According to a new report from Stanford University, titled “Drought impacts on the western system, emissions, and air quality in the western United States,” climate-driven changes in drought levels could disrupt electricity systems that depend heavily on hydropower, potentially creating an increased need for generation from fossil fuel sources.

Impacts from the associated emissions and air pollution could represent a large and unaccounted-for social cost of climate change. “Damages through these channels are estimated to be 1.2 to 2.5x the increase in direct economic cost of drought-induced fossil fuel electricity generation,” said the report. “Under future climate, these drought-induced impacts likely remain large due to increasing drought risks, and we find that even rapid expansion of renewable energy has limited ability to curb these impacts.”

Going into more detail, the report noted that the western United States has experienced severe drought in recent decades, and climate models project increased drought risk in the future. This increased drying could have important implications for the region’s interconnected, hydropower-dependent electricity systems.

“Using power-plant level generation and emissions data from 2001 to 2021, we quantify the impacts of drought on the operation of fossil fuel plants and the associated impacts on greenhouse gas (GHG) emissions, air quality, and human health,” said the report. “We find that under extreme drought, electricity generation from individual fossil fuel plants can increase up to 65% relative to average conditions, mainly due to the need to substitute for reduced hydropower.”

Over 54 percent of this drought-induced generation is transboundary, with drought in one electricity region leading to net imports of electricity, and thus increased pollutant emissions, from power plants in other regions. The report added that these drought-induced emission increases have detectable impacts on local air quality, as measured by proximate pollution monitors.

“We estimate that the monetized costs of excess mortality and GHG emissions from drought-induced fossil generation are 1.2 to 2.5x the reported direct economic costs from lost hydro production and increased demand,” said the report.

Combining climate model estimates of future drying with stylized energy-transition scenarios suggests that these drought-induced impacts are likely to remain large even under aggressive renewables expansion, suggesting that more ambitious and targeted measures are needed to mitigate the emissions and health burden from the electricity sector during drought.