Science Sunday: The Holy Grail of Climate Science

CU scientists work on making regional climate predictions.The next major frontier in the science of climate change is going to be the attempt to refine the prediction of impacts to smaller geographic areas, determining which regions of the earth will affected in what ways.

To date, most studies of climate change have been “global,” measuring the impacts of what scientists call climate “forcings” on the globe.

A “forcing” is specific technical term in climate science which covers an externally imposed perturbation on the globe’s climate system that changes the climate. For instance using climate models, scientists set up the current climate, then impose a “forcing,” like increasing carbon dioxide levels, or the sun’s power, or setting off a hypothetical volcano, then look at what changes occur in the climate from that effect.

Climate models – essentially complex computer simulations of the climate system — have been refined over the last ten years or so to the point where they are remarkably accurate in describing these global changes. But now, the “holy grail” of climate science, says Boulder’s National Center of Atmospheric Research’s climatologist Caspar Ammann, is to look at the impacts of these forcings on a smaller scale.

“The holy grail question now,” Ammann says, “is, when we change radiative forcing – that can be greenhouse gases or solar variations or volcanoes – the question is, Is the only forcing that comes from that signal simply in the globally averaged balance?

“In other words, if you kick the system, does the whole system warm up, or are there are particular impacts on that system that give you on a regional basis more information?”

CU’s SORCE satellite. NASA illustration
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The answer to these regional impacts is what most people really want know. How will climate change affect me? The most recent Intergovernmental Panel on Climate Change report took some tentative steps in this direction predicting, for instance, that climate in the southwestern U.S., including Colorado, would become drier over time, and that precipitation patterns in the Rockies would change. But these regional predictions are neither very detailed nor very reliable.

Now a NASA satellite designed, built and controlled by the University of Colorado-Boulder is going to help scientists with one aspect of the regional prediction issue by measuring the climate impact of the solar cycle peak that’s coming in 2012.

In 1610, Galileo Galilei, peering through his new telescope at the sun, found that its surface was dotted with dark spots. In 1843, a German astronomer named Heinrich Schwabe found that the number of sunspots varied in a cycle of 11 years. When the number of sunspots is greatest – known as the “solar maximum” – the sun’s energy output is also highest.

Solar max can have a number of effects. The increase in magnetic radiation from the sun can knock out satellites and even electric power plants on Earth. It can also cause beautiful auroras in the atmosphere.

The global impact of the solar cycle on climate is small. During the last solar max in 2000-2001, the global mean temperature on earth increased only 0.2 degrees Fahrenheit. But parts of the central U.S. warmed by 0.7 degrees, and a region off the coast of California cooled slightly, according to a paper by Judith Lean of Naval Research Laboratory and CU’s Tom Woods, who is chief investigator for the CU satellite mission, known as the Solar Radiation and Climate Experiment (SORCE).

Solar activity alters interactions between Earth’s surface and its atmosphere, which drive global circulation patterns, said Woods. While warming on Earth from increased solar brightness is modest compared to the natural effects of volcanic eruptions, cyclical weather patterns like El Nino or human emissions of greenhouse gases, regional temperature changes can vary by a factor of eight.

In addition to looking at climate impacts of the solar max, SORCE will help scientists better understand violent space weather episodes triggered by solar flares and coronal mass ejections that affect the upper atmosphere and are more prevalent in solar maximum and declining solar cycle phases, said Woods. The severe “Halloween Storms” in October and November 2003 disrupted GPS navigation and communications, causing extensive and costly rerouting of commercial “over-the-poles” jet flights to lower latitudes, he said.

NASA’s $88 million SORCE mission was launched in 2003. The mission was extended in August through 2012 to, providing about $18 million to CU’s Laboratory for Atmospheric and Space Physics.

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Dan Whipple

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