Muddying the Waters
Robbing Peter to Pay Paul: The Impact of California’s Cap-and-Trade Program on Toxic Emissions
Narae Lee & Aseem Kaul
Management Science, June 2025, Pages 5409-5418
Abstract:
We empirically examine the consequences of the introduction of a cap-and-trade program in California, showing that although the program helped reduce greenhouse gas (GHG) emissions, it had the unintended consequence of increasing toxic emissions from treated facilities, as facilities cut back on their waste-treatment efforts to reduce GHG emissions. We further show that this effect was weaker for more harmful toxins, for facilities that had invested in reducing toxic waste at source, and for those that were subject to close scrutiny from regulators, consistent with it being the result of strategic firm actions.
From Tank to Odometer: Winners and Losers from a Gas-to-VMT Tax Shift
Christopher Knittel, Gilbert Metcalf & Shereein Saraf
NBER Working Paper, June 2025
Abstract:
With the increase in fuel economy of the personal transportation fleet along with the increased penetration of hybrid and electric vehicles, federal motor vehicle fuel excise tax revenue has been steadily declining. This has led to calls for finding a replacement for this tax. One option is to replace the gas tax with a vehicle miles traveled (VMT) tax. To investigate the impact of such a tax swap, we combine data from the 2017 National Household Transportation Survey (NHTS) and the American Community Survey (ACS). Using machine learning techniques, we generate estimates of VMT and gasoline tax collections at the census tract level. This allows us to explore the distributional implications of this tax swap at a geographically disaggregated level. We find, as have previous researchers, that this tax swap is modestly progressive. Our more granular geographic analysis highlights striking disparities not previously reported. We find that rural areas and census tracts in the center of the country generally benefit from this tax swap, while urban and bicoastal areas generally experience higher taxation. Additionally, Republican-leaning districts, which overlap significantly with rural areas, see marked gains compared to Democratic districts.
Climbing the Energy Ladder: How Energy Resources Hinder, Facilitate, and Fuel Economic Growth
Derek Lemoine
NBER Working Paper, May 2025
Abstract:
I show that the nature of the energy resources available to an economy qualitatively determines long-run growth outcomes. A harvested resource such as biomass drags on growth, a mined resource such as coal enables output per capita to hold constant, and both a tapped resource such as oil and a manufactured resource such as solar panels risk degrowth if energy return on energy invested (EROI) cannot stay above a threshold. The only energy resource that can fuel long-run growth is a manufactured resource such as solar panels. Either that resource must rely on substitutable energy inputs that have a sufficiently large EROI, or it must be produced by robots that are themselves produced from robots and energy. Even in these cases, coal and oil economies may have been necessary stages on the way from a biomass economy to a solar economy.
The Drivers of Science Referenced in US EPA Regulatory Impact Analyses: Open Access, Professional Popularity, and Agency Involvement
Tyler Scott, Sojeong Kim & Liza Wood
Regulation & Governance, forthcoming
Abstract:
We perform bibliometric analysis on documents for 255 Regulatory Impact Analyzes (RIAs) prepared by the US Environmental Protection Agency (EPA) from 1980 through 2024. Using a series of automated information extraction methods, we extract references from these documents and match them to bibliographic records. We then build a database of relevant articles (whether cited in an RIA or not) and fit a two-stage regression model that predicts whether, and how many times, a reference is used in RIAs as a function of journal prestige, professional popularity, article accessibility, EPA funding, and involvement of EPA employees as co-authors. By considering cited and uncited articles related to similar scientific concepts, we can observe systematic differences in what types of research products get used in policy analysis. Academic popularity, open access status, and EPA authorship and sponsorship all predict more likely and more frequent article use. Articles in prestigious journals are no more likely to be referenced, but once referenced in the corpus are then referenced more frequently.
Bioremediation of complex organic pollutants by engineered Vibrio natriegens
Cong Su et al.
Nature, forthcoming
Abstract:
Industrial wastewater, petroleum pollution and plastic contamination are significant threats to global marine biosecurity because of their toxic, mutagenic and persistent nature. The use of microorganisms in bioremediation has been constrained by the complexity of organic pollutants and limited tolerance to saline stress. In this study, we used synthetic biology to engineer Vibrio natriegens into a strain capable of bioremediating complex organic pollutants in saline wastewater and soils. The competence master regulator gene tfoX was inserted into chromosome 1 of the V. natriegens strain Vmax and overexpressed to enhance DNA uptake and integration. Degradation gene clusters were chemically synthesized and assembled in yeast. We developed a genome engineering method (iterative natural transformation based on Vmax with amplified tfoX effect) to transfer five gene clusters (43 kb total) into Vmax. The engineered strain has the ability to bioremediate five organic pollutants (biphenyl, phenol, naphthalene, dibenzofuran and toluene) covering a broad substrate range, from monocyclic to multicyclic compounds, in industrial wastewater samples from a chlor–alkali plant and a petroleum refinery.
Greenhouse gases reduce the satellite carrying capacity of low Earth orbit
William Parker, Matthew Brown & Richard Linares
Nature Sustainability, April 2025, Pages 363-372
Abstract:
Anthropogenic contributions of greenhouse gases in Earth’s atmosphere have been observed to cause cooling and contraction in the thermosphere, which is projected to continue for many decades. This contraction results in a secular reduction in atmospheric mass density where most satellites operate in low Earth orbit. Decreasing density reduces drag on debris objects and extends their lifetime in orbit, posing a persistent collision hazard to other satellites and risking the cascading generation of more debris. This work uses projected CO2 emissions from the shared socio-economic pathways to investigate the impact of greenhouse gas emissions on the satellite carrying capacity of low Earth orbit. The instantaneous Kessler capacity is introduced to compute the maximum number and optimal distribution of characteristic satellites that keep debris populations in stable equilibrium. Modelled CO2 emissions scenarios from years 2000–2100 indicate a potential 50–66% reduction in satellite carrying capacity between the altitudes of 200 and 1,000 km. Considering the recent, rapid expansion in the number of satellites in low Earth orbit, understanding environmental variability and its impact on sustainable operations is necessary to prevent over-exploitation of the region.
