Kevin Lewis

November 03, 2021

Estimating a social cost of carbon for global energy consumption
Ashwin Rode et al.
Nature, 14 October 2021, Pages 308–314

Estimates of global economic damage caused by carbon dioxide (CO2) emissions can inform climate policy. The social cost of carbon (SCC) quantifies these damages by characterizing how additional CO2 emissions today impact future economic outcomes through altering the climate. Previous estimates have suggested that large, warming-driven increases in energy expenditures could dominate the SCC, but they rely on models that are spatially coarse and not tightly linked to data. Here we show that the release of one ton of CO2 today is projected to reduce total future energy expenditures, with most estimates valued between −US$3 and −US$1, depending on discount rates. Our results are based on an architecture that integrates global data, econometrics and climate science to estimate local damages worldwide. Notably, we project that emerging economies in the tropics will dramatically increase electricity consumption owing to warming, which requires critical infrastructure planning. However, heating reductions in colder countries offset this increase globally. We estimate that 2099 annual global electricity consumption increases by about 4.5 exajoules (7 per cent of current global consumption) per one-degree-Celsius increase in global mean surface temperature (GMST), whereas direct consumption of other fuels declines by about 11.3 exajoules (7 per cent of current global consumption) per one-degree-Celsius increase in GMST. Our finding of net savings contradicts previous research, because global data indicate that many populations will remain too poor for most of the twenty-first century to substantially increase energy consumption in response to warming. Importantly, damage estimates would differ if poorer populations were given greater weight. 

National growth dynamics of wind and solar power compared to the growth required for global climate targets
Aleh Cherp et al.
Nature Energy, July 2021, Pages 742–754

Climate mitigation scenarios envision considerable growth of wind and solar power, but scholars disagree on how this growth compares with historical trends. Here we fit growth models to wind and solar trajectories to identify countries in which growth has already stabilized after the initial acceleration. National growth has followed S-curves to reach maximum annual rates of 0.8% (interquartile range of 0.6–1.1%) of the total electricity supply for onshore wind and 0.6% (0.4–0.9%) for solar. In comparison, one-half of 1.5 °C-compatible scenarios envision global growth of wind power above 1.3% and of solar power above 1.4%, while one-quarter of these scenarios envision global growth of solar above 3.3% per year. Replicating or exceeding the fastest national growth globally may be challenging because, so far, countries that introduced wind and solar power later have not achieved higher maximum growth rates, despite their generally speedier progression through the technology adoption cycle. 

Electricity consumption changes following solar adoption: Testing for a solar rebound
Ross Beppler, Daniel Matisoff & Matthew Oliver
Economic Inquiry, forthcoming

We use household-level data to explore residential electricity use patterns following installation of solar panels. Solar adoption leads to an increase in total electricity consumption relative to a matched non-adopting control group. Our point estimate translates to a rebound effect of 28.5%, suggesting that nearly a third of the electricity produced by a customer's solar panels is used for increased energy services, rather than reduced grid electricity consumption. We explore several potential drivers of an increase in electricity consumption. These results have important implications for electricity planning and policy, suggesting that rooftop solar stimulates additional demand for electricity. 

Do genetically fragmented societies respond less to global warming? Diversity and climate change policies
Trung Vu
Energy Economics, forthcoming

This research empirically establishes that interpersonal population diversity helps explain worldwide differences in climate change policies. It advances the hypothesis that heterogeneity in the composition of genetic traits, originating from the prehistoric course of the exodus of Homo sapiens from East Africa tens of thousands of years ago, is a major barrier to implementing stringent climate-friendly policies and measures. The underlying intuition is that genetically fragmented societies, characterized by mistrust, preference heterogeneity and persistent poor-quality institutions, find it difficult to sustain collective climate action. Using data for 84 world economies, I find evidence that prehistorically determined genetic diversity has a negative influence on the stringency of climate-related policies and measures. Furthermore, I document that descendants of ancestral societies with greater genetic diversity are less likely to exhibit pro-climate behaviour, consistent with a mechanism of inter-generational transmission of cultural norms of mistrust and non-cooperation. The findings suggest that strengthening responses to changing climate conditions requires considering the long-term legacy of interpersonal population diversity.\ 

