About the Lab
The Climate Impact Lab is a unique collaboration of 30 climate scientists, economists, computational experts, researchers, analysts, and students from some of the nation’s leading research institutions.
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Trevor Houser is a partner with the Rhodium Group, an independent research company, and leads the firm’s Energy & Climate team. This interdisciplinary group of policy experts, economic analysts, energy modelers, data engineers and climate scientists analyzes the market impact of energy and climate policy and the economic risks of global climate change. During 2009, Trevor left Rhodium temporarily to serve as a senior advisor at the US State Department where he worked on international energy, natural resource and environmental policy issues. He serves on the finance committee of the Colin Powell School for Civic and Global Leadership at the City College of New York, his alma mater. He is a member of the Council on Foreign Relations and the National Committee on US-China Relations and serves on the Advisory Board of Center for US-China Relations at the Asia Society.
Michael Greenstone is the Milton Friedman Professor in Economics, the College, and the Harris School, as well as the Director of the interdisciplinary Energy Policy Institute at the University of Chicago (EPIC). His other current positions and affiliations include Elected Member of the American Academy of Arts and Sciences, Editor of the Journal of Political Economy, Faculty Director of the E2e Project, Head of the JPAL Environment and Energy Program, co‐Director of the International Growth Centre’s Energy Research Programme, and Nonresident Senior Fellow in Economic Studies at the Brookings Institution. Prior to rejoining the faculty at Chicago, Professor Greenstone was the 3M Professor of Environmental Economics at MIT.
Solomon Hsiang combines data with mathematical models to understand how society and the environment influence one another. In particular, he focuses on how policy can encourage economic development while managing the global climate. His research has been published in Nature, Science, and the Proceedings of the National Academy of Sciences. Hsiang was Lead Economist for the 2014 analysis Economic Risks of Climate Change: An American Prospectus, the scientific analysis behind the Risky Business report published by Michael Bloomberg, Hank Paulson, Thomas Steyer and colleagues. Hsiang earned a BS in Earth, Atmospheric and Planetary Science and a BS in Urban Studies and Planning from the Massachusetts Institute of Technology, and he received a PhD in Sustainable Development from Columbia University. He was a Post-Doctoral Fellow in Applied Econometrics at the National Bureau of Economic Research (NBER) and a Post-Doctoral Fellow in Science, Technology and Environmental Policy at Princeton University. Hsiang is currently the Chancellor’s Associate Professor of Public Policy at the University of California, Berkeley and a Faculty Research Fellow at the NBER. In 2013, Hsiang became the inaugural recipient of the American Geophysical Union’s Science for Solutions Award for “significant contributions in the application and use of Earth and space sciences to solve societal problems”. In 2014, Hsiang was named in Forbes Magazine’s 30 Under 30 in Law and Policy.
Robert Kopp is Director of the Rutgers Institute of Earth, Ocean & Atmospheric Sciences and a Professor in the Department of Earth & Planetary Sciences at Rutgers University. He also serves as co-director of Rutgers’ transdisciplinary Coastal Climate Risk & Resilience (C2R2) initiative, a training program which brings graduate students in the natural sciences, social sciences, engineering, and urban planning together with coastal stakeholders to tackle the challenges that climate change poses to the world’s coastlines.
Prof. Kopp’s research focuses on understanding uncertainty in past and future climate change, with major emphases on sea-level change and on the interactions between physical climate change and the economy. He is a lead author of Economic Risks of Climate Change: An American Prospectus (Columbia University Press, 2015) and of the U.S. Global Change Research Program’s 2017 Climate Science Special Report, a member of the National Academies’ Committee on Assessing Approaches to Updating the Social Cost of Carbon, and a contributing author of the Intergovernmental Panel on Climate Change’s 2014 Fifth Assessment Report. He has authored over sixty scientific papers and several popular articles in venues including the New York Times.
Prior to joining the Rutgers faculty in 2011, Prof. Kopp served as a AAAS Science & Technology Policy Fellow at the U.S. Department of Energy, where he worked on the U.S. government’s efforts to incorporate climate change into benefit-cost analysis and on the development and launch of the Clean Energy Ministerial. He was previously a postdoctoral fellow in geosciences and public policy at Princeton University. He received his Ph.D. in geobiology from Caltech and his undergraduate degree in geophysical sciences from the University of Chicago. Prof. Kopp is a Rutgers-New Brunswick Chancellor’s Scholar and a past Leopold Leadership Fellow. He is a recipient of the American Geophysical Union’s James B. Macelwane and William Gilbert Medals and the International Union for Quaternary Research (INQUA)’s Sir Nicholas Shackleton Medal.
