VOX outlines research estimating the discount rate, for households, at lengths over a century to be 2.6% per year.
Interestingly, that gives a half-life of (just about exactly) 27 years. This means that you’re indifferent between $100 today and $200 received in 27 years, or $400 received in 54 years, or $800 to be received in 81 years.
I strongly advise you to note that this a rate that’s low enough to justify quite a bit of current spending on abatement policies for anthropogenic global warming.
Personally, I still don’t think the statistics warrant being worried, but this definitely suggests that the financial argument against doing something isn’t that strong.
This is based on an NBER paper I’d missed:
Giglio, Stefano, Matteo Maggiori, and Johannes Stroebel (2014), “Very Long-Run Discount Rates.” National Bureau of Economic Research Working Paper 20133.