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Wouldn't growing trees solve Global Warming?

  1. Jun 8, 2007 #1
    Since rising CO2 levels are the problem and trees take in CO2 while giving off oxygen, wouldn't growing a vast amount of trees solve Global Warming at a significant level or am I missing another element here?
  2. jcsd
  3. Jun 8, 2007 #2
    Having actually asked this question myself to an Oxford professor that claimed to actually know something about this, I happen to know that the answer to this question is "no". The unfortunate thing however, is that I do not remember the exact details of the full answer she provided me.

    I believe green has a low albedo, so the more green the more absorption of solar radiation. I also believe that trees give of methane, and also when they die they rot, and greenhouse gases are released into the atmosphere. These things together will mean that growing more trees won't actually help to cool the earth.
  4. Jun 8, 2007 #3


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    There is a bigger picture when considering the earth's carbon cycle. Certainly trees do sink CO2 and so does the ocean's algae. See this reference especially Figure 5, for relative contributions from various sources in our carbon cycle.

    Planting more trees is a good means of sinking atmospheric CO2. The best areas for growth are the tropical rainforests. Unfortunately, there the opposite is taking place. Large scale cattle ranchers have the financial clout to buy up large tracts of rainforest in tropical regions, burn them to the ground and then let grasses grow for grazing their animals. (ref2)
    These soils will not sustain grass pasture very long and so the ranchers move on and burn down more rainforest. It would take serious political maneuvering to convince the governments of these countries, to change this policy.
    Last edited: Jun 9, 2007
  5. Jun 11, 2007 #4
    Is there any way of restoring a rain forest?
  6. Jun 24, 2007 #5


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    Yes, replant indigenous species that lived in the forest.
    In a nursery located in the same region, you may grow trees, shrubs and other understory plants for transplanting.

    Here is a http://www.news.cornell.edu/Chronicle/99/5.27.99/Michelson.html [Broken] doing just that, in a rain forest in the Republic of Gabon, Africa. In his project, they are reclaiming rainforest that was damaged during use by the petroleum industry.

    Some are taking a more scientific approach and study mechanisms of natural regrowth to facilitate development of restoration methods. This http://www.ioe.ucla.edu/Ctr/research/seed_dispersal.htm [Broken] at UCLA are researching these things in Ecuador, South America and Cameroon, Africa.
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  7. Jul 29, 2007 #6
    I've read that planting trees in the tropics is better than planting trees farther north, which is something to do with the dark leaves trapping more heat and actually contributing to global warming.

    Planting trees is a good idea, but there are so many people on Earth that you would run out of room. Especially as the population grows and there are more and more greenhouse gases being released into the atmosphere.

    Maybe the best idea would be to plant trees AND reduce needless waste
  8. Jul 29, 2007 #7
    Increased CO2 certainly would benefit plants and allow many more types of plants to grow (at least things seem to grow better in a greenhouse than they do in the desert). The problem is that even the most intense tree planting program you can think of will not keep pace with the amount of CO2 rising into the skies on a daly basis while everyone drives to work. Just think of how many cars are on the freeway in say Los Angeles on a saturday afternoon and imagine how many trees you would need to plant to compensate.
  9. Aug 9, 2007 #8
    If you stop trying to beat it back, it will take over. It's worse than trying to keep your lawn mowed after fertilizing and watering it to excess.

    As for the jungle, it's got a rather low albedo. That means it absorbs lots of energy. It also emits lots of moisture, which is a powerful ghg. In addition, it's the home for tons and tons of termites who are busy munching on dead wood and putting out copious amounts of methane which is far worse than co2 over the lifetime of the longer lasting co2 molecule, by something like a factor of 7 or a factor of 21.

    Desert makes about the best surface for high albedo, followed by pasture land and crop land.

    Perhaps you should send a thank you card to those destroying the rain forest as it would appear they are saving the planet from even worse global warming LOL.

