Monday, July 5, 2010
We begin with Bob O'Hara, from Deep Thoughts and Silliness, bringing us a thoughtful review of the book, Elegance in Science: The Beauty of Simplicity, by Ian Glynn. You all know as well as Bob that the conventional wisdom puts great scientific stock in simplicity, not without good reason. Might even have something to do with the popularity of Occam's Razor, but does Ian Glynn explain why simplicity makes for elegant science? Bob's Book Review: Elegance in Science gives us an answer, and of course, a question.
Next comes a little-known biographic detail about Sir Isaac Newton, who apparently dabbled in a greater variety of intellectual pursuits than most of us thought. Romeo Vitelli sheds light on Newton's ventures into alchemy and theology at Providentia with his contribution entitled Newton's Revelation.
Several contributions involve nature and the environment. First, Ninjameys continues to fulfill his pledge to raise the profile of the lesser-known but still important species threatened with extinction by completing Parts 4 and 5 of his twelve-part Endangered Species 2010 Series: Dicotyledons (Part 1) and Dicotyledons (Part 2). We also get a bonus this time around with Plants and Fungi Map showing the geographic location of each of the species described in Parts 1 through 5! Parts 1, 2, and 3 included fungi and bryophytes; club mosses, quillworts, ferns, and red algae; as well as conifers, cycads, and monocots. Although I am partial to plants, Ninjameys' mission includes critically endangered species from twelve different taxonomic categories populating IUCN's Red List 2010, so the animal-lovers among us have much to look forward to.
Bridget Nicholson submitted 10 Biggest Health Dangers Behind the Oil Spill, where you will find the health dangers categorized as either "Right Now" or "In the Future", a useful dichotomy given that the effects are being felt at the moment, but will also be with us for a long time to come. Has this oil disaster prompted anyone else to wonder what might be the nuclear power industry's equivalent to the oil industry's "blind shear ram" that failed so appallingly beneath the Deepwater Horizon platform?
Birds, especially ravens, are noted for their intelligence. Now, as suggested in a research study reviewed by Grrlscientist in Living the Scientific Life (Scientist, Interrupted), ravens may exhibit empathy. The study, by Orlaith Fraser and Thomas Bugnyar at the University of Vienna, involved 13 ravens observed interacting with each other over a nearly two-year time period. The key interactions were conflicts (chase flights, hitting, or forced retreats), and an affiliative, or consoling, behavior characterized by "contact sitting, preening or beak-to-beak or beak-to-body touching. Examine the evidence as described by Grrrlscientist and judge for yourself whether or not Distressed Ravens Show That Empathy Is For The Birds, Too
Human health and behavior is a focus of three contributions. In Unmaking the Disease (Part 1),
Romeo Vitelli begins a brief history of the study of homosexuality. Part 1 concludes with the first of the dissenters from the conventional wisdom of their day, Alfred Kinsey and Evelyn Hooker. We await Parts 2 and 3 where Romeo promises to describe the scientific community's removal of the disease label from homosexuality.
Mind over matter oversimplifies the findings of a study Faith Martin reviews on Highlight HEALTH. Relating how a patient thinks about their illness to their emotional and physical well-being makes for interesting advice for healthcare providers and anyone who knows someone with a chronic affliction. How Your Head Can Influence Your Heart offers valuable insight with relevance far beyond those concerned with cardiac care.
Our favorite 360 Degree Skeptic challenges readers to find the flaws in a study he reviews entitled "Greater religiosity during adolescence may protect against developing problem alcohol use." In Spot the Flaws: Unpacking the Religion Variable skeptic Andrew Bernardin suggests we examine the validity of the conclusions of the study, and includes a link to the original report as well, if you need it to help identify any scientific and/or logical error(s).
Finally, we venture to the outer limits with John at Kind of Curious, who is reading "The Varieties of Scientific Experience" by Carl Sagan. John introduces us to a fine opportunity to participate in one of Carl Sagan's passions, the search for extraterrestrial intelligence (SETI). In Searching for Aliens, John describes how the SETI@home project encourages ordinary citizens to donate spare processing power from their Internet-connected home computers to assist with the search for ET. Best of all, John reports that "If your computer is the one that finds ET, you get named as a co-discoverer." Be careful what you wish for!