Environmental Drivers of Agricultural Productivity Growth: CO2 Fertilization of US Field Crops
Charles Taylor & Wolfram Schlenker
NBER Working Paper, October 2021

We assess the CO2 fertilization effect on US agriculture using spatially-varying CO2 data from NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite covering the majority of US cropland under actual growing conditions. This study complements the many CO2 enrichment experiments that have found important interactions between CO2 and local environmental conditions in controlled settings. We use three empirical strategies: (i) a panel of CO2 anomalies and county yields, (ii) a panel of spatial first-differences between neighboring counties, and (iii) a cross-sectional spatial first-difference. We find consistently high fertilization effects: a 1 ppm increase in CO2 equates to a 0.5%, 0.6%, and 0.8% yield increase for corn, soybeans, and wheat, respectively. Viewed retrospectively, 10%, 30%, and 40% of each crop's yield improvements since 1940 are attributable to rising CO2. 

Recent increases in tropical cyclone precipitation extremes over the US east coast
Justin Maxwell et al.
Proceedings of the National Academy of Sciences, 12 October 2021

The impacts of inland flooding caused by tropical cyclones (TCs), including loss of life, infrastructure disruption, and alteration of natural landscapes, have increased over recent decades. While these impacts are well documented, changes in TC precipitation extremes — the proximate cause of such inland flooding — have been more difficult to detect. Here, we present a latewood tree-ring–based record of seasonal (June 1 through October 15) TC precipitation sums (ΣTCP) from the region in North America that receives the most ΣTCP: coastal North and South Carolina. Our 319-y-long ΣTCP reconstruction reveals that ΣTCP extremes (≥0.95 quantile) have increased by 2 to 4 mm/decade since 1700 CE, with most of the increase occurring in the last 60 y. Consistent with the hypothesis that TCs are moving slower under anthropogenic climate change, we show that seasonal ΣTCP along the US East Coast are positively related to seasonal average TC duration and TC translation speed. 

Influence of the Atlantic meridional overturning circulation on the U.S. extreme cold weather
Jianjun Yin & Ming Zhao
Communications Earth & Environment, October 2021

Due to its large northward heat transport, the Atlantic meridional overturning circulation influences both weather and climate at the mid-latitude Northern Hemisphere. Here we use a state-of-the-art global weather/climate modeling system with high resolution (GFDL CM4C192) to quantify this influence focusing on the U.S. extreme cold weather during winter. We perform a control simulation and the water-hosing experiment to obtain two climate states with and without a vigorous Atlantic meridional overturning circulation. We find that in the control simulation with an overturning circulation, the U.S. east of the Rockies is a region characterized by intense north-south heat exchange in the atmosphere during winter. Without the northward heat transport by the overturning circulation in the hosing experiment, this channel of atmospheric heat exchange becomes even more active through the Bjerknes compensation mechanism. Over the U.S., extreme cold weather intensifies disproportionately compared with the mean climate response after the shutdown of the overturning circulation. Our results suggest that an active overturning circulation in the present-day climate likely makes the U.S. winter less harsh and extreme. 

Global potential for harvesting drinking water from air using solar energy
Jackson Lord et al.
Nature, 28 October 2021, Pages 611–617

Access to safely managed drinking water (SMDW) remains a global challenge, and affects 2.2 billion people. Solar-driven atmospheric water harvesting (AWH) devices with continuous cycling may accelerate progress by enabling decentralized extraction of water from air, but low specific yields (SY) and low daytime relative humidity (RH) have raised questions about their performance (in litres of water output per day). However, to our knowledge, no analysis has mapped the global potential of AWH despite favourable conditions in tropical regions, where two-thirds of people without SMDW live. Here we show that AWH could provide SMDW for a billion people. Our assessment — using Google Earth Engine — introduces a hypothetical 1-metre-square device with a SY profile of 0.2 to 2.5 litres per kilowatt-hour (0.1 to 1.25 litres per kilowatt-hour for a 2-metre-square device) at 30% to 90% RH, respectively. Such a device could meet a target average daily drinking water requirement of 5 litres per day per person. We plot the impact potential of existing devices and new sorbent classes, which suggests that these targets could be met with continued technological development, and well within thermodynamic limits. Indeed, these performance targets have been achieved experimentally in demonstrations of sorbent materials. Our tools can inform design trade-offs for atmospheric water harvesting devices that maximize global impact, alongside ongoing efforts to meet Sustainable Development Goals (SDGs) with existing technologies. 