Laura is a Pre-Doctoral Fellow with the Energy Policy Institute at the University of Chicago (EPIC). She works primarily with the Climate Impact Lab, a multi-organization, multidisciplinary research group co-led by EPIC Director Michael Greenstone that works to calculate the social impacts of climate change. Laura previously worked as a consultant at Energea, a consulting firm that specializes in energy project development in Mexico, assisting in the restructuring of a government agency in charge of regulating industrial safety and environmental protection in the Mexican hydrocarbons sector. She earned her bachelor’s in economics from Instituto Tecnológico Autónomo de México and a master’s in economics from The University of Texas at Austin. Laura is broadly interested in environmental and energy policy and industrial organization.
Tom Bearpark is a Pre-Doctoral Fellow with the Climate Impact Lab (CIL), a multidisciplinary team of researchers from EPIC, the University of California, Berkeley, Rutgers University and Rhodium Group. His work primarily focuses on quantifying the effects of climate change on conflict and migration patterns. Before joining EPIC, Tom earned a master’s degree in Economic Research at the University of Cambridge and a bachelor’s degree in philosophy and economics from the London School of Economics. He also spent two years working as an economist in the United Kingdom’s energy regulator, the Office for Gas and Electricity Markets; during that time he also spent three months in Brussels working for the European Union’s energy regulators. Tom’s research interests are in policy analysis and the role of climate change in economic development.
Ian is currently a PhD student in Berkeley’s Energy and Resources Group, where he is National Defense Science and Engineering Graduate Fellow. In addition to his position in the Global Policy Lab, he is a graduate of the “Environment and Society: Data Sciences for the 21st Century” NSF Research Traineeship and a member of the Renewable and Appropriate Energy Laboratory. He is also the co-founder and Program Manager for an interdisciplinary student team that designed and built an off-grid, 100% solar-powered tiny house in Richmond, CA. Before coming to UC Berkeley, he modeled global disease and injury trends at the Institute for Health Metrics and Evaluation in his hometown of Seattle, WA. Outside of academia, Ian volunteers for the Tahoe Backcountry Ski Patrol and spends as much time as possible in the Sierras.
Ian holds a BA in Applied Mathematics from Harvard University, with a focus on earth systems science. He received an MS from ERG in 2016 and another from the Department of Civil and Environmental Engineering (with a focus in Systems Engineering) in 2017.
Tamma Carleton is a postdoctoral scholar in the Kenneth C. Griffin Department of Economics at the University of Chicago. She works with the Climate Impact Lab (CIL), a multi-disciplinary, multi-organizational research group that partners with EPIC to calculate the social and economic costs of climate change. More broadly, Tamma’s research seeks to improve quantitative understanding of how global environmental change influences and is shaped by economic development. Tamma worked with CIL while completing her PhD in Agricultural and Resource Economics at the University of California, Berkeley, where she was also an EPA STAR Fellow and Doctoral Fellow in the Global Policy Lab at the Goldman School of Public Policy. A Rhodes Scholar, Tamma earned master’s degrees in Environmental Change & Management and in Economics for Development at University of Oxford. She has a BA in Economics from Lewis & Clark College in Portland, Oregon, and was a Research Analyst at the Federal Trade Commission’s Bureau of Economics.
Jack Chang is a master’s candidate at the Energy & Resources Group and at the Goldman School of Public Policy, both at UC Berkeley, and project manager at the Climate Impact Lab. Jack has focused his graduate studies on renewable energy and climate policy in California and internationally. He has also helped edit the Bay Area Report of California’s 4th Climate Change Assessment and is working with the UC Berkeley Sustainability Office on a campuswide sustainability assessment. Previously, Jack worked for two decades as a reporter and editor on three continents, including as the South America bureau chief for McClatchy/Knight Ridder and as a Beijing-based correspondent for The Associated Press. He earned a bachelor’s degree in English at UC Berkeley and a master’s degree in journalism at Northwestern University.
