Lesson Objectives:

By the end of the lesson, all students will:

1.      Engage in a class-wide discussion introducing the topics of global warming and climate change.

2.      Investigate, organize, and interpret evidence extracted from the UConn Virtual Herbarium and NOAA's Earth System Research Laboratory.

3.      Construct graphs in Microsoft Excel that relate temperature trends in Connecticut with flowering dates of plant specimens.

4.      Share their conclusions in a classwide discussion about their findings and their implications for Connecticut.

Related Connecticut State DOE Core Science Curricular Standards:
Grades 9-10

      D INQ. 2 – Read, interpret, and examine credibility and validity.
      D INQ. 5 – Identify independent and dependent variables, including those that are kept constant and those used as controls.
      D INQ. 6 – Use appropriate tools and techniques to make observations and gather data.
      D INQ. 9 – Articulate conclusions and explanations based on research data, and assess results based on the design of the investigation
      D INQ. 10 – Communicate about science in different formats, using relevant science   vocabulary, supporting evidence, and clear logic.

Estimated Time to Complete Lesson:
Two to three 50-minute class periods.  Depending upon internet and computer availability in the students' homes and students' levels of independence, much of the graphing and researching can done at home, allowing more classroom time for discussions.

Materials needed:
Computers with internet and printer access, and Microsoft Excel (or similar spreadsheet program)
Projector
Student worksheets

Background for Teachers:
It is accepted throughout the scientific community that the Earth is not static. The earth’s climate changes because of plate tectonics, variation in solar output, cycles in the earth’s orbit, vulcanism, and bombardment of extraterrestrial debris, among other factors. These changes usually are experienced over the periods of tens to hundreds to thousands of years. In recent decades, however, climatologists have seen rapid changes in conditions as a result of human activity. These changes include rising global temperature as a result of the burning of fossil fuels, which increases the level of “greenhouse gases” such as methane and carbon dioxide in the atmosphere. Changes in climatic conditions such as the mean temperature are likely to affect us and the other organism living in Southern New England.

Cameron Wake, a scientist with the University of New Hampshire’s Climate Change Research Center, warns that changes in temperature can affect “the ski industry, tourism, transportation, agriculture, emergency management, health, and fuel consumption for heating and cooling.”

In fact, the effects of warming already are evident. Previous research (Primack et al., 2004) has shown that plants in southern New England now flower 6 – 10 days earlier than they did a century ago, and this change is correlated with warmer mean temperatures. Plant collections have been important in identifying this trend, and students can use online collections information to verify this change.

Assumed Student Prior Knowledge:
Students should be familiar with the terms “global warming,” “climate change” and “herbarium.”  They should have basic knowledge of computer use, including general functionality of the internet and spreadsheet programs (such as Microsoft Excel).  Students should have a background in first-year algebra; they need to have a foundational comprehension of the various parts of a graph and linear functions, including being able to make real-world analyses of the coefficient of x, and independent and dependent variables. Simple tutorials can be given if needed to ensure that all students have at minimum the base level of skill.
 

PART I: Introduction to climate change and herbaria

25-30 minutes

To start the lesson, begin by asking students to take a minute to write down a few things they think of when they hear the terms “global warming” and “climate change.” Then open the floor to a classwide student-led discussion on the terms.  Allow students to share their knowledge, opinions and questions on the subjects, and feel free to write on the board any key topics, terms, or interpretations that are brought up.  Try to initiate discussion and introduce the lesson plan with such questions as:

      “In your opinion, is climate change occurring?”
      “What might be some ways in which we could determine if climate change is occurring?”

PART II: Investigation of Connecticut temperature trends

25-30 minutes

Students start by investigating whether there is evidence that the climate is changing.  Many conditions may be changing, and there are many ways to investigate these changes. Measuring the amount and intensity of precipitation, measuring whether glaciers are growing or shrinking, and measuring ocean surface levels are a few of these ways.  Students will focus in this exercise on Connecticut temperature trends over the past century.

