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.
Hmm, and back on planet earth… people are starving due to high food prices, but that’s aright because at least we avoid those 50 Million climate refugees.
Patrick Kelly “Is there not an equally commensurate CO2 emission from burning the chemically similar biofuel?”
The idea is supposed to be that the carbon in biofuel has been sequestered from CO2 in the atmosphere, so burning it is simply putting it back where it was a few months earlier (so-called ‘carbon neutral’), whereas ‘fossil’ fuels are supposedly putting carbon back that was in the atmosphere millions of years ago when CO2 levels were supposedly higher. In other words, compared to recent conditions, fossil fuel burning is said to be adding to the burden of atmospheric CO2 in our time.
The sentence “It’s becoming increasingly clear…” is a positive development.
Tells us that a few “scientists” are reluctantly and hesitantly starting to observe the same facts that everyone else has observed for 10000 years, instead of looking only at their computer screens and their LaTeX formulae.
CO2 is supposed to be bad because it will warm the Earth and it increases water vapor and that further warm the earth in a positive feedback death spiral. When water vapor is decreased because of deforestation, that is almost as evil as increasing CO2 which seemingly has the opposite effect. Now these guys, whatever their stance on AGW, they seem to be saying that water vapor cools the planet. They said cooler water vapor but all transpiration of water releases the same heat. Maybe it is just the water vapor that was caused by increased CO2 warming that is supposed to warm . The rest of water vapor molecules cool because they didn’t get the memo. Clearly water vapor is a greenhouse gas and they are claiming that increasing that greenhouse gas cools. I must be totally confused because it seems like they just say whatever feels right at the moment. They sound like the group that is promoting sugar cane.
oldseadog says:
April 18, 2011 at 12:48 am
> Pity they couldn’t make a decision about which temperature scale to use.
Now, “they” say diversity is a Good Thing.
They also could have said “transpiration” instead of the plants “exhale” cooler water [vapor (vapour)].
OK, this study is a study in conflicts.
So, we have a bio-fuel that marginally decreases CO2 when burned (what is the reduction in CO2 from bio fuels? A couple %?). But it ‘cools’ the region by evaporating more H2O (‘breathing? Are they serious?). QED: It reduces CO2 and increases H2O in the atmosphere.
So how is it this plant which emits the much more powerful GHG H2O and also reflects solar heat back into the atmosphere that contains this extra GHG supposedly cooling??? Doesn’t this increase the GHG capture of solar heat?
Violates every mythical rule of AGW I have heard.
Let’s not overlook the fact that scientists from one of the bastions of liberalism have recognized that land use has a serious impact on temperatures. No, we are not going to cover the world with sugarcane. However, further research might reveal that locals can have greater impacts on local temperature through choices regarding vegetation.
Also, doesn’t this research drive another nail in the coffin of the claim that UHI is not important in temperature measurements? If crops can be important, surely cities can be important.
There is another aspect that needs to be considered. While the dry bulb temperature can can cool as transipriation increases, the actual heat content of the air per kilogram can be higher due to the added water vapor; e.g. see
Pielke Sr., R.A., C. Davey, and J. Morgan, 2004: Assessing “global warming” with surface heat content. Eos, 85, No. 21, 210-211. http://pielkeclimatesci.wordpress.com/files/2009/10/r-290.pdf
Only if an albedo change is large enough such that the net radiation received at the surface is sufficiently reduced, will there be actual cooling.
This study does show, of course, an issue on using the dry bulb temperature trends at specific sites when making claims about the magnitude of annual average global warming.
Tim Folkerts says:
April 18, 2011 at 4:16 am
“@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). ”
That’s besides the point. The post and my comment is about local temperatures around fields. Your point is about averaging out over cycles. If you have an endothermic process locking up lots of energy, which is then transported a long way away to liberate the stored energy, then the result is local cooling. The plant biomass in the leaves etc of course is produced locally, and may be burned or rot locally, but my point (and calculations) were related to the sucrose, which is transported away from the field.
Let’s see here….
So a study funded by who knows, comes out saying sugar cane is good…
….Soros is the largest investor in Brazilian sugar cane for ethanol
http://www.grist.org/article/george-soros-vs-the-planet
I don’t see a connection there, do you?
