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Top stories: What a Trump presidency means for science, rats giggle when tickled, and more

What Trump can—and can't—do all by himself on climate

Despite the vulnerability of many of his own properties to sea level rise, on the campaign trail President-elect Donald Trump stuck with Republican orthodoxy in questioning human-driven climate change, and criticizing the steps the Obama administration has taken to combat it. Trump claimed he would “cancel” the Paris agreement, a global deal to curb global warming, in his first 100 days in office. He put a climate change skeptic at the head of his transition team. His term will likely mimic Reagan’s, which was riddled with info leaks, resignations, and lawsuits in environmental agencies. States and cities can still promote their own policy in protest, however. Most importantly: Scientists will need to find ways to make their concerns crystal clear to the president-elect.

Here’s some advice for you, President Trump, from scientists

The voters have chosen Donald J. Trump as the 45th president of the United States. So now it’s time for scientists to share their thoughts with the business tycoon who triumphed over both Democrat Hillary Clinton and much of the Republican Party he represented in the election. There has been almost no interaction between the science community and the campaign over the past 18 months. Most academics didn’t support Trump and never expected him to beat Clinton. Trump operatives didn’t do any outreach to the scientific establishment, and its agenda wasn’t addressed during the campaign. The election results confirmed the community’s status as outsiders.

Watch these ticklish rats laugh and jump for joy

For the ticklish among us, just the approach of wiggling fingers is enough to elicit squeals, if not screams. And it turns out we’re not the only ones. Now, a study in rats pinpoints the “tickle center” of the mammalian brain, showing for the first time that stimulating neurons in that region can elicit a paroxysm of ultrasonic squeaks, the rat version of human laughter. They also jump for joy. Ticklishness does, however, depend on their mood. But, of course, who wants to be tickled when they’re stressed out anyway?

Why did Greenland’s Vikings disappear?

In 1721, missionary Hans Egede sailed a ship called The Hope from Norway to Greenland, seeking Norse farmers whom Europeans hadn’t heard from in 200 years in order to convert them to Protestantism. He explored iceberg-dotted fjords that gave way to gentle valleys, and silver lakes that shimmered below the massive ice cap. But when he asked the Inuit hunters he met about the Norse, they showed him crumbling stone church walls: the only remnants of 500 years of occupation. Archaeologists still wonder today. No chapter of Arctic history is more mysterious than the disappearance of these Norse settlements sometime in the 15th century. Over the last decade, however, new excavations across the North Atlantic have forced archaeologists to revise some of these long-held views.