This is the third in a series of reposts from gregladen.com on global warming. Why It Matters What you Burn and When you Burn ItCarbon Dioxide is a deadly poison. It is about 50% heavier than air, so where it occurs in density, in mines or certain natural vents associated with volcanics, it can accumulate in low spots. There are places in the Western Rift Valley where puddles of Carbon Dioxide form overnight while the air is still. These gas puddles can occur over puddles of water. When animals (such as antelopes) put their head down to the water to drink, they take a few whiffs of the gas and die. A scavenger (a bird, a hyena, a lion) that comes along while the gas is still settled, to feed on the antelope carcass, can suffer the same fate. It will never be long before the gas blows off, so this sort of carcass accumulation is rare and modest but it does happen.There are lakes (also in Africa) that are saturated, at depth, with carbon dioxide gas dissolved in water. If the lake happens to turn over, the deep water heads to the surface where it is under the influence of less pressure, and thus is capable of holding less gas. So it fizzes, like bubbles in a bottle of soda that is shaken. This accentuates whatever movement originally stirred up the gas, and a huge volume of carbon dioxide is converted from dissolved gas into bubbles in a matter of minutes. The cold (cold because it was down deep) carbon dioxide out-gases at the surface, fills the lake basin, and spreads across nearby settlements potentially killing hundreds. This is what happened at Lake Nyos, Cameroon, in 1986, killing almost 2,000 people.Small amounts of carbon dioxide cause toxic reactions. You need about 15% or so of the atmosphere to be carbon dioxide to see serious effects, and before you reach about 20% it is deadly. At 25% or more death is very very quick.Of course, in mines, this is complicated by the fact that the carbon dioxide may be coming from the combustion of the oxygen you are supposed to be breathing. If enough oxygen is burning to generate nine or 10 percent carbon dioxide, virtually instant death from combined lack of oxygen and presence of carbon dioxide ensues.This has little to do with Carbon Dioxide as a greenhouse gas. But since I’ve seen efforts by the global warming deniers to point out that carbon dioxide is a harmless gas that we put in soda, I figured I’d take this opportunity to lay a little truth on you.Carbon Dioxide is a greenhouse gas at much lower densities. It is the most important anthropogenic greenhouse gas. Global concentration of this gas fluctuated between about 260 and 280 parts per million (ppm) over the period of a few thousand years prior to human caused increase, but is now at about 380 ppm. This level is the highest in about 650,000 years, over which it may have fluctuated between as little as 180 ppm and 300 ppm. (This is based on measurements from ice cores.)Of all of the years for which measurements are available and analyzed, the most rapid increase in carbon dioxide concentration are the most recent, from 1995-2005. In other words, despite increased awareness of the importance of carbon dioxide, we (humans) have managed to make the problem exponentially worse. That this has happened is entirely the responsibility of the so called Global Warming Deniers, such as the present American administration.Other than the fact that carbon dioxide is a greenhouse gas, and that these changes are very large even though the numbers themselves seem small, the most important message of this discussion is this: The carbon in this added carbon dioxide is primarily from fossil sources.This is very important. It turns out that it matters what you burn. The little bit of gasoline you burn in your car to go to a campsite is much more serious than the huge amount of wood you burn for the next ten days cooking fish and toasting marshmallows. This is because the wood is from trees that have been sucking that carbon out of the atmosphere for the last 50 years or so, but the gasoline is carbon that was safely tucked away in the crust of the earth until Exxon-Mobile or BP sucked it out and refined it for your use. Where those trees you burned up grew … well, there are already trees growing there sucking this carbon back into their tissues. But where that crude oil came out of the ground … the process of re-storing the carbon in those deposits will take a couple million years or so. That is a genie you can’t put back into the bottle in a thousand lifetimes.Over any given long period of time … millions of years … there is a steady (or maybe not so steady) “sinking” of carbon into fixed sources in the geological column. Living stuff always includes carbon as an important element. When living stuff dies, some of it seeps into the ground, some of it is trapped in biogenic duracrust (rocky hard stuff on the surface of the earth, like the caliche of the American Southwest), and a significant part of it runs off into low basins as part of the water cycle and, since it does not evaporate (like the water itself does) settles and builds up in deltas, lake bottoms, along the continental shelf, etc.At any given point over this long time scale, chunks of this carbon get released. Plate tectonics may cause a low area that has been accumulating carbon to rise up and erode. For instance, the Himalayas are mountains pushed up from a very low area that had been accumulating carbon for a very long time, and as they have risen, they probably released a lot of this carbon. (The reaction between the Himalayas and the water and air eroding them also resulted in carbon being chemically trapped and drained off into the Indian Ocean and the Pacific … so this is actually very complicated.)Much of Texas (especially the Permian Basin, in the west, around Odessa) is a low area that has been accumulating carbon for a long time. If plate tectonics mushed up Texas to make a big mountain where there is now unending flatness, there might be a huge release of carbon (over tens or hundreds of thousands of years) as the carbon-containing material is lifted to the surface to react with various agents and become atmospheric.But wait, that has already happened, hasn’t it!?!?!? This is, indeed the whole point! Huge stores of ancient carbon in this ancient basin in Texas, beneath the sands of the Arabian Peninsula (the bottom of an ancient sea called Tethys), in the ancient delta of the Tigris and Euphrates, along the extensive continental shelves, in the Gulf of Mexico, in various inland deep valleys and subuction zones … areas that individually may someday experience uplift and thus release of carbon, over long periods of time, one at a time, now and then … have ALL experienced a sudden and simultaneous, very rapid artificial uplift and release of this carbon, and that carbon, trapped in various complex molecules, has reacted with forces on the surface, converting to carbon dioxide, all being released into the atmosphere at a catastrophic rate.This uplift consists of the excavation of coal mines, the release of combustible gas, and the pumping of liquid hydrocarbon fuels (crude oil) by humans, and the reaction consists of the burning of these materials at wellheads (for the gases) and in factories and cars.The key point is this: The big problem … not the only problem but the number one problem … is the release of previously trapped fossil carbon into the atmosphere as carbon dioxide, where it acts as a greenhouse gas.The Intergovernmental Panel on Climate Change provides this excellent summary graphic:In this graphic you see the last 10,000 years of time over which Carbon Dioxide, Methane and Nitrous Oxide (greenhouse gases released by industrial processes) fluctuate a bit then suddenly, catastrophically increase. Notice there is a little bit of an increase around 5,000 years ago. I suspect this is the rapid spread of both agriculture and metal (smelting) technologies around that time, during which we see large forest areas being cut down and burned up, shifting the carbon balance a little from living trees to smoke. But the most significant effect is since the industrial revolution, which involved the tapping of fossil carbon first mainly from coal and later also from oil.So you can burn your stuff fast, get lots of carbon dioxide, and die right away. Or you can burn your stuff very very slowly, leaving the sleeping dragons lie, and cycle carbon through the system at a gentle rate, or you can dig up all the old carbon you can get your hands on, distribute it widely, burn it for all imaginable purposes… this will get you the occasional deadly concentrations of carbon monoxide or carbon dioxide, but mostly it will get you nothing other than massive climate change in one direction.But so what? Who cares if the climate gets a little warmer? Well, we are not dealing with that topic now. We are taking this one step at a time. Previously we came to understand what the “greenhouse effect” is, what a greenhouse gas is and how it works. Now we see that increase in carbon dioxide in the atmosphere is really a matter of mucking around with a giant balancing act this planet has been engaged in for hundreds of millions of years … by employing virtually every machine we have ever produced in the modern era. If future installments we’ll look at some of the effects of warming.