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Wildfires are thought to be increasing in severity and frequency as a result of climate change1-5. Air pollution from landscape fires can negatively affect human health4-6, but human exposure to landscape fire-sourced (LFS) air pollution has not been well characterized at the global scale7-23. Here, we estimate global daily LFS outdoor fine particulate matter (PM2.5) and surface ozone concentrations at 0.25° × 0.25° resolution during the period 2000-2019 with the help of machine learning and chemical transport models. We found that overall population-weighted average LFS PM2.5 and ozone concentrations were 2.5 µg m-3 (6.1% of all-source PM2.5) and 3.2 µg m-3 (3.6% of all-source ozone), respectively, in 2010-2019, with a slight increase for PM2.5, but not for ozone, compared with 2000-2009. Central Africa, Southeast Asia, South America and Siberia experienced the highest LFS PM2.5 and ozone concentrations. The concentrations of LFS PM2.5 and ozone were about four times higher in low-income countries than in high-income countries. During the period 2010-2019, 2.18 billion people were exposed to at least 1 day of substantial LFS air pollution per year, with each person in the world having, on average, 9.9 days of exposure per year. These two metrics increased by 6.8% and 2.1%, respectively, compared with 2000-2009. Overall, we find that the global population is increasingly exposed to LFS air pollution, with socioeconomic disparities.
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Poluição do Ar , Incêndios , Ozônio , Material Particulado , Humanos , Poluição do Ar/análise , Poluição do Ar/estatística & dados numéricos , Incêndios/estatística & dados numéricos , Ozônio/análise , Ozônio/provisão & distribuição , Material Particulado/análise , Material Particulado/provisão & distribuição , Incêndios Florestais/estatística & dados numéricos , Disparidades Socioeconômicas em SaúdeRESUMO
Ozone (O3) pollution threatens global public health and damages ecosystem productivity. Droughts modulate surface O3 through meteorological processes and vegetation feedbacks. Unraveling these influences is difficult with traditional chemical transport models. Here, using an atmospheric chemistry-vegetation coupled model in combination with a suite of existing measurements, we investigate the drought impacts on global surface O3 and explore the main driving processes. Relative to the mean state, accelerated photochemical rates dominate the surface O3 enhancement during droughts except for eastern U.S. and western Europe, where reduced stomatal uptakes make comparable contributions. During 1990-2012, the simulated frequency of O3 pollution episodes in western Europe decreases greatly with a negative trend of -5.5 ± 6.6 days per decade following the reductions in anthropogenic emissions if meteorology is fixed. However, such decreased trend is weakened to -2.1 ± 3.8 days per decade, which is closer to the observed trend of -2.9 ± 1.1 days per decade when year-to-year meteorology is applied because increased droughts alone offset 43% of the effects from air pollution control. Our results highlight that more stringent controls of O3 precursors are necessary to mitigate the higher risks of O3 pollution episodes by more droughts in a warming world.
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Poluentes Atmosféricos , Poluição do Ar , Ozônio , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Secas , Ecossistema , Monitoramento Ambiental , Ozônio/análiseRESUMO
China implemented continuous forestation and experienced significant greening tendency in the past several decades. While the ecological project brings benefits to regional carbon assimilation, it also affects surface ozone (O3) pollution level through perturbations in biogenic emissions and dry deposition. Here, we use a coupled chemistry-vegetation model to assess the impacts of land use and land cover change (LULCC) on summertime surface O3 in China during 2000-2019. The LULCC is found to enhance O3 by 1-2 ppbv in already-polluted areas. In contrast, moderate reductions of -0.4 to -0.8 ppbv are predicted in southern China where the largest forest cover changes locate. Such inconsistency is attributed to the background chemical regimes with positive O3 changes over VOC-limited regions but negative changes in NOx-limited regions. The net contribution of LULCC to O3 budget in China is 24.17 Kg/s, in which the positive contribution by more isoprene emissions almost triples the negative effects by the increased dry deposition. Although the LULCC-induced O3 perturbation is much lower than the effects of anthropogenic emissions, forest expansion has exacerbated regional O3 pollution in North China Plain and is expected to further enhance surface O3 with continuous forestation in the future.
