Before beginning a discussion of temperature, one should first understand the difference between temperature and heat. Temperature is a measure of the average kinetic energy of atoms or molecules in a substance. For example, the molecules in a pot of boiling water will move much faster than in a pot of cold water, thus giving boiling water a higher temperature. Heat, however, is a measure of the total kinetic energy of a substance. Therefore, a large cup of hot coffee would possess more heat than a smaller cup.

Temperature affects the smallest details of our daily life—from what we wear to how we get to work to what we eat for lunch. Seldom can we go even a day without needing to know what the temperature is or will be. After all, few people would want to walk to work or school in a snow storm, or can enjoy a bowl of hot soup when it is upwards of 90 degrees outside. Therefore, temperature plays an important role and it is valuable to know what temperature is, how it is measured, and what implications it may have for society as a whole.

One of the first scientists to devote serious study to temperature was the famed Italian, Galileo Galilee. Most are familiar with the thermometer he developed in the early 1600s, commonly known as the Galileo Thermometer. Though rudimentary in its design, the device was surprisingly accurate. The next great breakthrough in the study of temperature came with Daniel Gabriel Fahrenheit’s invention of the mercury thermometer. He also invented the temperature scale that bears his name—the Fahrenheit scale—which set zero degrees as the coldest temperatures one would likely experience in Western Europe. An alternative temperature scale—the Celsius scale—was invented by Anders Celsius in 1742. His Celsius scale set zero as the point at which water boiled and 100 as the point at which it froze. In the late 1700s when Carl Linnaeus inverted the scale to make zero degrees reflect water’s freezing point and 100 degrees to reflect its boiling point, the Celsius scale became popular. The conversion for Celsius, Fahrenheit, and Kelvin is seen below.

Source: BalmoralSoftware

While many might assume that understanding temperature can do nothing more than help us decide which jacket to wear before going out in the morning, temperature research has provided scientists with clues about both the history and future of our planet’s climate. On a localized scale, microclimates—small areas with a different climate than their surrounding areas—have taught scientists a great deal about how temperature can affect life. One example is an urban heat island, a city or urban area with temperatures several degrees higher than its surrounding suburbs or countryside. By understanding how and why temperatures fluctuate in these urban heat islands, planners and architects can create more efficient and comfortable approaches to city living.

Temperature records have also become a key focal point for researchers attempting to understand global climate change. Some of the most convincing evidence that human activity plays an important role in climate change has come from studying changes in temperature. While there have been natural fluctuations in temperature since the Earth was formed, the drastic change in the Earth’s average temperature since the Industrial Age began has led many—though not all—scientists to conclude that humans are indeed a factor in global warming.

Source: Project Learn at the University
Corporation for Atmospheric Research

Global temperature change is the key aspect of climate receiving the most attention from scientists and policy makers, primarily since it affects other climate patterns. For example, a drastic drop in average temperatures could seriously reduce the amount of precipitation that falls, thus diminishing crop production. Other impacts of rising temperatures may include more severe and destructive weather patterns, while the melting of glaciers could cause sea levels to rise. Since temperatures are expected to continue to increase, it is important to understand how the Earth has responded to climate change over the past century so we can be better able to predict how it may respond in the future.

Recommended Resources

Project Skymath: About Temperature
The National Center for Atmospheric Research prepared this basic resource to explain many of the central concepts related to temperature, how thermometers work, and the evolution of the study of temperature.

Online Conversion
This website has an easy to use temperature converter that requires no downloading. One can convert to and from degrees Celsius, Fahrenheit, Kelvin, Rankine, and Reaumur.

Data & Maps

National Weather Service
The National Weather Service provides this comprehensive temperature map for the United States, updated several times a day.

For the Classroom

What’s Up With the Weather?
This PBS NOVA teacher’s guide, developed to accompany NOVA’s 2000 broadcast on weather and climate, includes an activity, with handouts and graphs, for students to examine trends in regional temperature data. [Grades 5-12]

Activities and Experiments with Temperature and Heat
NASA and the California Institute of Technology created ‘Cool Cosmos,’ a public outreach and education effort. The activities page presents students with a variety of options that can help to explain heat and other temperature-related concepts. [Grades 6-12]