I bet all environmental economists know about MAC (Marginal Abatement/Control Cost) and MDC (Marginal Damage Cost). In terms of climate change mitigation, the MAC curves could be useful in presenting different alternative projects and policies for decision making.
MAC Tool (by Sustain Success Ltd.) is an Excel add-in that can help constructing the curves, which I recently got to know about from reviewing a PhD thesis in National Economics University Vietnam. The PhD candidate had to buy it for $30, but now it is free of charge here.
The software is fairly simple and easy to use, but it could produce some intuitive results for policy makers.
P/S: If you are interested in analyzing climate change, some more tools could be found in NDC Partnership website (e.g. Cost of Renewable Energy Spreadsheet Tool – CREST, COBRA and Climate Change and Health)