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The Tibetan Plateau (TP), known as the Asian water tower, has been getting wetter since the 1970s. However, the primary drivers behind this phenomenon are still highly controversial. Here, we isolate the impacts of greenhouse gases (GHG), aerosols, natural forcings and internal climate variability on the decadal change of summer water vapor budget (WVB) over the TP using multi-model ensemble simulations. We show that an anomalous Rossby wave train in the upper troposphere travelling eastward from central Europe and equatorward temperature gradient in eastern China due to the inhomogeneous aerosol forcing in Eurasia jointly contribute to anomalous easterly winds over the eastern TP. Such anomalous easterly winds result in a significant decrease in water vapor export from the eastern boundary of the TP and dominate the enhanced summer WVB over the TP during 1979-2014. Our results highlight that spatial variation of aerosol forcing can be used as an important indicator to project future WVB over the TP.
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The terrestrial ecosystem in China mitigates 21%-45% of the national contemporary fossil fuel CO2 emissions every year. Maintaining and strengthening the land carbon sink is essential for reaching China's target of carbon neutrality. However, this sink is subject to large uncertainties due to the joint impacts of climate change, air pollution, and human activities. Here, we explore the potential of strengthening land carbon sink in China through anthropogenic interventions, including forestation, ozone reduction, and litter removal, taking advantage of a well-validated dynamic vegetation model and meteorological forcings from 16 climate models. Without anthropogenic interventions, considering Shared Socioeconomic Pathways (SSP) scenarios, the land sink is projected to be 0.26-0.56 Pg C a-1 at 2060, to which climate change contributes 0.06-0.13 Pg C a-1 and CO2 fertilization contributes 0.08-0.44 Pg C a-1 with the stronger effects for higher emission scenarios. With anthropogenic interventions, under a close-to-neutral emission scenario (SSP1-2.6), the land sink becomes 0.47-0.57 Pg C a-1 at 2060, including the contributions of 0.12 Pg C a-1 by conservative forestation, 0.07 Pg C a-1 by ozone pollution control, and 0.06-0.16 Pg C a-1 by 20% litter removal over planted forest. This sink can mitigate 90%-110% of the residue anthropogenic carbon emissions in 2060, providing a solid foundation for the carbon neutrality in China.
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BACKGROUND: Wildfire activity is an important source of tropospheric ozone (O3) pollution. However, no study to date has systematically examined the associations of wildfire-related O3 exposure with mortality globally. METHODS: We did a multicountry two-stage time series analysis. From the Multi-City Multi-Country (MCC) Collaborative Research Network, data on daily all-cause, cardiovascular, and respiratory deaths were obtained from 749 locations in 43 countries or areas, representing overlapping periods from Jan 1, 2000, to Dec 31, 2016. We estimated the daily concentration of wildfire-related O3 in study locations using a chemical transport model, and then calibrated and downscaled O3 estimates to a resolution of 0·25°â×â0·25° (approximately 28 km2 at the equator). Using a random-effects meta-analysis, we examined the associations of short-term wildfire-related O3 exposure (lag period of 0-2 days) with daily mortality, first at the location level and then pooled at the country, regional, and global levels. Annual excess mortality fraction in each location attributable to wildfire-related O3 was calculated with pooled effect estimates and used to obtain excess mortality fractions at country, regional, and global levels. FINDINGS: Between 2000 and 2016, the highest maximum daily wildfire-related O3 concentrations (≥30 µg/m3) were observed in locations in South America, central America, and southeastern Asia, and the country of South Africa. Across all locations, an increase of 1 µg/m3 in the mean daily concentration of wildfire-related O3 during lag 0-2 days was associated with increases of 0·55% (95% CI 0·29 to 0·80) in daily all-cause mortality, 0·44% (-0·10 to 0·99) in daily cardiovascular mortality, and 0·82% (0·18 to 1·47) in daily respiratory mortality. The associations of daily mortality rates with wildfire-related O3 exposure showed substantial geographical heterogeneity at the country and regional levels. Across all locations, estimated annual excess mortality fractions of 0·58% (95% CI 0·31 to 0·85; 31â606 deaths [95% CI 17â038 to 46â027]) for all-cause mortality, 0·41% (-0·10 to 0·91; 5249 [-1244 to 11â620]) for cardiovascular mortality, and 0·86% (0·18 to 1·51; 4657 [999 to 8206]) for respiratory mortality were attributable to short-term exposure to wildfire-related O3. INTERPRETATION: In this study, we observed an increase in all-cause and respiratory mortality associated with short-term wildfire-related O3 exposure. Effective risk and smoke management strategies should be implemented to protect the public from the impacts of wildfires. FUNDING: Australian Research Council and the Australian National Health and Medical Research Council.
