Wouldn't growing trees solve Global Warming?

[vivesdn]

So the right answer to the question is 'we don't know the precise effect of growing trees massively'. A wrong answer is that trees are a low albedo cover and will increase the greenhouse effect. Another wrong answer is that trees would absorb CO2 in 5 years and climate change would stop. But as we are deforesting at a high pace, trying to grow trees seems that should help in stoping climate change.

 

[cbacba]

doing something like expending all of mankind's wealth to turn the sahara into a jungle over the next millenia would probably be an extremely bad idea. The trees would capture far more energy than they would use, create a muggy moist air - jungles are known for being very hot and very steamy and the reduced albedo does mean more energy will be absorbed until temperatures rise to re emit the power. Plus one has the added problems of decaying vegetation emits methane and it's possible that having your carbon sequestration in flammable form results in a giant pulse of CO2 when something goes seriously wrong. It seems that forest fires in the US got extremely bad when loonies got in power that successfully crippled the logging industry and destroyed many logging roads that operate as fire breaks. It seems to that it was the best of causes that prompted people to fight and try to prevent fires back early in the 20th century that led to a buildup of dead brush and conditions that turned the normal and natural minor fire occurances into mass total anahilations we're experiencing now. It's disheartening to realize that the whacko pervert with a zippo and a penchent for watching flames might have been doing more of a service to forests back a hundred years ago than those people who spent the best portions of their lives trying to protect and preserve those forests.

Then again, the question arises as to which would be easiest, gathering up all the sand in the sahara, mixing it into concrete and building a pyramid that reaches up to the geostationary orbit radius or to turn it into a nice little central park for all the african, middle eastern and european tourists to come visit.

 

[Skyhunter]

cbaca,

Sorry I took so long to respond.

You are simply taking numbers and putting them together like tiles in a scrabble game.

TSI is not 168 W/m². The solar constant is 367 W/m². So all your calculations based on your simple model using the http://cfa-www.harvard.edu/hitran//" database are meaningless, ie garbage in equals garbage out.

The reason that planting trees in the NH is at best GW neutral is because of winter albedo. trees break up snow cover reducing the albedo during NH winter.

Clouds vary in their effect on temperature depending on what kind and where they form. High thin clouds contribute significantly to warming, while low cumulus clouds have a negative impact on warming.

 

[vivesdn]

Deserts like the Saharan are extremely hot during day but are also quite cold in night. Land and air loose their warmth as the cloudless night sky allows full radiative cooling. I find surprising (at best) the reduction of the problem to a high/low albedo.
Is it really important that northern trees reduce the albedo in winter because they avoid the snow cover? May low temperatures (low humidity->less GH) and less light hours counterpart this issue in winter? What is the overall effect all the year round? Part of the summer radiation is converted into sugars, part is used to evaporate deep water, keeping the forest much cooler than a meadow (wich evaporates surface water and allowing a higher temperature increase at surface level) or a concrete surface.

Can you afford scientific and quantitative proof of the relevance of each factor to global warming? Nowdays, I think that no one can.

In my opinion (just an opinion) growing trees is not the solution. But I also think that, in any case, growing trees is better than not growing them.

 

[cbacba]

cbaca,

Sorry I took so long to respond.

You are simply taking numbers and putting them together like tiles in a scrabble game.

TSI is not 168 W/m². The solar constant is 367 W/m². So all your calculations based on your simple model using the http://cfa-www.harvard.edu/hitran//" database are meaningless, ie garbage in equals garbage out.

The reason that planting trees in the NH is at best GW neutral is because of winter albedo. trees break up snow cover reducing the albedo during NH winter.

Clouds vary in their effect on temperature depending on what kind and where they form. High thin clouds contribute significantly to warming, while low cumulus clouds have a negative impact on warming.

Actually, 167 W/m^2 is an average surface insolation. About 350W/m^2 is top of the atmosphere insolation averaged over the entire surface. Total radiation not reflected (albedo) amounts to an average of about 235 W/m^2 which becomes the amount absorbed by surface and atmosphere. For greenhouse effects to occur, an additional amount of insolation and/or absorption must occur such that there is a change in surface temperature required to achieve that radiation balance such that incoming absorbed and outgoing emitted must be equalized.