    While it seems most attribute way too much importance to co2 and other ghgs, they also don't seem to recognize that albedo and cloud cover are, if anything, substantially more important.
  10. Aug 29, 2007 #9
    i agree with idea to plant trees not in one country beacuse it hasnt influence in earth atmosphere . idea is to plant in all the globe
    benefit of this is not to decrease co2 in atmosphere however to enhance 02 in atmosphere
    other benefit is to decrease many pollutant from factory
    maybe i dont write good but you can undestand me
  11. Aug 29, 2007 #10
    It is true what Kusha02 points out that trees remove some pollutants and improve air quality locally. However, planting trees requires arable land, so agricultural output is reduced by this strategy. Since people need food, this might not be a viable strategy. For the purpose of reducing the greenhouse effect, I believe that better use of surplus land is to grow fuel crops, such as rapeseed (for oil) or sugar cane or similar (for ethanol). These fuels are CO2 neutral, and for every car running a mile on biologic fuel, a mile's use of gasoline is saved and the corresponding emission is avoided.
  12. Aug 29, 2007 #11
    In fact, there is a theory to explain the Little Ice Age (there are some of them...): black death killed people by thousands, millions, both in Europe and Asia. Thousands of acres of crop land were abandoned and forests recovered naturally. The less greenhouse gases production (rice is responsible of methane production as it grows on water) and higher CO2 sinking produced a global cooling for several centuries.

    While the theory might be correct, what is important to understand is that forests are absorbing CO2. And the albedo is lower than crops but a higher proportion of radiation is converted to organic CO2. Most of it as cellulose, which has been the origin of oil. So forests are important to keep CO2 levels low.

    For methane, there are crops (as rice) that produce more of it than forests do, and for sure cows are a major source of it.

    To reduce CO2 levels, I've seen out there the proposal of fertilizing the see wih iron or urea to allow algae to grow on extense areas of now empty ocean. Easier and faster than growing forests, and for sure with no claims for the land.
  13. Aug 29, 2007 #12
    All actions have reactions and unintended consequences can be substantial. Global temperature depends more on albedo and cloud cover than it does on a minor variation in the concentrations of a minor ghg. Methane is created by rice and other plants. Some plants help filter out the air and some put more crap in it than they filter out. Also, there can be tremendous amounts of insects - like termites involved in an area - depending upon what is there. These little buggers produce lots of co2 and methane per their size (mass) when compared to just about anything else and there is substantially more mass of termites on earth than there is mass of people on earth. In the realm of albedo, croplands reflect better than most surface items. Jungles tend to absorb much more than cropland and dirt plus creating large amounts of humidity and homes for tremendous masses of termites and other insects. Other than snow, desert sand is about the best albedo surface.

    Doing things in moderation has little effect. Trying to make changes to large regions - like greening the sahara could have an effect assuming it didn't bankrupt the world economy before it was implemented. Unfortunately, all these nice touchie feely good feeling things like replacing the desert with jungle - or saving the rain forests - often tend to actually have detrimental effects on climate balance - for whatever effects they might have. In other words, those greedy land grabbing agribusinesses cutting down the rainforests in south america are actually helping reduce global warming - regardless of what damage they may or may not be doing otherwise. Many things in this arena also have dual effects. A giant forest fire might might put lots of co2 in the air - but it will likely put lots of aerosols and particulates up in the atmosphere which might counteract warming more than the co2 promotes the warming. It would appear at present that the push to establish pollution controls on coal burning may have made cleaner air, cleaner snow and a hotter climate. For certain, those people in the antinuke protesting business undoubtedly helped force the use of more coal for electrical generation in the US helping create more pollution and more co2 emissions to a measurable point.

    I've seen that some think human agriculture is responsible for our failure to return yet to another major ice age. This may or may not be accurate. However, a major ice age will be devastating for many centuries when (or if) it occurs. Most of the global warming hysteria is only that. It is apparently being generated to counteract the notion that such an event - if it were to happen - might even be beneficial overall to man and most species of plants and animals.
  14. Aug 29, 2007 #13
    i know what are you say and i understand
    but i talk to plant trees in mountain not in field
    and to ask for help in genessis biology to find if is absorb of co2 in gene and to modify it to absorbe more c02
    i dont say to plant only wood but also to plant apple trees , pear etc

    for car i think to use hidrogen for carburant or bio gas
  15. Aug 30, 2007 #14
    If destroying the rain forest is actually reducing global warming, then what the hell is all the uproar about deforestation? Unless all the whiners are a bunch of spiritual new agers. There are so many misconceptions about global warming and its causes. Until this thread, I did not know cloud cover was a much bigger cause of global warming then of deforestation. Never did I hear anyone mention cloud cover. Unbelievable.

