PERSPECTIVES There are amendments to this paper science in the 1980s, global expansion in the 1990s and present-day ESS. A timeline of The emergence and evolution key events, publications and organizations that characterize the evolution of ESS is of Earth System Science shown in Fig. 1. Will Steffen , Katherine Richardson, Johan Rockström, Beginnings (pre-1970s). Past Hans Joachim Schellnhuber, Opha Pauline Dube, Sébastien Dutreuil, conceptualizations of the Earth formed important precursors to the contemporary Timothy M. Lenton and Jane Lubchenco understanding of the Earth System. Abstract | Earth System Science (ESS) is a rapidly emerging transdisciplinary Examples include J. Hutton’s 1788 ‘theory endeavour aimed at understanding the structure and functioning of the Earth as a of the Earth’, Humboldtian science in the 19th century and V. Vernadsky’s 1926 complex, adaptive system. Here, we discuss the emergence and evolution of ESS, ‘The Biosphere’7. Understanding outlining the importance of these developments in advancing our understanding of the historical roots of ESS, however, global change. Inspired by early work on biosphere–geosphere interactions and by requires a focus on the second half of the novel perspectives such as the Gaia hypothesis, ESS emerged in the 1980s following 20th century when, in a Cold War context, demands for a new ‘science of the Earth’. The International Geosphere-Biosphere important shifts occurred in the Earth 8 Programme soon followed, leading to an unprecedented level of international and environmental sciences . Thanks to military patronage taking precedence commitment and disciplinary integration. ESS has produced new concepts and over traditional sources of funding for frameworks central to the global-change discourse, including the Anthropocene, Earth sciences, geophysics experienced tipping elements and planetary boundaries. Moving forward, the grand challenge unprecedented growth9. Moreover, for ESS is to achieve a deep integration of biophysical processes and human surveying and monitoring the global dynamics to build a truly unified understanding of the Earth System. environment became a strategic imperative, providing information that would later be useful for contemporary ESS10,11. For tens of thousands of years, indigenous such as climate change, biodiversity loss and In the middle of the 20th century, cultures around the world have recognized nutrient loading. Indeed, one of the most international science started to develop, cycles and systems in the environment, pressing challenges of ESS is to determine epitomized by the International Geophysical and that humans are an integral part of whether past warm periods in Earth history Year (IGY) 1957–1958 (REF.12). This these. However, it was only in the early are a possible outcome of current human unprecedented research campaign 20th century that contemporary systems pressures and, if so, how they can best be coordinated the efforts of 67 countries to thinking was applied to the Earth, initiating avoided. obtain a more integrated understanding the emergence of Earth System Science In this Perspective, we explore the of the geosphere, particularly glaciology, (ESS). Building on the recognition that emergence and evolution of ESS, outlining oceanography and meteorology. One of life exerts a strong influence on the Earth’s its history, tools and approaches, new the key impacts of the IGY was a lasting chemical and physical environment, ESS concepts and future directions. We focus transformation in the practices used to originated in a Cold War context with the largely on the surface Earth System, that understand how the Earth works. The rise of environmental and complex system is, the interacting physical, chemical interpretative and qualitative geological sciences1–3. and biological processes between the and climatological research based on The ESS framework has since become a atmosphere, cryosphere, land, ocean and field observations — as classically powerful tool for understanding how Earth lithosphere. Although other definitions of studied by geographers — was replaced operates as a single, complex, adaptive ESS include the whole planetary interior4,5, by field instrumentation, continuous system, driven by the diverse interactions the processes of which become increasingly and quantitative monitoring of multiple between energy, matter and organisms. important as the timescale of consideration variables and numerical models13. This In particular, it connects traditional increases6, we focus on the surface, where transformation led to the two contemporary disciplines — which typically examine the majority of materials are cycled paradigms that structure the Earth sciences: components in isolation — to build a within the