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Saturday, October 11, 2008

Pablo Campra et al.: Roofs of hothouse farms in Almeria, Spain, reflect so much sunlight that they may be pushing down local temperatures

NewScientist, October 10, 2008

HERE is one greenhouse effect that is welcome: the roofs of hothouse farms in Spain reflect so much sunlight that they may be pushing down local temperatures.

Since the 1970s, semi-arid pasture land in Almeria, south-eastern Spain, has been replaced by greenhouse horticulture. Today, Almeria has the largest expanse of greenhouses in the world - around 26,000 hectares.

Pablo Campra of the University of Almeria and colleagues studied temperature trends from weather stations inside the region, and from other areas of Spain. With the help of satellite data they compared semi-arid pasture land and greenhouses, looking for differences in surface radiation and albedo -- the ability to reflect sunlight.

In the greenhouse region, air temperature has cooled by an average of 0.3 °C per decade since 1983. In the rest of Spain it has risen by around 0.5 °C. The satellite data revealed that the white greenhouses were much more reflective than farmland. (Journal of Geophysical Research, DOI: 10.1029/2008JD009912).

The team thinks that the white roofs are key to the cooling, demonstrating the potential for placing reflective surfaces in semi-arid regions of the world to offset climate change.

Link to article: http://environment.newscientist.com/article/mg20026775.000

7 comments:

Owl said...

This looks fishy. Compare areas that are closer in size and express albedo's that can be compared. There's a disinformation crowd that believes part of the artificial boost to AGW is heat from paved roads around the world. This looks like the other side of the same kind of coin.

Tenney said...

Look, black asphalt gets bloody hot in the sun -- no doubt about it.

Of course there is a difference in albedo between white greenhouse roofs and any other type of surface.

I live in the tropics, so if I have to choose between buying a black car or a white car, what do you think I would choose?

pablo campra said...

Hi, I am P. Campra co-author of this research on greenhouse farming mitigation effect. In my personal web
www.ual.es/~pcampra

you can download the FULL TEXT in english of the research published at Journal of Geophysical Research. Sorry the web is still in spanish.

Tenney said...

Dear Dr. Campra,

Thank you so much for the link. I was able to find the paper in English, here:

http://www.ual.es/~pcampra/index_archivos/mypaper.pdf

I will post the abstract later this evening or tomorrow, as I have to go out now.

Thanks again!

Tenney said...

p.s. I wish I knew Spanish, but I only learned Dutch, Greek, and Portuguese.

Owl said...

Dr. Campra. Thanks for access to the article. In the conclusions at the end, the bias being very localized to the albedo influence is different than my original impression of a larger rebgion showing the effect.

pablo campra said...

Well, according to our data of control stations located more than 100 km away from greenhouses main area, there is no influence on the temperature series. The global influence of this land use is other: according to Dr. Akbari's thesis (see link below)the forcing generated in the area is equal to the removal of around 400 TCO2/ha, so in total the forcing of 10 million TCO2 would have been masked by greehouse development. Also every year 10 TCO2/ha are removed in vegetables and residue, in total around 300.000 TCO2 in the 30.000 ha of greenhouses in the province of Almeria.

www.climatechange.ca.gov/events/2008_conference/presentations/2008-09-09/Hashem_Akbari.pdf