Climate Change 2001:
Working Group I: The Scientific Basis
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14.1 Introduction

There has been encouraging progress over this first decade of the IPCC process. We understand better the coupling of the atmosphere and ocean. Significant steps have been taken in linking the atmosphere and the terrestrial systems although the focus tends to be on water-energy and the biosphere with fixed vegetation patterns. Even so, revealing and unexpected teleconnections are being discovered; moreover, progress is being made towards model structures and data sets that will allow implementation of coupled atmosphere-ocean-terrestrial models that include key biological-biogeochemical feedbacks. There is also encouraging progress in developing integrated assessment models that couple economic activity, with associated emissions and impacts, with models of the biogeochemical and climate systems. This work has yielded preliminary insights into system behaviour and key policy-relevant uncertainties.

The challenges are significant, but the record of progress suggests that within the next decade the scientific community will develop fully coupled dynamical (prognostic) models of the full Earth system (e.g., the coupled physical climate, biogeochemical, human sub-systems) that can be employed on multi-decadal time-scales and at spatial scales relevant to strategic impact assessment. Future models should certainly advance in completeness and sophistication; however, the key will be to demonstrate some degree of prognostic skill. The strategy will be to couple the biogeochemical-physical climate system to representations of key aspects of the human system, and then to develop more coherent scenarios of human actions in the context of feedbacks from the biogeochemical-physical climate system.

Developing these coupled models is an important step. From the perspective of understanding the Earth system, determining the nature of the link between the biogeochemical system and the physical climate system represents a fundamental scientific goal. Present understanding is incomplete, and a successful attack will require extensive interdisciplinary collaboration. It will also require global data that clearly document the state of the system and how that state is changing as well as observations to illuminate important processes more clearly.

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