Perhaps the first data set of New Zealand carbon prices was the Ministry for the Environment's carbon prices used to calculate New Zealand's net position (either financial asset or liability) under the Kyoto Protocol.
The Ministry for the Environment had a web page About the 2008-2012 net position under the Kyoto Protocol
There was also a web page providing the Latest update on New Zealand's net position.
The net position was updated monthly in the crown financial statements for New Zealand issued by Treasury. A monthly data set of carbon prices was needed. From 2005, international carbon prices from either the United States ($USD) or Europe (euro) were converted to New Zealand dollars using the relevant foreign currency rate.
Another web page displayed the historic updates of the Kyoto Protocol financial information in the form of a table of eight columns. The seventh column was the carbon price in New Zealand dollars.
Here is what the table looked like.
Some years ago I saved an html file of that web page. I read the html file into R and tidied it into a data set with one row for every month and seven columns of variables. I even made a couple of charts!
In 2017, the Ministry for the Environment redesigned their website and the net position pages and the data set disappeared. I had thought about preserving it for the public record. I didn't get around to it.
I have just noticed I still have a folder of my R analysis. So I created a Github repository called Historic updates of the Kyoto Protocol carbon price. This now records the original .html file, some R script, the tidied data as a .csv file, a 'Readme' file and some charts.
I updated my chart!
I can't remember how I chose the colour of the line. It's "#D2691E" or "hot cinnamon".
What key point does the chart make?
The international market was flooded with "hot air" emission units from 2011. As the Morgan Foundation report Climate Cheats sets out.
One type of Kyoto carbon credit (the Emission Reduction Unit) was overcome by fraud and corruption in Ukraine and Russia. Virtually all of the credits issued by these countries are ‘hot air’ – they do not represent true emissions reductions. (Chapter 2)
Proportional to our emissions, New Zealand has been by far the largest purchaser of these Ukrainian and Russian credits through our Emissions Trading Scheme. This was due to deliberate decisions by the National-led Government to – unlike any other country – continue allowing unlimited use of these and other foreign credits for as long as the international community let us. (Chapter 3)
This fraud has had several nasty side-effects: It sent the price of carbon units in our Emissions Trading Scheme (ETS) to virtually zero, hammering our nascent carbon forestry industry.