Trinetta is a Pre-Doctoral Fellow with the Energy Policy Institute at the University of Chicago (EPIC). She works primarily on the Climate Impact Lab helping to calculate the economic impacts of climate change. Her interests are focused on environment policy and international development, particularly on issues pertaining to agriculture, nutrition and poverty. Prior to joining EPIC, she worked with the International Food Policy Research Institute (IFPRI) to examine the effects of early-life rainfall on child nutrition in Bangladesh. She also worked for several years at Singapore’s national water agency, the Public Utilities Board (PUB), under the Ministry of Environment and Water Resources. Trinetta graduated with a Masters of Public Policy from the Goldman School at the University of California, Berkeley.
Michael Delgado is a Senior Analyst at Rhodium Group focusing on the science, economics, and policy of climate change. Mike develops and deploys a range of quantitative tools to study climate change and its impacts, assess risks to human and economic systems, and analyze policy responses. Mike’s team contributes tools, data, and analysis to the Climate Impact Lab as well as to Rhodium’s clean energy and climate impacts work. Prior to RHG, Mike worked with John Weyant at Stanford University as an energy modeler and for the NIF/LIFE team at Lawrence Livermore National Laboratory. He has a Bachelor’s degree and Master’s degree from Stanford.
Greg was a Pre-Doctoral Fellow with EPIC working on the Climate Impact Lab, which looks to better understand the global impacts of climate change. His research interests center on markets for agriculture, energy, and natural resources in developing economies. Prior to joining EPIC, Greg worked with Innovations for Poverty Action as a Research Associate on multiple development economics studies in Uganda and as a Policy Associate working on issues of financial inclusion in New Haven, CT. Previously, he worked with a USAID funded export promotion project in Ghana. Greg holds a BA in Economics and Government from Cornell University.
Radhika is a predoctoral fellow at the Energy Policy Institute of Chicago (EPIC) working on the Social Cost of Carbon project which is aimed at providing a global assessment of climate change impacts. Prior to joining the University of Chicago, Radhika was a research analyst at the Brookings Institution in Washington DC where she conducted research on fiscal policy, agriculture, and political economy for Sub-Saharan Africa. Previously, she worked for the International Growth Centre (directed by London School of Economics and University of Oxford) in the Rwanda and Oxford offices where her research focused on a range of themes including public finance, education, poverty, urbanization and agriculture. She has also consulted for the World Bank and Oxford Policy Management and engaged in fieldwork across Africa and Southeast Asia. Radhika holds an MSc in Economics for Development and a BA in Economics and Management from the University of Oxford and was a Ministry of Education (Singapore) Agency for Science, Technology and Research scholar.
Simon Greenhill is a Pre-Doctoral Fellow at the Energy Policy Institute at the University of Chicago, where he is a member of the Climate Impact Lab (CIL), a multi-institution collaboration seeking to measure the social cost of carbon. At CIL, Simon primarily studies how climate change will affect human migration. He earned bachelor’s degrees in economics and Arabic from the University of California, Berkeley. While at Berkeley, Simon contributed to research on the labor market effects of the Syrian refugee crisis in neighboring countries and spent a semester studying in Amman, Jordan. He is broadly interested in economic questions at the intersection of energy, climate change and development.
Bethel is senior manager of programs and operations with EPIC working to help coordinate operations of theClimate Impact Lab, which looks to better understand the global impacts of climate change.
Ali has a background in statistical and physical-based hydrologic modeling of pluvial and fluvial flooding. Prior to joining Rhodium, Ali was a postdoctoral researcher in Scripps Institution of Oceanography at the University of California, San Diego. His main responsibility at Scripps was to improve hydrological model performance associated with extreme rainfall events and evaluate the hydrological implications of climate models for use in Forecast Informed Reservoir Operations. Ali earned his Ph.D. from the City College of New York in Civil Engineering with the major of Water Resources. His Ph.D. research focused on the spatial-temporal variation of extreme rainfall and its effects on urban infrastructure systems.
Hannah Hess is a Communications Manager at Rhodium Group. Hannah also manages communications for the Climate Impact Lab. She joined RHG after five years as a journalist in Washington, D.C., where she most recently reported on federal climate policy for E&E News. She now helps RHG ensure its research and findings are broadly and accurately portrayed. Hannah holds two degrees from the University of Illinois, a Bachelor’s degree in Media Studies and a Master’s degree in Public Affairs Reporting.
