Dear leaders, experts, alumni, teachers, students and friends,

Upon the advent of the New Year in 2023, we would like to extend our highest respect, sincerest greetings and New Year's wishes to all faculty, students and their families, global alumni, leaders at all levels, brother departments and friends from all walks of life who have long cared for and supported the development of the Department of Earth System Science (DESS), Tsinghua University!

In 2022, we thoroughly studied and implemented the spirit of the 20th National Congress of the Communist Party of China, deeply realized that education, science and technology, and human resources are the foundational and strategic pillars for building a modern socialist country in all respects, strove to practice the ideas that science and technology are our primary productive force, talent is our primary resource, and innovation is our primary driver of growth, and constantly enhanced our capability to contribute to promoting green development and harmonious coexistence between man and nature. In the year 2022, which also witnessed a new starting point for the second decade of Tsinghua's new century, the 15th Party Member Congress was held in the university, which drew a beautiful blueprint for high-quality development in the critical period of marching towards the forefront of world-class universities. Faculty members, students and staff of the DESS have earnestly implemented the university’s "14th Five-Year Plan" and medium-and long-term development goals, and accelerated their pace to score delightful new achievements.

Over the past year, the DESS served the country's major strategic demands to achieve the goals of “carbon peaking and carbon neutrality”, further conducted interdisciplinary joint research in carbon emission accounting technology, coordinated response to pollution reduction and carbon mitigation, climate change and human health, and continued to promote the development of various disciplines such as Earth system observation, Earth system process, Earth system model and Earth system management. The Earth System Science Numerical Simulator Facility, which was jointly built by the DESS of Tsinghua, passed the national acceptance, and contributed Tsinghua’s wisdom to the construction of the “Pillars of a Great Power”. We strive to open up new fields and tracks for the development of Earth system science, constantly shape new kinetic energy and advantages for development, bravely grasp new opportunities and new situations for development, and accelerate the construction of a world-class discipline of Earth system science with Tsinghua style and China characteristics.

With regard to the development of the faculty team, the DESS, centering on the overall goal of talent work in the 14th Five-Year Plan, has followed "Several Opinions of Tsinghua University on Further Implementing the Core Strategy of Strengthening the University with Talents in the New Era", and endeavored to cultivate top-notch innovative talents on campus to address the problems and deficiencies in talent resources. Bai Yuqi, Huang Xiaomeng and Cai Wenjia were promoted to permanent professorships. Lin Yanluan and Yu Le were selected into national talent programs.

In improving the quality of independent cultivation of talents, the DESS has strengthened the ideological and political elements of courses and further improved and optimized the curriculum system. The department has completed the qualification evaluation of ecology and atmospheric science disciplines, and been authorized to offer doctorate degree in atmospheric science. The undergraduate minor in Earth System Science was approved, with enrollment starting in the fall of 2022. The Party branch of graduate students fully played its role as a battle stronghold, and actively participated in voluntary activities to combat the COVID-19 pandemic. As a result the general branch of the Youth League of the DESS and other collectives won the collective honor of the “Tsinghua Youth Pioneers Combating Covind-19”. Yue Siyu, a 2022 graduate, won the Tsinghua University Graduate Sailing Award, Ren Zhehao, a 2018 doctoral student, won the Tsinghua University Jiang Nanxiang Scholarship and Lin Feng Counselor Award, and Zhou Yufeng, a 2021 doctoral student, won Tsinghua University's "December 9th" Counselor Award.

Over the past year, the DESS continued to leverage its distinctive features and obvious advantages in the fields of earth system model, atmospheric chemistry and atmospheric environment, weather and climate, among others. In 2022, atmospheric science rose to the 26^th place in the Shanghai Ranking's Global Ranking of Academic Subjects (GRAS); it ranked the ninth in the world in atmosphere and meteorology of the 2023 US News Rankings. Tsinghua's ecology discipline has developed a good academic reputation in the fields of ecosystem ecology, global change ecology, sustainable development ecology, etc., ranking the fourth in the world in environmental/ecological disciplines in the 2023 US News Rankings.

