It has long been known that changes in land use can affect local temperatures. Switching from forest to pastureland to a concrete jungle has a measurable effect. Here, we see that the type of crop associated has a dramatic effect:
The scientists found that converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 °F (1.55 °C), but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 °F (0.93°C).
Via Eurekalert: Sugarcane cools climate
Palo Alto, CA—Brazilians are world leaders in using biofuels for gasoline. About a quarter of their automobile fuel consumption comes from sugarcane, which significantly reduces carbon dioxide emissions that otherwise would be emitted from using gasoline. Now scientists from the Carnegie Institution’s Department of Global Ecology have found that sugarcane has a double benefit. Expansion of the crop in areas previously occupied by other Brazilian crops cools the local climate. It does so by reflecting sunlight back into space and by lowering the temperature of the surrounding air as the plants “exhale” cooler water. The study is published in the 2nd issue of Nature Climate Change, posted on-line April 17.
The research team,* led by Carnegie’s Scott Loarie, is the first to quantify the direct effects on the climate from sugarcane expansion in areas of existing crop and pastureland of the cerrado, in central Brazil.
The researchers used data from hundreds of satellite images over 733,000 square miles—an area larger than the state of Alaska. They measured temperature, reflectivity (also called albedo), and evapotranspiration—the water loss from the soil and from plants as they exhale water vapor.
As Loarie explained: “We found that shifting from natural vegetation to crops or pasture results in local warming because the plants give off less beneficial water. But the bamboo-like sugarcane is more reflective and gives off more water—much like the natural vegetation. It’s a potential win-win for the climate—using sugarcane to power vehicles reduces carbon emissions, while growing it lowers the local air temperature.”
The scientists found that converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 °F (1.55 °C), but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 °F (0.93°C).
The researchers emphasize that the beneficial effects are contingent on the fact sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.
So far most of the thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions. But according to coauthor Greg Asner, “It’s becoming increasingly clear that direct climate effects on local climate from land-use decisions constitute significant impacts that need to be considered core elements of human-caused climate change.”
*Co-authors on the study are David Lobell of the Program for Food Security and the Environment at Stanford University, Gregory Asner and Christopher Field of Carnegie’s Department of Global Ecology, and Qiaozhen Mu of the University of Montana. The work was made possible through the support of the Stanford University Global Climate and Energy Project.
The Department of Global Ecology was established in 2002 to help build the scientific foundations for a sustainable future. The department is located on the campus of Stanford University, but is an independent research organization funded by the Carnegie Institution. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.
The Carnegie Institution for Science (www.carnegieScience.edu) has been a pioneering force in basic scientific research since 1902. It is a private, nonprofit organization with six research departments throughout the U.S. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
So the temperature increase they didn’t show was going from natural vegetation to sugarcane, warming the surrounding air by 1.22 °F (0.62°C).
That’s a really sweet story.
Pity they couldn’t make a decision about which temperature scale to use.
What happens when you burn it off to get rid of the foliage and snakes?
you’re on shaky ground here. land management and these stats are as contentious as cagw.
So if you’re worried about ‘global warming’ – buy some rum. 🙂
There is growing (!) evidence that land use changes from agriculture were much greater than previously estimated in the past with far larger areas of natural vegitation – primarily forest – being cleared thousands of years ago. This may have caused a pre-industrial rise in CO2 as well as the albedo and water vapour changes that make agricultural production (except for sugar cane ?!) a warming influence on the climate.
Sugar … is there nothing it can’t do?
w.
“The scientists found that converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 °F (1.55 °C), but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 °F (0.93°C).”
Gees, who would have thunk that increased biomass density had a cooling effect on local climate, amazing !!!.
As well as absorbing that most evil of pollutants, CO2 😉
And of course, the fact that raised CO2 concentrations increase biomass density doesn’t come into the equation either.
Its called “negative feedback” (which doesn’t exist under an IPCC scenario.)
“Sugar … is there nothing it can’t do?’
Trouble is that a diet consisting purely of sugar isn’t terrible good for one’s self.
So long as growing sugar cane doesn’t subtract from actually FOOD production, no problem.
IMO, ethanol producting should only ever be a bi-product from waste food production.
Efficiency is the word, produce the food first, THEN use the leftovers for ethanol and structural materials etc etc
So? And their point was?
Unless we start to eat sugar cane then this research does not help feed the world which is far more important than attacking the discredited cause of some theoretical non problem like CAGW.
“It does so by reflecting sunlight back into space and by lowering the temperature of the surrounding air as the plants “exhale” cooler water.”
Lets see. Sun light to sugar cane – sugar cane to water vapor = cooler temperature. I think one would call that a “negative feedback”
Sweet!
(OK, somebody had to say it.)
So when the Little and Big Chills hit, sugar cane will have to go …
Food prices through the roof so poeple starve, but that’s alright!
“which significantly reduces carbon dioxide emissions that otherwise would be emitted from using gasoline.”
