From NASA:
download large image (700 KB, JPEG) acquired January 1, 2000 – December 31, 2009
download large Hemispheric Trends image (81 KB, PDF)
Conventional wisdom holds that plants should thrive when temperatures warm and the growing season lengthens under a changing climate. A 2003 study showed that plant growth indeed increased as temperatures warmed between 1982 and 1999. But when researchers at the University of Montana updated the study for the last decade, 2000–2009, they discovered that even though the decade was the warmest since instrumental recordkeeping began, plant growth slowed.
The study is significant because plants soak up carbon from the atmosphere as they grow. As growth slows, the amount of carbon plants take up slows as well, leaving more carbon in the atmosphere to contribute to climate change. It is also a warning that a warming climate could bring a decrease in food and biofuel production.
Researchers Maozheng Zhou and Steven Running published the work in Science on August 20, 2010. They used data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite to monitor plant growth and calculate the total amount of carbon plants store as they grow, a value called net primary productivity. Their results are illustrated in this image, which shows the change in the amount of carbon consumed by plants between 2000 and 2009. Green areas show where plants grew more (and consumed more carbon), and brown areas show where they grew less. The deeper the color, the stronger the trend.
In general plant growth and consequently the amount of carbon plants store increased in the Northern Hemisphere and decreased in the Southern Hemisphere. The difference, say Zhou and Running, is water. Three things limit plant growth: light, water, and temperature. In the Northern Hemisphere, warmer temperatures and a longer growing season allowed plants to grow more. But in the Southern Hemisphere, drought dominated the decade. Higher temperatures dried plants and soil, generally slowing growth. The attached graphs illustrate the direct relationship between drought and the amount of carbon plants absorbed between 2000 and 2009.
During the decade, large-scale droughts, primarily in the Southern Hemisphere, were strong enough to overwhelm increased plant growth in other places, resulting in decreased plant growth overall. While 65 percent of the Northern Hemisphere’s vegetated land had increasing growth, 70 percent of the Southern Hemisphere’s vegetated land had decreasing growth. Added together, global plant growth decreased slightly in the decade, reducing carbon uptake by an estimated 0.55 petagrams, a one percent decrease.
It is too early to tell if the recent decade marks the beginning of a longer term trend in plant growth related to long-term climate change. Climate is defined by patterns seen over longer periods of time, at least 20-30 years. In the previous 20 years (1982–1999), plant growth and the related carbon uptake increased as much as six percent. Regardless, the observed decrease in plant growth between 2000 and 2009 helps researchers better understand how plants might respond to a changing climate.
“We see this as a bit of a surprise, and potentially significant on a policy level because previous interpretations suggested that global warming might actually help plant growth around the world,” Running said. “This is a pretty serious warning that warmer temperatures are not going to endlessly improve plant growth.”
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A longer NASA feature article and videos describe the results in greater detail. (below)
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From NASA
Drought Drives Decade-Long Decline in Plant Growth
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A snapshot of Earth’s plant productivity in 2003 shows regions of increased productivity (green) and decreased productivity (red). Tracking productivity between 2000 and 2009, researchers found a global net decrease due to regional drought. Credit: NASA Goddard Space Flight Center Scientific Visualization Studio
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Interannual shifts in plant productivity (green line) fluctuated in step with shifts in atmospheric carbon dioxide (red line) between 2000 through 2009. Credit: Maosheng Zhao and Steven Running Earth has done an ecological about-face: Global plant productivity that once flourished under warming temperatures and a lengthened growing season is now on the decline, struck by the stress of drought.
NASA-funded researchers Maosheng Zhao and Steven Running, of the University of Montana in Missoula, discovered the global shift during an analysis of NASA satellite data. Compared with a six-percent increase spanning two earlier decades, the recent ten-year decline is slight — just one percent. The shift, however, could impact food security, biofuels, and the global carbon cycle.
“We see this as a bit of a surprise, and potentially significant on a policy level because previous interpretations suggested that global warming might actually help plant growth around the world,” Running said.
“These results are extraordinarily significant because they show that the global net effect of climatic warming on the productivity of terrestrial vegetation need not be positive — as was documented for the 1980’s and 1990’s,” said Diane Wickland, of NASA Headquarters and manager of NASA’s Terrestrial Ecology research program.