Dylan is a Pre-Doctoral Fellow with the Energy Policy Institute at the University of Chicago (EPIC), where he works primarily with the Climate Impact Lab, a multi-organization, multidisciplinary research group co-led by EPIC Director Michael Greenstone that works to calculate the social impacts of climate change. Prior to joining EPIC, Dylan worked for several years as an economic consultant at NERA Economic Consulting, advising clients in the energy sector on environmental and economic issues. As an undergraduate research assistant at Brown University, he contributed to research in education and development economics. His current research interests lie broadly in environmental policy and international development. Dylan has a bachelor’s in applied mathematics and economics from Brown.
Andy is currently a PhD student in Berkeley’s Agricultural and Resource Economics program, where he is a fellow with the National Science Foundation’s Data Sciences for the 21st Century initiative. Before returning to school, Andy provided climate change analysis services for several federal agency regulatory proceedings and advised numerous local governments and private businesses on approaches to reduce their greenhouse gas emissions. Along with his wife and two kids, he also spent two years in the Argentine Patagonia studying sustainable construction techniques.
Andy holds a Master’s in Public Policy from U.C. Berkeley and a BSE in Chemical Engineering from Princeton University.
Azhar was a Pre-Doctoral fellow with EPIC at the University of Chicago working on the Climate Impact Lab. He is interested in energy and environment economics research, and has already worked on a study named Light Up Bihar in India with J-PAL for over two years. The study focuses on improving the revenue parameters and checking commercial losses incurred by the Power Distribution Companies in Bihar. It also tries to reinstate the fact that electricity service delivery in India is a collective-action problem; and to make it sustainable, we need not only well-functioning power markets, but also people’s understanding of the fact that electricity is a private good, and not a free commodity. Azhar received his undergraduate degree in Mining Engineering from the Indian Institute of Technology, Varanasi.
Amir Jina is an assistant professor at the Harris School of Public Policy. He previously served as a postdoctoral scholar at the Economics Department of the University of Chicago. An environmental and development economist, his research focuses on the role of the environment and environmental change in the shaping how societies develop. He uses applied economic techniques combined with methods from climate science and remote sensing to understand the impacts of climate in both rich and poor countries, and has conducted fieldwork related to climate change adaptation with communities in India, Bangladesh, Kenya, and Uganda. Prior to University of Chicago, Amir was a visiting scholar at the Goldman School of Public Policy in University of California, Berkeley where he worked on the economic analysis of the Risky Business initiative, an independent assessment of the economic risks posed by a changing climate in the U.S commissioned by co-chairs Michael R. Bloomberg, Henry Paulson, and Tom Steyer. Amir received his Ph.D. in Sustainable Development and M.A. in Climate and Society both from Columbia University, B.A.s in Mathematics and Theoretical Physics from Trinity College, Dublin, and previously worked with the Red Cross/Red Crescent in South Asia.
Theo is a Pre-Doctoral Fellow with EPIC. When it comes to his research, Theo’s interested in making the representation of energy systems and energy use in Integrated Assessment Models more realistic and useful. Before coming to EPIC, Theo completed his Master of Science in Environmental Science and Policy (MSESP) degree at the University of Chicago Harris School of Public Policy.
Megan was project manager for the Climate Impact Lab in 2016. She received her Masters in Public Policy at the Goldman School of Public Policy at UC Berkeley. Previously, Megan was the Assistant Director of Global and Executive Programs at the Goldman School where she developed leadership and management programs for governments and institutions from around the world. Megan earned a BA in Political Science from the University of California, Berkeley.
Kate Larsen is a Director at Rhodium Group and manages the firm’s work on US and global climate change, including RHG’s work estimating the costs of climate change as part of the Climate Impact Lab.
Prior to joining RHG, Kate worked at the White House Council on Environmental Quality where she was Deputy Director for Energy and Climate Change where she helped develop President Obama’s Climate Action Plan. From 2007 to 2013, Kate worked in the Office of Climate Change at the US Department of State, serving as lead US negotiator on mitigation commitments and compliance in the UN climate negotiations. She was one of the lead contributors in designing the first universal system for measurement, reporting, and verification of developed and developing country emissions and commitments under the UN. Prior to the State Department, Kate worked at the International Energy Agency in Paris, the World Resources Institute in Washington, and the Environmental Defense Fund in California. She received a Bachelor’s in Human Biology from Stanford University and a Master’s of Public Administration from the University of Texas, Austin.