However, not all W/m^2 are created equal. A change in concentrations of ghgs resulting in a change in absorption also creates a change in emissivity which may or may not require a change in temperature to gain balance. On the other hand, a change in insolation at the TOA doesn't affect the absorption/emission of the atmosphere, requiring a pure T^4 variation in temperature to adjust to the new value.

As for my model, it is being upgraded from a 0 dimension model to a one dimensional radiative model with over 40 layers. Work has been slow as the calculation load and memory requirements have been difficult to deal with. File sizes for a variety of calculation files range from 60mb to 230mb.

 

[cbacba]

Deserts like the Saharan are extremely hot during day but are also quite cold in night. Land and air loose their warmth as the cloudless night sky allows full radiative cooling. I find surprising (at best) the reduction of the problem to a high/low albedo.
Is it really important that northern trees reduce the albedo in winter because they avoid the snow cover? May low temperatures (low humidity->less GH) and less light hours counterpart this issue in winter? What is the overall effect all the year round? Part of the summer radiation is converted into sugars, part is used to evaporate deep water, keeping the forest much cooler than a meadow (wich evaporates surface water and allowing a higher temperature increase at surface level) or a concrete surface.

Can you afford scientific and quantitative proof of the relevance of each factor to global warming? Nowdays, I think that no one can.

In my opinion (just an opinion) growing trees is not the solution. But I also think that, in any case, growing trees is better than not growing them.

Vivesdn,

I would think you're quite right. There's nothing wrong with having trees but they aren't going to help, probably more likely that they'd hurt if some supermassive project were invoked, like to reclaim the sahara and turn it into a rain forest. That would take a significant area of land and convert it from some of the highest albedo surface into something rather low. That would result in a measurable increase in absorbed energy via reduced albedo and possibly due to added moisture content as well.

Of course I'm not really worried about that happening as mankind doesn't have the resources to accomplish it. What is worrisome is that some idiots might try with tragic consequences for the majority of humans currently living on planet earth.

 

[Skyhunter]

Unless rainfall patterns change, restoring the Sahara would be costly to maintain.

Thanks for the clarification cbaca, good luck with your model.

 

[cbacba]

The model is a real pain to deal with. The final calculations are in a file over 209mb in size. A file load or save takes a number of minutes. The final part is an excel spreadsheet format. The front end takes a Hitran output file and processes it into a series of line strengths by wavelength and creates a file of absorption coefficients by wavelength bin. For a segmented (one dimensional model) output, it takes about an hour and this is from a c++ program. It's taken most of the day just to generate up a new result such as a change in molecular concentrations. Consequently, I now have the 1976 std atmosphere average and the std atmosphere with 2x the CO2 levels present in 1976.

Doubling the CO2 level results in 2.7W/m^2 decrease in the TOA radiation and it takes 1.5 degrees K increase in the surface (and 0-1km) temperature to compensate.

What's interesting also is that the std atm provides emissions of 233.9 W/m^2 at the TOA and the graph looks somewhat like what one would expect to see from the nimbus satellite spectrum with components showing from various levels of the atmosphere. It looks more like the tropical measurements than the polar ones. Unfortunately, I haven't had time to create a graph version that uses wavenumbers instead of wavelength or create any but the simplest of graphs but it definitely looks like the real thing at first blush.

Trying to model cloudy skies is going to be a real bear though as is trying to make a variety of atmospheres. Also, establishing a lapse rate variation looks to be potentially challenging as well - at least in the amount of time needed for the processing.

It would seem though that the atmospheric sensitivity is somewhat less than is being pushed by many, at least with the simplistic approach of changing only the surface temperature which is quite dubious considering that there is increased absorption for inbound energy as well as for outbout.

 

[Andre]

... Consequently, I now have the 1976 std atmosphere average and the std atmosphere with 2x the CO2 levels present in 1976.

Doubling the CO2 level results in 2.7W/m^2 decrease in the TOA radiation and it takes 1.5degrees K increase in the surface (and 0-1km) temperature to compensate.

Good job, interesting. Important question: did you model increase in evaporation as well. The 1.5 degrees would roughly compare when keeping relative humidity constant MODTRAN gives 1.3 K in that case. But the big question is, has the 'loss'/diversion of energy for evaporating the addition water been accounted for?

