NASA Satellite Measures Earth's Carbon Metabolism

Roland Piquepaille writes "To celebrate Earth Day, the NASA Earth Observatory recently revealed global measurements of the Earth's metabolism. 'Combining space-based measurements of a range of plant properties collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) with a suite of other satellite and surface-based measurements, NASA scientists produce composite maps of our world's 'net primary production' every 8 days. This new measurement is called net production because it indicates how much carbon dioxide is taken in by vegetation during photosynthesis minus how much is given off during respiration.' Check this column for a summary including the usefulness of such measurements. You'll also find maps showing the seasonal variation of Earth's net primary production."

Comments

The Earth's not fat...

[gpinzone]

It just has a low metabolism.

Now show where carbon get produced!

[Ja-Ja-Jamin]

Show where it gets produced contrasted with where it gets consumed and show the rate of the difference. Combine that with charts showing how typical day to day activities contribute to either column. Now you'll have something that can help the average person make a difference! This is a good start!

Re:Now show where carbon get produced!

[Anonymous Coward]

Nah, most people will probably just leave it for someone else to take care of, like their children. I mean, making a difference takes effort, and Joe Public is too lazy to put in effort that doesn't directly benefit himself.

These kinds of studies...

[Ratphace]

...are really important IMHO. Studying the carbon dioxide levels of any system is important because with the talks about someday inhabiting other planets like Mars, one of our first objectives would be getting greenhouse gases into the planet's atmosphere and then waiting many years for the planet to warm up enough to be inhabitable, both from a temperature standpoint and melting the ice caps at the poles (speaking of Mars of course).

I am glad to see some useful studies being done. Once a planet warms up enough with green house gases, we can get some plant life on the planet to assist in the creation of oxygen through this same cycle and eventually make a planet liveable. Though it's not something we'll see in our lifetimes, studies such as these benefit the species as a whole in the long run (i.e. big picture of time).

Re:These kinds of studies...

[sigep_ohio]

I always thought that Mars lacked the gravity to hold a sufficient amount of greenhouse gases. I mean doesn't it have like 1/3 the gravity of earth, which means it wouldn't be able to hold the same amount of atmosphere. Additionally, it is farther from the sun, so it gets less light. That would mean it would need more greenhouse gases than earth does. Added together it means that Mars can't be terraformed like in the movies.

Maybe I am missing something, but thats how I figure it. I am certainly no expert in the field, so anyone no better?

Re:These kinds of studies...

[Daniel Dvorkin]

It seems to me that both the Earth and Mars are far below the limit of possible atmospheric density for their size. Consider Venus: slightly smaller than Earth, but it has a much, much denser atmosphere. If that kind of stuff scales linearly (and I don't have any idea of it does; I'm just guessing) then Mars would have no trouble holding on to an atmosphere as dense as Earth's.

I think I remember reading somewhere that the Moon -- with its surface gravity of 1/6 g -- could hold on to an Earth-density atmosphere for something like 10,000 years. Wish I could remember more.

Re:These kinds of studies...

[JordanH]

I agree with everything you say, but thought it worth pointing out that it's not as simple as you make it out to be.

Venus is not just slightly smaller than the Earth. The Earth is around 20% more massive than Venus, being somewhat denser, so notwithstanding the relatively small difference in radius, the surface gravity on Venus is only about .91g. Mars is not nearly as dense as the earth and is quite a bit smaller, which accounts for its .38g surface gravity.

What you say is true, though. Venus holds a very dense atmosphere even with its lower gravity.

Re:These kinds of studies...

[Idarubicin]

I always thought that Mars lacked the gravity to hold a sufficient amount of greenhouse gases.

Well, that depends on how long you want to hold the gases. At any given temperature, the molecules of a gas at thermal equilibrium (or practically speaking, anywhere close to it) will have some distribution of speeds. Some molecules will travel faster, some slower. The mathematical expression characterizing this range of speeds is the Maxwell distribution. Here's a mathematical treatment of the Maxwell distribution; this page presents a nifty Java applet showing how this equilibrium takes place.

Note that a plot of population vs. speed, the Maxwell distribution tails off at higher velocities, but never actually goes to zero. In an atmosphere, this means that a small number of molecules will periodically get kicked up to above escape velocity through collisions with other molecules in the gas. If they happen to be heading the right direction, then they will escape into space.

Each molecule in a gas (on average) has roughly the same amount of kinetic energy. Earth's atmosphere contains very little hydrogen and helium because these light elements travel faster for a given amount of kinetic energy and escape more readily. A good part of the velocity distribution for these species is above escape velocity. Oxygen and nitrogen (not to mention water vapour and carbon dioxide) are significantly heavier, and bleed off at a much lower rate.

