'Greener' climate prediction shows plants slow warming

December 7, 2010 by Patrick Lynch
A new NASA modeling effort found that in a doubled-carbon dioxide world plant growth could lessen global warming by about 0.3 degrees C globally. The same model found that the world would warm by 1.94 degrees C without this cooling feedback factored in. Credit: National Park Service

(PhysOrg.com) -- A new NASA computer modeling effort has found that additional growth of plants and trees in a world with doubled atmospheric carbon dioxide levels would create a new negative feedback – a cooling effect – in the Earth's climate system that could work to reduce future global warming.

The cooling effect would be -0.3 degrees Celsius (C) (-0.5 Fahrenheit (F)) globally and -0.6 degrees C (-1.1 F) over land, compared to simulations where the feedback was not included, said Lahouari Bounoua, of Goddard Space Flight Center, Greenbelt, Md. Bounoua is lead author on a paper detailing the results that will be published Dec. 7 in the journal Geophysical Research Letters.

Without the negative feedback included, the model found a warming of 1.94 degrees C globally when carbon dioxide was doubled.

Bounoua stressed that while the model's results showed a negative feedback, it is not a strong enough response to alter the global warming trend that is expected. In fact, the present work is an example of how, over time, scientists will create more sophisticated models that will chip away at the uncertainty range of climate change and allow more accurate projections of future climate.

"This feedback slows but does not alleviate the projected warming," Bounoua said.

To date, only some models that predict how the planet would respond to a doubling of carbon dioxide have allowed for vegetation to grow as a response to higher carbon dioxide levels and associated increases in temperatures and precipitation.

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This animation shows seasonal vegetation changes on Earth in 2004, created using NASA satellite data. It is an animation of what is called the Normalized Vegetation Difference Index, which provides an indication of the health of plant life on Earth. Source: Scientific Visualization Studio, Goddard Space Flight Center

Of those that have attempted to model this feedback, this new effort differs in that it incorporates a specific response in plants to higher levels. When there is more carbon dioxide available, plants are able to use less water yet maintain previous levels of photosynthesis. The process is called "down-regulation." This more efficient use of water and nutrients has been observed in experimental studies and can ultimately lead to increased leaf growth. The ability to increase leaf growth due to changes in photosynthetic activity was also included in the model. The authors postulate that the greater leaf growth would increase evapotranspiration on a global scale and create an additional cooling effect.

"This is what is completely new," said Bounoua, referring to the incorporation of down-regulation and changed leaf growth into the model. "What we did is improve plants' physiological response in the model by including down-regulation. The end result is a stronger feedback than previously thought."

The modeling approach also investigated how stimulation of plant growth in a world with doubled carbon dioxide levels would be fueled by warmer temperatures, increased precipitation in some regions and plants' more efficient use of water due to carbon dioxide being more readily available in the atmosphere. Previous climate models have included these aspects but not down-regulation. The models without down-regulation projected little to no cooling from vegetative growth.

Scientists agree that in a world where carbon dioxide has doubled – a standard basis for many global warming modeling simulations – temperature would increase from 2 to 4.5 degrees C (3.5 to 8.0 F). (The model used in this study found warming – without incorporating the plant feedback – on the low end of this range.) The uncertainty in that range is mostly due to uncertainty about "feedbacks" – how different aspects of the Earth system will react to a warming world, and then how those changes will either amplify (positive feedback) or dampen (negative feedback) the overall warming.

An example of a positive feedback would be if warming temperatures caused forests to grow in the place of Arctic tundra. The darker surface of a forest canopy would absorb more solar radiation than the snowy tundra, which reflects more solar radiation. The greater absorption would amplify warming. The vegetative feedback modeled in this research, in which increased plant growth would exert a cooling effect, is an example of a negative feedback. The feedback quantified in this study is a result of an interaction between all these aspects: carbon dioxide enrichment, a warming and moistening climate, plants' more efficient use of water, down-regulation and the ability for leaf growth.

This new paper is one of many steps toward gradually improving overall future climate projections, a process that involves better modeling of both and cooling feedbacks.

