convection is important in cooling the body. In the absence of the evaporative cooling from the lungs and the skin by convection if the air is cooler than the skin, and by radiation, body temperature would rise by about 2°C per hour.

While doing continuous work, an adult person loses a liter of water in an hour which would absorb energy and produce a cooling effect if evaporated. In the absence of complete evaporation, the degree of cooling of the body is less resulting in sweat wetting the skin.

Wind, another climatic element, is also important for it accelerates heat transfer by turbulence and evaporative cooling. It also does not allow accumulation of high moisture content on the skin.

Thus it helps to maintain evaporative cooling. In this way wind can make an overheated body feel comfortable. On the contrary, wind can remove heat from a body and induce chill. In case the air temperature is more than skin temperature, the wind can increase the heat of the body.

Human comfort is also affected by the altitude of a place. At high altitudes the amount of oxygen is decreased which results in breathing difficulties.

Effective temperature, which is defined as the temperature of calm, saturated air which produces the same sensation of comfort to a normally clothed worker sitting for long at his working table.

Effective temperature is a useful and easily calculated comfort index. However, its application is limited to workers in sedentary occupations, and the significance of values more than 5° outside the common limits of 15-27°C is not clear.

Another measure of human comfort is the heat stress index. It is defined as the ratio between the amount of perspiration from the human body which must be evaporated from the skin to maintain thermal comfort, and the maximum amount of evaporation possible under the particular environmental conditions.

Air temperature and a moisture factor, according to Critchfield, have been the primary bases for an objective index of sensible temperature. The temperature the body actually feels, or senses, is called the sensible temperature.

It cannot be measured by any thermometer. When the skin is moist and exposed to normal dry bulb temperatures, the sensible temperature and wet-bulb temperature are almost the same. Under these conditions evaporation is the main cooling process.

High relative humidity along with high atmospheric temperature makes the weather uncomfortable, since the sensible temperature under these conditions is high.

To conclude, the range of comfortable sensible temperature for a particular group of persons depends on climatic conditions and the characteristics of the group. The concept of comfort is purely subjective.

Besides, the effective temperature and relative strain index are not very accurate because they overlook a number of factors influencing the feeling of comfort.