Regarding the possible cause/causes of climatic change: a few years back I heard of a theory, that simply stated, tied the CO2 content of the atmosphere to the activity level of plankton in the equatorial oceans. Iy you look at the sources and sinks of CO2 and O2, you find that human activity contributes a fair amount of CO2 (since the Industrial Revolution) to the atmosphere. CO2 is absorbed by plants, which by means of chlorophyll and sunlight, convert CO2 to O2. Of all the plant matter in the world, all of the forests and grasslands are DWARFED by the oceanic planktons. These are very small plants, but they fill the oceans. Anyway, plankton growth is stimulated by iron-an element which is scarce in seawater. An experiment was done a few years ago, in the tropical pacific 9believe that it was off the coast of S. America. Powdered FeO (iron oxide) was dispersed on the sea. The result was a huge bloom of plankton. How does this tie in with the CO2/climate change? Well, before around the 1970’s Northern China was mostly a treeless plain (all of the trees were cut down in antiquity). The prevailing winter winds (blowing west to east) would regularly pickup huge amounts of soil and dust (containing a lot of iron oxide), and trnsport this dust into the upper atmosphere. Most of the dust would fall into the Pacific Ocean, precipitatiing these plankto blooms. However, this has largely stopped-China’s communist government started a campaign in the 1950’s, to plant trees on the north China plains. This has succeeded, to the point that this beneficial dust is no longer raining down on the Pacific.
Maybe what we ought to do is convince the Chinese to chop down all of those trees?
Has anybody heard of this theory, and has it been taken further?
It’s true that iron appears to be another limiting major nutrient for plankton (the other chief limiting nutrients being carbon, nitrogen and phosphorus), and that experiments releasing iron (in the form of reduced iron, which is soluble in water; oxidized iron is not) into the ocean have yielded plankton blooms. The general role of iron as a limiting nutrient is still very much under investigation; as you might imagine, there are lots of variables to consider, such as the species of plankton involved, the levels of other nutrients available, etc. (Morel et al., 1991).
If I understand your post correctly, someone has suggested that the cutback of iron-rich dust delivery from China to the Pacific since the 1970s has resulted in a decline of surface ocean productivity, leading to reduced planktonic intake of CO2 from the atmosphere and an increase in global temperatures. Interesting idea, but on the whole I don’t think that less dust from China has had much of an impact for a few reasons:
[ul]
[li]Research on global warming indicates that warming trends started long before the 1970s, so a relatively recent reforestation in China can’t be a triggering mechanism for warming.[/li][li]While windblown dust is an important source of iron nutrients for plankton, recent studies have suggested that recycled iron from the deep ocean is at least equally important, and perhaps even more so (Johnson et al., 1999; Archer and Johnson, 2000).[/li][li]The area of ocean directly impacted by dust from China is probably not big enough to make a difference. A computer simulation of iron cycling in the Pacific suggests that productivity here would have to reach unrealistically large levels (more than 100x present) to have a substantial impact on global atmospheric CO2 (Lefevre and Watson, 1999). Of course, such models are subject to revision, but it doesn’t look encouraging at the moment.[/li][/ul]
Those experimental iron-induced plankton blooms have given some folks another idea, though. In discussions of how to counteract global warming, it has been suggested that we should deliberately spread massive amounts of reduced iron across large areas of the tropical Pacific that are otherwise nutrient-rich and biomass-poor, in order to draw more CO2 out of the atmosphere (e.g., Martin, 1991). IIRC, the commentary on such a proposal has urged more research on iron limitation before trying any bioengineering on a large scale, because we have no good idea what the other consequences of a massive algal bloom might be.
BTW, Falkowski et al. (1998) have published a nice, brief review of biogeochemical processes in the ocean that discusses the interplay between nutrient supply, biological productivity and atmospheric CO2; it’s worth having a look at.
Archer, D.E., and K. Johnson, 2000, A model of the iron cycle in the ocean: Global Biogeochemical Cycles, v. 14, p. 269-279.
Falkowski, P.G., R.T. Barber, and V. Smetacek, 1998, Biogeochemical controls and feedbacks on ocean primary production: Science, v. 281, p. 200-206.
Johnson, K.S., F.P. Chavez, and G.E. Friederich, 1999, Continental-shelf sediment as a primary source of iron for coastal phytoplankton: Nature, v. 398, p. 697-700.
Martin, J.H., 1991, Iron, Liebig’s Law, and the greenhouse: Oceanography, v. 4, p. 52-55.
