Carbon pricings

A carbon pricing consists of a carbon price or price distribution for each calendar year.

The ACC Carbon Tool includes several predefined carbon pricings available to all users which you cannot overwrite, delete, or change. You can also add your own carbon pricings, which will be available only to you.

No assumption is made about the units of the carbon price: the prices in the predefined carbon pricings vary. The costs of carbon emissions are calculated by multiplying emissions by the relevant price, so you may wish to ensure that the emissions in your emitter groups and the prices in your carbon pricings are consistent. If they are inconsistent, the actual values of the calculated costs will be meaningless, although the patterns and shapes of the costs might provide useful insights.

You can see the definition of any carbon pricing by selecting it on the Carbon pricings page. A small chart indicates the shape of the prices in the selected carbon pricing.

Each carbon pricing has a unique name, an optional description, and information about the price in each calendar year. The prices have the same type of distribution in each year, but may have different parameters.

If no parameters are present for a particular year, the simulation will use the parameters for the last year for which they are present.

The predefined carbon pricings whose name begins with ACC IEA are based on prices from the scenarios presented in the IEA's World Energy Outlook 2021.

The ACC IEA stated policies carbon pricing is based on the price for the European Union in the Stated Policies scenario. The prices given in the report are $65, $75, and $90 for 2030, 2040 and 2050. Our predefined pricing uses a normal distribution with a mean price of $56 in 2020 with a constant annual growth rate of 1.5%, and a standard deviation of 25% of the mean. This gives mean prices of $65, $75, and $89 for 2030, 2040 and 2050.

The ACC IEA net zero 2050 carbon pricing is based on the price for advanced economies in the Net Zero Emissions by 2050 scenario. The prices given in the report are $130, $205, and $250 for 2030, 2040, and 2050. Our predefined pricing uses a normal distribution with a mean price of $205 in 2040, with an annual growth rate of 4.5% before 2040 and 2% thereafter, and a standard deviation of 25% of the mean. This gives mean prices of $132, $205, and $250 for 2030, 2040, and 2050.

The predefined carbon pricings whose name begins with ACC PRI are based on prices from the scenarios presented in the PRI's Inevitable Policy Response 2021. The Forecast Policy Scenario and the Required Policy Scenario use the same carbon prices. We have used the prices for Europe (including Eastern Europe, Western Europe, and UK) and less developed countries (including Central and South America, Eurasia, Gulf Cooperation Council, Indonesia, Middle East and North Africa, Russia, South Africa, South East Asia and Oceania, and Sub-Saharan Africa) in the predefined pricings ACC PRI Europe and ACC PRI less developed.

The PRI data includes prices for each year from 2020 to 2050. For years after we have assumed a constant growth rate of 4% for Europe and 2% for less developed countries (based on the growth between 2040 and 2050). We have assumed a normal distribution with a standard deviation of 25% of the mean for both.

The ACC Carbon Tool includes a number of predefined carbon pricings based on publicly available information.

Download a file that defines one of the NGFS carbon pricings.

The predefined carbon pricings whose names begin with NGFS have been autogenerated by the ACC Carbon Tool from NGFS data. They use the World Carbon price values generated by three different models to calculate the mean and standard deviation, and specify a normal distribution truncated below at zero (negative carbon prices are not permitted). More information about how NGFS scenarios can be used in the ACC Carbon tool is available on the Specifying the scenarios help page.

Download a file that defines one of the NGFS carbon pricings.

The UK BEIS appraisal predefined carbon pricing is based on the approach to valuing greenhouse gas emissions in policy appraisal published by the UK Department for Business, Energy and Industrial Strategy (BEIS) in 2021, which is available here.

The approach recommends a series of prices based on an anchor value in 2040 of £326 per tonne of CO2 (in £2020 prices), with a constant real annual growth rate of 1.5% for other years. The recommended sensitivity range to capture the uncertainty is plus or minus 50% around the central series. We have taken this to be equivalent to a normal distribution with a standard deviation of 25% of the central estimate.

The ACC Stern-Stiglitz predefined carbon pricing is based on the 2017 Report of the High-Level Commission on Carbon Prices. The Commission was chaired by Nobel Laureate Joseph Stiglitz and Sir Nicholas Stern, and concluded that:

in a supportive policy environment, the explicit carbon-price level consistent with the Paris temperature target is at least US$40–80/tCO2 by 2020 and US$50–100/tCO2 by 2030.

We have interpreted this as a normal distribution with mean price of $60 and standard deviation of $10 in 2020, with a constant annual growth rate of 2.5%.

Add a new carbon pricing by uploading a csv file containing its specification, using the file format described below. You can do this from the Carbon pricing page.

Any carbon pricings that you add will be available only to you. They will be available for up to two weeks after your most recent visit to the site from your current browser. You are advised to keep track of your csv files so that you can upload them again as necessary.

Once a carbon pricing has been uploaded you cannot edit it directly. However, you can upload a new file that overwrites an existing carbon pricing. Make sure you check the Overwrite existing carbon pricing? box

You can delete one of your carbon pricings by uploading a special deletion file, making sure you have checked the Overwrite existing carbon pricing? box. A deletion file contains just two rows:

Carbon pricings are specified in csv (comma separated variable) files. Csv files are plain text files, and can be created from spreadsheet apps such as Excel or text editors such as Notepad++. They consist of a number of rows of data, each row composed of a series of fields separated by commas. Each field can contain either a number or some text. Each field may be surrounded by quotation marks, but does not have to be. However, quotation marks must be used if the field is intended to contain a comma.

Download an example of a csv file specifying a carbon pricing.

Comments can be included in the file in three ways:

A carbon pricing file consists of

The carbon pricing row must be the first row in the file. It must contain three fields:

A distribution row is the second row in the file and must contain at least two fields:

The remaining fields, if any, are the distribution parameters. Distribution parameters are required only for some distributions. See the distributions help page for details.

The first field in the end row must be the word end. All rows in the file after the end row are ignored. This row is optional.