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Historically, human uses of land have transformed and fragmented ecosystems.sup.1,2, degraded biodiversity.sup.3,4, disrupted carbon and nitrogen cycles.sup.5,6 and added prodigious quantities of greenhouse gases (GHGs) to the atmosphere.sup.7,8. However, in contrast to fossil-fuel carbon dioxide (CO.sub.2) emissions, trends and drivers of GHG emissions from land management and land-use change (together referred to as 'land-use emissions') have not been as comprehensively and systematically assessed. Here we present country-, process-, GHG- and product-specific inventories of global land-use emissions from 1961 to 2017, we decompose key demographic, economic and technical drivers of emissions and we assess the uncertainties and the sensitivity of results to different accounting assumptions. Despite steady increases in population (+144 per cent) and agricultural production per capita (+58 per cent), as well as smaller increases in emissions per land area used (+8 per cent), decreases in land required per unit of agricultural production (-70 per cent) kept global annual land-use emissions relatively constant at about 11 gigatonnes CO.sub.2-equivalent until 2001. After 2001, driven by rising emissions per land area, emissions increased by 2.4 gigatonnes CO.sub.2-equivalent per decade to 14.6 gigatonnes CO.sub.2-equivalent in 2017 (about 25 per cent of total anthropogenic GHG emissions). Although emissions intensity decreased in all regions, large differences across regions persist over time. The three highest-emitting regions (Latin America, Southeast Asia and sub-Saharan Africa) dominate global emissions growth from 1961 to 2017, driven by rapid and extensive growth of agricultural production and related land-use change. In addition, disproportionate emissions are related to certain products: beef and a few other red meats supply only 1 per cent of calories worldwide, but account for 25 per cent of all land-use emissions. Even where land-use change emissions are negligible or negative, total per capita CO.sub.2-equivalent land-use emissions remain near 0.5 tonnes per capita, suggesting the current frontier of mitigation efforts. Our results are consistent with existing knowledge--for example, on the role of population and economic growth and dietary choice--but provide additional insight into regional and sectoral trends. Trends in the rate of region- and sector-specific land-use greenhouse gas emissions in 1961-2017 show an acceleration of about 20% per decade after 2001., Author(s): Chaopeng Hong [sup.1] , Jennifer A. Burney [sup.2] , Julia Pongratz [sup.3] [sup.4] , Julia E. M. S. Nabel [sup.4] , Nathaniel D. Mueller [sup.5] [sup.6] , Robert B. [...]

Solar radiation management is increasingly considered to be an option for managing global temperatures.sup.1,2, yet the economic effects of ameliorating climatic changes by scattering sunlight back to space remain largely unknown.sup.3. Although solar radiation management may increase crop yields by reducing heat stress.sup.4, the effects of concomitant changes in available sunlight have never been empirically estimated. Here we use the volcanic eruptions that inspired modern solar radiation management proposals as natural experiments to provide the first estimates, to our knowledge, of how the stratospheric sulfate aerosols created by the eruptions of El Chichón and Mount Pinatubo altered the quantity and quality of global sunlight, and how these changes in sunlight affected global crop yields. We find that the sunlight-mediated effect of stratospheric sulfate aerosols on yields is negative for both C4 (maize) and C3 (soy, rice and wheat) crops. Applying our yield model to a solar radiation management scenario based on stratospheric sulfate aerosols, we find that projected mid-twenty-first century damages due to scattering sunlight caused by solar radiation management are roughly equal in magnitude to benefits from cooling. This suggests that solar radiation management--if deployed using stratospheric sulfate aerosols similar to those emitted by the volcanic eruptions it seeks to mimic--would, on net, attenuate little of the global agricultural damage from climate change. Our approach could be extended to study the effects of solar radiation management on other global systems, such as human health or ecosystem function.Analysis of the El Chichón and Mount Pinatubo volcanic eruptions suggests that solar radiation management strategies using stratospheric sulfate aerosols would do little to counterbalance the effects of climate change on global crop yields., Author(s): Jonathan Proctor [sup.1] [sup.2] , Solomon Hsiang [sup.1] [sup.3] , Jennifer Burney [sup.4] , Marshall Burke [sup.3] [sup.5] , Wolfram Schlenker [sup.3] [sup.6] Author Affiliations:(1) Global Policy Laboratory, Goldman [...]

