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Pulitzer Prize-winning presidential historian Doris Kearns Goodwin shared 50 years' worth of research and insights on four U.S. presidents with a sold-out crowd at Macky Auditorium on Thursday. She was this year's featured speaker in the fourth annual Leo Hill Leadership Speaker Series.

Abrupt thawing of permafrost will double previous estimates of potential carbon emissions from permafrost thaw in the Arctic and is already rapidly changing the landscape and ecology of the circumpolar north, a new ¶¶ÒõÂÃÐÐÉä Boulder-led study finds.