Morel, F.M.M., J.G. Rueter, and N.M. Price, 1991, Iron nutrition of phytoplankton and its possible importance in the ecology of ocean regions with high nutrient and low biomass: Oceanography, v. 4, p. 56-61.
…for your very erudite answer to my question. Seriously, would the deforestation of China have made a difference in the climate? I would think that changing the albedo of such a large area of the earth would itself provoke many changes. As far as I know, N. China has been deforested for so long, that there are loess deposits several hundred feet thich in manchuria.
Another question (if I may):when man cuts down the trees in the amazon basin, and replaces the forest with grasslands, will there be any net change in the oxygen generated? I t seems to me that grasslands have far more area of photosynthesis than trees-any thoughts on this?
Fillet wrote:
Really? According to a chart they threw up on the screen really quickly in that Nova/Frontline PBS special on global warming a couple of months ago, global average temperatures have fluctuated over a certain range of a degree Celsuis or two over the last thousand years. Only starting in the mid-1970s did the chart show the global average temperature rising above this fluctuation range.
The real cause of the climate change is the sun, a solar flare occured and will make everything a few degrees higher for the next 10,000 years. 
Yeah, the sun is an 11% variable star, and can be more variable at times.
We are currently living in an Ice Age, either in a warm spell in the middle of it or at the end of it. During most of the Earth’s history, we didn’t have permanent ice caps at the poles (when you have those, it’s an ice age).
Sorry to take so long to reply - I just hate it when work gets in the way of my posting. 
For egkelly:
Although northern China is a big place, I don’t think that changing its albedo would make a huge difference in global temperatures (but regional effects are likely). The average albedo of vegetated areas is considerably lower than that of desert areas (12-17 % vs. 30-35%, respectively), but northern China lies squarely in the mid-latitudes. To have a significant impact on climate though albedo alone, you’d really want to make a major change somewhere in the low latitudes (below 30 degrees). That’s because the tropical regions of the Earth receive the most incoming solar radiation per square meter of any place on earth, since the Sun’s radiation strikes the earth at angles that are vertical or close to the vertical all year round. At ever higher latitudes, the energy received per square meter drops off proportionately all the way to the poles. In the wintertime, polar regions actually have a net loss of heat energy (no incoming solar radiation received).
So, in my estimation, re-vegetating northern China = changing the albedo over a fraction of the mid latitudes does not = large global climate impact. If you were to find a way to re-vegetate the Sahara Desert, though, I think we’d have a different situation on our hands.
As for plants… I’m not a plant physiologist, so this is really getting on the fringes of what I know. In terms of efficient photosynthesis, there is a division between two plant types, referred to as C3 and C4, with C4 plants having a greater efficiency. (See this link for a discussion of factors affecting photosynthesis, and this link on C4 plants in particular.) As I understand it, there are grasses and trees in both categories. Since C4 plants are warm-climate plants, and C3 plants prefer cooler climate, I would guess that Amazon vegetation is of the C4 variety in general. Whether C4 grasses produce more oxygen than C4 trees, I don’t know; I suppose you’d have to compare the leaf surface area available for grasses vs. trees in a given area. Any plant folks out there who can answer this one?
For Tracer:
I didn’t see this particular special, but I suspect some simplification at work on Nova’s part. There has actually been some significant variability in global climate over the last 2000 years; e.g., we had the Medieval Warm Period from about 1100-1250 AD, and the Little Ice Age from 1300-1500 and 1550 to 1700 AD. After 1700, global climate warmed up a bit to more “normal” temperatures. Since the late 1800s, there has in fact been measurable warming on a global scale, most pronounced between 1890-1940 (+0.33 deg. C), and again after the mid-1970s (Jones et al., 1986).
In talking about statistically measurable warming since the 1970s, my WAG is that they are indirectly referring to the fact that “reliable, global” coverage of temp. and other climate data is really only available for the past few decades - since 1957, in fact, when weather observations first began to be made in Antarctica. There certainly exists weather data for time prior to the 1950s; the problem is that the instruments were not as good, and there wasn’t anything akin to global recording of data (Jones et al. estimate data coverage as <33% of the world prior to 1900, and <20% before the 1860s). Going back more than 100 years, we largely have to rely on historical records, which may not be fully accurate, or complete; and climate proxy data (e.g., tree-ring data, stable isotope data) which are useful, but do have errors associated with them and thus are not the best data for making precise calculations of global temperature change. The difference in data quality between the last few decades and times prior to that have fueled a lot of the arguments about whether anthropogenic warming was in fact occurring.