 Introduce students to the NOAA website (http://www.esrl.noaa.gov/psd/data/timeseries/) where they will download and evaluate temperature trends in Connecticut for the past 100 years.  The NOAA website is easy to negotiate and has vast amounts of information.  For this lesson:

1.      From the page that's loaded with the link, select the fourth option titled “US Climate Division.”

2.      Under “State,” select Connecticut, and under “Division” choose to show data for the “State area averaged.”

3.      Set the “Year Range” to span the period from 1900 to 2009.

You then can choose to obtain data from every month, January through December, during the range of years, or you can pick “seasons.”  The NOAA website defines a “season” as the period between any two months, so for spring, you can select “Seasonal average” and set the “First month of season” as March or April and the “second month” (technically the last month of the season) to June.  To determine the average annual temperature, simply select “Seasonal average” and set the “First month of season” to January and the “second month” to December, essentially averaging every month together to produce a yearly mean temperature.

The output format must be “Raw data values” so students may copy-and-paste it into an associated Excel file called AverageTemperatureGraphs.

Every student (or pair) should be able to access the NOAA website and pull up data on the annual (January through December) mean temperature.  Students should copy-and-paste this data into Column A of the Excel file named AverageTemperatureGraphs. This Excel file can be found on the Virtual Herbarium.  The file has been formated to display the data so it can be graphed (in its raw form, the data paste in a single column).  Columns E and F (not C and D) contain the graphable forms of the data. Create an XY Scatterplot and include a “best-fit line,” which displays the general trend in the data. Do this by right-clicking on a data point and select “Insert Best Fit Line” (which must be linear).  Make sure the R² value (which represents the strength of the relationship between the X and Y coordinates) is included.   The long series of more than 100 data points do not need to be printed.

If students are not strong in algebra, take the time to explain what the linear equation means in terms of real-world application (also explaining the meaning of the “independent” and “dependent” variables).  For example, the function for the changing mean annual temperature in Connecticut over the past century should be:

      y = 0.0152x + 18.825

The dependent variable is the variable that we are investigating. It is the variable that is responding to the independent variable. It is the “response” variable and is displayed on the Y axis. In this case, Mean Temperature is the dependent variable. In the linear equation, the Y-intercept (the value of Y when X is the Year 0) is of little relevance. The coefficient of X has more meaning and importance in this exercise. It is the slope of the trend line, and it tells us that the annual temperature in Connecticut has increased 0.0152 degrees Fahrenheit per year on average during the period studied.  Over the course of a century, the average annual temperature has risen 1.52 degrees Fahrenheit

Students then will be able to investigate a specific season or month of their choice (or your assignment) and determine if there has been, for example, a stronger warming trend in the fall than the spring, or in April than in November.  Students would compare their one or two seasonal graphs with those of other students in the class.

An Excel file for teachers on the UConn Herbarium website contains data and graphs for annual, seasonal, and several monthly mean temperatures for the past century.  Access these beforehand and familiarize yourself especially with the strong warming trends (almost 3.3 degrees over the past century) that have occurred during the spring and early flowering/budding season (February-April).
 

PART III: Herbarium data extraction and graphing

15-20 minutes

Now that all students have been able to observe the temperature trend in Connecticut over the past 100 years, they will investigate whether plants are responding to the changing temperatures.

Explain to students that an herbarium is a collection of preserved plants used for research and education – something like a library of pressed plant specimens, some of them very old. An herbarium typically has thousands of specimens (some have millions), each with information on when and where it was collected. If a projector is available and connected to a computer, pull up the UConn Virtual Herbarium (http://bgbaseserver.eeb.uconn.edu/index.htm) and show students how they can search for, organize, and download data.  Show them where they can access the Excel spreadsheets for individual species (the choices are listed below).

Depending on class size, students may work independently or in pairs. Each student (or pair) should select one species to investigate. Most of the species are flowering earlier, but a few are not, which illustrates that organisms are  responding differently to environmental change.

These are the species for which good database information is available:

Acer pensylvanicum
Amaranthus cannabinus
Lilaeopis chinensis
Aster laterifloris
Bidens laevis
Conyza canadensis
Erigeron philadelphicus
Heracium aurantiacum
Solidago gigantea
Silene antirrhina
Arabidopsis thaliana
Barbarea vulgaris
Draba verna
Hesperis matronalis
Panax trifolius