5. Anthropocene

Could the Earth system be on the brink of another revolutionary change, thanks to human activities? We humans are very recent products of evolution, yet already we are transforming the planet at a global scale. The recognition that humans are now a key component of the Earth system was encapsulated in the Bretherton diagram. More recently, the term ‘Anthropocene’ has been coined to describe a new geological epoch in which human activities are transforming the Earth system at a global scale. ‘Anthropocene’ introduces how human evolution was shaped by changes in the Earth system and how we have gone on to transform the Earth system—tracing the key events on a timeline.

2. Recycling

How does the Earth system support such a flourishing of life? A habitable climate and water are essential, but organisms also need energy and materials out of which to build their bodies. The Sun provides a plentiful supply of energy, which drives the water cycle and fuels the biosphere, via photosynthesis. However, due to an almost closed system, all the elements needed by life must be efficiently recycled within the Earth system, which then need energy to transform materials chemically and to move them physically around the planet. ‘Recycling’ introduces the life-sustaining global biogeochemical cycles of matter between the biosphere, atmosphere, ocean, land, and crust.

8. Generalization

This VSI has introduced how one habitable planet—the Earth—can be studied as a system. However, in just the past few years, scientists have made the remarkable discovery that there are potentially habitable planets—exoplanets—orbiting other stars. Just as humanity’s first view of the Earth from space changed how we saw and studied our home planet, our first ‘view’ of an Earth-like planet around another star will surely change our perspective again. ‘Generalization’ explores how our understanding of the Earth system can be generalized into a science of habitable worlds in general.

7. Sustainability

Whilst human transformation of the planet was initially unwitting, now we are increasingly collectively aware of it. This changes the Earth system fundamentally, because it means that one species can consciously and collectively shape the future trajectory of our planet. We know our current way of living is unsustainable, but we are still trying to work out what a sustainable and prosperous future looks like. This is an opportunity for Earth system science, because it can tell us what makes a sustainable Earth system and what does not. ‘Sustainability’ outlines how Earth system science can help humanity in our quest for long-term sustainability, starting with the lessons we can learn from Earth history.

3. Regulation

The Earth system has maintained habitable conditions for life over geological periods of time. These conditions include an equable global temperature, enough atmospheric carbon dioxide to fuel photosynthesis, and sufficient nutrients to grow. Furthermore, for at least the past 370 million years there has been enough atmospheric oxygen to support complex, mobile animal life, but not so much that wildfires decimated vegetation. ‘Regulation’ introduces the ways in which the biogeochemical cycles of the Earth system are self-regulated, how they are coupled to the Earth’s climate, and how scientists study this regulation.

6. Projection

Where is the Earth system heading in the Anthropocene? To even begin to answer this question requires a model of how the Earth system works, and the answer depends on our collective activities as a species, and how the Earth system responds to those. The model’s role is to forecast the consequences of different assumptions about future human activities. ‘Projection’ introduces ‘Earth system models’ and some of the crucial assumptions that go into using them to forecast the future. It outlines their projections, going from shorter to longer timescales, and from the specific challenge of projecting climate change to the broader challenge of exploring other global changes.

4. Revolutions

How did today’s Earth system become so radically different from those of our planetary neighbours, Mars and Venus? The presence of life is clearly a big part of the answer. Earth system scientists now recognize that the evolution of life has shaped the planet, changes in the planetary environment have shaped life, and together they can be viewed as one process. ‘Revolutions’ shows that when this ‘co-evolution’ over Earth history is considered, three revolutionary changes leap out: the inception of life and biogeochemical cycling; the origin of oxygenic photosynthesis and the Great Oxidation; and the origin of complex life out of the Neoproterozoic environmental turmoil. Without them we would not be here.

1. Home

Earth system science is the research field that seeks to understand how our planet functions as a whole system. Its scope is broad; it spans 4.5 billion years of Earth history, how the system functions now, projections of its future state, and its ultimate fate. It also considers how humans as a species are reshaping the planet. Earth system science is a deeply interdisciplinary field, which synthesizes elements of geology, biology, chemistry, physics, and mathematics. ‘Home’ explains how Earth system science emerged and introduces some of its fundamental concepts, including James Lovelock’s Gaia hypothesis, climate regulation, feedback mechanisms, the ‘snowball Earth’ state, and how to combat global warming.