Global Warming? Could we have some of the warmth please?

I have been trying my very hardest to ignore the fact that it is July. Because I live in Ireland. And I used to live in South Africa. And I am pretty darn sure that their winter is probably a little bit warmer than our summer this year. Now don't get me wrong, Ireland has a lot of good things going for it. Lovely people. Lovely beaches. Lovely scenery. Just not so lovely bbq weather.

So I was wondering today whether I am being a bit thick-skulled. I mean, I have lived here for nigh on eight years. I should be used to the non-event that is summer. My husband talks fondly of his hot childhood summers in Cork. Even I remember a couple of good weeks of sunshine when I first moved here. So am I just being silly, wanting a few days of sun?

I don't like thinking I may be losing my mind, so I decided to do what all good analysts should. I graphed the data. This data is all from www.met.ie. So, from 2000 to 2012, the total rainfall and mean temperatures recorded in June at Cork Airport have been:

If we start by just doing a simple bar graph of the temperatures, it looks like this:

I have added a trendline, and just look at that. Things are definitely slipping. To add a trendline, double click on one of the bars to select your series, right click and select Add Trendline. You can change the look of the line through the options in the dialog box that pops up.

Now, we add in the rainfall, just for the laugh. If we maintain the graph as is, it will look like this:

Not so helpful. What we need to do is plot the rainfall on the secondary vertical axis. You need to follow a couple of steps to do this:
1) Select the rainfall series by either double clicking on one of the bars, or going to your Chart Tools tab on your menu ribbon and going to Format. At the top left hand side you will see a drop down box. Select the Rainfall series, like so:

2) Once the series is highlighted, right click and select Change Series Chart Type. Select a basic line graph.
3) Right click again and select Format Data Series. The following Dialog box will pop up:

Under Series Options, click on the Secondary Axis and you're sorted. Add another trendline for the rainfall, make your lines pretty, and your graph will look like this spectacular specimen below:

Thankfully, this graph proved I wasn't completely losing my mind. Temperatures are going down and rainfall is going up. Not a good recipe for planning bbq parties.

However, I would be a very bad analyst if I didn't point out that the ridiculous amount of rainfall in June 2012 is definitely skewing the trendline. So I re-did the graph up to 2011:

Looks kinda different, doesn't it? Rainfall is still on the way up, but the downward trend on temperature needed another year of low temperature to materialise. No wonder I expected a little bit of heat this year.

Now, unless you work at Met Eireann, these graphs may seem a bit useless. But using the secondary axis is one of my favourite ways of comparing sets of data that have very different number ranges. You can even use percentages. It sometimes really brings home the point you are trying to make with data, when you show not one, but two trends, telling the same story.

This week my newsletter is going to cover something completely different and a little bit fun...how to format your cell comments to make them a little bit more exciting than the drab yellow box. Change the shape, add in pictures. Interested? Sign up here.

Hope you have some sunshine in your spreadsheets this week!