While some of the costs of climate change won’t be incurred for centuries, the actions to mitigate them need to be taken today. Over such a long timespan, small changes in discount rates can drastically change the attractiveness of such investments. This column presents estimates of appropriate discount rates for very long time horizons. The long-run discount rate for one important risky asset class – real estate – is estimated at 2.6%. This provides an upper bound on long-run discount rates for climate change abatement, one that is substantially lower than some of the rates currently being employed.