The Full Picture

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a given socio-economic or environmental outcome. It is

recognized that mitigation and adaptation strategies

require predictions of the probability and uncertainty of

occurrence of extreme events on both weather and

climate timescales. The occurrence of extreme weather

and climate events may be infrequent, but the conse-

quences can be catastrophic to those societies and

ecosystems that are affected.

Recent progress in the atmospheric, oceanographic,

Earth system and socio-economic sciences; observations,

computer technology and global communication

systems, affords the opportunity to accelerate further

advances in the accuracy of weather, climate prediction

information and its use. These advances include greatly

expanded observations of the atmosphere, oceans, land

and ice surface, including their biogeochemical proper-

ties, more accurate weather, climate and Earth system

prediction models, aided by improvements in numerical

methods, representations of physical processes, proba-

bilistic (ensemble) prediction systems and the

continuous increase in the capacity of high-performance

computers; advanced knowledge of the theoretical and

practical limits of atmospheric and oceanic predictabil-

ity, including the influence of climate variability and

change on high-impact weather events, and the societal,

economic and environmental utilization of weather,

climate and Earth system information to assess, miti-

gate and adapt to natural and human-induced

environmental disasters.

Core elements

The core elements of an international weather, climate

and Earth system prediction project will build upon the

above achievements and will include the following.

High-resolution observations and models

– High-reso-

lution observations and models of the atmosphere,

ocean, land and biogeochemical processes will monitor

and predict the seamless interaction among weather,

climate, the Earth system and global socio-economics;

resolve the detailed properties of the atmosphere, land

surface, atmospheric composition, biogeochemistry, and

energetic oceanic eddies and boundary currents with

computational resolution consistent with the spatial

scale of the applications; address daily, seasonal, inter-

annual and multi-decadal prediction for short-term

societal functions and long-term policy decisions, and

provide scientifically-based assessments of the impacts

of predicted changes and actions to mitigate them,

including assessments of the potential consequences of

emerging geo-engineering intervention hypotheses

designed to modulate climate variability and change and

associated high-impact weather.

High-resolution assimilation and analysis

– High-reso-

lution global and regional data-assimilation and analysis

systems are needed to enhance the utility of the full

spatial/temporal resolution of observations from space,

land/ice surfaces and oceans. This requires advanced high-

resolution data-assimilation systems which employ

weather, climate and Earth system prediction models as

prediction has advanced to the point that national weather centres

routinely provide useful forecasts with a five-day forecast accuracy

comparable to the two-day forecasts of 25 years ago, including

ensemble prediction systems that provide probability estimates of

their expected level of skill for a week or more (see Bougeault and

Toth, this Volume). Climate projections of global temperature and

precipitation distribution over timescales from seasons to centuries

provide the scientific underpinning for international treaties to limit

activities that contribute to the emission of carbon dioxide and other

greenhouse gases. The consequent assessment models have become

increasingly important tools in evaluating the socio-economic and

environmental benefits and outcomes of different decisions. These

accomplishments represent some of the most significant scientific,

technological and societal achievements of the 20th century.

Building on the advances in observing systems and predictive skill

over the past three decades, there is potential for further major scien-

tific breakthroughs that will enable governments to achieve a more

effective mitigation of and adaptation to extreme weather and

climate, and to realize higher levels of societal, economic and envi-

ronmental benefits. The high priority of expanding our weather,

climate and Earth system observation, analysis and prediction capa-

bility is justified by both evidence of the increasing incidence of

weather and climate extremes as reported by the International Panel

for Climate Change,

and by the ever-increasing vulnerability of

society, economies and the environment to high-impact weather, and

climate variability and change. More than 75 per cent of the natural

disasters around the world are triggered directly or indirectly by

weather and climate events.

The artificial distinction between weather, climate and Earth

system prediction, and the link with its socio-economic and natural-

hazards mitigation applications is transitioning into a seamless suite

of models applicable over all relevant decision-making spatial and

temporal scales. Within this paradigm shift, socio-economic and

environmental demands are an integral component in the design and

implementation of a new generation of science-based global to

regional early warning systems that will enable major advances in

mitigation and adaptation to daily through multi-decadal hazards of

high-impact weather, and climate variability and change. In the same

way that the atmosphere encompasses the Earth, the expertise to

exploit further advances in observations, monitoring and prediction

of the physical-biological-chemical Earth system and its interaction

with the global socio-economic system, resides across many nations,

international organizations and diverse scientific disciplines.

Advancing the skill of weather, climate and Earth system prediction

to enable sound decisions to minimize and adapt to the societal,

economic and environmental vulnerabilities arising from high-impact

weather and climate is a global enterprise for the 21st century.

Recent progress

Global societies of today reap substantial benefits from weather and

climate observations, analyses and predictions. These benefits

include early warning systems to assess risk and reduce vulnerabil-

ity arising from weather, climate, and air-quality hazards; weather,

climate, and complex Earth system prediction systems tailored for the

specific needs of societal, economic, and environmentally sensitive

sectors (e.g. energy, water resource management, health, air and

water quality, transportation; agriculture, fisheries, leisure indus-

tries, ecosystems, biodiversity and national security), and quantitative

measures of the probability of occurrence and potential severity of

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