Jaecheol is a PhD student in Agricultural and Resource Economics at UC Berkeley. He graduated from Seoul National University (SNU) with a BA in Economics and Hispanic Linguistics and Literature. He also earned a Master’s in International Studies in the same university with a concentration in development. Prior to coming to Berkeley, he participated in a project analyzing the trade effect of non-tariff measures as a consultant at Deloitte LLC. He is a grantee of the 2017 Fulbright Graduate Study Award, which is funded by the United States Department of State. His research currently focuses on the impact of transboundary air pollution. Specifically, he is interested in identifying the effects of Chinese air pollution on South Korea, which is a growing issue between the neighboring countries.
Terin Mayer was project manager for the Climate Impact Lab. He received his Masters in Public Policy at the Goldman School of Public Policy at UC Berkeley in 2018. Before graduate school, Terin worked with community-based nonprofits and labor unions in Minnesota to build organizational capacity, drive civic engagement and foster grassroots participation in state budgeting and workplace policy making. Terin received his bachelor’s degree in Philosophy (magna cum laude) from Carleton College. He spent ten years of his childhood in Bolivia, Spain, and Chile with his sister and parents, an elementary school educator and a US Air Force officer.
Kelly McCusker is a Climate Scientist at Rhodium Group lending climate science expertise to a range of projects and software development support to the Climate Impact Lab. Previously, Kelly was a Postdoctoral Fellow and Research Associate at the University of Washington and the University of Victoria in British Columbia, Canada where she studied the role of the changing Arctic sea ice cover on global circulation, weather, and climate using a hierarchy of numerical global climate models. She received a Bachelor’s in Mathematics from Providence College and a Ph.D. in Atmospheric Sciences with a concentration in Climate Science from the University of Washington, and in between worked as a software developer in defense, finance, and astrophysics.
Shashank Mohan is Director of Quantitative Analysis at Rhodium Group. He leads the development and management of RHG’s suite of economic models and other quantitative tools. Shashank joined RHG in 2008 as research analyst, and has since worked across RHG’s practice areas to analyze the impact of policy proposals and structural developments on specific markets and broader economic trends.
Shashank has extensive experience building and leveraging a wide variety of economic and energy system modeling, including computable general equilibrium models, econometric growth models, National Energy Modeling System, and input-output analysis, to inform market and policy-relevant energy, economic and environmental analysis. Prior to joining RHG, Shashank was software engineer at Microsoft.
Shashank holds an Master’s degree from School of International and Public Affairs at Columbia University and is a Mathematics and Computer Science graduate of the Indian Institute of Technology (IIT), Kharagpur.
Ishan Nath is an Economics PhD student at the University of Chicago interested in growth, development, the economic impact of climate change, and the ways in which these topics interact. Prior to beginning his PhD, Ishan earned an MPhil in Economics from the University of Oxford, where he studied as a Rhodes Scholar. He also holds a B.A. in Economics and a B.S. in Earth Systems, with honors and distinction, from Stanford University, where he was a Truman Scholar and a Udall Scholar. In addition to his studies, Ishan has policy experience as an intern at the White House, U.S. Treasury, and The Carter Center, and as a consultant for the National Commission on the BP Deepwater Horizon Oil Spill and the Environmental Defense Fund.
Maya Norman is a Pre-Doctoral Fellow working with the Climate Impact Lab, a multi-organization, multidisciplinary research group co-led by EPIC Director Michael Greenstone that works to calculate the social impacts of climate change, where she primarily works on calculating the impact of energy consumption on climate change. Before joining EPIC, Maya was a research intern with Earth Economics, where she assisted with the benefit-cost analysis of navigation expansion project on the Upper Mississippi River. As an undergraduate Maya studied how to optimize trash production levels and the role of aquaculture in alleviating policy tensions surrounding Maine fisheries. She is broadly interested in the intersection between natural systems and human infrastructure as well as how policy can better optimize resource use. Maya has a bachelor’s in economics from Bowdoin College.