Earth's Albedo 1998–2017 as Measured From Earthshine
Philip Goode et al.
Geophysical Research Letters, 8 September 2021

The reflectance of the Earth is a fundamental climate parameter that we measured from Big Bear Solar Observatory between 1998 and 2017 by observing the earthshine using modern photometric techniques to precisely determine daily, monthly, seasonal, yearly and decadal changes in terrestrial albedo from earthshine. We find the inter-annual fluctuations in albedo to be global, while the large variations in albedo within individual nights and seasonal wanderings tend to average out over each year. We measure a gradual, but climatologically significant ~0.5 W/m^2 decline in the global albedo over the two decades of data. We found no correlation between the changes in the terrestrial albedo and measures of solar activity. The inter-annual pattern of earthshine fluctuations are in good agreement with those measured by CERES (data began in 2001) even though the satellite observations are sensitive to retroflected light while earthshine is sensitive to wide-angle reflectivity. The CERES decline is about twice that of earthshine. 

Rethinking Salt Supply Chains: Cost and Emissions Analysis for Coproduction of Salt and Fresh Water from U.S. Seawater
Greys Sošić
Management Science, forthcoming

Is it feasible to build desalination plants for the coproduction of salt and fresh water from U.S. seawater that could lead to a restructuring of supply chains for salt imports? As it is predicted that climate change will increase water stress worldwide, an increasing number of countries are using desalination plants to generate fresh water. In most such cases, residual concentrates must be disposed of, and the disposal cost is increasing as countries are becoming more environmentally conscious. Selective salt recovery can help to alleviate this issue as it reduces the need for concentrate disposal and generates additional revenue. To gain some insights into the costs and benefits of coproduction plants, we have collected data on current desalination practices and salt imports in the United States along with the manufacturing costs and energy requirements for coproduction plants. We have used this data to build an optimization model to determine an optimal number and location of coproduction plants in the United States and their potential markets for the sale of coproduced salt. In our analysis, we consider a different total number of coproduction facilities, and for each configuration, we evaluate the resulting net water cost and carbon emissions impact. Our results indicate that there exists the potential for building several coproduction plants in the United States that would be both financially competitive with existing desalination plants and lead to a reduction in carbon emissions. This information might be of use to both governments and businesses when they make decisions about the type of desalination facilities built and the implemented “polluter pays” policies. 

Enhanced hydrological cycle increases ocean heat uptake and moderates transient climate change
Maofeng Liu et al.
Nature Climate Change, October 2021, Pages 848–853

The large-scale moistening of the atmosphere in response to increasing greenhouse gases amplifies the existing patterns of precipitation minus evaporation (P − E), which, in turn, amplifies the spatial contrast in sea surface salinity. Here, by performing a series of transient CO2 doubling experiments, we demonstrate that surface salinification driven by the amplified dry conditions (P − E < 0), primarily in the subtropical ocean, accelerates ocean heat uptake. The salinification also drives the sequestration of upper-level heat into the deeper ocean, reducing the thermal stratification and increasing the heat uptake through positive feedback. The change in Atlantic Meridional Overturning Circulation due to salinification has a secondary role in heat uptake. Consistent with the heat uptake changes, the transient climate response would increase by approximately 0.4 K without this process. Observed multidecadal changes in subsurface temperature and salinity resemble those simulated, indicating that anthropogenically forced changes in salinity are probably enhancing ocean heat uptake.


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