 

[cbacba]

Good job, interesting. Important question: did you model increase in evaporation as well. The 1.5 degrees would roughly compare when keeping relative humidity constant MODTRAN gives 1.3 K in that case. But the big question is, has the 'loss'/diversion of energy for evaporating the addition water been accounted for?

Andre,

Actually, the comparison is merely a rebalance of radiative amounts due to a simple increase in surface temperature - which in my case affects the temperature in the bottom 1km as well. It seems that the difference between 330ppm of CO2 as used in the 1976 std atmosphere provides 2.7 W/m^2 increase when the CO2 is doubled to 660ppm.

As such, it would appear that the absolute humidity - or water vapor concentration would be fixed while the relative humidity would have dropped slightly.

This was a 'what if' experiment which was "what if the balance restoration was done totally by increasing temperature at the surface?" and would seem to be a worse case scenario for temperature rise. Considering calculations took the better part of the day for doing 1 scenario, it's difficult to do much at the moment.

It would seem the next step is to do a detailed energy balance of the model and determine the actual amounts of energy balance occurring from radiation and that required for a balance with that required for energy balance with the added co2. Note - there is a graph on ukweatherwrld I posted yesterday of the TOA spectrum generated by the std atm calc.

cba

 

[mgb_phys]

Without wishing to wade into a global warming debate.
One problem with trees is that they are mostly 'C4' photosynthesisers and so also respire, regenerating CO2 when they use the sugars they made form CO2 in the first place - they permantly capture only very little of the CO2 the adsorb. Unfortunately most grasses and other quick growing species (suitable for biofuel) are also C4.

I think rice is probably the only common 'C3' species - which converts most of the absorbed CO2 into permanent structures. Until we eat it and breathe it back out again!

 

[cbacba]

Without wishing to wade into a global warming debate.
One problem with trees is that they are mostly 'C4' photosynthesisers and so also respire, regenerating CO2 when they use the sugars they made form CO2 in the first place - they permantly capture only very little of the CO2 the adsorb. Unfortunately most grasses and other quick growing species (suitable for biofuel) are also C4.

I think rice is probably the only common 'C3' species - which converts most of the absorbed CO2 into permanent structures. Until we eat it and breathe it back out again!

isn't rice a serious methane releaser?

 

[mgb_phys]

isn't rice a serious methane releaser?

Yes, well the fields it's grown in are, pity there aren't any easy solutions isn't it!

 

[Skyhunter]

I think you have that backwards mqb_phys.

Only recently did nature evolve a plant, capable of converting carbon dioxide more efficiently than any other plant, while also using less water. Their photosynthetic conversion requires four biochemical steps, rather than the usual three, a process that saves it both energy and water. These plants, called C4 plants, include the bamboo-like grasses, and the agricultural crops sugarcane, maize and sorghum. They are about twice as efficient in converting sunlight and need four times less water. C3 plants have maximum sunlight conversion efficiency of 15% and C4 grasses up to 24%. In practice, due to leaf shading, these figures are five times lower. Photosynthesis in C3 plants converts 0.1-0.4 g CO2 with 1 kg water, whereas C4 plants convert 0.4-0.8 gram.
http://www.seafriends.org.nz/enviro/soil/fertile.htm"

Have you looked into http://www.bambootechnologies.com/allabout.htm" ?

 

[vivesdn]

I also think that trying to grow trees on the saharan desert is quite stupid. What I have in mind is trying to recover the forests we had some time ago.
It would be interesting also to study if a forest can produce more food that a wheat crops.

What about algae? Some species fix CO2 not only as sugars but also as calcium carbonates (ask why Dolomiti are there...)

 

[cbacba]

In general, no. Forests tend to grow in fairly poor soils. Trees are also quite slow growth and obscure much of the solar energy for other plants as well as absorbing moisture and nutrients. Now forests may produce soil suitable for the higher performance plants and eventually tend to form meadows for grasses and small plants but that is not food production. Actually, considered another way, who eats trees other than termites and a few other bugs (and maybe a little by goats)?

Wheat and rice are very much high performance crops, genetically engineered through millenia of manipulation and substantial amounts of the growth go into edible portions. The same thing goes with grasses and domestic animals.

