We used an Earth System Model to assess global air pollution changes and their impacts over the 1... more We used an Earth System Model to assess global air pollution changes and their impacts over the 1970-2010 period. We found emergence of a strong North-South divide driven by anthropogenic air pollutant emissions, with a secondary contribution from greenhouse gas increases. Increased concentrations of PM2.5 and O3 have respectively led to an additional 2.4 (95% confidence interval: 2.0-2.6) million and 0.8 (0.6-0.9) million premature deaths. Increases in O3 have also led to an extra 173±8 million tonnes annual staple crop losses at a cost of ~55 billion US$2010. Increased energy use dominates the worsening air pollution in global south regions, while technologies lowering emissions and mitigating impacts have been important in Europe, and to a lesser extent in North America. Reductions in energy-intensive sectors, not technologies alone, are required worldwide to protect global air quality, human health, and food security.
Data supporting the manuscript "Effective radiative forcing and climate responses to 1970-2010 changes in greenhouse gases, anthropogenic aerosols and ozone
This folder contains six files numbered in order. File01: The global mean surface temperature evo... more This folder contains six files numbered in order. File01: The global mean surface temperature evolution from all the experiments analyzed File02; The CESM1 simulated aerosol burdens and AOD, used to plot both the bars and spatial maps in Figure 2 File03: The longitude, latitude grids, as well as the spatial map of 1970-2010 temperature and precipitation changes, used to plot the zonal mean and spatial maps. The observational and reanalysis data can be obtained from corresponding data sources cited in the paper File04: The spatial maps of effective radiative forcing and surface temperature responses to GHGs, aerosols and ozone. This dataset is used to plot both the spatial patterns in Figure 4, the regional mean ERF in Figure 5, the temperature sensitivity estimates in Figure 6, as well as the supporting Figure S2 and S3. File05:The spatial maps of precipitation responses to GHGs, aerosols and ozone, being used to plot the spatial patterns in Figure 7 and the zonal mean in Figure S4. File06: The probability distribution and the of global and regional mean daily precipitation. All these datasets are produced and can be read using the Python cPickle package.
Mineral dust impacts key processes in the Earth system, including the radiation budget, clouds, a... more Mineral dust impacts key processes in the Earth system, including the radiation budget, clouds, and nutrient cycles. We evaluate dust aerosols in 16 models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) against multiple reanalyses and observations. We note that both the reanalyses and observations used here have their limitations and particularly that dust emission and deposition in reanalyses are poorly constrained. Most models, and particularly the multi-model ensemble mean (MEM), capture the spatial patterns and seasonal cycles of global dust processes well. However, large uncertainties and inter-model diversity are found. For example, global dust emissions, primarily driven by model-simulated surface winds, vary by a factor of 5 across models, while the MEM estimate is double the amount in reanalyses. The ranges of CMIP6 model-simulated global dust emission, deposition, burden, and optical depth (DOD) are larger than previous generations of models. Models present considerable disagreement in dust seasonal cycles over North China and North America. Here, DOD values are overestimated by most CMIP6 models, with the MEM estimate 1.2-1.7 times larger compared to satellite and reanalysis datasets. Such overestimates can reach up to a factor of 5 in individual models. Models also fail to reproduce some key features of the regional dust distribution, such as dust accumulation along the southern edge of the Himalayas. Overall, there are still large uncertainties in CMIP6 models' simulated dust processes, which feature inconsistent biases throughout the dust life cycle between models, particularly in the relationship connecting dust mass to DOD. Our results imply that modelled dust processes are becoming more uncertain as models become more sophisticated. More detailed output and dust size-resolved variables in particular, relating to the dust cycle in future intercomparison projects, are needed to enable better constraints of global dust cycles and enable the potential identification of observationally constrained links between dust cycles and optical properties.
Evaluating Tropospheric Nitrogen Dioxide over South and East Asia in UKCA using OMI Satellite data
<p>We compare tropospheric nitrogen dioxide (NO<sub&... more <p>We compare tropospheric nitrogen dioxide (NO<sub>2</sub>) in the United Kingdom Chemistry and Aerosol (UKCA) model v11.0 with satellite measurements from NASA Earth Observing System (EOS) Aura satellite Ozone Monitoring Instrument (OMI) troposphere NO<sub>2</sub> data over South and East Asia (S/A). UKCA is the atmospheric composition component of the UK Earth System Model (UKESM). UKCA has been run on ARCHER (UK National Supercomputing Service) with (a) nudged hourly outputs over S/A as well as monthly outputs globally and (b) free run monthly globally output for 2005-2015. OMI satellite Averaging Kernels (AK) has been applied on the model hourly outputs for accurate model satellite comparison for 2005 - 2015. OMI and UKCA data has been analysed spatially and temporally. Background UKCA and OMI tropospheric column NO<sub>2</sub> typically ranges between 0-3 x 10<sup>15</sup> molecules/cm<sup>2</sup>. Model is overestimating tropospheric NO<sub>2</sub> over the S/A predominantly during winter by a factor of ~2.5. </p>
Journal of Geophysical Research: Atmospheres, 2019
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as
This article has been accepted for publication and undergone full peer review but has not been th... more This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as
The role of anthropogenic aerosols in future projections (up to 2100) of summertime precipitation... more The role of anthropogenic aerosols in future projections (up to 2100) of summertime precipitation and precipitation extremes over the Asian monsoon region is investigated, by comparing two sets of the Community Earth System Model (CESM1) large ensemble simulations under the Representative Concentration Pathway 8.5 scenario (RCP8.5) and the corresponding scenario with aerosol fixed at 2005 levels (RCP8.5_FixA). The model is verified to be performing well in capturing presentday (1986-2005) climate and precipitation extremes. Our results suggest that the Asian monsoon region would become progressively warmer and wetter in the future under RCP8.5, while precipitation extremes will be significantly aggravated due to anthropogenic aerosol mitigation, particularly over East Asia. Specifically, aerosol reductions are found to shift the distribution of precipitation mean and extremes to larger values. For example, aerosol reductions would result in an increased likelihood of extreme precipitation (e.g. the maximum consecutive 5-day precipitation amount) and related disasters. Sensitivities of changes in precipitation mean and extremes to local warming from aerosol reductions are much larger than that from greenhouse gas increases. This is particularly important over East Asia in accordance with larger magnitudes of aerosol reductions compared to South Asia. Finally, by investigating the response of the climate system to aerosol changes, our findings demonstrate that aerosol induced precipitation changes would be dominated by aerosol-radiation-cloud forcing over northern East Asia and aerosol forcing induced large-scale circulation anomalies over southern East and South Asia.
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Papers by Alcide Zhao