Moving to Mars. The surface gravity is only about forty percent that on Earth, if I remember correctly. It's a much shallower gravity well, and escape velocity is much lower (5 km/s on Mars vs. 11 km/s for Earth). Since kinetic energy is a function of the square of velocity, it takes a significantly smaller push to move a molecule out of Mars' hold. Nevertheless, there actually is still only a very small tail of the Maxwell distribution that sits above Mars' escape velocity.

I should also mention that there are sputtering processes that remove gas from the Martian atmosphere. Lacking a strong magnetic field to deflect the solar wind, a significant amount of gas is lost to sputtering, as well.

Nevertheless, even the most pessimistic estimates suggest that an atmosphere similar to Earth's would last tens of thousands on years on Mars. A short lifespan in terms of planetary evolution--a long time for human beings. Even the Moon would take from one to ten thousand years (depending upon who you ask) to bleed off an Earth-like atmosphere. Recall that Mars has surface features strongly suggestive of flowing surface water. (Liquid water requires an appreciable atmosphere, otherwise it just boils off.) That sort of erosion takes a long time to happen, which further supports the notion that Mars can hold on to an atmosphere, at least for a few million years at a time.

This is a job for....

[ihatewinXP]

Dr Atkins!

-Oh wait, he died last week... In our hour of need, no less.

Coniferous forests

[Anonymous Coward]

I'm surprised that the coniferous forests in far north North America and Eurasia are more productive than the deciduous forests of more temperate climates. I'm wondering if the results of this are skewed because the temperate regions produce more carbon dioxide in the form of combustion emissions.

Re:Coniferous forests

[sigep_ohio]

Well in June the earth's northern hemisphere is facing the sun, so norhtern plants are more productive. In December the Southern hemisphere is facing the sun, and so plants in the south are more productive. Meanwhile between the tropics light levels do not differ significantly throughout the year, so there is not much fluctuation in plant productivity.

atleast thats how I read the pictures.

Re:Coniferous forests

[SEWilco]

Um.. That's relatively more productive. See how much more active the Amazon area is? Now, that blue ring southeast of it is not a desert, it is merely covered with trees and grass similar to what you'd imagine the Iowa farmland to be (yes, the color of Minas Gerais and Iowa are similar). The purple is less active, like the grasslands of Wyoming (indeed, the "northeast Brazil" area is known for its dry land and ranchers, as are the pampas further south).

The forests along the east coast of the USA include those on the minor mountains of the Appalatian range -- a difficult area to farm. Also in there are the Smoky Mountains, named because often there is a haze due to the volatile chemicals (terpenes) released by the forest there.

Re:Coniferous forests

[Porag_Spliffing]

The old rain forests are in equilibrium. Old trees die and rot (or burn) and only some carbon is fixed most is re-released and balanced out by the growth replacing the old trees.

The coniferous forests of the northern hemisphere are often actively logged so have much young vigourous carbon fixing growth with the carbon being cut down and dragged off to make paper/ikea furniture.

Re:Coniferous forests

[SEWilco]

Any area which is extracting more carbon than is emitted will build up soil. That's why the prairies of the US midwest had six feet of black dirt.

There are many reports that the layer of topsoil in the Amazon is thin, which indicates it either is in a delicate balance or, more likely, negative balance. Probably a lot of the carbon is being washed away, and the forest is living on the recently produced soil. The Amazon is consuming more carbon than it emits in the air, but is leaking carbon downstream.

As long as the soil replacement is keeping ahead of the erosion this will work. Note that "erosion" can include holes carved by floods, which are then filled in -- a marsh becomes a black dirt plain in a short geologic time. Erosion down toward sea level can continue as long as that thin layer of topsoil slows it down, else a desert or canyon appears. Upstream of the Amazon are mountain ranges which can keep providing minerals for quite a while.

I suppose harvesting forests and locking the carbon in paper and wooden furniture/walls is a form of erosion also...

Interesting

[Musashi Miyamoto]

If I understand the pictures correctly, it's amazing to see how much carbon is converted in the northern hemisphere... in Canada and Russia. It counters the conventional wisdom of the Amazon as being the primary oxygen producing region.

It will make me doubt all those "save the rain forest" tree-huggers.

I wonder if they could do the same thing to show the amount of carbon being produced.

Re:Interesting

[edgrale]

Please note that the amazon rain forest is producing oxygen all year long, even when the northern hemisphere has winter. And when the amazon is producing less it is "winter" over there.

Unlike the northern hemisphere, the amazon produces oxygen even when it is "cooler" there. To quote the article, you did read it and not just look at the pictures?

"However, tropical forests are more productive over a full year because of their longer growing season."

Re:Interesting

[Catskul]

Well there is alot of importance to the rainforests besides their carbon consumption. I think one of the real resources is the bio-diversity.

If (notice the emphasis) the carbon consumpton of the rainforests is, as it seems in these diagrams, not as significant as many have been lead to believe, then it has been irresponsible for those who are trying to protect this resource to over emphasize some particular data just because they believe they can get more attention that way. It seems to happen in every aspect of politics though. The use of half-truths is a powerfull political weapon that many cant resist using.