Poor air quality is thought to be an important mortality risk factor globally.sup.1-3, but there is little direct evidence from the developing world on how mortality risk varies with changing exposure to ambient particulate matter. Current global estimates apply exposure-response relationships that have been derived mostly from wealthy, mid-latitude countries to spatial population data.sup.4, and these estimates remain unvalidated across large portions of the globe. Here we combine household survey-based information on the location and timing of nearly 1 million births across sub-Saharan Africa with satellite-based estimates.sup.5 of exposure to ambient respirable particulate matter with an aerodynamic diameter less than 2.5 [mu]m (PM.sub.2.5) to estimate the impact of air quality on mortality rates among infants in Africa. We find that a 10 [mu]g m.sup.-3 increase in PM.sub.2.5 concentration is associated with a 9% (95% confidence interval, 4-14%) rise in infant mortality across the dataset. This effect has not declined over the last 15 years and does not diminish with higher levels of household wealth. Our estimates suggest that PM.sub.2.5 concentrations above minimum exposure levels were responsible for 22% (95% confidence interval, 9-35%) of infant deaths in our 30 study countries and led to 449,000 (95% confidence interval, 194,000-709,000) additional deaths of infants in 2015, an estimate that is more than three times higher than existing estimates that attribute death of infants to poor air quality for these countries.sup.2,6. Upward revision of disease-burden estimates in the studied countries in Africa alone would result in a doubling of current estimates of global deaths of infants that are associated with air pollution, and modest reductions in African PM.sub.2.5 exposures are predicted to have health benefits to infants that are larger than most known health interventions. A 10 [mu]g m.sup.-3 increase in the concentration of ambient respirable particulate matter is associated with a 9% rise in infant mortality in Africa and this increase is not affected by household wealth., Author(s): Sam Heft-Neal [sup.1] , Jennifer Burney [sup.2] , Eran Bendavid [sup.3] , Marshall Burke [sup.1] [sup.4] [sup.5] Author Affiliations: (1) Center on Food Security and the Environment, Stanford University, [...]

In a single-site study (San Diego, CA, USA), we previously showed that Kawasaki Disease (KD) cases cluster temporally in bursts of approximately 7 days. These clusters occurred more often than would be expected at random even after accounting for long-term trends and seasonality. This finding raised the question of whether other locations around the world experience similar temporal clusters of KD that might offer clues to disease etiology. Here we combine data from San Diego and nine additional sites around the world with hospitals that care for large numbers of KD patients, as well as two multi-hospital catchment regions. We found that across these sites, KD cases clustered at short time scales and there were anomalously long quiet periods with no cases. Both of these phenomena occurred more often than would be expected given local trends and seasonality. Additionally, we found unusually frequent temporal overlaps of KD clusters and quiet periods between pairs of sites. These findings suggest that regional and planetary range environmental influences create periods of higher or lower exposure to KD triggers that may offer clues to the etiology of KD., (© 2021. The Author(s).)

Kawasaki Disease (KD) is the most common cause of pediatric acquired heart disease, but its etiology remains unknown. We examined 1164 cases of KD treated at a regional children's hospital in San Diego over a period of 15 years and uncovered novel structure to disease incidence. KD cases showed a well-defined seasonal variability, but also clustered temporally at much shorter time scales (days to weeks), and spatiotemporally on time scales of up to 10 days and spatial scales of 10-100 km. Temporal clusters of KD cases were associated with strongly significant regional-scale air temperature anomalies and consistent larger-scale atmospheric circulation patterns. Gene expression analysis further revealed a natural partitioning of KD patients into distinct groups based on their gene expression pattern, and that the different groups were associated with certain clinical characteristics that also exhibit temporal autocorrelation. Our data suggest that one or more environmental triggers exist, and that episodic exposures are modulated at least in part by regional weather conditions. We propose that characterization of the environmental factors that trigger KD in genetically susceptible children should focus on aerosols inhaled by patients who share common disease characteristics.