Conventional wisdom based on previous research held that land plant productivity was on the rise. A 2003 paper in Science led by then University of Montana scientist Ramakrishna Nemani (now at NASA Ames Research Center, Moffett Field, Calif.) showed that global terrestrial plant productivity increased as much as six percent between 1982 and 1999. That’s because for nearly two decades, temperature, solar radiation and water availability — influenced by climate change — were favorable for growth.
Setting out to update that analysis, Zhao and Running expected to see similar results as global average temperatures have continued to climb. Instead, they found that the impact of regional drought overwhelmed the positive influence of a longer growing season, driving down global plant productivity between 2000 and 2009. The team published their findings Aug. 20 in Science.
“This is a pretty serious warning that warmer temperatures are not going to endlessly improve plant growth,” Running said.
The discovery comes from an analysis of plant productivity data from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, combined with growing season climate variables including temperature, solar radiation and water. The plant and climate data are factored into an algorithm that describes constraints on plant growth at different geographical locations.
For example, growth is generally limited in high latitudes by temperature and in deserts by water. But regional limitations can very in their degree of impact on growth throughout the growing season.
Zhao and Running’s analysis showed that since 2000, high-latitude northern hemisphere ecosystems have continued to benefit from warmer temperatures and a longer growing season. But that effect was offset by warming-associated drought that limited growth in the southern hemisphere, resulting in a net global loss of land productivity.
“This past decade’s net decline in terrestrial productivity illustrates that a complex interplay between temperature, rainfall, cloudiness, and carbon dioxide, probably in combination with other factors such as nutrients and land management, will determine future patterns and trends in productivity,” Wickland said.
Related Links: > Related video
This narrated video gives an overview of net primary production and the carbon cycle. High-resolution data from the Moderate Resolution Imaging Spectroradiometer, or MODIS, indicate a net decrease in NPP from 2000-2009, as compared to the previous two decades. Credit: NASA/Michelle Williams
Researchers are keen on maintaining a record of the trends into the future. For one reason, plants act as a carbon dioxide “sink,” and shifting plant productivity is linked to shifting levels of the greenhouse gas in the atmosphere. Also, stresses on plant growth could challenge food production.
“The potential that future warming would cause additional declines does not bode well for the ability of the biosphere to support multiple societal demands for agricultural production, fiber needs, and increasingly, biofuel production,” Zhao said.
“Even if the declining trend of the past decade does not continue, managing forests and croplands for multiple benefits to include food production, biofuel harvest, and carbon storage may become exceedingly challenging in light of the possible impacts of such decadal-scale changes,” Wickland said.
It seems the nitrogen fixation by plants is reduced at high levels of CO2 also; in particular C3 plants. The experiment which refers to this problem with the nitrogen fixation at high concentrations of CO2 was published at http://www.pnas.org/content/101/31/11506.full.pdf
On the other hand, we know that C3 plants growth starts slowing at temperatures above 20-25 °C (Odum, Eugene P. and Barrel, Gary W. Fundamentos de Ecología-Quinta Edición. 2006. International Thompson Editores, S. A. de C. V. México, Distrito Federal. Pp. 48-50). The advantage of C3 plants over C4 plants is that C3 plants survive to cold temperatures. 20 °C is the peak temperature at which the growth of C3 plants is optimum. Below and above this temperature the growth of C3 plants unavoidably slows; even if the CO2 in the environment is abundant.
I have insisted frequently on these failures on plant physiology under diverse shifts on the ecological conditions. The status on this situation is that, on biological problems, we cannot oversimplify from particular experiments, to be precise, in biology we must always have in mind the axiom that says: “The whole is much greater that the sum of its parts”.
Increase the CO2 levels all you want; it still won’t do you any good in the face of a major drought. And just look at that — a hemispheric decadal drought coupled with increasing levels of Antarctic sea ice. Fascinating. Meanwhile, the rest of the planet keeps on greening.
Let’s say Earth’s atmosphere warmed during a time that by happenstance
wetness was widespread and CO2 was increasing. Green plants naturally expand their area and also grow better and are planted where they had been absent for years. Following this the general wetness stalls and shifts to more concentrated areas or to over the oceans. Temperature and CO2 are not changing much but the areal expansion and productivity also stall and begin to regress. Thus, there is a slight overall decrease.
