Supercomputer travels back in time to predict climate future

One of the reasons that new stage is needed is because of the findings of the Intergovernmental Panel on Climate Change, an international body involving some 2,500 scientists in 130 countries. The IPCC released a report on climate change in November that it believed made a conclusive case about the certainty of impending climate change. "Today, the time for doubt has passed," Chairman RK Pachauri said when the report was released.

Supercomputers have assembled a big climate-change picture, so to speak, that can show some of the things that may happen as CO² emissions increase further. But another need in climate research, said Hack, is to understand the impact of climate change on a regional level, such as what it would mean for the manager of a water project in the southwestern U.S. who wants to know how groundwater levels may be affected by warming temperatures.

"There are a lot of issues that have some practical consequences for society, and I think the next phase in the science is to develop the capabilities to answer those questions," Hack said. For that to happen, though, faster machines will be needed, he added.

For instance, developing the ability to look at how climate change may affect certain areas, and how to mitigate or adapt to the changes, will require more precision and specificity in the resolution of computer models. Liu said that just doubling a model's resolution may require an approximately tenfold increase in compute time.

But it isn't an issue of simply adding more chips and building bigger systems, although more performance would help. The effort also has to include the development of applications that combine a multidisciplinary range of sciences, such as algorithms that can scale across many processing cores. "Your applications need to scale, and they need to scale well," Hack said.

The problem is that climatic events are nonlinear, which means there's no straightforward path to a solution.

Oak Ridge is expecting the arrival of petascale systems next year, according to Hack. And while there are researchers who feel that "you can't build fast-enough computers," he said, others think that the rate of progress has been remarkable. "On some levels, we are being paced by our ability to incorporate more realistic physics," as well as other observational data about the earth, into the systems, he said.