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Poluentes Atmosféricos , Doenças Cardiovasculares , Ozônio , Doenças Respiratórias , Incêndios Florestais , Ozônio/efeitos adversos , Ozônio/análise , Humanos , Doenças Cardiovasculares/mortalidade , Poluentes Atmosféricos/efeitos adversos , Poluentes Atmosféricos/análise , Doenças Respiratórias/mortalidade , Exposição Ambiental/efeitos adversos , Saúde Global , Poluição do Ar/efeitos adversos , Poluição do Ar/análiseRESUMO
Fire is a major source of atmospheric aerosols and trace gases. Projection of future fire activities is challenging due to the joint impacts of climate, vegetation, and human activities. Here, we project global changes of fire-induced particulate matter smaller than 2.5 µm (PM2.5) and ozone (O3) under 1.5 °C/2 °C warming using a climate-chemistry-vegetation coupled model in combination with site-level and satellite-based observations. Compared to the present day, fire emissions of varied air pollutants increase by 10.0%-15.4% at the 1.5 °C warming period and 15.1%-22.5% at the 2 °C warming period, with the most significant enhancements in Amazon, southern Africa, and boreal Eurasia. The warmer climate promotes fuel dryness and the higher leaf area index increases fuel availability, leading to escalated fire flammability globally. However, moderate declines in fire emissions are predicted over the Sahel region, because the higher population density increases fire suppressions and consequently inhibits fire activities over central Africa. Following the changes in fire emissions, the population-weighted exposure to fire PM2.5 increases by 5.1% under 1.5 °C warming and 13.0% under 2 °C warming. Meanwhile, the exposure to fire O3 enhances by 10.2% and 16.0% in response to global warming of 1.5 °C and 2 °C, respectively. As a result, limiting global temperature increase to 1.5 °C can greatly reduce the risks of exposure to fire-induced air pollution compared to 2 °C.
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Poluentes Atmosféricos , Poluição do Ar , Humanos , Aquecimento Global , Biodiversidade , Temperatura , Poluentes Atmosféricos/análise , Material Particulado/análiseRESUMO
BACKGROUND: Short-term exposure to ambient PM2·5 is a leading contributor to the global burden of diseases and mortality. However, few studies have provided the global spatiotemporal variations of daily PM2·5 concentrations over recent decades. METHODS: In this modelling study, we implemented deep ensemble machine learning (DEML) to estimate global daily ambient PM2·5 concentrations at 0·1° × 0·1° spatial resolution between Jan 1, 2000, and Dec 31, 2019. In the DEML framework, ground-based PM2·5 measurements from 5446 monitoring stations in 65 countries worldwide were combined with GEOS-Chem chemical transport model simulations of PM2·5 concentration, meteorological data, and geographical features. At the global and regional levels, we investigated annual population-weighted PM2·5 concentrations and annual population-weighted exposed days to PM2·5 concentrations higher than 15 µg/m3 (2021 WHO daily limit) to assess spatiotemporal exposure in 2000, 2010, and 2019. Land area and population exposures to PM2·5 above 5 µg/m3 (2021 WHO annual limit) were also assessed for the year 2019. PM2·5 concentrations for each calendar month were averaged across the 20-year period to investigate global seasonal patterns. FINDINGS: Our DEML model showed good performance in capturing the global variability in ground-measured daily PM2·5, with a cross-validation R2 of 0·91 and root mean square error of 7·86 µg/m3. Globally, across 175 countries, the mean annual population-weighted PM2·5 concentration for the period 2000-19 was estimated at 32·8 µg/m3 (SD 0·6). During the two decades, population-weighted PM2·5 concentration and annual population-weighted exposed days (PM2·5 >15 µg/m3) decreased in Europe and northern America, whereas exposures increased in southern Asia, Australia and New Zealand, and Latin America and the Caribbean. In 2019, only 0·18% of the global land area and 0·001% of the global population had an annual exposure to PM2·5 at concentrations lower than 5 µg/m3, with more than 70% of days having daily PM2·5 concentrations higher than 15 µg/m3. Distinct seasonal patterns were indicated in many regions of the world. INTERPRETATION: The high-resolution estimates of daily PM2·5 provide the first global view of the unequal spatiotemporal distribution of PM2·5 exposure for a recent 20-year period, which is of value for assessing short-term and long-term health effects of PM2·5, especially for areas where monitoring station data are not available. FUNDING: Australian Research Council, Australian Medical Research Future Fund, and the Australian National Health and Medical Research Council.