However, it is beyond me how both the prior “good” period of wetness and expansion and the more recent “bad” period of little or no temperature increase along with drought can have the same cause. One will have to produce an argument with multiple twists and turns to fit the facts into a coherent explanation.
Here is another twist. Regarding the time period 1953 to 1993, there is a report on part of the Sahel, here:
http://www.eden-foundation.org/project/desertif.html
“ Nowadays Malam Garba’s field is three times larger, but his harvest is only 1/7 of what it used to be 40 years ago. … This is just sufficient for his family. The lower yields have been caused by the destruction of perennials that used to shelter the annuals and contribute to soil fertility.”
The big news then wasn’t global warming, it was “desertification” and the magazines and newspapers and TV were consumed by it. Following this – as explained in this post, and elsewhere, there was a “greening” that now seems to have stopped.
These broad cyclical patterns should not be happening with just slow CO2 growth and global warming. It seems some one a single simple answer and there isn’t one.
Plants can’t tell lies. People will tell you any story they want you to hear. pg
Look at all the pleading twards public policy in this one… boy these guys are getting desparate… I say cut NASA’s budget to help kick start paying down the deficit
“…..leaving more carbon in the atmosphere to contribute to climate change.”
Aha. Warmers at work.
Another example of cherry-picking and statistical santerism.
Southern Africa: not much of a trend
http://climexp.knmi.nl/data/iprca_15-40E_-15–35N_na.png
Argentina:
http://climexp.knmi.nl/data/iprca_290-305E_-20–40N_na.png
By selecting 2009 as end year, those “researchers” get decadal precipitation trend falling down, however, when updating to 2010, there is not much of it.. and more, precipitation is now reaching the levels in the early part of 20th century.
There was no warming in 2000-2009.
Why plant growth would not slow down?
This is called “science”?
Is the variation within one standard deviation?
Did I miss something?
So plant growth increased by 6% and has now decreased by 1%. So I should be 1% less afraid of the TRIFFID which is tapping on my window trying to get inside to sit by the fire!!
Looks like the areas doing extremely “bad” are the ones that have their rainforests cut down to produce biofuel and other land use issues regarding removal of forests to support the polpulace.
I am no expert but I will make 2 claims:
1 acre of rainforest grows more biomass than 1 acre of dead, cut down, rainforest.
and
Annual changes in plant growth are many orders of magnitude greater for natural reasons than “measured” in the article and claimed for co2.
Another proxy showing a cooling trend.
This is Lysenkoism, the theory is always right, it is nature who is behaving wrong.
Solution: Destroy real data and replace with politically corrected data.
I think that all that was shown by this study was a confirmation of general understanding that water is significant to plant growth, viz:
Northern hemisphere, no drought, increased growth.
Southern hemisphere, drought, reduced growth.
All other considerations being equal.
quote
“These results are extraordinarily significant because they show that the global net effect of climatic warming on the productivity of terrestrial vegetation need not be positive — as was documented for the 1980’s and 1990’s,” said Diane Wickland, of NASA Headquarters and manager of NASA’s Terrestrial Ecology research program.
unquote
Professor Running,
If your analysis is correct (I have no reason to suppose it is not although you will get people who question it — some people will question anything), you have failed to carry your conclusion on to the next question. In a warming world there should be more water vapour (required for the positive water vapour greenhouse feedback that the models use) which one might naively assume means more precipitation, not less. So you have demonstrated that a warming world is dryer.
Any suggestions why? I realise that this is peripheral to biology but climate science is a very flexible discipline — a geology and geophysics doctorate allows one to become the leading expert after all — and the role of the ocean surface (the boundary layer so-called) in the production of biological CCNs puts it firmly in your area of expertise. Cuff a passing post-doc and set him to checking the records of oceanic biological CCNs measured over the last…. well as far back as you can go. Tell him to look at all the CCNs while he’s at it.
Invite me to the Nobel ceremony please.
JF
(Please excuse me from banging on about the Kriegesmarine Hypothesis one more time. The increased surface salinity in the oceans, BTW, seems to show that the reduction in CCNs — leading to precipitation reduction and thus less dilution of the surface waters — is more important than the increased coalescence and thus raining out of clouds. The clouds, in other words, don’t form, rather than form and then rain and thin more rapidly.
If I were an Australian I’d be checking ocean currents to see where the oceanic surface oil and surfactant pollution from India and southern China is going: it won’t all be warming the Andaman Sea and, as those two giants industrialise, the run-off is going to dry the west coast. Hint: look at Australian pan evaporation rates.)
