Decadal Warning Systems - Reducing Disaster: Early Warning Systems for Climate Change - page 295

Chapter 16
Decadal Warning Systems

Doug Smith

Abstract Early warning of changes in environmental factors, such as the frequency,
intensity and duration of extreme weather events, are needed to guide infrastructure
and resilience planning and to enable early action for disaster relief. Climate has
already changed in response to human emissions of greenhouse gases, and even
larger changes are expected by the end of the century. However, the coming decade
or two will likely be infl uenced by natural internal variability and other external
forcing factors, such as changes in aerosols, which will either reduce or exacerbate
the long-term trends in many regions. The new and rapidly evolving fi eld of decadal
climate prediction uses climate models initialized with observations to provide pol-
icy makers and planners with the most accurate information possible on the climate
for the next decade or so, taking into account both natural internal variability and all
external forcing factors. This chapter reviews the current state of the art of decadal
climate prediction, focusing on the potential sources of skill, forecasting techniques,
current capability and future prospects.

Keywords Decadal climate prediction • Early warning system • External forcing •
Internal variability • Initialization

16.1 Introduction

Warming of the climate system is unequivocal (IPCC 2007 ). Since 1850, globally
averaged temperatures have increased by about 0.7°C. The fi rst decade of the
twenty-fi rst century is the warmest in the instrumental record. Observations since
1961 show that global ocean temperatures have increased to depths of at least