Research

Food-Water Systems

Changing global climate is increasing risk to agricultural systems and altering where crops and livestock perform best. Our group aims to better understand land-atmosphere interactions in agricultural landscapes, changes to the productivity and distribution of global agricultural lands, the effects of agricultural management on greenhouse gas emissions, and adaptation strategies for agriculture under climate change.

Agriculture is also the largest use of water worldwide, and our group is increasingly considering and quantifying the linkages of resources and impacts among food, water, and energy systems.

Recent and pending publications:

Hong et al., "Impacts of ozone and climate change on yields of perennial crops in California,"
Nature Food | March 16, 2020
Analyzing 35 years of temperature, ozone levels, and crop yields, we estimate the impacts of warming and ozone pollution on perennial fruits and nuts in California. We find ozone damages of about $1 billion per year in recent years.

Qin et al., "Flexibility,intensity, and vulnerability of global water use,"
Nature Sustainability | June 3, 2019
We quantify global water uses and develop a metric for vulnerability related to the flexibility of these uses. We also show the large range of water use intensity at the level of major basins.

Sloat et al., "Increasing importance of precipitation variability on global livestock grazing lands,"
Nature Climate Change | 2018
We find that global pastures experience higher precipitation variability than the rest of the land surface, and that this variability has increased since the beginning of the century, threatening global meat and milk production.

Ecosystem Services

We are also interested in mapping and valuing of ecosystem services to understanding the economic consequences of land degradation on human well-being; understanding links between ecosystem services and underpinning biodiversity; and the implementation of current policies related to biodiversity and ecosystem services and options that exist to safeguard or restore priority areas important for both.

Recent and pending publications:

Bengtsson et al., "Increasing probability of mass mortality during Indian heat waves,"
Ecosphere | 2019
Integrating grasslands into agricultural production systems and land-use decisions locally and regionally can contribute to functional landscapes and food security while enhancing sustainable livelihoods.

Willemen et al., "Identifying ecosystem service hotspots for targeting land degradation neutrality investments in south-eastern Africa,"
J. of Arid Environments | 2018
Ecosystem services that are identified as “important” by diverse stakeholder groups could therefore drive motivations, commitments, and actions towards improved land management, contributing to land degradation neutrality.

La Notte et al., "Ecosystem services classification: A systems ecology perspective of the cascade framework,"
Ecological Indicators | 2017
We argue that ecosystem services should be defined as the interactions (i.e. processes) of the ecosystem that produce a change in human well-being, while ecosystem components or goods, i.e. countable as biomass units, are only proxies in the assessment of such changes.

Energy Systems

Deep decarbonization of electricity and fuels is central to climate goals in California and around the world. We are therefore researching the technological and resource challenges and cost-effective solutions for such radical decarbonization.

Recent and pending publications:

Tong et al., "Committed emissions jeopardize 1.5°C climate target,"
Nature | July 1, 2019
If operated as historically, existing and proposed energy infrastrcuture commit us to ~850 Gt of future CO2 emissions, which is more than the entire carbon budget to limit mean warming to 1.5°C with 50-66% probability, and perhaps two-thirds of the budget required to similarly limit warming to below 2°C.

Davis et al., "Net-zero emissions energy systems,"
Science | June 29, 2018
We review technological opportunities and barriers for eliminating and/or managing difficult-to-decarbonize services, and critical areas for further research, development, demonstration and deployment.

Shaner et al., "Geophysical constraints on the reliability of solar and wind power in the U.S.,"
Energy & Environmental Science | February 27, 2018
We show that meeting >80% of U.S. electricity demand with only solar and wind would require days' or weeks' worth of energy storage--even assuming a continental-scale transmission grid.

Human Health

Our group also conducts research on the effects of climate and other pollution on human health.

Recent and pending publications:

Hong et al., "Radiative effects of aerosols may offset the air quality penalty of climate change,"
Nature Climate Change | 2020
We show that direct radiative effects of short-lived aerosols may substantially offset the "climate penalty" that prior studies have shown (i.e. that future climate change is likely to worsen air quality and thereby human health in most regions by favoring weather conditions that increase concentrations of air pollution).

Mazdiyasni et al., "Increasing probability of mass mortality during Indian heat waves,"
Science Advances | 2017
Even moderate increases in mean temperatures may cause great increases in heat-related mortality and support the efforts of governments and international organizations to build up the resilience of these vulnerable regions to more severe heat waves.

Zhao et al., "Effects of atmospheric transport and trade on air pollution mortality in China,"
Atmospheric Chemistry and Physics | 2017
More than 1/3 of premature deaths caused by China's PM2.5 emissions in 2010 were emitted in a different region of the country than where the deaths occurred, and more than 1.2 were related to goods and services consumed in a different region (or country).

Trade

International and intraregional trade can have a profound affect on the distribution of environmental insults. Quantifying those spatial dislocations is thus a perennial topic of research in our group.

Recent and pending publications:

Guan et al., "Global supply-chain effects of COVID-19 control measures,"
Nature Human Behaviour | 2020
We show that stricter, shorter COVID lockdowns reduce overall losses relative to weaker but longer ones. But even a lengthy period of moderate restrictions is economically preferable to lifting all restrictions if it can avoid the need for another round of strict lockdowns. Regardless, losses propagate via global supply chains; best case responses are globally coordinated.

Stephenson et al., "Future climate impacts of Arctic shipping,"
Geophysical Research Letters | 2018
In the first study to use a fully-coupled Earth system model to look at the future climatic effects of trans-Arctic shipping, we find that clouds formed in response to shipping emissions may offset ~1°C of the overall warming trend in the Arctic by the end of the century.

Meng et al., "The rise of South-South trade and its effect of global CO₂ emissions,"
Nature Communications | 2018
"South-South" trade among developing countries is increasing, and helping to reduce China’s emissions by shifting energy-intensive production to less developed regions. But this may make climate mitigation more challenging; emissions are spread among more and less-developed countries.