As for algae, evidently there are plenty of them out there that do such things. However, man's efforts into serious biological manipulations usually result in what was best described long ago by Mary Shelly in her infamous first novel.

 

[mheslep]

Without wishing to wade into a global warming debate.
One problem with trees is that they are mostly 'C4' photosynthesisers and so also respire, regenerating CO2 when they use the sugars they made form CO2 in the first place - they permantly capture only very little of the CO2 the adsorb. Unfortunately most grasses and other quick growing species (suitable for biofuel) are also C4.
...

Hold on. There must be significant carbon captured into the hydrocarbon mass of the tree (the wood). That must come from the C in CO2 through some process, or from the soil. I don't know that trees need soils with much C compounds to flourish so I am thinking CO2 must be supplying most of the C mass in the tree.

 

[cbacba]

Hold on. There must be significant carbon captured into the hydrocarbon mass of the tree (the wood). That must come from the C in CO2 through some process, or from the soil. I don't know that trees need soils with much C compounds to flourish so I am thinking CO2 must be supplying most of the C mass in the tree.

Sure the CO2 goes into the wood but you're looking at a 15 year crop versus a 15 week crop. Of course just planting trees results eventually in lots of deadwood - unless it's a crop. It's what happens with the breakdown of that wood that can matter. Termites eat it, resulting in the rerelease of CO2 in some cases and in the formation and release of methane, which is considered far worse than CO2 over the life cycle of both molecules even though ch4 supposedly has a far shorter lifespan in the atmosphere.

I guess my point should be that all ideas have consequences which include negative consequences but big ideas generally have the most serious consequences. That means if the idea implementation is big enough to have any discernable effect, it's big enough to have some really serious unintended negative consequences.

 

[vivesdn]

I guess my point should be that all ideas have consequences which include negative consequences but big ideas generally have the most serious consequences. That means if the idea implementation is big enough to have any discernable effect, it's big enough to have some really serious unintended negative consequences.

I'll fully sign this statement.
But thousands of planes flying every day, millions of cars, manufacturing plants, etc, this is also a big idea that for sure is having a really unintended negative effect.

 

[cbacba]

I'll fully sign this statement.
But thousands of planes flying every day, millions of cars, manufacturing plants, etc, this is also a big idea that for sure is having a really unintended negative effect.

I would suspect you're probably off by some orders of magnitude in level of efforts required to achieve this versus the other.

 

[Plastic Photon]

Digging up dinosaur fossils won't solve the debate over the cause of the K/T, as such, planting trees won't solve the debate over global warming. Nothing in geology is cut and dry.

 

[lazypast]

you hear a lot about china building one new coal powerstation every 10days, but you don't hear so much about the amount of new tree plantations they create.ive forgotten the amount in relation to the amazon rainforest but it is a greatly significant amount.

just also heard recently the hopes of reducing global warming might lie with algae, since it produces about 80% of the oxygen on earth.

 

[cbacba]

So the questions become for china, will the tree plantations compensate for the added co2? and will the plantations reduce the albedo such that the consequences are even more than the added co2?

Those coal fired plants are just a scam because china didn't have to agree to cut back on creating them and those countries that did aren't restricted from buying 'used' plants.

 

[lazypast]

dont know what you mean by buying used plants. but i do believe china didnt sign the kyoto protocol and would doubt their plantations don't compensate.

people do care on a scale that big though, id think the plantations would be very consuming in money and time etc

 

[cbacba]

used plants = used coal fired power plants, nothing to do with plantations. China builds power plants, then dismantles them and sells them to whomever who can now purchase them second hand - avoiding any kyoto or other agreements about creating or obtaining new coal fired power plants - ie - a scam.

not sure what you mean by the double negative.

 

[Evo]

Those coal fired plants are just a scam because china didn't have to agree to cut back on creating them and those countries that did aren't restricted from buying 'used' plants.

Please post a link to where it says it's ok to set up new coal burning facilities using "used" parts.

 

[cbacba]

Please post a link to where it says it's ok to set up new coal burning facilities using "used" parts.

that's not what i said.

I said building new coal fired plants then dismantling and selling them as second hand