MUSIC: "Our World" theme
Straight ahead on "Our World" ... The Arctic icecap isn't just smaller, it's thinner, too ... A sobering update for World TB Day ... And a public health menace on wheels
KRUG: "Everyday around the world we see new roads being built, new drivers taking the road, but unfortunately these developments are not being matched with safety measures."
Those stories, spreading the flu by just breathing, and more. I'm Art Chimes. Welcome to VOA's science and technology magazine, "Our World."
U.S. scientists this week reported a decline in the older and thicker ice that is a key measure of the health of the icecap around the North Pole.
The arctic icecap normally expands in the winter and melts back in the summer, but there has been a slow and steady decline over recent years, culminating in a dramatic falloff six months ago, in September.
In a briefing for reporters this week, scientists focused not just on how large the polar icecap is, but also on how thick it is. And according to Walter Meier of the National Snow and Ice Data Center at the University of Colorado, the once-robust ice sheets are getting thinner.
MEIER: "It's like looking at a Hollywood set. You may see a facade of a building and it may look OK, but if you could see behind it you see that it's just a set, there's not a real building there. And what we're seeing with the ice cover is, we're getting thinner and thinner ice, and that ice is much more susceptible to melting during the summer, and it's much more likely to melt away."
Meier and other scientists stress that so-called "perennial" sea ice ? thicker ice that has survived at least one summer melting season, and especially older and even thicker perennial ice that has not melted in years ? is key to the health of the polar ice sheet.
In the 1980s, perennial ice covered half the Arctic Ocean. This winter it was only 30 percent.
Over this year's northern winter just ended, the arctic ice ? including the newly formed seasonal ice ? has bounced back from its record low extent in September, but if the icecap is thinner than in prior years, it means, as Meier says, that the downward trend in polar ice could continue.
Meier says a big loss of ice could have a dramatic impact on weather patterns far beyond the Arctic.
MEIER: "That's going to affect the difference in temperatures and the difference in heat near the North Pole, in mid-latitudes and lower latitudes, so that affects your ocean circulations potentially and your atmospheric circulation, your weather patterns. Exactly how it will impact, I don't think we really know yet. But there definitely will be wider climate impacts from the declining sea ice than just in the Arctic."
One thing you won't have to worry about: melting Arctic sea ice won't affect sea levels. That's not true, however, for ice that now sits on land, such as the nearby massive Greenland ice sheet.
Mention Post Traumatic Stress Disorder, or PTSD, and you possibly think of a soldier returning from war, or perhaps the dazed survivors of a natural disaster. But not every veteran or homeless earthquake victim suffers from PTSD. Scientists are trying to figure out why some people are more likely to experience symptoms than others. And as we hear from VOA's Rosanne Skirble, they're focusing on some possibilities.
SKIRBLE: PTSD is a debilitating stress-related psychiatric disorder triggered by trauma. Rates are highest among war veterans and people living in high-crime areas.
The 900 low-income urban people surveyed reported multiple traumatic events over the course of their lives, notes study co-author Rebekah Bradley, assistant professor of Psychiatry at Emory School of Medicine.
BRADLEY: "Slightly over 40 percent of our sample reports exposure to four or more different types of traumatic events. So this would be a natural disaster, a car accident, a friend or family member who had been murdered and some other kind of assault."
SKIRBLE: But not everyone exposed to trauma develops PTSD, and the researchers wanted to find out why. They studied three factors: childhood sexual and physical abuse, other types of trauma and genetic factors.
Thirty percent of the people in the study reported a history of child abuse. Those who had later also experienced other traumas had twice the number of PTSD symptoms as the adults who were not abused as children.
But a history of abuse was not enough to explain increased PTSD symptoms among adults. Rebekah Bradley says researchers suspected genetics could be a factor. They analyzed DNA samples to determine whether certain variations of a stress-related gene were present or not.