As others have pointed out global temps have not increased over that timeframe. Did they consider the obvious as well, like seasonal variation from hemisphere to hemisphere, land management, agricultural practices generally, crop varieties, general plant variation across hemispheres?
“The plant and climate data are factored into an algorithm that describes constraints on plant growth at different geographical locations.” Are, that all important AlGorerithm, thought this was some kind of contraception technique!
Ah, ah another divergence
When temperatures rise so less CO2 is adsorbed by the oceans leaving more for plants to feed on. Plants respond to CO2 more than temperature.
Plant growth is governed by many chaotic inputs so why concentrate on but one. This does not seem to be science to me but a system to prove a point and give government more leverage to increase taxes and control our lives.
There didn’t seem to be any on ground confirmation of productivity. Nor were a myriad of crop and growth factors taken into account. In China for example there are less farmers and they are older. Makes a difference. Also there has been a significant increase in population which would lead to forrests being replaced by crops. After all 60 million extra people is an increase of 1 percent. There was a large rise in the cost of nitrogenous fertilizers during this time. Probably the biggest factor is the slowing of the nearly annual productivity improvement in many crops. The green revolution of the 70s has all but petered out.
All in all there are any number of reasons for a 1% decrease in growth none of which include CO2 or temperature.
It’s really my fault.
I stopped watering the backyard this year.
Sorry.
I’ll turn the sprinklers back on tomorrow. Next week we’ll be right as rain.
There have always been variations in crops of any kind which are grown out of doors, in soils and in whatever arrives as weather and a 1% fall in growth must fall within accepted natural variability. And we define those who divine the future from studying chicken entrails as primitives?
Another ill thought through paper which simplifies the factors upon which plant growth depends to show a tiny change which is beyond our technology to measure accurately.
Yet another example of cargo cult science which produces the answers the researchers expect to see.
Re. davidmhoffer says:
August 22, 2010 at 9:54 pm
I be gobsmacked.
They were very explicit that the SH plant productivity dropped due to DROUGHT not temperature. NH plant productivity increased even though temperatures increased BECAUSE THERE WERE NO DROUGHT CONDITIONS. The only logical conclusion one can draw from this is that temperature increases support plant productivity.
I thought this ias well. I remember that the
We see this as a bit of a surprise, and potentially significant on a policy level because previous interpretations suggested that global warming might actually help plant growth around the world,” Running said.
“These results are extraordinarily significant because they show that the global net effect of climatic warming on the productivity of terrestrial vegetation need not be positive — as was documented for the 1980’s and 1990’s,” said Diane Wickland, of NASA Headquarters and manager of NASA’s Terrestrial Ecology research program.
Amazing general statements that are very serious. I thought scientist had to back up their claims, offer other possible explanations, (There are dozens not even mentioned) show the satelite measured warming rates in specific areas, demonstrate that the drought areas were not natural, ( I thought anything less then 30 years is just weather?) show charts and graphs with error bars, given such extrordinary claims. I guess general alarmist statements are the normal now. If we in fact had unusual drought, then without the increase in CO-2 the 1% decline in plant growth would have been greater.
Interestingly A recent paper by Jones (Jones, P.D., D.E. Parker, T.J. Osborn, and K.R. Briffa. 2010. Global and hemispheric temperature anomalies—land and marine instrumental records. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi: 10.3334/CDIAC/cli.002) shows that the Southern Hemisphere is warming significantly more slowly than the Northern.
Yet Zhou and Running’s paper shows reduced (1% over a decade!!) NPP in the South, yet an increase in the WARMER North.
Pretty poor evidence that Global WARMING has an adverse effect.
When you read deeper it is all down to increased drought over the last decade in the Southern Hemisphere.
Of course this is “unprecedented” and all sorts of Doom may follow unless you give us more money to investigate further.
Surely the fact that you can clearly see the border between Malaysia and Thailand on the top image shows this is a political map, not a climatology map.
As previously noted, nothing but deforestation could have caused this.
Sorry, very late and poorly written.
Extrordinary broad alarmist claims from these “scientist”
No other reasons offered, even though their could be dozens.
No detailed explanation of vague alarmist warnings based on a minor 1% decline.
No error bars associated with alarmist warnings.
Is this science?