December 12, 2006

Night Lights

"While winter may be approaching, researchers using data from satellites and weather stations around the world have found the air temperature near the Earth's surface has warmed on average by 1 degree F (0.6 degree C) globally over the last century, and they cite human influence as at least a partial cause. NASA researchers James Hansen and Marc Imhoff analyzed records for 7,200 global weather stations and used satellite observations of night-lights to identify stations with minimal local human influence. U.S. Defense Meteorological Satellites measure the brightness of nighttime lights all over the Earth's surface as seen in the images above. The brightest areas in these satellite images clearly depict populated areas, which are the areas most likely to exhibit urban heat island effects.

Urban heat island effects are created when cities grow and asphalt roads and tar roofs and other features are substituted for areas where plants would otherwise grow. Because dark surfaces like pavements store heat during the day, which is released at night, they keep cities hotter for longer periods of time. The researchers used the night light brightness to classify the location of each weather station as urban, near-urban or rural. They found more warming generally occurred at urban stations, and used neighboring rural stations to adjust the long-term temperature trend at urban stations, thus obtaining a better measure of the true climate change."

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happy and blue 2 said...

The pictures are very interesting. The southern hemisphere is, for the most part, quite dark. As is Canada above the southern border..

Jeff said...

To get that second shot, I imagine they had to overlay two night shots. I remember seeing a series of pictures similar to these ones. They were of earth, similar to the second photo, but part of the earth was dark because it was night and the other part was day.

Another cool thing about those photos was that they showed a time lapse series where people in Italy were turning on their lights when it got dark and you could see it growing with the line where the sun set.

I wonder if "heat island effects" will be another form of urban pollution, much like light pollution.

tishabest said...

I found that very informative technobabe thanks. While I know every little on the topic (I always have an opinion anyway right?) I suppose that these urban heat island effects are changing the ecosystems in those areas. Maybe we'll soon have orange trees here in Brussels :-)