# Calculating Rates of Change

#### Summary

This in class activity allows students to calculate rates of change from graphs of glacial-interglacial temperatures and CO2 and modern temperatures and CO2.

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## Context

#### Audience

Undergraduate courses in geology and biology

#### Skills and concepts that students must have mastered

Students should be able to read a graph, understand what a rate is, and calculate a slope.

#### How the activity is situated in the course

This activity is used as part of a lecture that introduces the main controls on climate change.

## Goals

#### Content/concepts goals for this activity

The goal is for students to understand that the rate of current climate change is one of the reasons that we consider current changes to be unnatural (and therefore attributed to human activity).

#### Higher order thinking skills goals for this activity

Graph interpretation
Calculating rates and slopes, comparing results.
Evaluation and interpretation of results.

## Description and Teaching Materials

After handing out the graphs, I ask students to calculate the rate of change during a period over the past 160 thousand years using the Vostok ice core data (for both temperature and CO2). In order to orient the students, I might ask them about the length of the glacial period vs an interglacial period, or when the most rapid change occurred. The students often work in small groups or check their answers with each other. I ask them to put their answers on the board (there will be a range of answers).
Then I ask them to do the same thing for the modern datasets. Once all the data are on the board, we compare the rates of change. Typically, students have used different units (change per 1000 years vs change per year).
The power of this activity comes from the fact that students have done all the math themselves. So when they are shocked at how different the glacial vs current rates of changes are, I can ask them if they think they made any mathematical mistakes, and since the math is relatively simple (and they can see everyone's answers), they realize that these numbers are correct and these differences in rates are real.

Student Handout as PDF (Acrobat (PDF) 53kB May13 13)
Student Handout in Excel (Excel 237kB May13 13)

## Assessment

I typically include test questions that ask about factors that control climate and that ask how we know that current change is due to human activity. These questions can be written in multiple choice or open-ended formats.
I sometimes conduct pre-topic 'quizzes' that include similar questions (open ended). One of the goals of these quizzes is to help students realize that they don't really know the answers to these questions, so that they [hopefully] pay more attention when we do the lecture/activities.
For the question 'What evidence supports the fact that current climate change is driven by human activities?" correct responses increased from 2.5% before the activity to nearly 100% after the activity, even though the answer was not something that I explicitly ever wrote down.