In terms of scientific research output, in 2022, the faculty and students of the DESS published more than 290 papers indexed by SCI and SSCI. The research teams of Guan Dabo and Cai Wenjia of the DESS respectively released the Annual Report 2022 for Carbon Dioxide Emission Accounts of Global Emerging Economies and the Lancet Countdown on Health and Climate Change, 2022 (global report and China report). Zhang Qiang, Yang Kun, Guan Dabo, Liu Zhu and Tong Dan were listed as Highly Cited Researchers 2022 by Clarivate. The achievement of Lu Hui's research group, “Long term surface soil moisture (SSM) dataset”, won the top ten most valuable shared open remote sensing dataset awards in 2021. The research achievement "Research on Drivers of Spatio-Temporal Changes of Air Pollution" led by Zhang Qiang's research group was selected as "Top Ten Scientific and Technological Progress of Ecological Environment in China in 2021". Zhang Qiang won the "Scientific Exploration Award" in 2022, and Tong Dan the fifth Damo Academy Young Fellow Award. The "Computational Earth Science Team" won the title of "Tsinghua University Advanced Collective" in 2021. Liu Zhu was invited to be a judge of Frontier Planet Prize. In 2022, the faculty members in the DESS received financial support for 34 vertical projects, including 13 projects supported by the National Natural Science Foundation of and 7 national key R&D projects. Representative achievements include:

1. To quantify the co-benefits of CO₂ emission reduction nationwide contributed by China’s clean air actions since the implementation of the Air Pollution Prevention and Control Action Plan in 2013, Zhang Qiang's Research Group reviewed the five major clean air measures which may also lead to co-reductions on CO₂ emissions, such as phasing out outdated industrial capacity and upgrades on industrial boilers, developed measure-specific co-reduction effect assessment technology on the basis of the independently developed model of the Multi-resolution Emission Inventory of China (MEIC), and finally estimated the co-benefits of CO₂ emission reduction from China’s clean air actions. This achievement has been recently published in Nature Communications as an article titled “Co-benefits of CO₂ emission reduction from China’s clean air actions during 2013-2020”.

2. Liu Zhu's Research Group realized the near-real-time monitoring of global CO₂ emissions by using the global near-real-time database “Carbon Monitor”, and updated the latest global surplus carbon budget. The results were published in Nature Reviews: Earth and Environment as an article titled " Monitoring global carbon emissions in 2021". Based on statistics, remote sensing, observation and other multi-source data, the team has built a near-real-time accounting model of anthropogenic carbon emissions, quantitatively evaluated the daily carbon emissions changes of global power generation, industry, transportation, residential and other sectors, and systematically analyzed the characteristics of daily carbon emissions of various countries and sectors during the first year of the COVID-19 pandemic (2020). The research results were published online in the journal Nature Geoscience as an article titled “Global patterns of daily CO2 emissions reductions in the first year of COVID-19”. The research group also analyzed the health co-benefits of Beijing residents' travel modes to different age groups and genders. The results were published in the journal The Lancet Planetary Health as an article titled "Scenarios of demographic distributional aspects of health co-benefits from decarbonizing urban transport".

3. Wang Yong, in conjunction with several research groups at home and abroad, analyzed how the black carbon aerosol in the early Indian monsoon regulated the dust concentration and its influence on monsoon precipitation through the interaction with climate by means of observational data, long-term reanalysis data, and climate model simulations, and made a detailed mechanism analysis especially for the situation during the COVID-19 pandemic in 2020. The results were published in Nature Communications as an article titled “Black Carbon-Climate Interactions Regulate Dust Burdens over India Revealed during COVID-19”. Based on the multi-model and multi-set climate simulation test and temperature-economic evaluation model of the Sixth Coupled Model Comparison Program (CMIP6), the research group studied the impact of land use on the global surface average temperature and daily temperature variability and the global economy through biogeochemical processes and biogeochemical processes since 1850. The results were published in Nature Communications as an article titled “Contrasting influences of biogeophysical and biogeochemical impacts of historical land use on global economic inequality”.

4. Yu Le and Li Wei’s Research Groups organized international cooperation at home and abroad to estimate the cumulative loss of forest biomass caused by oil palm encroachment on forests from 2001 to 2015 in the light of high-resolution biomass data and data set of oil palm plantation area change, finding that the expansion of oil palm plantations encroached forests with higher carbon density after 2007. The results were published in Nature Sustainability as an article titled "Recent expansion of oil palm plantations into carbon-rich forests".