Jones, P.D., T.M.L. Wigley, and P.B. Wright, 1986, Global temperature variations between 1861 and 1984: Nature, v. 322, p. 430-434.
For Asmodean: Been astrally traveling to Alpha Centauri again, have we?
For Badtz Maru: Spot on. Btw, even though anthropogenic warming is a big issue right now, there are those who think that ultimately the Earth will say “Fi on you humans!” and cool off again enough for the ice to advance, perhaps in the not-too-distant future (geologically speaking, of course)… see this link.
Just a real quick note. The ice core research that’s been done in the Antarctic and Greenland has been able to document the change in global temperature with CO2. These changes are old enough that they are not anthropomorphic and thus are a good baseline for comparison.
Fillet wrote:
Funny you should mention those, because so did the Nova/Frontline special I was referring to. In fact, they said that the “little ice age” was pretty much restricted to Europe, and that by looking at clues elsewhere on the globe (such as the Greenland ice sheet), the global average temperature throughout the last thousand years only varied up or down within a span of about one degree Celsius – and global average temperatures are now about half a degree Celsius higher than the upper limit of that earlier span.
There was an article on this a couple of years ago…
http://208.245.156.153/archive/output.cfm?ID=385
From the article adam yax just posted a link to:
sigh One more nail in the coffin of any plans to combat potential global warming with iron…
To be honest with you, I was really surprised to hear that anyone said that the Medieval Warm Period and Little Ice Age were European phenomena. This morning I did a literature search through GeoRef, an earth sciences reference database, looking for any references to Little Ice Age outside of Europe or the North Atlantic; 190 papers and abstracts matched the search criteria. Below I’ve listed some of those that happen to mention specific dates (with the respective paleoclimate proxy data noted in parentheses after):
These are all recently published studies, true, but I just stopped going through the list after reference #40; I’m sure that plenty more are older than these. But you get the idea here that widely spaced regions over the globe also experienced climatic shifts in time with the Medieval Warm Period and Little Ice Age, so these are NOT just European phenomena. Moreover, the supporting data come from a variety of paleoclimate proxies, which strongly suggests that the warming and cooling trends implied by the data are genuine.
There has been a lot of interest expressed in determining whether short-term solar variability may be a significant contributor to decadal-millenial times scale climate change, e.g.:
There’s also been plenty of discussion on the role that volcanic eruptions may play in short-term climate change. There’s a related discussion that was going on in GQ here just a few days ago.
I really wish I had seen this Nova special, to know who was making the statement about climate being relatively invariable over the past 2000 years (scientist or Nova producer?). It’s a little bit disingenuous to imply that global average temperature shifts of a few tenths of a degree are unimportant, because the regional paleoclimate proxy records clearly indicate broad patterns of climatic change over the time period in which global temperatures “only varied up or down within a span of about one degree Celsius.” Also, it is interesting to note that the Lean et al. (1992) reference above attributes a 0.2 to 0.6 deg. C drop in global average temperature to a 0.24% decrease in total solar irradiance during the later stages of the Little Ice Age (1645-1715), when some of the coldest average temperatures were also measured in Europe. IMHO, this is a good illustration of how a “minor” change in global average temperature actually has significant effects.
Just a comment on Nova and similar programs - I’m glad that someone is making an effort to get scientific issues across to the general public, especially since many people in this country end their schooling having learned a woefully small amount of science. However, television is still an entertainment medium, and everyone loves a bit of juicy controversy… the producers know if they don’t “spice it up” a little, and play up the differences between various individual perspectives, the program is likely to be perceived as boring by the viewing public. (This was confirmed for me recently by a BBC producer who is currently creating a show for their “Horizon” series.) I have the feeling that Nova may have resorted to just this tactic in discussing climate variability over the past 2000 years; it makes recent anthropogenic warming sound so much more out of the norm if the preceding two millenia are characterized as being climatically stable.
Here is a new article on this “iron loading” theory. This time it is accompanied by old fashioned capitalism.
http://abcnews.go.com/sections/science/DailyNews/ironoceans001012.html
Discover magazine has a sall blurb on a new satellite that monitors Ice movement in the Arctic. THey had thought that the ice was recedeing. Turns out it was due to annual fluctuations in the large cracks in the ice.