Re:Interesting

[robsimmon]

Actually the Amazon takes up 10% of the carbon absorbed by the Earth's land surface with only 5% of the land area--so it's a major source of oxygen. But the Amazon's a pretty complicated place--these maps only show part of what's going on there. Read (shameless plug, but then again the original story is from my site, too) Escape from the Amazon for a few details on the other half of the process.

Re:Interesting

[SEWilco]

Look at the code key under the images again. Yellow and red are the most productive. The Amazon is consuming carbon dioxide at a faster rate than Florida.

However, this only shows there are a lot of plants hard at work on the atmosphere there. It does not show what is happening to the carbon in dead trees, soil, mud flowing down the river, carbon entering from the mountains upstream...

Carbon Budget

[SEWilco]

That's a nice picture of plant activity. Now if the carbon budget could get balanced, so we know how much carbon is going where... and NASA may have a little difficulty measuring how much is landing on the ocean bottom.

Oh, why does it matter? If more carbon is being removed by the carbon cycle than is being released -- we'll run out of carbon dioxide. No plant respiration. No oxygen production.

Re:I don't entirely buy this...

[enronman]

Fosil fuels. They produce CO2 and are why the numbers don't "balance".

The Oceans

[jolyonr]

It's quite interesting to see how much carbon is being soaked up by the oceans. Much of this carbon eventually ends up as deposits on the sea floor and, after millions of years, limestone. It may be a lower amount of carbon intake than the forests, but then forest fires and biological action on dead trees can eventually release a percentage of the carbon that's trapped by trees.

What happens when all the carbon is gone?

[Hao Wu]

Do we start burning bed rock instead? What about geotherms from the earth's magma. Why can't we use it (they do in Iceland) as a carbon substitute.

Re:Lazy Oceans

[matt_morgan]

The Oceans are probably a buffered carbon dioxide sink. A LOT of climate research goes into the topic of how much CO2 they contain, and how much more they might contain.

For example, CO2 appears not to be increasing in the atmosphere as fast as it should be, given increased emissions. One likely carbon sink may be forests--that is, maybe production in forests increases when CO2 availability increases. However, many people doubt that forests are CO2-limited in terms of their growth. More likely, there's more than enough CO2 to go around and trees don't grow more than they do because they're limited by some other necessary ingredient (phosphorous, nitrogen, micro-nutrients, etc.). Of course, it's possible that forests are expanding--it's probably not the case, but it's conceivable given that large, previously cleared areas (the suburban northeast of the US) are growing more trees back.

The Oceans also may be absorbing CO2. One great environmental fear is that there is a limit to this absorption. Remember how buffered solutions worked in Chemistry 1? The ph goes down really slowly as you add acid, until the buffering is overwhelmed and then wham!, the ph increases rapidly with additional acid. Same thing with CO2 buffering in the Oceans, only we don't know when the buffering may be overwhelmed. If that happens, global warming rates should dramatically increase over what we see today.

Wally Broecker from Lamont-Dougherty Earth Observatory used to do a lot of work on this. I don't know if he still does, or who else might be doing it now.

Geeky SIde of NPP Calculation.

[JungleBoy]

The Land NPP algorithm was developed at the NTSG at the University of Montana. I am the Sys Admin for this group.

We developed the software to do the Gross and Net primary productivity calculations (as well as some others), but the main production runs are done at the Goddard Space Flight Center in a room full of SGI Origin servers. Our development environment consists of several smallish linux beowulf clusters (32x1Ghz P3), a few Althon MP boxes, some old AIX dev boxes, and one SGI Oxygen for nasa code certification. Our largest resource is disk space, we have about 12TB of capacity. Keep in mind that this is just for algorithm development and testing. Goddard's production facility is huge, but that's becuase they are producing tons of other data products as well including all the land, ocean, and atmospheric products off of both the Terra and Aqua Satellites. This land productivity data (MOD17 in nasa speak) is derived in part from the MODIS sensor on Terra.

Both of these satellites are in sun syncronous polar orbits meaning that they come down over the earth's day side. This is because many of the sensors (like MODIS) are passive. Terra is the 'AM' satellite, it crosses the equator about mid morning local time, and Aqua being the 'PM' satellite crosses in the afternoon. The reason for this is because there is a significance in AM and PM cloud cover. Cloud cover is difficult to correct for (in fact with MODIS, sometimes you can't correct).

-JungleBoy (aka tweaker)
Melt our server room Axis Camera
Automated GPP Images Site (in devel)
My Lame Website.

Im confused...

[t0ny]

Once a planet warms up enough with green house gases, we can get some plant life on the planet to assist in the creation of oxygen through this same cycle and eventually make a planet liveable. Though it's not something we'll see in our lifetimes, studies such as these benefit the species as a whole in the long run (i.e. big picture of time).

But... I dont understand... Rush Limbaugh tells us that there is no such thing as the greenhouse effect...