    So I guess to sum up, my father's idea which I inquired about was a pretty stupid idea. My dad is an idiot. And yeah, my father should just stick to mathematics.
  16. Aug 30, 2007 #15
    it isnt only this idea
    we can send large mirror in the space to return back light or to send another mirror to warm mars
    it is very expensive but is good idea

    if in big city like in new york , LA , washingont etc we use bike not cars we do good job in this case beacuse the contaminations of air 60% is from cars

    we have many alternative to change the world but we all must contribute in this no olny sience
  17. Aug 30, 2007 #16
    There's nothing wrong with forests and from an emotional view, they are very pleasing. It's a rather large planet and we are actually a rather small force among many greater forces. Actually, different trees and forests offer different reflectivity as well. Jungle, or rain forest is the lowest, meaning it absorbs the most heat.

    As for commuting in LA, if it takes 90 minutes of driving on the freeway to go from home to work, how long do you think it might take by bicycle each way?

    One should also be reminded or warned of solutions mandated by governments. I remember that the california government decreed that almost 10% of new cars to be sold would have to be electric, either now or in the next few years. This was before the great electric power debacle where it was discoverd that californians did not have enough electric production to cover their current usage and that they were having to pay outrageous amounts for peak load power bought from other areas of the country. Apparently, the realization that adding far more electric usage to recharge millions of electric automobiles took some time to sink in although maybe it finally did.

    As for why is there uproar over deforestation, there could be many reasons. Those upset may not know or care about the climate ramifications for large scale activities. Since it's an emotional response, it is not subject to being rational. When DDT was banned in most countries and methods of persuasion used on the other countries not to use it, those wanting it banned were joyous over it - despite the fact that millions of poor people would die or have life long chronic diseases. Since most (but not all) of those celebrating were unaware of the consequences, only some were celebrating the death and disease.

    My point was there are no actions without reactions. No drug cures a patient without some patients suffering from side effects. I doubt that few nuclear power protestors realize they are substantially responsible for the current high level of use of coal in electric power production now. And, coal is a significant contribution to overall green house gases and it is expanding. It would seem too that perhaps those wanting clean burning coal - without the aerosols and particulates in the atmosphere may have contributed to temperature rise as well, preventing the cooling counterbalance to added CO2.

    Please note that my comments concerning global warming concerns are for your benefit and do not necessarily convey anything of my views or concerns on the subject. Besides, historically over all of the 20th century, the warming / cooling disaster hype cycles about every 20 to 30 years and it's getting time for the media to switch over to the coming ice age disaster hype again.
  18. Aug 30, 2007 #17
    Forests host a huge biodiversity, a substantial part of which has yet to be described. This alone justifies preserving forests. One should not let oneself be blinded by one cause so as to let it take precedence over other less discussed but possibly equally important causes. In order to find sustainable solutions to the world's problems a holistic approach is necessary.
  19. Aug 31, 2007 #18
    Just take care on the meaning of albedo. Snow has the higher albedo, because most of the light is reflected. A black surface has a low albedo, reflects a low percentage of light, and it warms a lot. And trees may have a low albedo too, but the absorbed light is not converted into heat, but into sugars. And the shadow they generate allows the surface to keep cooler, minimising water loss. Prairie and crops are much less efficient on this.
  20. Aug 31, 2007 #19
    Unless one is referring to Bond albedo which is visible light, it covers all wavelengths. A black body radiator the temperature of the sun's surface emits about 46 % in the moderately near IR and only 41% in the visible (balance being uV). One gets quite a different picture - so to say - when covering the bandwidth of solar radiant energy from uV to about 15microns. Also, albedo is a concept that compares energy going into the TOA (from the sun) to energy reflected out after it goes past the TOA (top of atmosphere). Hence, albedo and actual reflectivity of the object or material can differ substantially as there is atmospheric absorption going on in both the downward and upward path.

    Different types of trees and plants vary in their reflectivity as do different types of forests and different types of snow, dirts, crops and sands. There are some interesting datasets one can view or download from the web, most going from about 300nm to around 15microns providing the information on this for both manmade and natural surfaces.

    Suffice to say that even snow can start looking rather dark as the wavelengths increase - indicating that at wavelengths associated with emissions from 287K temperatures and below, it too has very high emissivity and very low reflectivity in this realm.

    An example of snow might be 78% reflectivity over the solar insolation wavelength region. Applying atmospheric absorption to the atmospheric pathlength can result in a value of around 43% for the actual albedo of that snow patch.