Earth System. modern climatology and plate tectonics14,15. unified understanding of the Earth. With Ecology and environmental sciences human activities increasingly destabilizing The emergence of ESS also developed rapidly16. Ecosystem ecology the system over the last two centuries, We begin with a brief history of ESS, emerged with the work of G. E. Hutchinson this perspective is necessary for studying outlining important historical phases, and the brothers H. Odum and E. Odum, global changes and their planetary-level including: precursors and beginnings up supported by the Scientific Committee on impacts and risks, including phenomena through the 1970s, the founding of a new Problems of the Environment (SCOPE). 54 | JANUARY 2020 | VOLUME 1 www.nature.com/natrevearthenviron PERSPECTIVES Organizations 1920 1920 1920 Vernadsky’s Publications biogeosphere 2 Campaigns interaction , 1926 and events International Keeling atmospheric CO2 Geophysical measurements begin, Year (IGY), 1958–present day 1957–58 1970 1970 1970 Lovelock’s Gaia NASA’s ‘The Blue Marble’ 30 hypothesis , 1972 image taken, 1972 World Climate Research Programme (WCRP), 1980– 1980 1980 1980 present day International ‘Earth System Science’ Bretherton Geosphere-Biosphere coined, 1983 diagram4, 1986 Programme (IGBP), 1986–2015 Brundtland 45 Intergovernmental report , 1987 Panel on Climate 1990 1990 1990 Change (IPCC), 1988– DIVERSITAS, present day 1991–2014 International Human Dimensions Programme (IHDP) on Schellnhuber’s second Large-scale Global Environmental Copernican Crutzen proposed the Biosphere- Change, 1996–2014 revolution53, 1999 concept ‘Anthropocene’, Atmosphere 2000 Experiment in 2000 2000 2000 Amazonia (LBA) Earth System Science Vostok ice core record66, 1999 Amsterdam conference begins, 1999– Partnership (ESSP), present day 2001–2012 ‘Challenges of a IGBP synthesis55, 2004 Changing Earth’, 2001 Rockström et al’s planetary boundaries 2010 framework119, 2009 2010 2010 Future Earth, 2012–present day Steffen et al.’s ‘Hothouse 117 2020 Earth’ , 2018 2020 2020 Fig. 1 | Timeline illustrating the development of Earth System Science from the mid-20th century. The figure shows the key organizations, events and concepts that have helped to define and develop Earth System Science. Large projects such as the International the publication of R. Carson’s Silent Spring22, spacecraft on 7 December 1972, sharpened Biological Program (IBP) were a major step the ‘Only One Earth’ discourse at the 1972 the research focus on the planet as a whole towards a global ecological study. These United Nations Conference on the Human and highlighted its vulnerability to the efforts provided the basis for understanding Environment, the first alerts on ozone general public27–29. the role of the biosphere in the functioning depletion and climatic change23,24 and the Amidst these developments, J. Lovelock of the Earth System as a whole17–21. Club of Rome’s publication of the Limits to introduced the term Gaia in 1972 as an The 1960s and 1970s were marked Growth report25, the latter warning of the entity comprised of the total ensemble of by a broadening cultural awareness of finitude of economic growth due to resource living beings and the environment with environmental issues in both the scientific depletion and pollution26. Visual images of which they interact, and hypothesized community and the general public. the Earth, in particular ‘The Blue Marble’ that living beings regulate the global Driving this increased awareness were image taken by the crew of the Apollo 17 environment by generating homeostatic NATURE REVIEWS | EARTH & ENVIRONMENT VOLUME 1 | JANUARY 2020 | 55 PERSPECTIVES and biological processes. This created a Physical climate system Climate significant challenge in bringing different Atmospheric physics/dynamics change disciplines together to study the Earth System as a whole. The challenge of international Ocean Terrestrial energy Sun dynamics moisture commitment and disciplinary integration was addressed in 1986 by the International cing Council for Science (ICSU) with the Human Global moisture Soil CO 2 activities formation of the International Geosphere- 5,41–43 atospheric Biosphere Programme (IGBP) , Str which joined the World Climate Research External for s Marine Terrestrial Land chemistry/dynamics biogeochemistry ecosystems use Programme (WCRP), formed in 1980 to study the physical-climate component of lcanoe Vo the Earth System. The IGBP was originally structured around a number of core projects Tropospheric chemistry CO2 on biogeochemical aspects of the Earth Biogeochemical cycles Pollutants System: ocean carbon cycle, terrestrial ecosystems, atmospheric chemistry, the Fig. 2 | The NASA Bretherton diagram of the Earth System. The classical, simplified