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Poluentes Atmosféricos , Material Particulado , Material Particulado/análise , Poluentes Atmosféricos/efeitos adversos , Poluentes Atmosféricos/análise , Monitoramento Ambiental , Austrália , Aprendizado de MáquinaRESUMO
The effect of vegetation seasonal cycle alterations to aerosol dry deposition on PM2.5 concentrations (hereafter referred as the VSC effect) in China was investigated using a numerical modelling system (WRF/CUACE). Two simulation experiments using the vegetation parameters in particle dry deposition schemes typical for January and July revealed an absolute increase in surface PM2.5 concentrations of about 2.4 µg/m3 and a 5.5% relative increase in China (within model domain 2). The effect in non-urban areas was more significant than that in urban areas. The increases in PM2.5 concentrations in Beijing-Tianjin-Hebei (BTH), Yangtze River Delta (YRD), Pearl River Delta (PRD), Sichuan Basin (SCB), and Central China (CC) were calculated as 1.9 µg/m3, 3.4 µg/m3, 3.1 µg/m3, 4.3 µg/m3, and 4.9 µg/m3, respectively, corresponding to relative increases of 2.9%, 4.5%, 5.4%, 5.8%, and 5.9%. These results demonstrate that the effect of decreased particle dry deposition due to reduced vegetation in southern areas was stronger, which was partially attributed to the increased vegetation cover and more significant seasonal changes in those regions. Furthermore, the increased PM2.5 concentrations caused by the VSC effect were transported from north to south via the winter northerly winds, which weakened the effect in North China Plain and enhanced the effect in parts of central and southern China, such as the south of CC. Although the surface PM2.5 concentration was relatively high in North China Plain, the effects of the northerly wind and relatively small dry deposition velocity meant that the removal of PM2.5 in that region was relatively less than in southern areas of China. These results will contribute to understanding of the underlying mechanisms of PM2.5 enhancement during winter in China.
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Poluentes Atmosféricos , Poluição do Ar , Aerossóis/análise , Poluentes Atmosféricos/análise , Poluição do Ar/análise , China , Monitoramento Ambiental/métodos , Material Particulado/análise , Estações do AnoRESUMO
Accurate simulation of gross primary productivity (GPP) is essential for estimating the global carbon budget. However, GPP modeling is subject to various sources of uncertainties, among which the impacts of biases in climate forcing data have not been well quantified. Here, using a well-validated vegetation model, we compare site-level simulations using either ground-based meteorology or assimilated reanalyses to identify climate-driven uncertainties in the predicted GPP at 91 FLUXNET sites. Simulations yield the lowest root mean square errors (RMSE) in GPP relative to observations when all site-level meteorology and CO2 concentrations are used. Sensitivity tests conducted with Modern-Era Retrospective Analysis (MERRA) reanalyses increase GPP RMSE by 30%. Replacement of site-level CO2 with global annual average values provides limited contributions to these changes. In contrast, GPP uncertainties increase almost linearly with the biases in meteorology. Among all factors, photosynthetically active radiation (PAR), especially diffuse PAR, plays dominant roles in modulating GPP uncertainties. Simulations using all MERRA forcings but with site-level diffuse PAR help reduce over 50% of the climate-driven biases in GPP. Our study reveals that biases in meteorological forcings, especially the variabilities at diurnal to seasonal time scales, can induce significant uncertainties in the simulated GPP at FLUXET sites. We suggest cautions in simulating global GPP using climate reanalyses for dynamic global vegetation models and urgent improvements in climatic variability in reanalyses data, especially for diffuse radiation.