Mr. Zambezi, is this the article you’re referring to (“Birth of an Antarctic Super-berg,” October 2000)? The story refers to the fact that a large piece of the Ross Ice Shelf, which broke off last March, is currently being tracked by weather satellites, although the researchers mentioned are hoping to plant GPS receivers on the berg as well.
I think that perhaps you mixed up a few things; there is no mention of “annual fluctuations” in the cracks, but rather that large pieces of the ice shelf (about 20 miles wide) appear to break off and drift as icebergs every 50 years or so. The article also reports that while one of the principal investigators (Doug MacAyeal of the U. of Chicago) doesn’t think that the calving pattern of the Ross Ice Shelf is influenced by global warming trends, some other feel that a thinning of the Ross Ice Shelf in some areas may be related to warming.
See this page for a brief discussion of Antarctic ice sheets and global warming in general.
Nope fillet, I saw that article too. No, this is one of those really short articles at the front of each issue. It made no mention of icebergs. CHeck it out when you get the new issue.
Will do. I was hoping the website would have the November issue posted if it’s already in the mail, but no… I guess I’ll just have to wait. ::taps foot patiently::
[QUOTE]
*Originally posted by Fillet *
…
Since C4 plants are warm-climate plants, and C3 plants prefer cooler climate, I would guess that Amazon vegetation is of the C4 variety in general. Whether C4 grasses produce more oxygen than C4 trees, I don’t know; I suppose you’d have to compare the leaf surface area available for grasses vs. trees in a given area. Any plant folks out there who can answer this one?
Sorry - you are wrong on two counts:
1.) C4 plant are prevalent in hot >and dry< areas. They need more light per oxygen evolution (hence" warm countries") but are more efficient in retaining water - meaning the C4 grasses make more oxygen with the same amount of water. (The same is true, but for other reasons for the so-called CAM-plants CAM=crassulacean acid metabolism. These are mostly succulent plants (thick leaves, green stems)
2.) while there are also some C4 trees, they are the large exception. They are built different (have a look at a Yucca or a Draceana - I think that about covers all C4 trees) and also grow in semi-arid areas.
Therefore, the Amazonas plants are overwhelmingly C3, since there is no reason to save water for the plants there.
oops - grassland can never have more area for photosynthesis that a forest - don’t forget the third dimenion.
The sentence before is not right but not that wrong either:
>In the long run< any forest - and any grassland, too - will have a net carbon exchange of zero - meaning that everything growing there will eventually decay again, setting the carbon free in the form of CO2.
A good example for the former is the siberian tundra, where trees grow, die, fall down, decay, and sometimes burn.
The same with the grassland, which in nature is mostly in dry areas (steppes) which often burn.
This equation is changed when: a) there is organic sediment (like in a swamp, where decay is stopped by acid environment), or b) humans interfere by taking out trees (and burn them) or slaughtering and shipping off the grazing animals.
What is rarely appreciated is that the forests - except for being treasures of genetic diversity - store carbon for a long time. They also minimize erosion - forests need water (rain), which will induce large scale erosion without forests (no, grass doesn’t really help, especially not with large cattle which damage the root system, which in time will denude the ground, leaving it barren. Forests also slow down the ground flow of rain water. In the absence of forests, rain will lead to much faster and heavier flooding.
So if you go ahead and burn down the amazonas (in tropic forests, very few trees are actually shipped off, for most the shipping costs would exceed the money you get for the wood), and let cattle graze, you
- set free quite a fair amount of carbon from the trees
- increase erosion manyfold
- increase frequency and size of flooding
- decrease evaporation and likely reduce the rain in areas which could use more
- incidentally destroy one of the most diverse ecosystems in the world, containing a large number of unknown genetic, pharmaceutic, biological and esthetic treasures.
[A typical forest in Europe or Northern America contains on the order of 5-20 different tree species per hectare (square kilometer? I’m not sure), in tropical forests the typical number is ca.200 for the same area.
Also the absolute amount of species is much higher in tropical areas. This is at least partially due to the ice ages a few millennias ago: The climate changes were faster than some of the plants could move south/north from generation to generation. These died, and with them all animals depending directly on them.]
What do you gain?
- A few pieces of rare woods, largely irreplacable in the future.
- Lots of meat for many decades - but not for many centuries.
- Lots of money and power for the local barons, which will just be happy to take the lands from the indians
- Another monoculture.
- Don`t forget the methane production from the farting cows. It sounds incredible, but cattle is alleged to be a major source of atmospheric methane, which, like CO2, is a substantial climate gas.
Spend winter in Central New York (I’m in Syracuse) and you will be all for global warming.