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The past 30 years has seen more "hot" (orange), "very hot" (red) and "extremely hot" (brown) summers, compared to a base period defined in this study from 1951 to 1980  (Source: NASA/Goddard Space Flight Center Scientific Visualization Studio)
Hotter summers have become the norm from 1980 to present compared to 1951 to 1980 (the base period)

NASA researchers have claimed to find new evidence for everyone's favorite topic: global warming
 
James Hansen, study leader from NASA's Goddard Institute for Space Studies (GISS), as well as GISS researchers Makiko Sato and Reto Ruedy, have concluded that summer heat waves (mainly in the U.S. Midwest) have become the norm over the last 30 years compared to a base period 30 years before 1980 -- and it's because of global warming. 
 
Their study works like this: the team collected mean summer temperatures from 1951 to 1980. This was considered the base period for the study. They then looked at the surface temperature data from the last 30 years (1980 until now) to determine whether extreme heat events were increasing. 
 
From there, the team wanted to see how much heating and cooling occurred in both time periods. To do this, they used a bell curve, which is a common tool that places the middle ground at the top of the bell (for instance, if this were a grading curve, a "C" would be at the top while the next tier down on each side would be a "B" and a "D," and the bottom of the bell would be an "A" and an "F). In this case, the top of the bell would be mean temperature, the next tier down would be "cold" on one side and "hot" on the other, then "very cold" and "extremely cold" on one side moving down while "very hot" and "extremely hot" are moving down the bell on the other side. 
 
Researchers then applied mean temperatures from 1980 until present, and found that 1980s, 1990s and 2000s fell more to the hot side than cold. The curve widened and flattened as well, which means there was a broader range of variability. This is important because Hansen once predicted that global warming's connection to extreme events would become more apparent in the decades from 1980 to present, but natural variability can play a role too and actually mask the trend. It was important to distinguish the two. 
 
This wider curve created the new "extremely hot" category, which was barely there in the base period. However, hot has become considered normal in the last 30 years. To be more specific, 75 percent of land area on Earth had "hot" summers in the last decade alone, where only 33 percent had "hot" summers from 1951 to 1980 total. 
 
According to the researchers, an "extremely hot" summer is considered a mean summer temperature that is experienced by less than one percent of Earth's land area during the base period. But since 2006 alone, approximately 10 percent of land area across the Northern Hemisphere had a summer like this. 
 
"This summer, people are seeing extreme heat and agricultural impacts," said Hansen. "We're asserting that this is casually connected to global warming, and in this paper, we present the scientific evidence for that."
 
The study noted "extremely hot" summers in other areas besides just the U.S. Midwest, like Texas, Mexico and Oklahoma in 2011 and Eastern Europe, Western Asia and the Middle East in 2010.
 
This study was published in the journal Proceedings of the National Academy of Sciences

Source: Science Daily



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RE: Ideological nonsense
By amosbatto on 8/9/2012 4:53:51 PM , Rating: 1
quote:
References to human caused extinctions get tossed around a lot. Sometimes it is claimed there have been thousands of extinction, that hundreds, sometimes even thousands, of species are going extinct every year. I say that's bullshit. If you say it isn't bullshit then please list at least some of the species that have been driven to extinction in, say, the last fifty years.


First of all, estimating extinction rates is very tricky and there is a great deal of debate whether biologists are doing it correctly. See: http://www.livescience.com/14216-overestimation-ex...

However, there is a wide consensus among biologists that the world is currently loosing species at a faster rate than in the past. The debate is whether we are currently entering a mass extinction and comparisons of the current extinction rate with the normal background extinction rate.

Here is the wikipedia summary on the issue:

According to a 1998 survey of 400 biologists conducted by New York's American Museum of Natural History, nearly 70 percent believed that they were currently in the early stages of a human-caused extinction,[33] known as the Holocene extinction. In that survey, the same proportion of respondents agreed with the prediction that up to 20 percent of all living populations could become extinct within 30 years (by 2028). Biologist E. O. Wilson estimated [6] in 2002 that if current rates of human destruction of the biosphere continue, one-half of all species of life on earth will be extinct in 100 years.[34] More significantly the rate of species extinctions at present is estimated at 100 to 1000 times "background" or average extinction rates in the evolutionary time scale of planet Earth.[35]

See: http://en.wikipedia.org/wiki/Extinction#Modern_ext...


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