Water, Energy and Climate

Solar energy is the fundamental driver of the Earth’s climate system, while infrared emission is the system coolant. Net heating in equatorial regions and net cooling in polar regions drive both atmospheric and oceanic circulations. It is water, however, in all its three phases that provides much of the complexity and variability in the Earth system, as well as being the fundamental determinant of habitability for most of the biota. Energy and water are inextricably intertwined in the climate system on spatial scales from the molecular to planetary and on timescales from the instantaneous to millennia. External forcing of climate, whether by solar variability or changes in atmospheric composition or volcanic eruptions, alters the energy and the water cycle, as well as the complex relationships between them. These alterations provide feedbacks in the climate system that both amplify and dampen aspects of the original change. It is these feedbacks and their coupling to the non-linear dynamics of the ocean-atmosphere system that are the most challenging issue in understanding climate and predicting the magnitude of climate change in this century. Consequently there is an urgent need to increase understanding of these complex processes and their interactions in climate system and improve their representation in climate models.

GEWEX currently leads WCRP’s studies of the dynamics and thermodynamics of the atmosphere, the atmosphere’s interactions with the Earth’s surface (especially over land), and the global water cycle. The oceans play a major role in energy and water cycle, and the lead has been with CLIVAR.
Key questions for the future include:
• How are the Earth’s energy budget and water cycle changing?
• Can we quantify feedback processes in the Earth system and determine how these processes are linked to natural variability?
• Can we predict climate variability on the seasonal to interannual timescale?

• What are the impacts of climate variability on these timescales on water resources?
• How does anthropogenic climate change couple with natural climate variability to alter regional water and energy budgets, particularly with regard to means and extremes?
• Can we track the flow of energy through the climate system and understand the nature of global warming?
These brief discussions of the climate system interactions illustrate the complexity of each of the variations and changes in the climate system components. Understanding the forcing and feedbacks among them requires a greater integration of the Programme than ever before. WCRP has a strong history of bringing together researchers to study the different components and the interactions among them, and it will continue to do so in the future. The following sections describe the contributions by the WCRP Core Projects, modelling groups and cross-cutting panels that will be coordinated and integrated to advance our understanding of the climate system and to deliver scientific knowledge that will be of use and benefit to all social and economic sectors worldwide.




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