06 June 2017

The latest inventory of New Zealand's greenhouse gases

On the Friday before last Friday, the 26 of May 2017, Minister for Climate Change Issues, Paula Bennett and the Ministry for the Environment released the latest inventory of New Zealand's greenhouse gases.

Minister Bennett and the Ministry have as their headline Greenhouse gas emissions decline.

I thought would I whip up a quick chart from the new data with R.

I pretty much doubted that there was any discernible decline in New Zealand's greenhouse gas emissions to justify Bennett's statement. We should always look at the data. Here is the chart of emissions from 1990 to 2015.

Although gross emissions (emissions excluding the carbon removals from Land Use Land Use Change and Forestry (LULUCF)) show a plateauing since the mid 2000s, with the actual gross emissions for the last few years sitting just below the linear trend line.

Gross 2015 emissions are still 24% greater than gross 1990 emissions.

For net emissions (emissions including the carbon removals from Land Use Land Use Change and Forestry) the data points for the years since 2012 sit exactly on the linear trend line. Net 2015 emissions are still 64% greater than net 1990 emissions.

There was of course more data wrangling and cleaning than I remembered from when I last made a chart of emissions!

The Ministry for the Environment's webpage for the Greenhouse Gas Inventory 2015 includes a link to a summary Excel spreadsheet. The Excel file includes two work-sheets.

One method of data-cleaning would be to save the two work sheets as two comma-separated values files after removing any formatting. I also like to reformat column headings by either adding double-speech marks or by concatenating the text into one text string with no spaces or by having a one-word header, say 'Gross' or 'Net'.

Of course, that's not what I did in the first instance!

Instead, I copied columns of data from the summary Excel sheet and pasted them into Convert Town's column to comma-separated list online tool. I then pasted the comma-separated lists into my R script file for the very simple step of assigning them into numeric vectors in R. Which looks like this.

Then the script for the chart is:

The result is that the two pieces of R script meet a standard of reproducible research, they contain all the data and code necessary to replicate the chart. Same data + Same script = Same results.

I also uploaded the chart to Wikimedia Commons and included the R script. Wikimedia Commons facilitates the use of R script by providing templates for syntax highlighting. So with the script included, the Wikimedia page for the chart is also reproducible. Here is the Wikimedia Commons version of the same chart.


For comparison, here is my equivalent chart of greenhouse gas emissions for 1990 to 2010. Gross emissions up 20% and net emissions up 59%.

What can I say to sum up - other than Plus ça change, plus c'est la même chose.

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