Can we trust climate models?

Scientists use models like the Community Climate System Model (CCSM, shown here) to increase their understanding of the world's climate patterns and learn how they may affect regions around the globe. Credit: PNNL

Scientists use models like the Community Climate System Model (CCSM, shown here) to increase their understanding of the world’s climate patterns and learn how they may affect regions around the globe. Credit: PNNL

Computers crash, freeze, corrupt documents, and otherwise make us swear at them every day. At such moments I briefly blow my own fuse, and my computer becomes my enemy – until I remember it’s revolutionised how I work, communicate and access information. But knowing how easily they can go wrong – and how easily a small, overlooked, mistake in a piece of software can cause unexpected problems later – makes me cautious. That extends to writing this blog, when I often wonder just how much we can rely on the computer models used so widely by scientists studying global warming. So this year I’ve been asking researchers questions like: Why even use models? How can we trust that they’re accurate? How should we understand what they come up with?

These questions go deep into how science works, using evidence from what people see, or experiments we conduct, to build or knock down ideas. The best evidence is directly measured, in as much detail as possible. Today that’s available in some cases, but not all, and we can’t go back in time to get data over the long time periods that might be ideal. For example, this previously limited our understanding of global warming’s effect on tropical cyclones, Bruno Chatenoux from the Global Change and Vulnerability Unit at the United Nations Environment Program in Geneva, Switzerland told me in February. “Formal detection of trends in the existing records is challenged by data quality issues and record length,” he told me. “Model projections suffer less from this, but have other challenges, such as whether they are accurately representing all of the relevant physical processes.”

And while there are a lot of processes to represent, researchers have worked hard to establish them, underlined Xuefeng Cui from Beijing Normal University, China, in July. “Climate models have been developed by groups of scientists to include atmosphere, oceanography, land, biology, chemistry, physics, computing science for about 40 years,” he said. “They have a solid scientific foundation and model the climate system in reasonable resolution.”

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