Society’s needs for the knowledge that Earth system science can provide are urgent, but the challenges of knowledge integration and application are substantial. This closing chapter explores some of the issues that arise with the move towards an increasingly ‘applied’ Earth system science.

Introduction

At the start of this book, we traced the development of Earth system science from its early foundations, including its evolving interfaces with other academic disciplines and policy. Here we take an exploratory forward look, with a particular focus on some of the more contentious issues that currently surround climate science. We draw attention to unaddressed knowledge gaps and unstated conceptual problems, which we believe are making it harder than it need be to establish an effective communication and accommodation between policy-making and science. We argue that it is important to recognize what science can and cannot achieve, and what scholarship could achieve in the service of good policy-making, if the right questions were addressed and methodologies developed.

Nothing we say should be interpreted as diminishing the value of Earth system science as a fundamental investigation of the interacting biological and physical/chemical processes that have sustained life on Earth. However, much of the funding that has supported the rapid advances in this field of research during the past two decades has been made available by governments with a more focused agenda, keen to assess the likely magnitude and consequences of anthropogenic climate change and (increasingly) the options for mitigation of, and necessities for adaptation to, climate change on a policy-relevant timescale. Like it or not, scientists have thereby become embroiled in debates and controversies for which they were not well prepared.

In this chapter, we explore the challenges that Earth system researchers face in addressing human-induced global environmental changes and the societal consequences of global change within their research toolkit. We focus on areas of research that have particular resonance with today’s social and political demands.

The Earth system and the ‘problematic human’

The state of play and our position

The great scientific challenge faced by today’s global change scientists is to understand the Earth system. Part of this is knowing that we ourselves, as human beings, are an influential component of that system and that the understanding we develop shapes our responses to the environmental changes we see around us. In scientific terms, most of the fundamental workings of our planet, including the processes that change climate and landscapes on short and long timescales, were already well understood by the end of the twentieth century. Earth system science is the field of study that has brought these areas of knowledge together. It has not just provided insight into the phenomena of global environmental change, but also explained the ‘hows’ and ‘whys’ behind them, bringing insights into the future prospects for our planet. The enormity of the challenge lies in the realization that we are seeking to understand and predict the properties of a complex adaptive system of which we are a part, recognizing that our choices and our agency as human beings are important controls on its workings. More than that, our ability to deploy our knowledge and make choices about our actions is an important facet, perhaps even a characterizing trait, of our existence.

This chapter provides an overview of Earth system models, the various model ‘flavours’, their state of development including model evaluation, benchmarking and optimization against observational data and their application to climate change issues.

Introduction

The Earth system can be conceptualized as a suite of interacting physical, chemical, biological and anthropogenic processes that regulate the planet’s low of matter and energy. Earth system models (ESMs; Box 5.1 ) are built to mirror these processes. In fact, ESMs are the only tool available to the scientific community to investigate the system properties of the Earth, as we do not have an alternative planet to manipulate that could serve as a scientist’s laboratory.

The term ‘Earth system model’ is commonly used to describe coupled land–ocean–atmosphere models that include interactive biogeochemical components. Such models have developed progressively from the physical climate models first created in the 1960s and 1970s. Conventional climate models apply physical laws to simulate the general circulation of atmosphere and ocean. As our understanding of the natural and anthropogenic controls on climate has grown, and given the steady advances in computing power, global climate models have been extended to include more comprehensive representations of biological and geochemical processes, involving the addition of the various interacting components of the Earth system with their own feedback mechanisms. Figure 5.1 shows the conceptual differences between a conventional global coupled atmosphere–ocean general circulation model (AOGCM) and an ESM. In terms of the coupling between components, ESMs are more complex, and they have correspondingly higher computational demands.

Why have we written this book?

In 2001, the former chief executive of the UK Natural Environment Research Council (NERC), Sir John Lawton (Lawton, 2001), wrote:

In the year that followed, the research council consulted widely among its scientists, policy stakeholders and the international research community about how to address that challenge. By the autumn of 2002, a plan of action was in place. The research council had earmarked a very substantial research budget for ‘Quantifying and Understanding the Earth System’, matched by an ambitious vision for the science that this research programme – QUEST – would address:

We, the authors of this book, have worked together over several years under the auspices of QUEST (Box 1). QUEST ran from 2003 to 2011, as one of several initiatives worldwide aligned with the internationally developed Earth system science agenda for collaborative research. The research programme sought to do more than ‘just’ provide a more robust understanding of the global carbon cycle, although interactions between biogeochemical cycles and climate have been at the heart of the programme.

In this chapter, we address the biophysical impacts of climate change, and the consequent impacts on socio-economic systems. Modelling the impacts associated with future climate change provides important information for society’s mitigation and adaptation responses. It also presents significant challenges for Earth system science. We discuss the ways in which uncertainty in impact modelling arises and how it can be managed.

Introduction

Key concepts

Changes in climate, including those arising as a consequence of anthropogenic perturbations of the climate system, can result in a wide variety of impacts on Earth’s ecosystems and the human activities that depend on them. There are two good practical reasons why it is important to understand the processes involved and assess the possible magnitudes of impacts.

First, an assessment of the extent to which continued anthropogenic climate change could inflict damage is needed in order that well-informed decisions can be made about the reduction of human influences on climate. Our understanding of Earth system behaviour alerts us to the fact that action to mitigate climate change through reductions in greenhouse-gas emissions is not without consequences; so decisions to pursue mitigation options need to be weighed up on the basis of reliable estimates of the costs, risks and benefits of different courses of action.

Secondly, the increase in atmospheric greenhouse-gas concentrations since the Industrial Revolution means that further climate change is inevitable even if greenhouse-gas emissions were to be reduced soon ( Figure 6.1 ). It is therefore necessary for society to adapt to unavoidable changes. Since adaptation action is also not without consequences, it is important that adaptive action addresses credible risks , and represents an efficient allocation of resources.