I am a climate modeler who used various numerical models to study climate variability and change at the decadal-to-centennial time scale. I am currently interested in working with interdisciplinary colleagues to study (1) the role of air pollutants as part of climate change mitigation solutions and (2) climate change impact on the physical, eco, and societal systems. For more details, please see a Research Statement I submitted for department review in the summer of 2021.
Below are a few examples of my research activities.
The full bibliography can be found on the Publication page.
Multi-decadal climate variability and associated hydrological responses.
The transport and removal processes of particulate matter pollutants are affected by greenhouse gas-driven global warming. Using CESM large ensemble, we are examining how global warming may change the pollution level in the 21st century, given a fixed emission at the present-day level.
Regional climate change is influenced by aerosols, in addition to greenhouse gases. We conduct GCM simulations with the Community Earth System Model (CESM) to assess the climate response to black carbon aerosols, focusing on the Himalayan snowpack (Xu et al., 2016, ACP). We have also studied the general circulation response to different types of aerosols and demonstrated that ocean temperature gradient plays a key role (Xu and Xie, 2015, ACP). Recently, we have started to contrast the role of aerosol and GHGs in the future projection of heat extremes (Xu et al., 2015, Climatic Change), precipitation extremes (Pendergrass et al., 2015, GRL), and terrestrial aridity (Lin et al., 2016, Climatic Change).
Mitigating short-lived climate pollutants is a win-win solution to fight climate change and air pollution. We project the global mean temperature change in the 21st century and show that mitigation of short-lived pollutants plays a vital role in reducing future global warming (Ramanathan and Xu, 2010, PNAS) and sea level rise (Hu et al., 2013, Nature Clim. Change). Specifically, we study the role of HFCs (hydrofluorocarbons, as a substitute of ozone-depleting substances) (Xu et al., 2013, ACP) in future climate change. The ultimate goal is to provide useful information for policy makers (Xu and Zaelke, 2013, Our Planet). The quantitative approach we use here rely on simple models and statistical methods, which are also my interests of research.
Below are a few examples of my research activities.
The full bibliography can be found on the Publication page.
- Hydroclimate at the global scale, including societally relevant extremes
Multi-decadal climate variability and associated hydrological responses.
- Kim, Y., Li, D., Xu, Y., Zhang, Y., Li, X., Muhlenforth, L., Xue, S., & Brown, R. (2023). Heat vulnerability and street-level outdoor thermal comfort in the city of Houston: Application of google street view image derived SVFs. Urban Climate, 51, 101617.
- Xiao, X., Xu, Y., Zhang, X., Wang, F., Lu, X., Cai, Z., Brasseur, G., & Gao, M. (2022). Amplified Upward Trend of the Joint Occurrences of Heat and Ozone Extremes in China over 2013–20. Bulletin of the American Meteorological Society, 103(5), E1330–E1342.
- Yan, Y., Xu, Y. & Yue, S. A high-spatial-resolution dataset of human thermal stress indices over South and East Asia. Sci Data 8, 229 (2021).
- Xu, Y., Wu, X., Kumar, R., Barth, M., Diao, C. ***, Gao, M., Lin, L., Jones, B., Meehl, G.A. (2020). Substantial increase in the joint occurrence and human exposure of heatwave and high‐PM hazards over South Asia in the mid‐21st century. AGU Advances, 1, e2019AV000103.
- Lin, L., Wang, Z., Xu, Y., Zhang, X., Zhang, H., & Dong, W. (2018). Additional intensification of seasonal heat and flooding extreme over China in a 2°C warmer world compared to 1.5°C. Earth's Future, 6, 968–978.
- Sanderson, B. M., Xu, Y., Tebaldi, C., Wehner, M., O'Neill, B., Jahn, A., Pendergrass, A. G., Lehner, F., Strand, W. G., Lin, L., Knutti, R., and J.F. Lamarque (2017), Community climate simulations to assess avoided impacts in 1.5 and 2 °C futures, Earth Syst. Dynam., 8, 827-847.
- Climate change's impact on particulate matter pollution
The transport and removal processes of particulate matter pollutants are affected by greenhouse gas-driven global warming. Using CESM large ensemble, we are examining how global warming may change the pollution level in the 21st century, given a fixed emission at the present-day level.
- He, C., Kumar, R., Tang, W., Pfister, G., Xu, Y., Qian, Y., Brasseur, G. Air Pollution Interactions with Weather and Climate Extremes: Current Knowledge, Gaps, and Future Directions. Curr Pollution Rep (2024). https://doi.org/10.1007/s40726-024-00296-9 (pdf)
- Wang, F., Xu, Y., Patel, P. N., Gautam, R., Gao, M., Liu, C., … McElroy, M. B. (2024). Arctic amplification–induced decline in West and South Asia dust warrants stronger anti-desertification toward carbon neutrality. Proceedings of the National Academy of Sciences, 121(14), e2317444121. doi:10.1073/pnas.2317444121
- Gao, M., Wang, F., Ding, Y., Wu, Z., Xu, Y., Lu, X., Wang, Z., Carmichael, G. R., & McElroy, M. B. (2023). Large-scale climate patterns offer preseasonal hints on the co-occurrence of heat wave and O3 pollution in China. Proceedings of the National Academy of Sciences, 120(26), e2218274120.