"As we learn more about how these systems react, we can learn more about how the climate will change," said co-author Forrest Hall, of the University of Maryland-Baltimore County and Goddard Space Flight Center. "Each year we get better and better. It's important to get these things right just as it's important to get the track of a hurricane right. We've got to get these models right, and improve our projections, so we'll know where to most effectively concentrate mitigation efforts."

The results presented here indicate that changes in the state of vegetation may already be playing a role in the continental water, energy and carbon budgets as atmospheric increases, said Piers Sellers, a co-author from NASA's Johnson Space Center, Houston, Texas.

"We're learning more and more about how our planet really works," Sellers said. "We have suspected for some time that the connection between vegetation photosynthesis and the surface energy balance could be a significant player in future climate. This study gives us an indication of the strength and sign of one of these biosphere-atmosphere feedbacks."

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3 / 5 (10) Dec 07, 2010
Funny. Didn't Dyson say, "if you're worried about globull warming, plants some trees"?

The polar bears will be fine.
2.3 / 5 (12) Dec 07, 2010
OMG! "Science" is just now figuring out that there is a complex feedback system between life and climate that stabilizes climate. And, that's why the earth has a long history of "temperate", if not "constant" climate conditions. Duh!
2.1 / 5 (7) Dec 07, 2010
Been saying this for years.

Sad it took the "Experts" 30 years to catch on...
4.1 / 5 (9) Dec 07, 2010
It's amusing that some people will hail any research that shows potential negative feedback loops, but will scream and denounce any research that shows positive feedback loops.

It's almost as if some people have an agenda other than the search for truth.
2.7 / 5 (7) Dec 08, 2010
@bhiestand The truth always takes longer to come out than the lies...
Here is a great example of the swine flu death numbers

Thousand of people died from the vaccine, 31 died of swine flu.
4.4 / 5 (7) Dec 08, 2010
MarcoB: I don't suppose you have any peer reviewed information about your absurd claim that "thousands of people died from the swine flue vaccine and only 31 died from the disease. First, it is very simple to falsify your second point that only 31 died of swine flue since there were more than 3000 dead before the vaccine was available. Are you proposing a time machine that let those people get their vaccinations before they were available?

Second, there appears to be evidence that less than 10 people died from the vaccine (which is about in line with normal flue vaccine statistics).

Finally, the guy on youtube had no references and babbled like he needed his meds adjusted or his tin-foil hat tightened.

Please show us any technical supporting information for your ignorant claim. You probably believe that the CIA brought down the twin towers and that the world economy is controlled by aliens. This is a scientific site and you have just thumbed your nose at science and lied.
3 / 5 (3) Dec 08, 2010
@thermodynamics After a long search, I concede I can't find any conclusive proof about the claims above and shouldn't have said fact. I'm interested to know why you didn't link your info? I'd like to look it over. Are you taking the vaccines? Also while I was trawling throught the masses, it is interesing that the numbers change from one article to the other, that there wasn't proper death counts before and after the vaccine was released, how do we know people that got the vaccine didn't die from the vaccine itself and while dying spread the flu to others. How accurate is the test that someone died from the h1n1 flu and not normal flu. I'm also interested in why you pulled 9/11 into it, from a pure scientific view, i can't see how 2 planes brought down 3 towers, that they all fell at free fall speed.
If you watch these videos and still feel no new investigation is needed, then that's cool.
5 / 5 (2) Dec 08, 2010
Cool (pun intended), but we are cutting them down to create a parking lot (apologies to Melanie) not planting more.
not rated yet Dec 08, 2010
Cool (pun intended), but we are cutting them down to create a parking lot (apologies to Melanie) not planting more.

That could be easily solved with new building codes and zoning codes for commercial and corporate buildings.

They should be required to have vertical schematics and vertical parking (i.e. multi-floored garages,) perhaps even under the office or shopping area. This way we greatly reduce the physical footprint of these shopping centers who often have ten or 20 acres of parking lot.

