Monday, 27 February 2012

Global warming and global dimming: Same cause, opposite effects; joint strike

http://facstaff.uww.edu/travisd/pdf/jetcontrailsrecentresearch.pdf
Calentamiento global y oscurecimiento global: Misma causa, efectos opuestos; un golpe conjunto al planeta 

Global dimming is a concept not often used in global warming research carried from an engineering perspective. Both are caused by the increase in air pollutants (greenhouse gases). How? Imagine the air pollutants are like small mirrors, which in one direction reflect the sun radiation before it reaches the earth surface, and on the other direction reflects back the heat released by the earth surface. The latter increases the earth surface temperature, and the former cools down the earth surface. Thus, to the profane eye, if the emission of pollutants were reduced, the global dimming would decrease its power as countermeasure against global warming (see the Fig. on the right). In conclusion, one would say, let´s pollute more! Unfortunately, the situation is not that simple because of several reasons.
1. Global dimming changes the global precipitation patterns, because a decrease in sea surface temperatures have a direct impact on the formation of the Asian Monsoon.
2. A decrease in air pollutants is not the solution to the problem, because the "countermeasure" effect of global dimming is likely to recede, and earth surface temperatures are likely to increase dramatically.
3. An increase in air pollutants is not the solution either, because of the health effects and the decrease in the availability of natural resources.

The experiment of David Travis: Jet contrails during the 9/11 events.
To show how relevant the effects of air pollutants in the reduction of surface air temperature, let´s give a look to the experiment of Dr. Travis. During the events of 9/11 in the US, it occurred an exceptional event. No planes flew over the skies of the US; consequently, no jet contrails pollution was seen fr a period of three days. The result: the temperature registers increased in 1C!!! (the average expected increase in global surface temperature for the last decades).
 
So, what is the solution? Agreeing with the BBC broadcast conclusion on the topic, the solution is not simply reducing the pollutants emission. We have to find a way to store the loads of air pollutants. A very complex situation.

References.
- Why the sun seems to be dimming?, by David Sington, Jan 2005. 
http://news.bbc.co.uk/2/hi/science/nature/4171591.stm
- Global dimming, programme transcript. 
http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_trans.shtml.
- Contrails reduce daily temperature range, David Travis et al., Nature 2002.
http://facstaff.uww.edu/travisd/pdf/jetcontrailsrecentresearch.pdf
- En español: El enfriamiento global.
http://library.thinkquest.org/06aug/00382/Espanol/causes_dimming.html

2 comments:

  1. This is a very beautiful and interesting research
    The most educating one i have read today!




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