Sulfate in ice sheets suggests cause of dark ages
Between 533 and 536 AD, a volcanic eruption spewed dust particles into the atmosphere, causing global cooling, according to new evidence published in a paper in the Geophysical Research Letters.
Historical records, such as a failure of bread in Ireland and summertime snow in China, indicate that the climate in the mid sixth century changed drastically. Yet, the cause of the global cooling during this period has been controversial. Of the hypotheses, the most likely was that a very large volcano erupted, but evidence of volcanic ash in ice sheets had not yet been found.
Now, an international team of researchers has detected the presence of a high concentration of sulphate both in the Greenland and Antarctic ice sheets. Since the unusual level of sulphate is found in both the northern and southern hemispheres, the researchers speculate that the volcano was located near the equator, allowing the dust to diffuse to both hemispheres.
Additionally, the eruption released 40 percent more dust than the 1815 eruption of Tambora, Indonesia, which resulted in a noticeable dust veil in the sky. The eruption may have been the worst to have occurred in the last 2,000 years and directly caused famine and is thought to have indirectly caused plague and cultural conflict. (nature.com/news)
Caffeine linked to miscarriage
Pregnant women who drink two cups of coffee or more, representing 200 milligrams or more of caffeine, have approximately twice as great of a risk to have a miscarriage than women who drink no caffeine, according to a survey of 1,063 women who were less than 15 weeks pregnant. The study provides further support for the relationship of caffeine to miscarriage, while previous studies had been confounded by other factors that cause miscarriage or biased by small sampling or recall bias.
The study was conducted at the Kaiser Foundation Research Institute in Oakland, Calif., and the researchers accounted for age, race, education, household income, martial status, smoking status, alcohol consumption, hot-tub use and levels of morning sickness.
Overall, 172 women out of the 1,063 miscarried, or 16.2 percent. Women who had higher rates of caffeine consumption were more likely to be white and to have a higher household income.
Caffeine changes the way cells function and reduces the blood flow to the fetus. It can also pass through the placental barrier and its affects on the fetus are poorly understood. (sciencenews.org)
Science Scene is compiled by JENNIFER WOLF, who can be reached at email@example.com.