We use machine learning algorithms to construct a novel news-based index of US environmental
and climate policy uncertainty (EnvPU) available on a monthly basis over the 1990-2019 period.
We find that our EnvPU index spikes during the environmental spending disputes of the
1995-1996 government shutdown, in the early 2010s due the failure of the national cap-and-trade
climate bill and during the Trump presidency. We examine how elevated levels of environmental
policy uncertainty relate to investments in the low-carbon economy. In firm-level estimations, we
find that a rise in the EnvPU index is associated with a reduced probability for cleantech startups
to receive venture capital (VC) funding. In financial markets, a rise in our EnvPU index is
associated with higher stock volatility for firms with above-average green revenue shares. At the
macro level, shocks in our index lead to declines in the number of cleantech VC deals and higher
volatility of the main benchmark clean energy exchange-traded fund. Overall, our results are
consistent with the notion that policy uncertainty has adverse effects on investments for the low-
carbon economy.