Nitrogen oxides (NOx = NO2 + NO) are a highly regulated species that play a major role in the formation of photochemical smog. While NOx emissions are generally decreasing over the U.S. as a result of more stringent environmental policies and improved emissions control technologies, the shale oil and natural gas industry is reversing this rate of changes in certain regions. We present here a quantitative analysis of NOx levels over the seven main U.S. shale plays (Bakken, Eagle Ford, Permian, Niobrara-Codell, Marcellus-Utica, Haynesville, and Barnett) between 2005 and 2015 using measurements of tropospheric NO2 from the Ozone Monitoring Instrument (OMI) aboard the NASA EOS-Aura aircraft. We develop and apply a methodology that seeks to maximise pollutant signals from oil and gas activities. For reference, we also examine the national trend averaged over the lower 48 states. Consistent with previous studies, we find NOx across the U.S. is generally declining. During the low-production phase of oil and natural gas production (2005–2009), we find declining trends in tropospheric NOx that are similar to the national trend (–4.6% yr–1) in 6 of the 7 study regions (–8 to –2% yr–1). In the high-production phase (2010–15), we find an increasing NOx trend in 5 of the 7 study basins (0.4 to 4.5% yr–1) while the national trend continued to decline (–0.3% yr–1). Over the most intensive oil-producing shale plays (Bakken, Eagle Ford, Permian and Niobrara-Codell), we observe a rapid growth (1–4.5% yr–1), which correlates well (r2 = 0.6–0.9) with their annual oil production rates and/or drilling rigs. In contrast, trends across the mainly gas-producing regions (Haynesville, Barnett, and Marcellus-Utica) show decreases (–0.4 to –1.7% yr–1) similar to the national trend, with the exception of the Marcellus-Utica where a slight increase (0.4 ± 0.2% yr–1) may be an indication of a small regional increase. Our study shows the important decadal effect that shale oil and natural gas operations has had on the tropospheric NO2 levels, and the potential consequences for regional air quality.

The water and wastewater sectors of England and Wales (E&W) are energy-intensive. Although E&W’s water sector is of international interest, in particular due to the early experience with privatisation, for the time being, few published data on energy usage exist. We analysed telemetry energy-use data from Thames Water Utilities Ltd. (TWUL), the largest water and wastewater company in the UK, which serves one of the largest mega-cities in the world, London. In our analysis, we: (1) break down energy use into their components; (2) present a statistical approach to handling seasonal and random cycles in data; and (3) derive energy-intensity (kWh m⁻³) metrics and compare them with other regions in the world. We show that electricity use in the sector grew by around 10.8 ± 0.4% year⁻¹ as the utility coped with growing demands and stormwater flooding. The energy-intensity of water services in each of the utility’s service zone was measured in the range 0.46–0.92 kWh m⁻³. Plans to improve the efficiency of the system could yield benefits in lower energy-intensity, but the overall energy saving would be temporary as external pressures from population and climate change are driving up water and energy use.

Energy system modelling can be used to provide scenario-based insights in energy system transition pathways. However, data accessibility is a common barrier for the model representation of energy systems, both regarding existing infrastructure, as well as planned developments consistent with current policies. This paper describes the ‘Global Transmission Database’, the first global dataset covering existing and planned electricity transmission developments between countries and selected regions. The dataset can be used as a starting point for the representation of cross-regional electricity grids globally in energy system models and other computational tools. All data is collected from publicly available sources and combined into a single machine-readable format for convenient application.

Urban water utilities are increasing their use of energy-intensive technologies such as desalination and long-distanced pumped transfers. Under pressure to reduce their energy-related carbon emissions to zero, water utilities have devised a variety of energy management strategies, including the purchase of renewable energy and self-generation of electricity using locally installed renewables. These strategies will incur different costs for the utility, whilst some may have implications for the reliability of water supply systems. Yet the trade-offs between costs, water security and energy sustainability remain unexplored. Here, we present a regional scale analysis to test competing energy strategies, mapping pathways to zero carbon energy and water security. Results from a case-study of the London water system show a balanced approach that allows for some energy self-generation, using biogas, solar and wind, while also purchasing green energy credits from the electricity supply grid can best navigate this trade-off. Balanced investment plans can accommodate energy-intensive water supply techniques such as long-distance transfers, desalination and effluent reuse while meeting energy targets. By becoming energy generators and also adopting more flexible arrangements for energy use, water utilities could become significant players in energy markets.