Over the last 40 years, the number of kids and teens with obesity has skyrocketed worldwide. In 1975, an estimated 5 million girls and 6 million boys were obese. By 2016, those numbers had risen to an estimated 50 million girls and 74 million boys, according to a report published online October 10 in the Lancet. While the increase in childhood obesity has slowed or leveled off in many high-income countries, it continues to grow in other parts of the world, especially in Asia.

Using the body mass index, a ratio of weight to height, of more than 30 million 5- to 19-year-olds, researchers tracked trends from 1975 to 2016 in five weight categories: moderate to severe underweight, mild underweight, healthy weight, overweight and obesity. The researchers defined obesity as having a BMI around 19 or higher for a 5-year-old up to around 30 or higher for a 19-year-old.

Globally, more kids and teens — an estimated 117 million boys and 75 million girls — were moderately or severely underweight in 2016 than were obese. But the total number of obese children is expected to overtake the moderately or severely underweight total by 2022, the researchers say.

The globalization of poor diet and inactivity is part of the problem, says William Dietz, a pediatrician at George Washington University in Washington D.C., who wrote a commentary that accompanies the study. Processed foods and sugary drinks have become widely available around the world. And urbanization, which also increased in the last four decades, tends to reduce physical activity, Dietz says.

While obesity rates for kids and teens have largely leveled off in most wealthy countries, those numbers continue to increase for adults. The findings in children are consistent with evidence showing a drop in the consumption of fast food among children and adults in the United States over the last decade, Dietz says. “Children are going to be much more susceptible to changes in caloric intake than adults.”

Many people may be fuzzy on the details of North America’s colonial history between Columbus’ arrival in 1492 and the Pilgrims’ landing on Plymouth Rock in 1620. But Europeans were actively attempting to colonize North America from the early 16th century onward, even though few colonies survived.

As historian Sam White explains in A Cold Welcome, most early attempts were doomed by fatally incorrect assumptions about geography and climate, poor planning and bad timing.
White weaves together evidence of past climates and written historical records in a comprehensive narrative of these failures. One contributing factor: Explorers assumed climates at the same latitude were the same worldwide. But in fact, ocean currents play a huge role in moderating land temperatures, which means Western Europe is warmer and less variable in temperature from season to season than eastern North America at the same latitude.

On top of that, explorations occurred during a time of global cooling known as the Little Ice Age, which stretched from the 13th to early 20th centuries. The height of exploration may have occurred at the peak of cooling: Starting in the late 16th century, a series of volcanic eruptions likely chilled the Northern Hemisphere by as much as 1.8 degrees Celsius below the long-term average, White says.

This cooling gave Europeans an especially distorted impression of their new lands. For instance, not long after Spanish explorer Sebastián Vizcaíno landed in California’s Monterey Bay in December 1602, men’s water jugs froze overnight — an unlikely scenario today. Weather dissuaded Spain from further attempts at colonizing California for over a century.
Harsh weather also heightened conflict when underprepared Europeans met Native Americans, whose own resources were stretched thin by unexpectedly bad growing seasons.

A Cold Welcome is organized largely by colonial power, which means findings on climate are repeated in each chapter. But White’s synthesis of climate and history is novel, and readers will see echoes of today’s ignorance about the local consequences of climate change. “Human psychology may be both too quick to grasp at false patterns and yet too slow to let go of familiar expectations,” White writes.

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A proposed form of ice acts like a cross between a solid and a liquid. Now, a new study strengthens the case that the weird state of matter really exists.

Hints of the special phase, called superionic ice, appeared in water ice exposed to high pressures and temperatures, researchers report February 5 in Nature Physics. Although such unusual ice isn’t found naturally on Earth, it might lurk deep inside frozen worlds like Uranus and Neptune (SN Online: 3/5/12).
Normal ice is composed of water molecules, each made of an oxygen atom bonded to two hydrogen atoms. As water freezes, those molecules link up to form a solid. But superionic ice is made up of ions, which are atoms with a positive or negative electric charge. Within the material, hydrogen ions flow freely through a solid crystal of oxygen ions.

“That’s really strange behavior for water,” says study coauthor Marius Millot, a physicist at Lawrence Livermore National Laboratory in California. Although the superionic state was first predicted 30 years ago, “up until now we didn’t really know whether this was something that was real.”

At extremely high pressures, familiar substances like water can behave in unusual ways (SN: 1/14/12, p. 26). Working with a sample of ice that was crushed between two diamonds, Millot and colleagues used a laser to create a shock wave that plowed through the ice, boosting the pressure even more. At first, the density and temperature of the ice ramped up smoothly as the pressure increased. But at around 1.9 million times atmospheric pressure and 4,800 kelvins (about 4,500° Celsius), the scientists observed a jump in density and temperature. That jump, the researchers say, is evidence that superionic ice melted at that point. Although we normally think of ice as being cold, at high pressures, superionic ice can form even when heated. The melting occurred at just the conditions that theoretical calculations predict such ice would melt. The physicists didn’t measure the pressure at which the superionic phase first formed.

The electrical conductivity of the material provided another hint of superionic ice: The level of conductivity was consistent with expectations for that phase of matter. Whereas metals conduct electricity via the motion of electrons, in superionic ice, the flowing hydrogen ions transmit electricity.
The researchers “provide quite good evidence” of the new phase, says Alexander Goncharov, a physicist at the Carnegie Institution for Science in Washington, D.C., who was not involved with the study.

Others are more cautious about the significance of the work. “It’s definitely providing more insight into water at these conditions,” says physicist Marcus Knudson of Washington State University in Pullman. But, he says, “I don’t see strong evidence that there’s a melting transition in their data.”

So more work remains before this weird kind of ice is fully understood. For now, the superionic state of water seems likelier, but still on thin ice.