“The scientists found that converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 °F (1.55 °C)…”
Theses grant trolling scientists “found” nothing of the sort. They didn’t get out into the brush and the mud with their amazingly accurate thermometers calibrated to 0.01° with no error bars, to measure 2.79°F [or 1.55°C – but 2.79° looks scarier]. This is speculation wrapped in a model.
And as usual the answer to the central question is avoided: is more CO2 a problem? If so, point out the global damage that has resulted. Where is the runaway global warming from more CO2?
Real world evidence confirms that CO2 is harmless and beneficial. More of this minor trace gas is better. If anyone has evidence to the contrary, please present it. Evidence, not speculation, please. We have had enough baseless “carbon” speculation.
I tried to post this to Tips and Notes but couldn’t. It is off topic so delet after considering.
Met Office Chief receives death threats.
At the bottom of the article a spokesman says the threats were not serious enough to involve the police?
http://www.telegraph.co.uk/earth/environment/climatechange/8458162/Met-Office-chief-receives-death-threats-from-climate-change-sceptics.html
There was a NBER paper on the effects of increasing night temps decreasing rice productivity. They missed that night temps rise because or rice production and that as more rice is produced, productivity will decline and regional temps will rise.
It was popular with the CAGW crowd as it is the only paper that seemed to suggest a negative effect on ag.
Another “team”. They need to come up with a new name as car dealers have beat them to this one.
“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).”
and
“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”
That seems to be some very selective wording. If I’m reading this correctly, then sugar cane doesn’t actually cool anything down. It just warms less than other crop types. So, rather than warming by 2.79F, it warms by 2.79-1.67=1.12F of warming?
I wonder if the actual difference is what they say, or just a byproduct of the irrigation schedules and near-surface humidity and the rate of night-time heat retention? They would at the very least need to control for this effect in order to validate the claims they made. I’d like to see comparisons of daytime highs and nighttime lows accross different sample areas.
I’m surprised they didn’t try to claim that the sugar caine sucks more CO2 from the air, therefore proving CO2 induced warming is real. That fits the agenda better. Maybe this study was funded by “Big Biogas” or “Big Biodeisel”!!! Oh No!!
Sorry for the double post, but I HAVE to say this:
If agricultural land use raises the temperature by nearly 3 F, then doesn’t that really blow the case for CO2 as “the” cause for warming?
“… sugarcane has a double benefit. Expansion of the crop in areas previously occupied by other Brazilian crops cools the local climate. …”
OK, so maybe in this local context they may be right but on a global basis, cooling is generally not beneficial, whereas warming is. I fear that in a few years’ time – if the solar physicists are right – we will find out just how damaging a serious global cooling can be.
Brazil fixed its automotive fuel scarcity by finding offshore oil.
*sigh* About as brilliant an insight as discovering that the corn monoculture of Illinois (aka. “corn desert” to we biologists) has the same effect.
Now, if we could only adapt sugar cane to grow in the Midwest of the USA, we’d be all set. Oh, wait….sugar beets in the Red River Valley, scratch that.
Do the “save the Earth” crowd cheer for the reduction of carbon emissions, or weep for the loss of habitat and diverse species? I can never tell what they are thinking. Thus far, biofuel production in places like Indonesia (oil palm) is an unmitigated disaster for the ecosystem, and I’d expect the same in Brazil.
All I know about sugar cane is that, in Trinidad, they use it to make ‘babash’. It tastes the same as Irish Poteen, made from potatoes, and Thai ‘lao khao’ made from rice. They are all slap-the-back-of-your-neck type drinks. Never actually tasted Moonshine but I reckon it would taste the same as babash…
Someone actually paid for a study to determine what anyone who has ever lived on or near a farm already knew?
what about the relative amounts of (cooling) flood irrigation used on sugar cane vs other crops vs pasture? would think sugar cane is getting the most water of any.
Are crops to be rated by global warming research?
They are established to support global warming theory and promote control of the world food supply is more like it.
Does this private organization rake off tax dollars to support their activities? Disclosure of financial support is always important to even the appearance of a conflict of interest between politics and science.
And good for Brazil, they are going to burn up their soil making fuel for cars unless they rotate their crops for grass or some sort of plant that will refresh the dirt.
BravoZulu says:
April 18, 2011 at 4:53 am
“They sound like the group that is promoting sugar cane.”
Yep. Watch the movement splinter. Like the enviros along the fault line nuclear/coal.