Thursday, July 1, 2010
"Prior to the sea trial, there were some doubts about whether the oil would reach the sea surface. It apparently did so during these experiments, but if the size of the oil droplets formed at the exit had been sufficiently small, the oil might not have surfaced."
Recent observations in the Gulf of Mexico of an unplanned experiment releasing a large quantity of oil at a depth of 1,500 meters suggest that a significant quantity of the oil has not reached the surface. Given that a large volume of oil dispersants have been intentionally added at the site of the Deepwater Horizon blowout, and that oil dispersants are designed and applied specifically to make the oil break up into smaller droplet sizes, one might anticipate that a significant portion of the oil released in the BP blowout would not reach the surface.
So it is more than a little surprising that BP's chief executive would, weeks after the blowout took place, be so ill-informed about the behavior of oil in deep water as to belittle claims that plumes of oil might exist beneath the surface of the Gulf of Mexico.
A key purpose of adding the dispersants is to make the oil break up into smaller droplets so that bacteria and physical action can break it down before it can harm wildlife or coastal habitats. It appears that these smaller droplets also keep a portion of the oil from surfacing, perhaps a good thing for plants along the coast, though maybe not so good for plankton and fish living out in the Gulf.
In any event, it should come as no surprise that scientists observing the spill find plumes of oil under the surface (see USF, and UGA). Oil experts discovered that could happen in an experiment almost 10 years ago, see Deep Spill Technical Report.
Tuesday, May 4, 2010
Sunday, April 25, 2010
Climate change is all about energy --- energy in --- energy out, the balance of energy coming to the Earth and leaving the Earth. The incoming energy is light from the Sun, the outgoing energy is earthshine, infrared radiation from the Earth. To the extent that greenhouse gases exist in our atmosphere, the incoming sunlight arrives unimpeded, but the outgoing infrared light is absorbed by those same gases, which in turn gain energy and increase in temperature, and themselves emit infrared light. In this way, the planet gains energy, and all things being equal and stable, eventually reaches a new, higher equilibrium temperature where the outgoing infrared energy matches the incoming sunlight. But the trouble is, all things are not equal. The concentrations of those greenhouse gases keeps going up, and more and more infrared light is being intercepted on its way out, and the planet's overall energy content continues rising.
How do we know all this is happening? Well, the measurement of the concentration of greenhouse gases is rather straightforward. And we can see from satellite measurements that less infrared light escapes the atmosphere as time passes. We can even estimate Earth's average temperature --- and this is where the oceans come in.
Air temperatures get lots of attention in measuring global warming, but the atmosphere is the least dense, and least massive, of the parts of the Earth that gain energy due to an increased greenhouse effect. Of much greater density, and much greater capacity to absorb energy, are the world's oceans. It will take much more energy to warm the oceans than to warm the atmosphere.
The oceans cover 70% of the planet and average 3,790 meters in depth. Up until recently, we have only measured sea surface temperatures. Limited past measurements of ocean temperatures below the surface exist, but are few in number and geographic extent. It is only since the beginning of this century that a network of bouys have been deployed that measure the heat content of the oceans down a significant 2000 meters in depth. That network is called Argo, and as of today it includes 3,254 bouys spread around the world's oceans.
So what do those bouys tell us about the ocean's heat content? If you can manage to read the smallish reproduction of a graph from a recent paper published using the Argo database (by J. von Schuckmann et al. in the Journal of Geophysical Research, Vol. 114, 2009), note that the line shows a heat content increasing from 2003 through 2008. There are ups and downs, but the trend is in one direction, increasing heat content. The average over the period is plus 0.77 Watts per square meter of ocean surface.
Doesn't sound like much, less than one Watt per square meter of the ocean. Imagine your typical neighborhood swimming pool, 25 meters long with six lanes each 5 meters wide. There would be 602 billion such pools needed to equal all the world's oceans, and for the six years between 2003 and 2008 each of those pools, assuming they were each 2000 meters deep (!) would experience an increased heat content equivalent to the heat from six 100 watt light bulbs. That adds up to 3.6 trillion 100 watt light bulbs in all the world's oceans, a lot of extra heat to evaporate more water, power more storms, and change climate in all sorts of energetic and surprising ways.