Increasing boreal fires reduce future global warming and sea ice loss
Edward Blanchard-Wrigglesworth, Patricia DeRepentigny & Dargan Frierson
Proceedings of the National Academy of Sciences, 10 June 2025
Abstract:
Biomass burning can affect climate via the emission of aerosols and their subsequent impact on radiation, cloud microphysics, and surface and atmospheric albedo. Biomass burning emissions (BBEs) over the boreal region have strongly increased during the last decade and are expected to continue increasing as the climate warms. Climate models simulate aerosol processes, yet historical and future Coupled Model Intercomparison Project (CMIP) simulations have no active fire component, and BBEs are prescribed as external forcings. Here, we show that CMIP6 used future boreal BBEs scenarios with unrealistic near-zero trends that have a large impact on climate trends. By running sensitivity experiments with ramped up boreal emissions based on observed trends, we find that increasing boreal BBEs reduces global warming by 12% and Arctic warming by 38%, reducing the loss of sea ice. Tropical precipitation shifts southward as a result of the hemispheric difference in boreal aerosol forcing and subsequent temperature response. These changes stem from the impact of aerosols on clouds, increasing cloud droplet number concentration, cloud optical depth, and low cloud cover, ultimately reducing surface shortwave flux over northern latitudes. Our results highlight the importance of realistic boreal BBEs in climate model simulations and the need for improved understanding of boreal emission trends and aerosol–climate interactions.
Declining coral calcification to enhance twenty-first-century ocean carbon uptake by gigatons
Lester Kwiatkowski et al.
Proceedings of the National Academy of Sciences, 10 June 2025
Abstract:
The sensitivity of coral reefs to climate change is well established. As the oceans warm and acidify, the calcification of coral reefs declines with net calcium carbonate dissolution projected under even moderate emissions trajectories. The impact of this on the global carbon cycle is however yet to be accounted for. Here, we use a synthesis of the sensitivity of coral reef calcification to climate change, alongside reef distribution products to estimate alkalinity and dissolved inorganic carbon fluxes resulting from reductions in reef calcification. Using a global ocean biogeochemical model, we simulate the impact on ocean carbon uptake under different emissions scenarios, accounting for uncertainty in present-day calcification rates. Reductions in net coral reef carbonate production can enhance the ocean carbon sink by up to 1.25 GtCO2 y−1 by midcentury (0.48 GtCO2 y−1 median estimate) with cumulative ocean carbon uptake up to 13% greater by 2300 (7% median estimate). Our findings indicate that accounting for the coral reef feedback in projections will increase estimates of the remaining carbon budget associated with global warming thresholds, as well as the likelihood that net zero emissions can be achieved without negative emissions.
Increased flood exposure in the Pacific Northwest following earthquake-driven subsidence and sea-level rise
Tina Dura et al.
Proceedings of the National Academy of Sciences, 6 May 2025
Abstract:
Climate-driven sea-level rise is increasing the frequency of coastal flooding worldwide, exacerbated locally by factors like land subsidence from groundwater and resource extraction. However, a process rarely considered in future sea-level rise scenarios is sudden (over minutes) land subsidence associated with great (>M8) earthquakes, which can exceed 1 m. Along the Washington, Oregon, and northern California coasts, the next great Cascadia subduction zone earthquake could cause up to 2 m of sudden coastal subsidence, dramatically raising sea level, expanding floodplains, and increasing the flood risk to local communities. Here, we quantify the potential expansion of the 1% floodplain (i.e., the area with an annual flood risk of 1%) under low (~0.5 m), medium (~1 m), and high (~2 m) earthquake-driven subsidence scenarios at 24 Cascadia estuaries. If a great earthquake occurred today, floodplains could expand by 90 km2 (low), 160 km2 (medium), or 300 km2 (high subsidence), more than doubling the flooding exposure of residents, structures, and roads under the high subsidence scenario. By 2100, when climate-driven sea-level rise will compound the hazard, a great earthquake could expand floodplains by 170 km2 (low), 240 km2 (medium), or 370 km2 (high subsidence), more than tripling the flooding exposure of residents, structures, and roads under the high subsidence scenario compared to the 2023 floodplain. Our findings can support decision-makers and coastal communities along the Cascadia subduction zone as they prepare for compound hazards from the earthquake cycle and climate-driven sea-level rise and provide critical insights for tectonically active coastlines globally.
What Matters for Electrification? Evidence from 70 Years of U.S. Home Heating Choices
Lucas Davis
Review of Economics and Statistics, May 2025, Pages 668-684
Abstract:
The percentage of U.S. homes heated with electricity has increased steadily from 1% in 1950 to 40% in 2020. Energy prices, geography, climate, housing characteristics, and income are shown to explain 90% of the increase, with energy prices by far the most important factor. The paper then estimates the cost of an electrification mandate for new homes. Households in warm states tend to prefer electricity anyway, so would be made worse off by less than $350 annually on average. Households in cold states, however, tend to prefer natural gas so would be made worse off by more than $1000 annually.