High impact startup idea: make a decent carbon emissions model for flights.

Current ones simply use flight emissions which makes direct flights look low-emission. But in reality, some of these flights wouldn't even be there if people could be spread over existing indirect flights more efficiently, which is why they're cheaper too. Emission models should be relative to counterfactual.

The startup can be for-profit. If you're lucky, better models already exist in scientific literature. Ideal for the AI for good-crowd.

My guess is that a few man-years work could have a big carbon emissions impact here.