Sunday, April 18, 2010
Even if you have not seen it, you have probably heard of Rainbow Bridge in Utah. This is as close as we got back in 2004 when we hiked the short trail in from Lake Powell. Judging the size is difficult, but if someone were standing on top, you would see little more than a tiny speck.
Big South Fork National River and Recreation Area, Tennessee
Take a moment to examine this second picture. Although this natural rock arch is also large, it can be tricky to pick out in the middle of a forest amidst all the leaves and tree trunks. But it is there, and it is big. Not as big as Rainbow Bridge in Utah, but still an impressive piece of rock.
The Twin Arches in north-central Tennessee are part of the Cumberland Plateau formation, made up of layers of sedimentary rock deposited at the bottom of a large inland sea that covered part of eastern North America a few hundred million years ago. These rock layers are mostly sandstone, relatively soft and easily eroded away.
In some places, the sandstone is covered by a layer of conglomerate, a sedimentary rock made up of a conglomeration of pebbles that first accumulated along the bottom of rivers and streams that developed when the inland sea dried up. The conglomerate is much more resistant to erosion than the underlying sandstone.
Thus the formation of large rock overhangs, abundant in the area, as well as quite a few arches. The conglomerate on top resists erosion, while the sandstone around it readily washes away. If the flowing water washes underneath the conglomerate, it can erode the underlying sandstone and create a natural rock arch as seen in the picture.
Not only is it difficult to see these arches in the middle of a forest, and difficult to take good photographs of them, their location also made for a humorous moment on our recent hike through the area.
At one point one of our group was walking near the arch pictured above and through the trees saw what appeared at first glance to be a large splash of blue paint on the side of the rock face. Connie was incredulous that someone would deface such a unique natural landmark by painting a large piece of rock blue. Maybe she was thinking about the Carolina Tar Heels and their off year in college basketball this past season. In any case, she immediately turned around and made her way back to the rest of us and insisted that we go see what she could barely believe had happened.
We followed her path, and for a brief moment saw the splash of blue she mentioned, but a few steps farther along the path noticed a large patch of blue sky visible through the arch. Her splash of blue paint was a beautiful blue patch of sky.
Saturday, February 27, 2010
Two years ago, the City of Raleigh, North Carolina proposed a ban of in-sink garbage disposals. It was a teachable moment, though city officials ultimately failed to take advantage of the moment. The ban was rescinded after a brief but loud public outcry.
The lesson that might have been taught would have reminded us that we all live in an ecosystem and a river basin, where everything is connected eventually to nearly everything else.
Throwing something in the trash or down the sink is not really throwing it "away". In an ecosystem, there is no "away"! We may embrace the concept, and practice something we call "throw it away", but ecologists know we are fooling ourselves. Each of us must learn a little about being good ecologists.
We burn gasoline in trucks hauling the contents of our trash cans to a landfill, where they take up space that could be forest or farm. The garbage very slowly decomposes, generating methane gas, and leaching toxins into the ground.
We must capture the methane lest it contribute to global warming more powerfully per molecule than carbon dioxide. We must collect the toxins so they won't poison groundwater beneath the landfill. And a lot of that stuff in the landfill, despite our recycling efforts, is valuable raw material today, or will be years from now. So much for throwing it all away.
Liquid and some solid wastes go down a pipe in toilets, dishwashers, clotheswashers, and sinks. These wastes go to a sewage treatment plant, a wonderful invention which breaks down the pathogenic, or disease-causing bacteria and viruses that can accompany the by-products of our lives.
When you also dump food or grease down your sink with the help of that garbage disposal and lots of water to hurry it along and keep the pipes from getting clogged, the food and grease goes to the sewage treatment plant. Problem #1 today, that is a waste of water. And as wonderful as sewage treatment plants are at killing bacteria and viruses, they are not so great at breaking down the nutrients in wastes and food. That is Problem #2.
In fact, the nutrients that a sewage treatment plant is not so good at breaking down, constitute the most important sources of water pollution today. Here's why.
First, these "nutrients" are essential chemicals that plants need to grow. Like fertilizer, they stimulate rapid growth of tiny plants called algae in a river or lake.
What's wrong with algae growing in a lake? Like all plants, algae produce more oxygen than they use, and that is good. But though a little is okay, too much means trouble, and we're not talking about the oxygen. The tiny algae do not live very long. As suddenly as they blossomed in response to the excess nutrients, they die and sink to the bottom of the lake.
