First, you need to collect some data to help with your recommendations. Specifically, you need data for 30 years to obtain a Climate Normal (e.g., 1991 – 2020) for June 21. In this exercise you will collect Maximum Temperature (°C) and Total Precipitation (mm).

You will have to get the record for each year individually.

Step 1: Open the Environment and Climate Change Canada website.

Step 2: Once you are on the website, search for your site by typing the name in the Name box.

Step 3: Select daily as the Data Interval. Change the year to 2020 and select June for the month. The days will become greyed out – you will be given the entire month. Click Go.

Step 4: On the data page, scroll down to June 21 to see the data you need. If you have a smaller screen but would like to see the column headings with the data, you can reduce the size of the font by clicking <Ctrl><-> on your keyboard. Once you have recorded the information you need, change the year using the drop-down menu at the bottom of the page. Continue this process until you have all your data.

1. Collect the data and add it to Table 5.1. The data for Vancouver Harbour are provided, as is the data for Okanagan Centre for 2020 (but check to make sure that it is correct). Bear in mind that there may be some missing data; if it’s missing then insert a dash (-). If precipitation is marked T then that means that there was just a trace. Enter the T on the table, but count is as zero in the calculation of the mean. Note that there is no data available at Okanagan Centre for 2019, but there is for all other years.

2. Calculate the mean value for each variable at both locations, and fill in the bottom row of Table 5.1. The mean can be calculated in Excel or Google Sheets using the expression =average(data), or you can calculate it by hand.
3. What are these numbers telling you about whether or not it is a good idea to hold the wedding at Vancouver Harbour vs. Okanagan Centre? (1 – 2 sentences)

With your friend’s comfort in mind, you will want to make sure that the probability for rain and ridiculously hot or cold temperatures is low. Based on the 30-year record you have created, it is possible to calculate these probabilities.

If we take the number of days that it rained over the 30-year normal period, and then calculate the percentage of times that it rained, then we know the probability of it raining on June 21. To do the calculations you will need to know how many years it rained. When doing the calculation do not include any years for which there is no record.

For example, suppose that it rained on that day 3 years out of 30, then

[latex]\dfrac{3}{30} \times 100\% = 10\%[/latex]

If on the other hand you only had 27 years of record and it rained on 3 of them then the probability would be

[latex]\dfrac{3}{27} \times 100\% = 11.1\%[/latex]

Your friend really doesn’t want it to rain on their wedding day, so even though the rain wasn’t measurable, count days with “Trace” rain as rainy days.

You also want to make sure that the temperatures aren’t too hot nor too cool. More specifically, your friend does not want the temperature to be over 30 °C, nor under 20 °C. To do the calculations you need to know how many days out of the 30-year record the temperatures were higher than 30 °C or were below 20 °C.

Use these guidelines to determine answers to the following questions. Show your work.

4. Based on what has happened over the past 30 years, what is the probability of it raining on June 21 at
   1. Vancouver Harbour?
   2. Okanagan Centre?
5. Based on what has happened over the past 30 years on June 21, what is the probability of temperatures
   1. exceeding 30 °C at Vancouver Harbour?
   2. being less than 20 °C at Vancouver Harbour?
   3. exceeding 30 °C at Okanagan Centre?
   4. being less than 20 °C at Okanagan Centre?
6. Based on your responses to the above questions, what are your conclusions about where to hold the wedding? (2 – 4 sentences)

When we calculate probabilities based on what has happened in the past, then we assume what statisticians call stationarity. Stationarity is an assumption that variations in measurements are due to random fluctuations, and are not associated with any systematic change. However, it is possible that there is some underlying pattern of climate change. One simple way of examining that is to graph the data over time. Here we will use bar graphs for precipitation and line graphs for temperature.

In this exercise, you will plot the total monthly precipitation and mean daily maximum temperature for June for Vancouver Harbour. Has it changed over the past 30 years? For your convenience, the data is listed in Table 5.2.

7. Construct a bar graph of June precipitation at Vancouver Harbour for the period 1991 – 2020.
   1. Copy and paste Table 5.2 into Google Sheets or Excel.
   2. Select the Year and Total June Precipitation columns and click on Insert/Chart/Column.
   3. Check that your labels, title, and axis are correct using the checklist for graphs and copy and paste your graph into your Worksheet.
8. Construct a line graph of June mean daily maximum temperature at Vancouver Harbour for the period 1991- 2020.
   1. Select the Year and June Mean Daily Temperature columns and click on Insert/Chart/Line.
   2. Check that your labels, title, and axis are correct using the checklist for graphs and copy and paste your graph into your Worksheet.
9. Are there any trends here? Your opinion will be a little subjective, but try to be as objective as possible. There are world-wide datasets that show warming trends. Explain your results in this world-wide context. (2 – 4 sentences)
10. In the context of climate change, is the average for the past 30 years a good way to estimate the probability of what will happen next year? On the basis of climate trends you identified, do you have any reason to adjust your thinking about the probability of rain or extreme temperatures in Vancouver? (2 – 4 sentences)