## Social cost of carbon

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Vermont
Posts: 1
Joined: Fri Jan 02, 2015 9:54 am

### Social cost of carbon

How recently was the default value for the price of carbon updated (currently at \$71.21/short ton C) in iTree Eco?

Thanks!
Jason.Henning
i-Tree Team
Posts: 172
Joined: Fri Dec 21, 2012 7:45 am

### Re: Social cost of carbon

The carbon value numbers come from this paper (http://www.itreetools.org/eco/resources ... b_2010.pdf) which estimates the Social Cost of Carbon. The \$71.21 value was calculated from values given in the table in the Executive Summary on Page 1. The value used is reported in the table for the 3% discount rate in 2010. This value of \$21.4 is for a metric ton of CO2. So it is converted to a metric ton of C and then to short tons. This conversion looks like:

1. The ratio of CO2 to C is 44/12 based on the atomic weights of C=12 and O=16
So the value per metric ton of carbon is \$21.4/mT CO2 * 44 mT CO2/12mT C = \$78.47/mT C.

2. Then to convert from metric tons to short tons.
\$78.47/mT C *1 mT/1.102short ton =\$71.21/short ton of C.

If you take a look at the paper linked above you will see that the value was estimated for 2010 and is in 2007 dollars. If you would like, you could use the 2015 value from that table and use an online conversion tool to convert 2007 dollars to 2015 dollars to find an updated value. You could then use this updated value in i-Tree Eco by going to the "Edit" menu, select "Benefit Prices" and then plugg in your desired value in the "Price of carbon" field.

Thanks for the question,
Jason
A member of the i-Tree Team
Jason.Henning
i-Tree Team
Posts: 172
Joined: Fri Dec 21, 2012 7:45 am

### Re: Social cost of carbon

UPDATE - As of 5/26/15 the carbon valuation has been updated in the i-Tree Suite

We have updated our carbon value from \$78.5 per metric ton of carbon to \$139.33. The new value comes from the following paper:

https://www.whitehouse.gov/sites/defaul ... update.pdf

From Table 2, page 13 of the document, we used the 3.0% average discount rate of the 2015 social cost of carbon dioxide (\$38 per metric ton) and converted it to \$139.33 per metric ton of carbon by multiplying by 44 mT CO2/12mT C.
A member of the i-Tree Team
Jason.Henning
i-Tree Team
Posts: 172
Joined: Fri Dec 21, 2012 7:45 am

### Re: Social cost of carbon

UPDATE: As of 2/21/17 i-Tree Eco is using the following Carbon valuation

Currently i-Tree Eco uses a value of \$146.66 per metric tonne. This value comes from this more recently updated Social Cost of Carbon Document, https://www.epa.gov/sites/production/fi ... t_2016.pdf. That document gives a 3% discount rate number for 2015 of \$36/metric tonne of CO2 (in 2007 dollars). This value was update conservatively from 2007 dollars to 2017 dollars to reach a value of \$39/metric tonne of CO2 (in 2017) dollars. This converts to the \$143.00 per metric tonne number using \$49/ metric tonne of CO2 * 44 metric tonne CO2/12 metric tonne C.
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Dan_Buckler
Posts: 3
Joined: Wed Jul 17, 2019 10:37 am

### Re: Social cost of carbon

Did the social cost change again? When I calculate carbon benefits of places, and divide the dollars by the short tons (in the benefits tab), I get about \$170.55/short ton. This is different than the \$129.76/short ton (\$143/metric) listed here and elsewhere. Or am I doing something wrong?
Erika.Teach
Posts: 12
Joined: Fri Feb 12, 2016 2:59 pm

### Re: Social cost of carbon

Hello Dan,
Yes, U.S. Carbon and CO2 dollar valuations have been updated to:
⦁ Carbon price per 1 metric ton is \$188.
⦁ CO2 equivalent price per 1 metric ton is \$188/3.67 or approximately \$51.22.
⦁ These values are taken from the Social Cost of Carbon (https://www.epa.gov/sites/production/fi ... t_2016.pdf) and are adjusted to 2018 dollars.
⦁ Eco previously used \$145.95 per metric ton of carbon.
Dan_Buckler
Posts: 3
Joined: Wed Jul 17, 2019 10:37 am

### Re: Social cost of carbon

Hi Erika, thanks so much for the quick reply! I don't know how easy it would be to change, but the Landscape reference page could then be changed to reflect that update. It currently says the 2017 value of carbon is \$143 / metric ton. Thanks again for your help.