Dead algae make good food for bacteria, so following the die-off of the algae comes a massive growth of bacteria. Although the bacteria themselves are not pathogenic, they require a lot of oxygen to grow.
The population explosion of bacteria decomposing the dead algae uses up all the oxygen in the water. Without oxygen in the water, the fish, indeed every living thing in the river or lake, dies.
So food scraps and grease that go down your drain add to the most important water pollution problem facing America today. But put them in the trash and they go to a landfill, which has an array of problems all its own. What can you do?
This is the part an ecologist loves.
Start a compost bin in your backyard! Composting allows us to "close the loop" on a lot of things we would otherwise "throw away". All those food scraps, egg shells, indeed, everything but meat scraps (which can attract unwanted animals), along with paper napkins, paper towels, even grass clippings and those leaves you love to rake up in the fall, all can contribute to the recycling of valuable nutrients in a compost bin.
And here's the exciting finale, what to do with the compost you create? Spread it in your garden, under plants in your yard or in a "natural area", you could even sprinkle a little as a natural fertilizer in your lawn. All those nutrients left over from delicious meals and lawn care can be recycled and reused. Spread and mixed into the ground, compost enriches soil, promoting better plant growth.
As ecologists we know we can't really throw anything away. But ecologists also know how to save water, reuse nutrients, protect water quality, limit landfills, enrich soil, and promote the growth of the beautiful trees, shrubs, flowers, and vegetables that can grace yards large and small.
Find out more about composting at http://www.p2pays.org/compost/.
Wednesday, February 24, 2010
In less than two months, this little seedling will be feeding me delicious spinach greens in a salad! And most of the solid material for the growth that will make that possible will come from the thin air surrounding the leaves. Carbon dioxide, a gas that makes up a growing proportion of our atmosphere, is the sole source for all of the carbon that will form the backbone of the proteins, carbohydrates, and fats contained in this plant. Water, of course, along with essential elements such as nitrogen, phosphorus, and potassium, will come up from the soil through the belowground roots.
All of that carbon dioxide will enter my spinach plant through many thousands of tiny pores spread all over the surface of the leaves, called stomates. Thus does most of the solid mass of any plant first pass through a microscopic hole in a leaf as a gas molecule - a gas molecule that currently makes up just under one-half of one percent of the air!
The energy to get this lettuce seedling to burst out of its seed capsule, still attached, and grow up through the soil, came from molecules stored in the first, specialized leaves, called cotyledons. The two cotyledons are at the top of the short stalk, already turning green with chlorophyll and switching from using the energy that they came with inside the seed to the energy from the light bathing them almost 12 hours every day. With the energy from that light, the chlorophyll molecules will work with the other cellular machinery in these leaves to split carbon from oxygen in the carbon dioxide coming into the leaf. That energy will also be used to split hydrogen from oxygen in water coming up from the roots, and then to attach the carbon atoms to each other and to other atoms to make more cells and grow this lettuce plant from a tiny seedling to a delicious meal.
Sunday, February 14, 2010
What better way to anticipate the coming spring amidst all this cold weather than to plan your vegetable garden. With that in mind, as you collect your supplies and get ready to plant your seeds, consider this. If you ever wondered why agricultural extension folks suggest sterilizing your soil before starting seeds for your vegetable garden, this picture might be worth all those words you didn't read. Each of the four small compartments received 10 clover seeds on February 3rd. As you can see, the two compartments on the left held soil that had been sterilized, in this case meaning the soil was heated to 200 degrees F for 20 minutes in a microwave oven in my kitchen. Two days later seeds were germinating in all compartments.
It is worth noting that I set up this little test to see if the sterilization process released any toxins into the soil that might inhibit seed germination, as that is one danger of heating soil to 200 degrees. So when the seeds in the sterilized soil germinated as readily as those in the untreated soil, I felt confident that I could use the sterilized soil to start the seeds for this coming spring's vegetable garden.
