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12 December 2013 1:00 pm ,
Vol. 342 ,
In an ambitious project to study 1000 years of sickness and health, researchers are excavating the graveyard of the now...
Stefan Behnisch has won awards for designing science labs and other buildings that are smart, sustainable, and...
The iconic 125-year-old Lick Observatory on Mount Hamilton near San Jose, California, is facing the threat of closure...
Recent results from the Curiosity Mars rover have helped scientists formulate a plan for the next phase of its mission...
A new, remarkably powerful drug that cripples the hepatitis C virus (HCV) came to market last week, but it sells for $...
In pretoothbrush populations, gumlines would often be marred by a thick, visible crust of calcium phosphate, food...
Evolutionary biologists have long studied how the Mexican tetra, a drab fish that lives in rivers and creeks but has...
Victorian astronomers spent countless hours laboriously charting the positions of stars in the sky. Such sky mapping,...
- 12 December 2013 1:00 pm , Vol. 342 , #6164
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Greenhouse Spied From Sky
10 September 2001 7:00 pm
The Northern Hemisphere is greening up, according to an analysis of 18 years of satellite data. Spring is coming earlier, fall later, and a measure of chlorophyll visible from orbit shows that plants are responding to the changed conditions. Researchers blame greenhouse gases and global warming.
To track Earth's greening, geographer Liming Zhou of Boston University and colleagues at NASA used a measure called the normalized difference vegetation index (NDVI), which relies on satellite-based spectral measurements that gauge chlorophyll levels in grass, shrubs, and trees. The phenomenon is especially pronounced in Siberia and eastern Russia, they found, where almost two-thirds of the vegetated areas above 40° north latitude (the level of New York City) show substantial increases in vegetation density over the 18-year period, compared with about 30% of such areas in North America, which has been warming up at a lower rate. Growing seasons in some parts of Eurasia, the analysis showed, have lengthened by as much as 18 days in the past 2 decades, the team reports in the 16 September issue of the Journal of Geophysical Research-Atmospheres.
Environmental scientist William Schlesinger of Duke University says the study is "a very solid piece of work, very intriguing ... it's exactly what you'd expect of a planet that's undergoing global warming." Indeed, the new measures correlate well with data from meteorological stations all over the Northern Hemisphere, which indicate an average rise of 0.8°C in surface temperature since the early 1970s.