WTF does this mean. If we don’t burn gasoline we get less CO2 emissions from gasoline burning? Is there not an equally comensurate CO2 emission from burning the chemically similar biofuel? Do Hydrocarbons of recent organic origin somehow release less emissions than hydrocarbons of earlier origin? Are internal combustion actually more efficient when powered by the fuels that they were designed for? If that is the case would biofuels actually produce more emissions? Aren’t biofuels mainly here as a hedge against “peak oil?” Please answer politely. Maybe I have this all wrong.
It’s not just ‘exhaling’ water. Photosynthesis is an endothermic process, and a crop that is vigorous in producing high calorie sucrose sugars especially so. I’m not sure how much off hand, but by looking at rough estimates there are over 15 megajoules of energy utilized to produce each kilogram of sucrose in the crop from CO2 and water. With yields of sucrose over 10 tonnes per hectare, that’s over 150 gigajoules per hectare just on the sucrose, not to mention the other plant matter. If the sugars are set down over 100 days (say, three harvests per year) and there are 10 hours of effective photosynthesis per day then that is 150 megajoules per hour during the day. Since the plant has a large surface area it will directly cool the air by conduction. This doesn’t seem to get a mention in this summary – is it just a minor factor? It comes out at over 4 watts per square metre, which doesn’t sound much, but is larger than supposed greenhouse forcing.
This is another of those groups that have co-opted a prestigious name.
Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity
Since it gives off so much water vapor, wonder how much irrigation it requires?
I think these boys are a bit shaky.
So, essentially, in countries that are heavily dependent on chopping down rainforest to grow sugar cane for tasty export friendly “green” fuel it is all good to chop down rainforest and keep growing sugar cane for tasty export friendly “green” fuel.
Sorry, folks, there’s no bias here, just money, move along.
Hmmmmm……
One major problem. Ethanol has no benefit for CO2 emissions. The lower energy requires more fuel to be burnt. That basis doesn’t even include the energy required to grow the crop.
http://theinconvenientskeptic.com/2010/10/ethanol-i-like-it-in-my-glass/
http://theinconvenientskeptic.com/2011/02/ethanol-vs-gasoline-mpg/
“The scientists found that converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 °F (1.55 °C), but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 °F (0.93°C).”
Hanglider and Paraglider pilots have known and expirienced this for many years.
rg
@-Patrick Kelly says:
April 18, 2011 at 2:58 am
“which significantly reduces carbon dioxide emissions that otherwise would be emitted from using gasoline.”
WTF does this mean. If we don’t burn gasoline we get less CO2 emissions from gasoline burning? Is there not an equally comensurate CO2 emission from burning the chemically similar biofuel? Do Hydrocarbons of recent organic origin somehow release less emissions than hydrocarbons of earlier origin?
————————
This is rather elementary, but the CO2 emissions from burning biofuel are CO2 that was already in the atmosphere right up until the piont when the biofuel crop made the hydrocarbon.
The CO2 from fossil fuels has NOT been in the atmosphere for several million years and was geologicaly sequestered from the active biological carbon cycle.
In one case the CO2 is part of the natural active carbon cycle, in the other it has been artificially re-introduced into the carbon cycle as ADDITIONAL carbon from geologically sequestered sources. In the normal course of events this carbon would not be returned to the surface cycle until the slow subduction of the tectonic plate returned it to the magma. Its return then would be MUCH slower than that engineered by exxon and BP.
The researchers emphasize that the beneficial effects are contingent on the fact sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.
Thus, as always, it’s a zero-sum game. We can’t develop any more agricultural land, thus the “choice” is to convert land used for growing food (including livestock) to growing sugarcane (for biofuels).
If you’re most worried about food availability and pricing, don’t convert.
If you’re most worried about diminishing water supplies, don’t convert. Note the increased evapotranspiration rate.
If you’re most worried about global warming, then stop growing food and let the land go back to natural vegetation. Get used to foraging like any other wild animal.
“The researchers emphasize that the beneficial effects are contingent on the fact sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.”
Which makes the research a pointless exercise.
@ScientistForTruth
The NET change in energy & CO2 is very little. Yes, photosynthesis is an endothermic process. But rotting/burning/getting eaten is an exothermic process. Only a NET increase in biomass will make a significant difference in stored energy (eg forming new fossil fuels).
@Patrick Kelly
The flipside of what I said is also true. Instead of letting the biomass rot (“wasting” all that energy), you could burn it is cars. Either would hve the same effect on CO2 levels and on energy released to the environment. Biomass is recycled, so it has almost no net effect (unless you count fossil fuels used to process it).
* The carbon from biomass that you burn today in your car was carbon in the atmosphere last year.
* The carbon from fossil fuels that you burn today in your car was carbon stored away in the ground last year.
There is a big difference.
Roughly, 100 ton of water for 1 ton of cane, for 100 Kg of sugar.
Thats with flood irrigation.
One harvest per year only, at least in Queensland. Every few years there is fallow from the harvesting winter-spring to planting the following autumn.
In some parts, 50 mm of rain every few weeks occurs naturally, and no irrigation is required. However the more rain, the less sun, the lighter the crop.
Heavy crops present significant material handling problems, especially if it rains while harvesting.