As the seeds came up, I continued to keep track of how many successfully germinated in both sterilized and unsterilized soil. Here are some of the results:
3 DAYS: STERILIZED - 17; UNSTERILIZED - 15
4 DAYS: STERILIZED - 18; UNSTERILIZED - 19
6 DAYS: STERILIZED - 18; UNSTERILIZED - 19
Yesterday, day 10, I first noticed that a couple of the seedlings in the unsterilized soil collapsed. Today, day 11, I took the picture above. Fungus is more than likely responsible, fungus that heating to 200 degrees F killed. In this case the fungus did not inhibit seed germination, but did kill several of the very young seedlings.
Saturday, February 13, 2010
The story of climate change is the story of energy, in particular, the Earth's balance between incoming and outgoing energy. Our planet's energy equation begins with sunlight. More and more sunlight energy arrives at Earth with each passing day. That sunlight energy warms the ground, bodies of water, plants and animals. Each of those objects in turn radiates its own energy according to its temperature. Since those objects are much cooler than the sun, they radiate energy of a different wavelength than the sun. The sun radiates in the visible wavelengths, but the Earth and everything on it radiates in the infrared wavelengths, which are invisible to our eyes.
Greenhouse gases such as carbon dioxide and methane in our atmosphere are transparent to sunlight just like the nitrogen and oxygen that make up most of our air. However, what makes CO2 and methane effective greenhouse gases is their ability to absorb infrared radiation, something nitrogen and oxygen cannot do. So the greenhouse gases let in sunlight, which warms the Earth, but they do not let infrared radiation escape. Instead, they absorb that infrared radiation and themselves get warmer. As CO2 and methane get warmer, they radiate more infrared radiation themselves, much of it heading back towards the Earth, adding to the warming effects of sunlight.
So the more greenhouse gases reach the atmosphere, the more infrared radiation is absorbed, and the warmer the entire planet becomes. But why would a warmer planet mean more snow or more severe storms?
It's all about the energy. More sunlight coming in and less infrared radiation going out means more energy here. And more energy means higher temperatures, on average. But how can higher temperatures mean more snow?
Because it takes energy to evaporate water. As temperatures rise everywhere, water evaporates faster and faster. More water evaporates from the oceans, from lakes and rivers, even from moist soil. More water even evaporates through the tiny pores covering the leaves of plants growing around the world.
More water evaporation means more total water vapor in the atmosphere, and that inevitably leads to more precipitation. With temperatures above freezing, that precipitation comes down as rain. Drop the temperature below 32°F, and the precipitation comes down as snow or sleet or freezing rain.
Ask a native of Buffalo, New York about the role that water evaporation plays in snowfall. "Lake effect" snow results when water evaporates from a nearby lake - in the case of Buffalo, Lake Erie to the west or Lake Ontario to the north. More water evaporating into the air means more precipitation, and in the winter, even with the greenhouse effect, temperatures can drop below freezing and that precipitation will be frozen. And remember that one inch of rainfall can, if frozen, produce somewhere between 6 and 10 inches of snow.
What is it about a warmer planet that can lead to more severe storms? Storms, with strong winds, heavy precipitation, perhaps even lightning, release a great deal of energy. Where does that energy come from?
Much of the energy in a storm comes from the water vapor in the air within the storm. Remember that it took energy to evaporate that water in the first place. Water vapor carries all the energy it took to evaporate it up into the atmosphere. And as that air rises it cools, and the water vapor cools with it. Eventually the cooling water vapor does not have enough energy to stay a gas, and condenses back into tiny droplets of liquid water, forming clouds. Condensation releases the energy it took to evaporate the water, and that released energy passes to the surrounding air, adding to the strength of the storm.
Global warming driven by a stronger greenhouse effect upsets the energy balance of the planet. More energy evaporates more water. More water vapor makes more precipitation and stronger storms. And in the winter, more precipitation and stronger storms can mean snow and blizzard conditions. Greg Craven, a high school physics teacher, suggested global "weirding" might be a better title than global warming. And that was before the 2010 snowpocalypse hit the mid-Atlantic states.
Tuesday, February 2, 2010
The next line of evidence includes current atmospheric and climate conditions, such as temperature data from around the world, glacier conditions in mountains and at the poles, and ocean chemistry.
Third-ranked by Hansen are computer-based climate simulations.
