An international team of climate scientists say they have developed a new approach to modeling the earth's climate that will improve the accuracy of future models utilized by the IPCC and provide the framework for thousands of individual scientific studies on climate impacts and adaptation, and changes in the way societies generate and use energy.

Previous scenarios used by the IPCC usually assumed that no one would try to reduce climate change. Today, policymakers and researchers are interested in exploring ways to limit changes. Understanding the impacts and interactions of activities such as increasing energy efficiency and conservation, developing new renewable fuels to replace fossil-based fuels, and regulating how land is used are crucial to better decision-making.

In the new process, researchers will use scenarios to evaluate human contributions to climate change, the response of the Earth system, the impacts of a wide range of future climates, and the effects of different response options and policies to reduce net emissions and adapt to new climate conditions.

"This is an open-ended approach that enables us to compare the environmental and socio-economic effects of different potential responses to climate change," said lead author Richard Moss, a scientist with the Department of Energy's Pacific Northwest National Laboratory who performs climate change impacts research at the Joint Global Change Research Institute in College Park, Md.

In the new study, published in Nature, scientists defined four possible climate futures by how much of the sun's energy the atmosphere retains. Multiple factors affect this, including greenhouse gas accumulation, the presence of atmospheric particles, land use and other features.

Each of these futures was labeled a "representative concentration pathway," or RCP. Many independent groups of scientists will use the RCPs in climate models to project changes in a range of climate conditions including temperature, precipitation and extreme events. In addition to focusing on the usual century-long time scales typical for climate studies, one set of experiments will focus intensively on the next few decades to provide better information on regional changes and extreme events, thus aiding decision-makers in planning adaptations to new, imminent conditions.

The new modeling technique also relies on the concept that many different human futures could produce any particular climate future or RCP. Integrated assessment modelers will research how different human futures increase or decrease emissions of pollutants and activities that cause climate change.

This type of modeling will focus on population and economic growth, the evolution of technologies, and other factors such as governmental policies and societal institutions. Analyses will include not only human activities that contribute to climate change but also the extent of vulnerability of different populations and what resources will be available to adapt to new conditions.

Following this initial modeling, other teams of researchers will then use the results of these climate and socio-economic studies in a wide range of research on the potential effects of climate change on natural resources, human health, coastal infrastructure, ecosystems and other sectors. This work will employ models of water resources, crop yields, disease vectors, ecosystems and other resources to assess how different levels of climate change will affect the things of greatest value to humankind.

Citation: Moss et al., 'The next generation of scenarios for climate change research and assessment', Nature, February 2010, 463, 747-756; doi: 10.1038/nature08823