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Global warming likely to be at high end of forecast range

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More accurate assessment of cloud dynamics and atmospheric processes in the subtropics the key to more accurate predictions

By Summit Voice

FRISCO — By now, everybody knows the Earth is steadily getting warmer. The big unanswered question is just how much more temperatures will rise, and a new analysis by scientists at the National Center for Atmospheric Research suggests the increases will be at the high end of predicted spectrum.

The key to the findings were accurate assessments of moisture processes in the atmosphere over the subtropics, according to NCAR scientists John Fasullo and Kevin Trenberth.

The seasonal drying in the subtropics and the associated decrease in clouds, especially during May through August, serve as a good analog for patterns projected by climate models.

“The dry subtropics are a critical element in our future climate,” Fasullo says. “If we can better represent these regions in models, we can improve our predictions and provide society with a better sense of the impacts to expect in a warming world.” Continue reading

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Global warming: Who has the burden of proof?

Researcher says it may be time shift focus of climate research

Global warming is changing snowfall patterns in the Rockies.

By Summit Voice

SUMMIT COUNTY —Instead of questioning if humans are influencing global climate, it might be time focus on the extent of that effect, said Dr. Kevin Trenberth, one of the country’s leading climate researchers based at the National Center for Atmospheric Research in Boulder.

In a new online paper, Trenberth argues that the evidence for anthropogenic climate change is now so clear that the burden of proof should lie with research which seeks to disprove the human role.

Trenberth’s paper is one of three published recently exploring the null hypothesis — the default position that serves as a starting point for research. Currently the null hypothesis for climate change attribution research is that humans have no influence.

“Humans are changing our climate. There is no doubt whatsoever,” said Trenberth. “Questions remain as to the extent of our collective contribution, but it is clear that the effects are not small and have emerged from the noise of natural variability. So why does the science community continue to do attribution studies and assume that humans have no influence as a null hypothesis?” Continue reading

Global warming: ‘Missing’ heat found deep in the ocean

New study explains why global surface temperatures don’t rise in a straight line

A NASA temperature anomaly map for Aug. 2011, showing departures from normal compared to a 1951 to 1980 base period. Click on the image to create a map.

By Summit Voice

SUMMIT COUNTY — Changes in ocean currents and circulation are capturing some of the sun’s incoming heat deep in the ocean, according to researchers with the National Center for Atmospheric Research, who said their latest computer models account for some of the global warming heat that’s “missing” from land and sea surface temperature readings.

The heat is stored at depths below 1,000 feet and could lead to periods as long as 10 years when the rate of heating on the Earth’s surface flattens. The findings also suggest that several more intervals like this can be expected over the next century, even as the trend toward overall warming continues.

“We will see global warming go through hiatus periods in the future,” said NCAR’s Gerald Meehl, lead author of the study. “However, these periods would likely last only about a decade or so, and warming would then resume. This study illustrates one reason why global temperatures do not simply rise in a straight line.” Continue reading

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