Dr. Hansen went to some length to explain the causes of historical climate variability. In addition to the climate forcings related to the Milankovitch cycles, he mentioned plate tectonic activity. When India was an island continent south of Asia, it was moving north through the Indian Ocean. During this time period, Hansen suggested that large amounts of carbon dioxide were released by volcanic activity triggered by this plate movement. This corresponds to a very warm period on the planet, much warmer than today, when sea levels were considerably higher as there were no large glaciers.
Some mention was also made of the oceans as a sink for atmospheric carbon dioxide, but I missed the reference (2009) and have not been able to find it. The new finding was of carbon measurements down to a depth of 2 km below the ocean's surface, and Hansen was quite excited about it. If any readers out there know of this study, please advise!
Monday, February 1, 2010
James Hansen, director of the NASA Goddard Institute for Space Studies, spoke at UNC Chapel Hill earlier this evening. As he put it himself, he is not a communicator, but a scientist who feels compelled to speak out because the gap between what is known by climate scientists and what is understood by a seeming majority of the public is very large and growing.
That he feels so compelled may be the most significant story, but it is not one that I want to tell.
I want to relate the important science story that he told.
He spoke of the inertia in a climate system that encompasses the entire planet. Estimates suggest that we have experienced about half of the warming expected based on the increases in atmospheric carbon dioxide since it was 280 ppm. That means if we immediately reduced our carbon emissions to the point where the atmospheric concentration rose no higher than it is today, we would continue to experience climate change and global warming for some time to come, and about double what has occurred thus far.
Dr. Hansen also spoke about tipping points, moments in time where the climate system may begin to change in ways and at rates over which we will have no control. These tipping points have most to do with positive feedbacks that may begin to operate. There are two big ones according to Hansen. First - melting ice sheets resulting in decreased surface albedo or reflectivity causing more absorption of sunlight and more heating, melting more ice sheets in a spiraling of warming.
Second, the danger of warming oceans allowing methane hydrates on the floor of the shallow areas of the oceans to "thaw" and bubble up to the surface and enter the atmosphere. Methane's greenhouse gas efficiency is more than 20 times that of carbon dioxide. More methane means more heating, meaning warmer oceans, causing the release of more ocean floor methane in a runaway greenhouse scenario. A 2009 story I summarized a while back goes into a little more detail on this feedback loop's scary possibilities.
There were a few other key concepts that will have to wait for a later posting. For now, the take home lesson is that Opa Hansen wants to remind us that global climate change's big losers have either only recently arrived on planet Earth, or have not yet even been born. The decisions we make in the next couple of decades will shape the face of this planet, and strongly influence the quality of life for our grandchildren, great grandchildren, and great great grandchildren.
Sunday, January 31, 2010
You know how the sunlight shining on fresh snow at a sharp angle can make the snow appear to sparkle? That's what you're looking at in the picture above, believe it or not. If you click on the image to look at a larger version, you should be able to make out different colors, probably a result of diffraction of the sunlight as it passes through tiny ice crystals. Our "snow" actually was sleet, three or four inches of it.
Saturday, January 30, 2010
These little guys are members of the Globigerinoides, planktonic foraminifera that have lived in the surface waters of the ocean for a very long time. The picture of their shell on the left (about the size of a grain of sand) and the living organism on the right, was found at Oceanus, the online magazine of the Woods Hole Oceanographic Institution. The composition of their shells when they lived millions of years ago contains a warning for us today.
But first, what is a foraminifera? Well, living things can be divided into the prokaryotes and the eukaryotes. The prokaryotes include the bacteria and other single-celled organisms without internal membranes, while the more complex eukaryotes have internal membranes around their nucleus and other organelles. The eukaryotes include multicellular plants and animals, the fungi, and a fourth group of single-celled organisms called the protists which are neither animals nor plants. Foraminifera are protists with shells. Their name derives from the tiny holes (foramina) that perforate their shells.
The shells of the foraminifera consist of calcium carbonate, and the changing ratio of boron to calcium in these shells indicates the concentration of carbon dioxide when they formed. The proportion of a particular isotope of oxygen (δ18O) indicates the temperature when they formed. Aradhna Tripati and her colleagues at UCLA, in work published in Science magazine on December 4th, 2009, measured the boron:calcium ratio and δ18O ratio in Globigerinoides shells over a 20 million year span of time, extending all the way back to the Miocene Epoch.