Sam Ori is the Executive Director at the Energy Policy Institute at the University of Chicago (EPIC). From 2013 to 2015, he served as Executive Vice President at Securing America’s Future Energy (SAFE), a Washington, DC-based organization dedicated to reducing American oil dependence in order to enhance economic and national security. From 2007 to 2013, Sam led SAFE’s policy work on a variety of topics, ranging from global oil and natural gas markets to transportation technology. Prior to joining SAFE, Sam spent four years working in the federal government at the Broadcasting Board of Governors and Department of State, including at the U.S. Embassy in New Delhi, India.
Sébastien is a Pre-Doctoral Fellow with EPIC. His research explores the impact of global warming on the economy, including labor productivity, mortality rate, and agriculture yields, among other economic factors. Sébastien received his B.A. in Economics from Ecole Normale Supérieure, in his home country of France, and an M.A. in Energy and Environmental Economics from Université Paris-Dauphine. Prior to joining EPIC, he worked on assessing the impact of intermittent renewable energies on electricity prices as a research assistant at the Chaire European Electricity Markets.
DJ is a PhD student at the Woodrow Wilson School of Public Policy and International Affairs at Princeton University. His interests lie at the intersection of Earth’s atmosphere, public affairs, and the economy. He uses numerical models and large data sets to study financial risks related to climate change impacts and extreme weather events. After graduating from UW-Madison with a BS in atmospheric science, DJ was a research fellow at the National Oceanic and Atmospheric Administration’s (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL). He received an MS in civil and environmental engineering from the University of California-Davis.
James Rising is a researcher at the Grantham Research Institute at the London School of Economics. He studies and develops frameworks to model the feedback loops between environmental and human systems. He hopes to use new technologies to help communities act on those insights to support sustainability and promote social justice.
Prior to joining LSE, James held postdoctoral positions at the Energy & Resources Group at UC Berkeley and the Energy Policy Institute at the University of Chicago. He received his Ph.D. from Columbia University’s program in Sustainable Development. He previously taught within MIT’s Experimental Study Group and at Franklin W. Olin College of Engineering. He has also had a career as a software developer, working with over a dozen companies on audio and video processing, social networks, and artificial intelligence.
Ashwin Rode is a postdoctoral scholar in the Department of Economics at the University of Chicago. At EPIC, he is working on the Climate Impact Lab, a multidisciplinary endeavor that will assess climate change impacts around the world. His other research areas include the political economy of environmental and climate policy and natural resource management. Ashwin received an A.B. in Economics from the University of Chicago, an M.S. in Economics from the University of Texas at Austin, and a Ph.D. in Economics from the University of California, Santa Barbara.
Justin was a data engineer with the Rhodium Group and 2-year member of the Climate Impact Lab.
joined RHG with a background in international affairs and defense. Prior to RHG, he worked as a Cryptologic Technician in the Navy, a Foreign Service Officer at State, and a defense contractor. He is a graduate of Boston University and the Defense Language Institute. He has also taken advanced graduate training in Chinese Studies at the University of Hawaii and data science and data engineering courses at Galvanize in San Francisco.
Yuqi was a Pre-Doctoral Fellow at EPIC working on the Climate Impact Lab. Her area of interest is inter-disciplinary research including economics of climate change and pollution. Prior to joining EPIC, she studied at the University of Chicago Booth School of Business with a focus on finance and received an MBA. She also holds a Bachelor of Science in Mathematics and Economics from MIT.
Jingyuan was a Pre-Doctoral Fellow at EPIC and works on the Climate Impact Lab with Michael Greenstone. She is interested in the economics of environmental degradation and climate change. Prior to joining the University of Chicago, she worked as a research assistant at Cornell Institute for China Economic Research. Jingyuan holds an MS in Applied Economics from Cornell University and a Bachelor degree in Environmental Science and Economics from Peking University.
Jiacan Yuan is a climatologist who is interested in understanding the fundamental dynamical processes in the atmosphere and improving climate models, which could give us better predictive power and risk assessment of the changing climate. Her research apparatus is built with a fusion of advanced statistical methods, idealized general circulation models (GCM), and state of the art climate models. At present, her research is focused on assessing economic risks from the projection of future climate. Jiacan has worked on several projects on climate dynamics, including the response of large-scale circulations in the warming climate, its effects on regional weather patterns and extreme events, tropical influence on mid-latitude weather, and dynamical mechanisms of sub-seasonal variability of mid-latitude jet streams.