Page 155 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 5 global Temperatures 119
The wind-chill index does not account for sunlight intensity, a person’s physical activity, or the use of pro- tective clothing, all of which mitigate wind-chill inten- sity. Imagine living in some of the coldest regions of the world. To what degree would you need to adjust your personal wardrobe and make other comfort adaptations?
Air temperature plays a remarkable role in human life at all levels, affecting not only personal comfort but also environmental processes across Earth. Land tem- peratures interact with atmospheric moisture and pre- cipitation to determine vegetation patterns and their associated habitats—for example, the high temperatures in deserts limit the presence of many plant and animal species. Ocean temperatures affect atmospheric moisture and weather, as well as ocean ecosystems such as coral reefs. Variations in average temperatures of air and water have far-ranging effects on Earth systems.
In addition to these considerations is the fact that temperatures are rising across the globe in response to car- bon dioxide emissions, mainly from the burning of fossil fuels and removal of forests, as discussed in Chapter 3. Present CO2 levels in the atmosphere are higher than at any time in the past 800000 years, and they are steadily increasing. Thus, temperature concepts are at the fore- front of understanding climate change and its far-reaching effects on Earth.
In this chapter: The temperature concepts presented in this chapter provide the foundation for our study of weather and climate systems. We first examine the prin- cipal temperature controls of latitude, altitude and eleva- tion, cloud cover, and land–water heating differences as they interact to produce Earth’s temperature patterns. We then look at a series of temperature maps illustrating Earth’s temperature patterns and discuss current tem- perature trends associated with global warming. Finally, we examine the effect of high air temperatures and hu- midity on the human body, with a look at heat waves and their increasing occurrence across the globe.
Temperature Concepts and Measurement
In Chapter 4, we discussed types of heat and mechanisms of heat transfer, such as conduction, convection, and radi- ation. In this chapter, we focus on temperature, which is
a different, though related, concept. We learned that heat is a form of energy that transfers among particles in a sub- stance or system by means of the kinetic energy, or energy of motion, of individual molecules. In a relatively hotter substance, molecules are moving with higher energy. The addition of more heat adds more energy, with associated increases in kinetic energy and molecular motion.
Unlike heat, temperature is not a form of energy; however, temperature is related to the amount of energy in a substance. Temperature is a measure of the average kinetic energy of individual molecules in matter. (Remem- ber that matter is mass that assumes a physical shape and occupies space.) Thus, temperature is a measure of heat.
Remember that heat always flows from matter at a higher temperature to matter at a lower temperature, and heat transfer usually results in a change in temperature. For example, when you jump into a cool lake, kinetic energy leaves your body and flows to the water, causing a transfer of heat and a lowering of the temperature of your skin. Heat transfer can also occur without a change in temperature when a substance changes state (as in latent heat transfer, discussed further in Chapter 7).
Temperature Scales
The temperature at which atomic and molecular motion in matter completely stops is absolute zero, or 0 absolute temperature. This value on three commonly encoun- tered temperature-measuring scales is –273° Celsius (C), –459.67° Fahrenheit (F), and 0 Kelvin (K; see Figure 5.3). (Formulas for converting between Celsius, SI (Système In- ternational), and English units are in Appendix C.)
The Fahrenheit scale is named for its developer, Dan- iel G. Fahrenheit, a German physicist (1686–1736). This temperature scale places the melting point of ice at 32°F, separated by 180 subdivisions from the boiling point of water at 212°F. Note that ice has only one melting point, but water has many freezing points, ranging from 32°F down to –40°F, depending on its purity, its volume, and certain conditions in the atmosphere.
About a year after the adoption of the Fahrenheit scale, Swedish astronomer Anders Celsius (1701–1744) developed the Celsius scale (formerly centigrade). He placed the melting point of ice at 0°C and the boiling tem- perature of water at sea level at 100°C, dividing his scale into 100 degrees using a decimal system.
Georeport 5.1 The Hottest Temperature on Earth
in 1922, a record-breaking temperature was reported on a hot summer day at al ‘azıˉzıˉya, libya—an almost unimaginable 58°C. in 2012, an international panel of scientists assembled by the World Meteorological Organization (WMO) concluded that this record for earth’s hottest temperature, in place for 90 years, was invalid. after an in-depth investigation, the panel identified several reasons for uncertainty regarding the 1922 measurement, including instrument problems and poor matching of the tempera-
ture to nearby locations. Their final decision rejected this temperature extreme, reinstating the 57°C temperature recorded in Death Valley, California, in 1913 as the record for hottest temperature ever measured on earth. The station where this temperature was recorded is one of the lowest on earth, at –54.3 m (the minus indicates metres below sea level). One hundred years later on June 29, 2013, the official national Park Service thermometer reached 129°F (53.9°C)—a U.S. record for June, although 2.8 C° lower than 1913. What do you think surface energy budgets were like on that day?