Up until now, the 800,000 year Vostok ice core record in Antarctica held the oldest measurements of atmospheric carbon dioxide and temperature, using air trapped in bubbles in the ice. This ice core record shows carbon dioxide and temperature closely tracking each other over 800,000 years, powerful evidence that CO2 influences climate. But now, Tripati, using the tiny shells of foraminifera dug up in layers of sediment at the bottom of the ocean, extends that correlation between CO2 and temperature 25 times further back in history, to 20 million years before the present.
The significance of this longer and older record of temperature tracking CO2 levels lies with the ice sheets of the Miocene and Late Pliocene. Starting 20 million years ago and continuing for five million years, the globe was warmer, no massive ice sheets covered Greenland and Antarctica, and sea levels may have been 25 to 40 meters higher than today. Atmospheric carbon dioxide during this time increased from around 375 ppm to 425 ppm as climate continued to warm.
Then, 14 million years ago, CO2 levels began a steady decrease over a five million year span of time from over 400 ppm down to 250 ppm. The climate cooled, closely tracking the carbon dioxide decrease, as ice sheets grew and sea levels likely dropped as much as 40 meters.
The take home lesson - massive ice sheets may not survive on planet Earth when atmospheric CO2 levels exceed 350 ppm for an extended period of time. Carbon dioxide reached 350 ppm back in the mid-1980s, peaked at 390 ppm in 2009, continues to increase more than 1.5 ppm every year, and that rate of increase is growing.
Without massive ice sheets, global sea levels can rise as much as 40 meters. That will not likely happen in this century, but the last time CO2 levels rose from 350 ppm to over 400 ppm, it took a million years to do so, and it happened in the Miocene Epoch at least 12 million years ago. We will see CO2 concentrations reach 400 ppm by 2015, just 30 years after CO2 passed 350 ppm.
A sea level rise of just a couple of meters in the next 100 years would constitute a major worldwide catastrophe.
The chemical make-up of ancient foraminifera shells suggests we may be headed to or may have already reached a level of carbon dioxide in our atmosphere that cannot maintain the large ice sheets now covering Greenland and Antarctica, making the Globigerinoides the tiniest air raid sirens in history. Listen to them.
Sunday, January 17, 2010
This is the bark on a dogwood tree growing near the Apex Reservoir in Cary, North Carolina. If you click on the image to see it full-sized, you can easily count layers along the descending sides of the fissures in the outer bark or cork. I have not found any confirmation that these layers represent annual growth increments of the outer bark, but if they do, I can count as many as 22 layers in this image.
This outer bark of a tree is a protective layer of dead cells meant to be partially shed as they shield the tree from physical impacts of the weather as well as the grazing of animals from deer, beavers, and birds to insects, and the biological attacks of bacteria, fungi, and viruses. In some trees, this outer bark layer contains materials that resist fire, allowing the tree to survive all but the most intense, canopy fires. A tree can also excrete waste products into the cells of the outer bark.
At or just below the base of the fissures seen in this photograph lies the cork cambium, a layer of actively dividing cells that produce the largely dead outer bark layers. Just beneath the cork cambium lies a layer of living cells called the phelloderm that can serve a variety of roles including photosynthesis, active disease defense, and storage.
Below the phelloderm lies the phloem, the inner bark layer filled with the vascular sieve tubes that carry the sugars produced during photosynthesis in the leaves down to the rest of the tree and its underground roots.
Dig just beneath the phloem and you hit the cambium, the layer of actively dividing cells that produces the thickening or radial growth of the tree trunk. This is the inner end of the bark of the tree, and also the outer beginning of the inside structure of the trunk.
The actively dividing cells of the cambium layer produce not only the bark of the tree, but also the entire inner trunk of the tree. This inner wood, called the xylem, includes a variety of tubes that carry water and dissolved minerals up from the roots to the stems and leaves. The xylem also contains stiff vertical tubes called fibers that support the heavy aboveground weight of the tree.
For an overview of bark found on trees around the world, take a look at ArtSylva's post on the biology of barks. This beautiful site created by photographer Cédric Pollet talks succinctly about the variety of barks, their function for the tree, and their uses for people. And the collection of pictures of bark of all colors and bark found on many different kinds of trees is amazing. If you have not seen a baobab tree, visit this site and find one in Cédric's "Photo Reports" link!