Review marginal intensity data

[fershad]

The marginal intensity data included in CO2.js dates back to 2021, and it very much out of date at this time.

The purpose of this issue is to track:

1. Whether we deprecate that data in a future release, or
2. If we keep marginal intensity data, where can we find a reliable, up-to-date source of data

[mrchrisadams]

hey @fershad,

For what it's worth, we had the marginal data when It was the only kind of carbon intensity data that was supported by software carbon intensity as a standard, and we got it from the UNFCCC. I'm not aware of new updated data from the UNFCC being easy to access, It took a bit of work to get it last time.

I'm not sure who uses it, and I'm not aware of any high profile users of the marginal data we have in CO2.js. I think it's a good candidate for deprecation in the future. Thanks for raising it.