1. Explain the difference between climate and weather. (Slides 3-8)
How can there be global warming if it is snowing outside in April when it should be 50 to 60 degrees Fahrenheit? This is a very common question, and the answer lies in the difference between weather and climate. Have students try to write definitions of “weather” and “climate” and include examples of each.
(Show the short video segment – 2:41 minutes) by the Wisconsin Educational Communications Board (WIECB) featuring University of Wisconsin-Madison researcher John Magnuson as he discusses the difference in the context of ice cover over winter. This video can be found on Teacher’s Domain at: http://www.teachersdomain.org/resource/ecb10.sci.ess.watcyc.weather/, or through a YouTube search of The Difference between Weather and Climate, posted by WIECB.
Have students revisit and refine their definitions, or begin with the definitions below.
Weather, which is highly variable, is made up of specific atmospheric conditions (temperature, rainfall, wind, and humidity), that occur at any given place and time.
What is the weather like today?
Climate (according to the National Weather Service’s definition) is the average of weather over at least a 30-year period.
Climate is what we expect and weather is what we get. As one perceptive middle school student said “Climate helps you decide what clothes to buy, weather helps you decide what clothes to wear.” Weather forecasts are short-terms predictions and future climate scenarios are projections.
2. Compare weather and climate.
In pairs, students put the Weather or Climate Cards on the Weather or Climate chart. Review as a class. (Answers on Slide 9)
To highlight the difference between weather and climate and to give students practice in extracting information from a data table, distribute Midland Precipitation student resource. This is a 30-year table of monthly average precipitation for Midland, Michigan. See Teacher Notes/Answer Key for introducing the Midland Precipitation student activity. (Answers on Slide 10)
3. How can we look at climate? (Slide 11)
A climagraph is a graphic representation of the three major elements of climate: temperature, precipitation and seasons for a specific location. Show Climagraph Example Transparency (Iron Mountain). (Slide 12)
• Months are labeled along the horizontal (x) axis.
• Precipitation is labeled on one vertical axis, and is represented by a bar graph showing the average precipitation for each month.
On average, what is the minimum amount of rain Iron Mountain gets in the lowest month? (one inch in February) What might this mean?
If we added the precipitation for every month, we could get the yearly average. What is the approximate yearly precipitation for Iron Mountain? (About 29 inches/year) All of Michigan receives more than 20 inches of precipitation a year, which means forests survive. (Below 20 inches per year the climate is characterized as semi-arid.)
• Temperature is labeled along the other vertical axis, and is represented by the curved line connecting the average temperature for each month.
• The information on this climagraph can be better understood by emphasizing two important temperature lines: 30 degrees F and 50 degrees F. (Teacher should trace these lines on the transparency). Why would the average temperature of 30 degrees F or 50 degrees F be important?
(Slide 13) 30 degrees is just below freezing, which means that most plants are dead (annuals and most agricultural crops which need to be replanted yearly) or dormant (perennials and trees).
When the average is above fifty degrees, the chance for frost is low, so that is the growing season for most plants and crops. What is the growing season for Iron Mountain, Michigan? (May-October)
Students make climagraphs with Making a Climagraph – Atlanta Georgia student activity. (Slides 14-17) An additional activity, to practice analyzing climagraphs, is Climates and Places student activity. (Slides 18-19)
4. Climate Variability. (Slide 20)
Climate variability is the way climatic variables (such as temperature and precipitation) depart from some average, either above or below. Climate change can be defined as a trend in one or more climatic variables characterized by a fairly smooth continuous increase or decrease of the average value during the period of record.
Look at the graph of Midland Precipitation Variability transparency master (Slide 21); it is an attempt to graphically summarize the last column from the table. Do you think there is a long-term upward or downward trend?
Now look at the Michigan Temperature Variability transparency master (Slide 22). NOAA added a trend line to summarize the data. Pose the following questions:
What is the range of years in this graph? (1980-2011)
What is significant about this range? (It is a 30+-year span that is used for climate trends)
What season is this graph showing? (winter)
What is the average winter temperature in Michigan? (21.58° F)
What years were used for this average temperature? (1901-2011)
How many years were below the average temperature? (11) Above the average temperature? (20)
What was the highest average temperature? (almost 30° F) The lowest average temperature? (16.5° F)
How is the average winter temperature changed since 1980? (an increase of 0.36° F per decade)
Point out that both of these graphs illustrate climate variability because they show how climate fluctuates yearly above or below a long-term average.
5. So what is the problem? (Slide 23)
Climate varies over time and space through both natural and man-made processes. Now that students have examined climate patterns and climate variability, use What is the difference? transparency master to discuss the definitions of ‘global warming,’ ‘climate change,’ and ‘global change.’
The term global warming refers to a sustained increase in global average surface temperature and the lowest layer of the atmosphere and is just one aspect of climate change. (Slide 24)
Climate change can be defined as a trend in one or more climatic variables characterized by a fairly smooth continuous increase or decrease of the average value during the period of record. (Slide 25)
What are some climatic variables that might change? (precipitation, temperature, extreme weather events)
Global change is the broadest term and it encompasses more than just climate change. According to the U.S. Global Change Research Act of 1990, global change is defined as: “changes in the global environment (including alterations in climate, land productivity, oceans or other water resources, atmospheric chemistry, and ecological systems) that may alter the capacity of the Earth to sustain life.” (Slide 26)