- Fiore, A. M., Milly, G. P., Hancock, S. E., Quiñones, L., Bowden, J. H., Helstrom, E., et al. (2022). Characterizing changes in eastern U.S. pollution events in a warming world. Journal of Geophysical Research: Atmospheres, 127, e2021JD035985.
- Banks, A., Kooperman, G. J., & Xu, Y. (2022). Meteorological influences on anthropogenic PM2.5 in future climates: Species level analysis in the Community Earth System Model v2. Earth's Future, 10, e2021EF002298.
- Wu, X. Xu, Y., Kumar, R., & Barth, M. (2019). Separating emission and meteorological drivers of mid‐21st‐century air quality changes in India based on multiyear global‐regional chemistry‐climate simulations. Journal of Geophysical Research: Atmospheres, 124, 13,420–13,438. https://doi.org/10.1029/2019JD030988.
- Xu, Y., and J.‐F. Lamarque (2018) Isolating the Meteorological Impact of 21st Century GHG Warming on the Removal and Atmospheric Loading of Anthropogenic Fine Particulate Matter Pollution at Global Scale. Earth's Future, 6, 428–440.
- Climate response to aerosols
Regional climate change is influenced by aerosols, in addition to greenhouse gases. We conduct GCM simulations with the Community Earth System Model (CESM) to assess the climate response to black carbon aerosols, focusing on the Himalayan snowpack (Xu et al., 2016, ACP). We have also studied the general circulation response to different types of aerosols and demonstrated that ocean temperature gradient plays a key role (Xu and Xie, 2015, ACP). Recently, we have started to contrast the role of aerosol and GHGs in the future projection of heat extremes (Xu et al., 2015, Climatic Change), precipitation extremes (Pendergrass et al., 2015, GRL), and terrestrial aridity (Lin et al., 2016, Climatic Change).
- Lei, Y., Wang, Z., Wang, D. et al. Co-benefits of carbon neutrality in enhancing and stabilizing solar and wind energy. Nat. Clim. Chang. (2023).
- Diao, C., Xu, Y. Reassessing the relative role of anthropogenic aerosols and natural decadal variability in driving the mid-twentieth century global “cooling”: a focus on the latitudinal gradient of tropospheric temperature. Clim Dyn (2022). https://doi.org/10.1007/s00382-022-06235-y
- Wang, Z., Lin, L., Xu, Y., Che, H., Zhang, X., Zhang, H., Dong, W., Wang, C., Gui, K., & Xie, B. (2021). Incorrect Asian aerosols affecting the attribution and projection of regional climate change in CMIP6 models. Npj Climate and Atmospheric Science, 4(1), 2.
- Xu, Y., Lin, L., Diao, C., Wang, Z., Bates, S., & Arblaster, J. (2022). The response of precipitation extremes to the twentieth- and twenty-first-century global temperature change in a comprehensive suite of CESM1 large ensemble simulation: Revisiting the role of forcing agents vs. the role of forcing magnitudes. Earth and Space Science, 9, e2021EA002010.
- Diao, C., Xu, Y., and Xie, S.-P.: Anthropogenic aerosol effects on tropospheric circulation and sea surface temperature (1980–2020): separating the role of zonally asymmetric forcings, Atmos. Chem. Phys., 21, 18499–18518, 2021.
- Wang Z., J. Feng, C. Diao, Y. Li, L. Lin and Y. Xu (2021), Reduction in European anthropogenic aerosols and the weather conditions conducive to PM2.5 pollution in North China: a potential global teleconnection pathway. Environ. Res. Lett. Volume 16, Number 10 104054
- Xu, Y., Lin, L., Tilmes, S., Dagon, K., Xia, L., Diao, C., Cheng, W., Wang, Z., Simpson, I., and Burnell, L.: Climate engineering to mitigate the projected 21st-century terrestrial drying of the Americas: a direct comparison of carbon capture and sulfur injection, Earth Syst. Dynam., 11, 673–695, 2020.
- Lin, L., Xu, Y., Wang, Z., Diao, C. , Dong, W., & Xie, S.‐P. (2018) Changes in extreme rainfall over India and China attributed to regional aerosol‐cloud interaction during the late 20th century rapid industrialization. Geophysical Research Letters, 45.
- Wang, Z., L. Lin, X. Zhang, H. Zhang, L. Liu, and Y. Xu (2017), Scenario dependence of future changes in climate extremes under 1.5 °C and 2 °C global warming, Scientific Report, 7, 46432.
