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Probabilities, Uncertainties & Units Used to Quantify Climate Change   Activities

"Most of the global average warming over the past 50 years is very likely due to
anthropogenic greenhouse gas increases…”

How does the IPCC know whether the statement about global warming’s cause is extremely likely, very likely, or more likely than not? In order to consistently, across many different disciplines, quantify uncertainty and communicate findings to the public, the IPCC conveys statistical data via a "Likelihood" scale to effectively communicate what we know (and don’t know) about global climate change.

In this activity, you will use statistics to analyze a 150 year dataset from Lake Mendota in Madison Wisconsin reflecting seasonal ice cover. Every year, since 1855, someone has recorded when the lake froze (ice on), and when the lake thawed (ice off). You'll use these data to ask, ‘Is ice off date on Lake Mendota in recent decades statistically different (earlier) than the first two decades of observed ice cover?’ To answer this question and at the same time quantify the uncertainty around the answer, you will use one of the "t-test", a basic and relatively simple statistical technique.

Download detailed instructions to analyze the data:

Excel 2003 Instructions (Word Document, PDF)

Excel 2007 Instructions (Word Document, PDF)

Mac 2011 Instructions (Word Document, PDF)

Educators who are registered for this course can get feedback on their answers to this activity by submitting this worksheet through Learn@UW.

(Or download the worksheet to use in your classroom)