5. Sergey Venevsky, a visiting associate professor in the DESS, and Wu Chao, a doctoral graduate of a research group and a postdoctoral fellow at Yale University, in conjunction with researchers from China, the United Kingdom, Germany and South Africa, used an atmosphere-fire-carbon cycle coupling model integrating 34 earth system models to quantitatively analyze the feedback effect of historical and future fire dynamic changes on the global atmosphere-carbon cycle. The research results were published in the Proceedings of the National Academy of Sciences in an article titled " Reduced global fire activity due to human demography slows global warming by enhanced land carbon uptake".

6. Zhang Qiang and Tong Dan's Research Groups built 18 groups of scenarios combining two types of policies with different strengths to evaluate the impact of climate control policies and air pollution control policies on protecting people's health. The simulation of the future changes of PM2.5 pollution exposure level in China under various scenarios and the related health loss estimation results show that reducing pollution and mitigating carbon emission is the only way to reduce the health loss of air pollution in China. The results were published in The Lancet Planetary Health as an article titled "Role of Climate Goals and Clean-air policies on reducing future air polarization deaths in China: a modeling study".

7. Cai Wenjia's Research Group, in conjunction with domestic and foreign teams, quantified the emission reduction costs to achieve carbon neutrality in 17 major countries and regions around the world, estimated the emission reduction benefits from reducing labor productivity losses related to high temperature, and identified the relative relationship and tempo-spatial distribution of cost benefits. The research results were published in The Lancet Planetary Health as an article titled "Labour productivity and economic impacts of carbon mitigation: a modelling study and benefit–cost analysis".

In terms of international cooperation and exchange, the department has initially reached a strategic cooperation intention with the World Meteorological Organization (WMO). The joint training program of doctoral students between the DESS and the University of Exeter in the United Kingdom is being advanced. Despite the impact of COVID-19 prevention and control, 12 teachers and students were sent to participate in international conferences and academic exchanges in 2022. We will continue the review work for the Global Change Young Talents Fund and reward outstanding young students in China engaged in the research of global change and earth system science.

In terms of laboratory construction, the leadership transition of the Ministry of Education Key Laboratory for Earth System Modeling has been completed, and the selection for the 11th Waves Award and the release of the 2022 Open Fund have been carried out. The Lake Poyang Base of the Field Scientific Observation and Research Station of East Asian Migratory Birds and Habitat Ecology under the Ministry of Education was unveiled, and the construction of the field observation system is being accelerated.

In 2022, under the strong leadership of Tsinghua University’s Party Committee, the Party Committee of the DESS set up a special work leading group and a special office for COVID-19 pandemic prevention and control, and detailed the safeguard measures for pandemic prevention and control services. At the critical moment when the COVID-19 epidemic in the school became severe and the original security system was severely impacted, the anti-epidemic commando of the DESS settled in the student dormitory, showing the courage and responsibility of people of the DESS, Tsinghua, and realizing the unremitting prevention and control of the COVID-19 epidemic with teaching and research, and reform and development still going on as usual.

When one drinks water, one must not forget where it comes from. We are well aware that these advances would not be achieved without the full support of members of the Scientific Steering Committee such as Academician Xu Guanhua and Academician Guo Huadong, leaders at all levels of the university, brother departments and colleagues from all walks of life! Once again, we would sincerely thank all of you for your love and guidance! We look forward to more care and support from you!

We should advance steadily with lofty ideals in mind. Looking back on the road, we have sailed through winds and waves with great courage and fortitude. Looking ahead, we will endeavor to score higher achievements. In 2023, the DESS of Tsinghua will continue to lay a solid foundation for the development of disciplines, adhere to the fundamental tasks of cultivating talents with great virtues, focus on improving the ability of training top-notch talents, serve the country's global change response, pursue the goals of “carbon neutrality and carbon peaking” and comprehensively promote the great rejuvenation of the Chinese nation with Chinese modernization as our highest purposes, and write a better new chapter in the emerging fields of earth system science research and interdisciplinary research.

We sincerely wish good health, every success in your work, happiness for you and your families in the coming year!

Tsinghua University Department of Earth System Science

January 1(st), 2023