- Liu, J., K. M. Rühland, J. Chen, Y. Xu, S. Chen, Q. Chen, W. Huang. Q. Xu, F. Chen, and J. P. Smol (2017), Aerosol-weakened summer monsoons decrease lake fertilization in the Chinese Loess Plateau, Nature Climate Change, 7(3), 190–194, doi:10.1038/nclimate3220.
- Lin, L., Z. Wang, Y. Xu, and Q. Fu (2016), Sensitivity of precipitation extremes to radiative forcing of greenhouse gases and aerosols, Geophysical Research Letters, 43(18), 9860–9868, doi:10.1002/2016GL070869.
- Xu, Y., V. Ramanathan, and W. M. Washington (2016), Observed high-altitude warming and snow cover retreat over Tibet and the Himalayas enhanced by black carbon aerosols, Atmospheric Chemistry and Physics, 16(3), 1303–1315, doi:10.5194/acp-16-1303-2016.
- Xu, Y., J.-F. Lamarque, and B. M. Sanderson (2015), The importance of aerosol scenarios in projections of future heat extremes, Climatic Change, 1–14, doi:10.1007/s10584-015-1565-1.
- Xu, Y., and S.-P. Xie (2015), Ocean mediation of tropospheric response to reflecting and absorbing aerosols, Atmospheric Chemistry and Physics, 15(10), 5827–5833, doi:10.5194/acp-15-5827-2015.
- Short-lived pollutants and climate change mitigation
Mitigating short-lived climate pollutants is a win-win solution to fight climate change and air pollution. We project the global mean temperature change in the 21st century and show that mitigation of short-lived pollutants plays a vital role in reducing future global warming (Ramanathan and Xu, 2010, PNAS) and sea level rise (Hu et al., 2013, Nature Clim. Change). Specifically, we study the role of HFCs (hydrofluorocarbons, as a substitute of ozone-depleting substances) (Xu et al., 2013, ACP) in future climate change. The ultimate goal is to provide useful information for policy makers (Xu and Zaelke, 2013, Our Planet). The quantitative approach we use here rely on simple models and statistical methods, which are also my interests of research.
- Dreyfus, G. B., Xu, Y., Shindell, D. T., Zaelke, D., & Ramanathan, V. (2022). Mitigating climate disruption in time: A self-consistent approach for avoiding both near-term and long-term global warming. Proceedings of the National Academy of Sciences, 119(22), e2123536119. (abstract, pdf, supplement)
- Ramanathan, V., Xu, Y. & Versaci, A. Modelling human–natural systems interactions with implications for twenty-first-century warming. Nat Sustain (2021). https://doi.org/10.1038/s41893-021-00826-z
- Chen J., H. Cui, Y. Xu and Q. Ge (2021) Long-term temperature and sea-level rise stabilization before and beyond 2100: Estimating the additional climate mitigation contribution from China's recent 2060 carbon neutrality pledge. Environ. Res. Lett. 16 074032
- Ocko, I. B., Sun, T., Shindell, D., Oppenheimer, M., Hristov, A. N., Pacala, S. W., Mauzerall, D. L., Xu, Y., & Hamburg, S. P. (2021). Acting rapidly to deploy readily available methane mitigation measures by sector can immediately slow global warming. Environmental Research Letters. 16 054042
- Hanna, R., Abdulla, A., Xu, Y., Victor, D. (2021) Emergency deployment of direct air capture as a response to the climate crisis. Nature Communication 12, 368.
- Hanna, R., Xu, Y., and Victor, D. G. (2020). After COVID-19, green investment must deliver jobs to get political traction. Nature, 582, 178–180.
- Xu, Y., V. Ramanathan, D.Victor (2018), Global warming will happen faster than we think, Nature, 564 (7734), 30.
- Xu, Y., and V. Ramanathan (2017), Well below 2 °C: Mitigation strategies for avoiding dangerous to catastrophic climate changes. Proc. Natl. Acad. Sci. , doi:10.1073/pnas.1618481114 .
- Xu, Y., D. Zaelke, G. J. M. Velders, and V. Ramanathan (2013), The role of HFCs in mitigating 21st century climate change, Atmospheric Chemistry and Physics, 13(12), 6083–6089, doi:10.5194/acp-13-6083-2013.
- Hu, A., Y. Xu, C. Tebaldi, W. M. Washington, and V. Ramanathan (2013), Mitigation of short-lived climate pollutants slows sea-level rise, Nature Climate Change, 3(8), 730–734, doi:10.1038/nclimate1869.
- Bahadur, R., P. S. Praveen, Y. Xu, and V. Ramanathan (2012), Solar absorption by elemental and brown carbon determined from spectral observations, Proceedings of the National Academy of Sciences, 109(43), 17366–17371, doi:10.1073/pnas.1205910109.
- Ramanathan, V., and Y. Xu (2010), The Copenhagen Accord for limiting global warming: criteria, constraints, and available avenues, Proceedings of the National Academy of Sciences, 107(18), 8055–8062, doi:10.1073/pnas.1002293107.