Key offenders:

Wal-mart, etc
Winn Dixie, etc
Hobby Lobby
2.6 / 5 (5) Dec 08, 2010
The new and more sophisticated model may be less wrong than it was but it is still worthless because it is created by people who seem to have a bafflingly bad understanding of basic physics. You can't just assign properties to greenhouse gas molecules in order to achieve whatever magical effects that you want for your outcome.
4 / 5 (4) Dec 08, 2010
required to have vertical schematics and vertical parking

When I was at Auburn they built a virtical parking deck next to one of the admin buildings where a normal parking lot had been previously. The net result when complete was the loss of several parking spaces according to the school newspaper. I don't remember the number of spaces, but a very cloudy number 9 comes to mind.

So, .3 degree difference out of between 2 and 4 degrees total. That's a correction of between 15 and 7.5 percent. Pink Elephant would say that the models are accurate, and this study must be wrong. I say there are still a few important feedbacks which are currently estimated rather than simulated, and I would not be surprised to see many more results similar to this one. I would also not be surprised to see someone dispute this rather quickly. I would wager good money that there are as many + errors in current models as there are - errors, by the way.
5 / 5 (3) Dec 08, 2010
Let's put it into perspective... they're introducing a potentially significant dynamic that can go be used in climate models.

There's always a huge variety of models, with all sorts of dynamics included or not included, and treated in different ways.

If these guys' way of accounting for down-regulation can be shown to be accurate, then it's a refinement (13% downwards, from their figures).

If not, then it's absorbed into the uncertainty. Temp rise for a doubling of CO2 is usually given as something like 3ºC±50%, so an additional uncertainty of 13% would hardly touch it.

Hopefully it's true.

Also it looks like it predicts lower temp increases but higher humidity increases, which brings in a whole other set of climate issues.
3 / 5 (2) Dec 08, 2010
..additional growth of plants and trees in a world with doubled atmospheric carbon dioxide levels would create a new negative feedback - a cooling effect..
Yes, if only the positive influence of carbon dioxide to photosynthesis will be considered. Not, if the negative influence of droughts to photosynthesis will be considered.

Global warming means more intensive vertical circulation in Earth atmosphere. More intensive vertical circulation means, most of water evaporated from oceans will condense at the coastal areas - the inland will suffer droughts.

BTW the destruction of tropical forests means, we cannot consider the cooling effect of plants, if we destroy the green lungs of planets before they could save us against warming.
1 / 5 (1) Dec 09, 2010
@ KwasniczJ:

That's not accurate. Warmer will mean wetter for most regions, especially in Northern areas like Canada and Siberia. The NASA model includes changes in precipitation. If you believe the models, then they are not saying what you are claiming.

In regard to tropical forests, you are wrong there too. Once a forest reaches maturity, it enters a state of equilibrium in terms of how much CO2 it consumes and how much CO2 and methane it gives off. Once the forest reaches it's maximum level of sustainable growth, it gives off almost exactly the same amount of CO2 (through decay) as it consumes from the air. Only a very tiny amount of forest material ends up getting burried permanently in the ground or at the bottom of a lake or ocean before it decays. CO2 is only sequestered when it's trapped in the ground, and tropical forests actually aren't very good at doing that. Material on the tropical forest floor decays so fast that very little gets sequestered permanently.
1 / 5 (1) Dec 09, 2010
In fact, tropical forests may have a net negative effect, since they take CO2 and turn it into more harmful greenhouse gases like methane, amonia and others. I know it's hard to think of it that way, because certain people want you to believe that forests are a never-ending bottomless pit of CO2 consumption and without them the world would be covered with a poisonous cloud of deadly gases. That's simply not the case though. According to official IPCC estimates, among the most efficient carbon sinks are commercially managed forests for logging. The reason those are such good carbon sinks is that they are constantly kept in a state of maximum growth rate, then the carbon gets turned into paper and other products and burried in landfills or dumped in the ocean, where it is likely to end up suquestered in sediment.
2.6 / 5 (5) Dec 11, 2010
Anthropogenic global warming is absolute and total bull***t.

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