About 34 million years ago, Earth's climate shifted from a relatively ice-free world to one with glacial conditions on Antarctica characterized by substantial ice sheets. How Earth's temperature changed during this climate transition remains poorly understood, and evidence for Northern Hemisphere polar ice is controversial. Here, we report proxy records of sea surface temperatures from multiple...

Vitamin D production in human skin occurs only when incident UV radiation exceeds a certain threshold. From simulations of UV irradiances worldwide and throughout the year, we have studied the dependency of the extent and duration of cutaneous vitamin D production in terms of latitude, time, total ozone, clouds, aerosols, surface reflectivity and altitude. For clear atmospheric conditions, no c...

Climate differences across latitude can result in seasonal constraints and selection on life history characters. Since Aedes albopictus (Skuse) invaded North America in the mid-1980s, it has spread across a range of approximately 14 degrees latitude and populations in the north experience complete adult mortality due to cold winter temperatures that are absent in the south. Life table experimen...

Studies of bird migration in the Beringia region of Alaska and eastern Siberia are of special interest for revealing the importance of bird migration between Eurasia and North America, for evaluating orientation principles used by the birds at polar latitudes and for understanding the evolutionary implications of intercontinental migratory connectivity among birds as well as their parasites. We...

to discover induced dipole sources, the best flight direction is defined as the one offered maximum target \\‘itlth by an anomaly. This direction may depend on the amplitude of the anomaly. h method is prolwsed for estimatingrftciency of direction for a range of anomaly amplitudes. The efficiencies of lines bearing north, northeast, and east are comparetl. At the equator, lines bearing north ar...

The literature reports strong correlations between UV exposure and latitude gradients of diseases. Evidence is emerging about the protective effects of UV exposure for cancer (breast, colo-rectal, prostate), autoimmune diseases (multiple sclerosis, type II diabetes) and even mental disorders, such as schizophrenia. For the first time, the available levels of vitamin D producing UV or "vitamin D...

Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66 degrees north between 1996 and 2000, which rapidly expanded to 70 degrees north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate ...

The beetle Cucujus clavipes is found in North America over a broad latitudinal range from North Carolina (latitude approximately 35 degrees N) to near tree line in the Brooks Range in Alaska (latitude, approximately 67 degrees 30' N). The cold adaptations of populations from northern Indiana (approximately 41 degrees 45' N) and Alaska were compared and, as expected, the supercooling points (the...

The rarity of symbiotic nitrogen-fixing trees in higher-latitude compared to lower-latitude forests is paradoxical because higher-latitude soils are relatively N poor. Using national-scale forest inventories from the United States and Mexico, we show that the latitudinal abundance distribution of N-fixing trees (more than 10 times less abundant poleward of 35 degrees N) coincides with a latitud...

BACKGROUND Current epidemiologic research shows consistently that increased number of acquired common melanocytic nevi (CMN) is an important risk factor for cutaneous malignant melanoma. The purpose of this study was to investigate the number of CMN in relation to tanning habits and complexion among 7-year-old children residing at different latitudes in Sweden. METHODS Two municipalities were...