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...

[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.

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.

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.

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.