    I would suggest that biological processes are nowhere close to 100% efficient in converting radiant thermal energy into stored chemical potential energy. What's more, that energy is liberated on decay or burning. Considering that the balances must be maintained that would imply most of what is currently absorbed into bioprocesses must be being liberated from relatively recent earlier processes at the same rate it's happening now or there is an imbalance which cannot last.

    Granted that bioprocesses probably have a far greater effect than they are given credit for or considered by the climate model players, but there is tremendous energy involved on average coming down from the sun. Probably on average, about 70W/m^2 reaches the surface when cloud cover is considered. On average it would seem too that about 8 of the 10 watts reflected from the surface reaches the TOA, leaving the surface about 60W/m^2 average incoming which is absorbed. Of that about 50W/m^2 radiated from an average surface temperature of 287K reaches the TOA - again considering cloudy and clear skies. I'd expect those numbers to be accurate to about 10% or so and perhaps somewhat better for some.
  21. Sep 3, 2007 #20
    If you mean that the whole thing is more complex than simply growing trees, then I agree. If you do mean that growing forests is useless as it increses methane production and reduces albedo, then I must disagree.
  22. Sep 3, 2007 #21
    Actually, I think we should do that which we desire to do, not what some think we should do based on flawed understanding.

    The fundamental falacy in the GHG argument is simple enough for most to comprehend once they see it.
  23. Sep 5, 2007 #22
    If you're talking about GHGs (hence the thread title "Global Warming"), cars produce relatively little of the overall anthropogenic GHGs from a global standpoint. Riding more bicycles would have no material affect on the problem.

    We know this because all cars on earth consume a fraction of global energy (mostly hydrocarbon-based). The majority of energy consumption (hence GHG production) is from the industrial, commercial and residential sectors.

    If we accept that anthropogenic GHGs cause global warming, even if every car on earth was replaced overnight with a perfectly clean "Mr. Fusion"-powered vehicle, it wouldn't hugely affect the global warming situation.

    The world uses about 877 million gallons of gasoline per day: http://www.gao.gov/new.items/d05525sp.pdf

    For rough purposes, we'll assume it's all used for transportation. Gasoline contains about 124,000 BTU/gal.

    How does this compare to TOTAL world energy consumption -- about 450 quadrillion BTU per year (most of which is hydrocarbon-based)? http://www.eia.doe.gov/oiaf/ieo/world.html

    877E6 gal/day * 124,000 BTU/gal * 365 days/yr = 39.7 quadrillion BTU for world automotive gasoline consumption.

    What % of global energy do all cars on earth consume? 39.7 quads / 450 quads = 8.9%.

    For very rough purposes, if we assume GHG production is proportional to hydrocarbon BTU consumption, this means all cars on earth produce a small % of global GHGs. Probably more than 8.9%, but probably much less than 20%. I'd guess closer to about 15%.

    This is admittedly rough, as various hydrocarbon sources (methane, coal, petroleum, etc) vary in their GHG emissions per BTU. Likewise the thermodynamic efficiency of a large coal-fired power plant differs from an automobile engine. And not all of the global energy consumption is hydrocarbon-based -- a little is hydro, nuclear, etc. But globally, most of it is hydrocarbons.

    Although approximate, this illustrates the futility of emphasizing the transportation sector when discussing the global warming problem.
    Last edited: Sep 5, 2007
  24. Sep 5, 2007 #23
    The reason that planting trees in the tropics is better than in the NH is albedo, But not the albedo of the trees vs the grassland, although dried grasses do have a higher albedo. But because the grasslands are white when covered with snow whereas it is harder to cover trees with snow. Therefore in the winter, trees tend to lower albedo. At least that is my understanding. Since it doesn't snow in the tropics the increased absorption of CO2 more than offsets any lowered albedo that lighter grasses would provide.

    Planting bamboo n the NH does help offset GW.
    Last edited by a moderator: Sep 5, 2007
  25. Sep 5, 2007 #24
    Where did you get your numbers from cbacba?