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Carbono , Ecossistema , Estudos Retrospectivos , Estações do Ano , IncertezaRESUMO
BACKGROUND: Many regions of the world are now facing more frequent and unprecedentedly large wildfires. However, the association between wildfire-related PM2·5 and mortality has not been well characterised. We aimed to comprehensively assess the association between short-term exposure to wildfire-related PM2·5 and mortality across various regions of the world. METHODS: For this time series study, data on daily counts of deaths for all causes, cardiovascular causes, and respiratory causes were collected from 749 cities in 43 countries and regions during 2000-16. Daily concentrations of wildfire-related PM2·5 were estimated using the three-dimensional chemical transport model GEOS-Chem at a 0·25°â×â0·25° resolution. The association between wildfire-related PM2·5 exposure and mortality was examined using a quasi-Poisson time series model in each city considering both the current-day and lag effects, and the effect estimates were then pooled using a random-effects meta-analysis. Based on these pooled effect estimates, the population attributable fraction and relative risk (RR) of annual mortality due to acute wildfire-related PM2·5 exposure was calculated. FINDINGS: 65·6 million all-cause deaths, 15·1 million cardiovascular deaths, and 6·8 million respiratory deaths were included in our analyses. The pooled RRs of mortality associated with each 10 µg/m3 increase in the 3-day moving average (lag 0-2 days) of wildfire-related PM2·5 exposure were 1·019 (95% CI 1·016-1·022) for all-cause mortality, 1·017 (1·012-1·021) for cardiovascular mortality, and 1·019 (1·013-1·025) for respiratory mortality. Overall, 0·62% (95% CI 0·48-0·75) of all-cause deaths, 0·55% (0·43-0·67) of cardiovascular deaths, and 0·64% (0·50-0·78) of respiratory deaths were annually attributable to the acute impacts of wildfire-related PM2·5 exposure during the study period. INTERPRETATION: Short-term exposure to wildfire-related PM2·5 was associated with increased risk of mortality. Urgent action is needed to reduce health risks from the increasing wildfires. FUNDING: Australian Research Council, Australian National Health & Medical Research Council.
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Poluentes Atmosféricos , Incêndios Florestais , Poluentes Atmosféricos/análise , Austrália , Exposição Ambiental , Material Particulado/análiseRESUMO
The COVID-19 pandemic is impacting human activities, and in turn energy use and carbon dioxide (CO2) emissions. Here we present daily estimates of country-level CO2 emissions for different sectors based on near-real-time activity data. The key result is an abrupt 8.8% decrease in global CO2 emissions (-1551 Mt CO2) in the first half of 2020 compared to the same period in 2019. The magnitude of this decrease is larger than during previous economic downturns or World War II. The timing of emissions decreases corresponds to lockdown measures in each country. By July 1st, the pandemic's effects on global emissions diminished as lockdown restrictions relaxed and some economic activities restarted, especially in China and several European countries, but substantial differences persist between countries, with continuing emission declines in the U.S. where coronavirus cases are still increasing substantially.
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Poluentes Atmosféricos/análise , Dióxido de Carbono/análise , Infecções por Coronavirus/epidemiologia , Pneumonia Viral/epidemiologia , Poluentes Atmosféricos/economia , Betacoronavirus , COVID-19 , Dióxido de Carbono/economia , Infecções por Coronavirus/economia , Infecções por Coronavirus/prevenção & controle , Monitoramento Ambiental , Combustíveis Fósseis/análise , Combustíveis Fósseis/economia , Humanos , Indústrias/economia , Dióxido de Nitrogênio/análise , Dióxido de Nitrogênio/economia , Pandemias/economia , Pandemias/prevenção & controle , Pneumonia Viral/economia , Pneumonia Viral/prevenção & controle , SARS-CoV-2RESUMO
A Correction to this paper has been published: https://doi.org/10.1038/s41467-020-20254-5.