Monday, February 15, 2010

Alternative futures of a warming world

Pacific Northwest National Laboratory has something so interesting that I couldn’t resist quoting it at length: An international team of climate scientists will take a new approach to modeling the Earth's climate future, according to a paper in 11 February Nature. The next set of models will include, for the first time, tightly linked analyses of greenhouse gas emissions, projections of the Earth's climate, impacts of climate change, and human decision-making.

This approach will influence the next international scientific assessment undertaken by the Intergovernmental Panel on Climate Change (IPCC). It will provide the framework for thousands of individual scientific studies on climate impacts and adaptation, climate modeling, and changes in the way societies generate and use energy.

"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. … "This comparative evaluation is extremely important to determine the technical, policy and economic requirements for reaching whatever society decides is a safe level of climate change. We hope to provide decision-makers with better tools to help people deal with a shifting climate," he said.

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. To do so, the scientists wanted a more comprehensive endpoint than greenhouse gas accumulation and a more comprehensive view of the world as the climate changes. "We wanted to explore how environmental and social vulnerability would evolve. In addition to considering how much, when and where climate changes, we also need to consider how different human futures will influence the impacts of climate change," said Moss.

The 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.

The scientists called each of these futures 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.

Another key innovation relies on the concept that many different human futures could produce any particular climate future or RCP. Integrated assessment modelers, such as those at PNNL's JGCRI, will research how different human futures increase or decrease emissions of pollutants and activities that cause climate change….

The next set of climate models by international teams will integrate many manmade and natural processes. Both manmade and natural processes interconnect a great deal in the climate system. Graphic courtesy of Moss et al, Nature 11 Feb 2010, from the PNNL website

1 comment:

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