    My understanding is that average solar input is 235W/m2. 67W/m2 absorbed by the atmosphere and 168W/m2 reaches the surface. 235W/m2 is about 70% of the total radiation striking the Earth, since approximately 30% is reflected back into space due to albedo.
  26. Sep 6, 2007 #25
    Using a very sophisticated (relative to most) molecular line database, the Hitran database, in my simplified modeling, it's almost the opposite result. Those numbers look like those from Kiehl and Trenberth '99. Considering that they have an average cloud cover of 62%, you'll note that 168 may not be bad for clear skies, but it shows up a bit high when that is considered. THink of it this way - 62% cloud cover = 38% direct radiation makes it to ground which is about 90w/m^2. Figure in the photovoltaic industries bragging assumption that 10% of the radiation makes it through in cloudy situations - that's about 23.5, that's 112.8 W/m^2 reaching the ground - with no absorption in the atmosphere considered. The numbers I got running the Hitran numbers was about 150W/m^2 absorption in the atmosphere and a little under 70W/m^2 reaching the ground. K&T only used some 7 molecule approximation for absorption as well. The way the chart is done, one would assume their 168 value is average but it is clearly a clear sky only value. It throws a few other things off as well. There is another serious problem with their analysis in that they don't take in to account outbound albedo absorption which, while small, is still a factor.

    The 31% albedo is a top of the atmosphere measured value at 107. Most of it is due to clouds reflecting. At 80% reflectivity for clouds located midway in the column, I came up with 46.6% albedo when incoming and outgoing absorption was considered. Measured values indicate 45-50% albedo for clouds. Also, snow varies but typically is 43% albedo when calculated with in/out absorption despite sometimes approach reflectivity of 70%. It has a longer path - 2x the incoming. The average albedo for the surface turns out to be more like 12% (based on my variant of K&T's study) which did use a number of K&T's assumptions like cloud cover fraction. Considering that roughly speaking the surface is 75% water, and that has an albedo of well under 10%, more like 3 or 3.5%, that puts a serious cap on what the surface can do. Ice is about the same as well. Only when stuff freezes over and substantial sea ice exists well down in lattitude does the effect get seriously important in raising albedo.

    Things get even better on surface outbound radiation as all this highly reflective stuff like snow really starts to crater as being low emissivity (being highly reflective). Even the incoming solar is more IR than visible (46% vs 41%) but it's near IR that really falls off in the few micron range - but even then lots of the highly reflective stuff ceases being very reflective. By the time the longer wavelengths are reached - it's down to a couple of percent or less - making the surface highly emissive - capable of radiating very well - virtually as a straight black body (to 98% or better).

    Trees like those in the rain forest are rather low albedo - seems like something around 10% or just above. Croplands can be 20% and dry sand approaching 40%. I'm thinking those are actually reflectivity - which is albedo without absorption so some grain of salt has to be taken with things referred to as albedo numbers that aren't taken through the atmosphere but rather measured locally. It appears that many do not recognize there is significant absorption of incoming and outgoing light when it's substantially visibile and near IR.

    The fact that trees allow some light in and trap it below tends to make for lower albedo as that is how the actual physics type blackbody absorber experiment is done - a hole in an object that allows light in then baffles and absorbs so that almost nothing comes out the opening other than the bb radiant energy.

    Throw in potentials for making ch4 by some vegetation and the habitat for termites ect. that produce significant ch4 and co2 for their mass and the creation of the humid environment which is another great ghg and you have the makings for having things worse rather than better. If the rainforest burns - it's a bunch of co2 and a bunch of particulates which tend to cool. Leave it stand and there's methane being produced which is more like 7-20 times more serious than co2 over the lifetime of the co2 (the methane is far worse but much shorted lived). Then that is assuming that ghgs truly have a significant effect on gw - which may not actually be the case (since increased absorption in the atmosphere means increased emissivity of the atmosphere which means more radiation outward by the atmosphere which may actually compensate for the increased absorption without requiring a change in the temperature).

    However, albedo can change the W/m^2 balance and it doesn't change atmospheric emissivity and so is subject to needing a corrective T adjustment to compensate for changes in the W/m^2. Fortunately, that is a T^4 factor so a little change goes a long way (stefan's law).

    Net result is - if such a action were taken on a grand scale as to try to suck up co2 with trees that did affect the albedo negatively, the consequences of the albedo change would be real and serious. The consequences of reducing the excess co2 would likely be negligeable. Growing crops instead of trees might tend to reduce both factors.

    Personally, I like trees. I just don't think it's a good idea to invest substantial fractions of mankind's productivity to convert the sahara desert into a rainforest to 'save the planet' when the consequences would actually be devastating on the planet - never mind the devastating consequences on mankind for doing such nonsense.
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