A new explanation of cold northeast winters, plus shrinking newborns and the Russian heat wave in this week’s news

A winter’s day
Scientists have found another reason why the northeastern parts of Asia and North America are so chilly in the winter, much colder than the same latitudes in Europe. Until now, researchers have blamed this observation on the interaction of weather systems and mountain ranges, and on the lack of a nearby ocean that could warm things via westerly winds. But in the March 31 Nature, Caltech researchers say they’ve spotted large-scale waves in the atmosphere that suck cold northern air over the eastern parts of the continents. —Alexandra Witze

Air pollution shrinks newborns
A woman’s exposure during pregnancy to nitrogen dioxide — a gaseous pollutant emitted by traffic and industrial smokestacks — can diminish a newborn’s size, a Spanish study finds. Scientists monitored the air pollution exposure of more than 2,000 pregnant Spanish women and identified NO2 as a major risk. For every 10-microgram-per-cubic-meter increase in NO2 exposure, a baby’s birth length was on average about 1 millimeter shorter. That tiny change boosted by 1.7 percent a baby’s risk of being unhealthily small for gestational age, the scientists reported online March 23 in Environmental Health Perspectives. —Janet Raloff

2010 Russian heat wave a surprise
Last year western Russia experienced its warmest July since 1880, with many regions setting all-time highs. But there’s no evidence that the crop-withering heat can be blamed on global warming, report university and federal scientists in Boulder, Colo. They used computer programs to analyze interactions between greenhouse gas concentrations, sea-surface temperatures and sea-ice conditions for signs of slowly evolving climate warming. Their finding, reported online March 19 in Geophysical Research Letters: “The intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability” — not to human influences or slowly evolving oceanic factors.  —Janet Raloff

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