Saturday, January 31, 2015

Climate Change Part 15: Linear and Abrupt Models

Note: This program first aired January 31, 2015.

It may be no surprise to you that anthropogenic climate change is paying dividends to the world already. No longer is this something we can think of as impacting the future. The future, as they say, is now. World wide glaciers, both continental and alpine are in rapid retreat, phenological changes that include earlier dates of ice out on lakes and rivers and earlier timing of spring tree, flower and phytoplankton blooms are being documented everywhere, tropical diseases are spreading, along with their host insects to higher latitudes whose climates can now support them, the intensity and frequency of extreme heat waves are increasing, Arctic sea ice is getting smaller and thinner each summer, and last year was the warmest year on record.

When we think about the consequences of climate change, there are two models that are used to conceptualize what might happen (as well as for comparison with what IS happening). The first model is linear. In this world view, incremental increases in green house gasses yield incremental changes in climate, it’s a y equals mx plus b vision of how the climate system works. The carbon dioxide level and average global temperature have a direct relationship. As carbon dioxide levels increase, average global temperature increases at some set proportion described by the slope of the line, and that relationship remains a constant straight line regardless of how high carbon dioxide levels get. It is a reassuring, predictable relationship, in that the math is simple. If we know the X value, a carbon dioxide level, we can get a Y value, the resulting temperature. Everyone can interpret a straight line graph. It’s worth noting that this is the model that the Intergovernmental Panel on Climate Change, the world’s preeminent climate change research and policy body, uses to makes its predictions, predictions that direct the course of global policy actions.

The problem is that Earth’s climate system is not actually linear. The relationship between carbon dioxide and temperature may appear to have simple causal attributes, but it is just the tip of the iceberg. Climate is defined as the long term average of weather, and weather is acknowledged to be a chaotic system, chaos in this sense as a technical term, meaning distinctly non linear. As we increase atmospheric carbon dioxide and thus increase average temperatures as expected, all kinds of other related processes can get triggered, and lead to rapid and unexpected effects. Take for example, last year’s intensely cold winter in North America, not the kind of thing you would expect if you used the simplistic model of increasing carbon dioxide leading to warmer temperatures. In fact the increasing temperatures have disrupted typical atmospheric pressure arrangements and thus wind patterns, which led to changes in the jet stream. Instead of running primarily west to east last winter, the jet stream (which is simply the boundary between polar and mid latitude air masses) was able to take large north and south running loops, bringing very dry cold polar air to lower latitudes than we are used to. Chaos.

The ultimate expression of this non linear climate system, and the one that keeps climate scientist up at night is the model of abrupt climate change. It’s what many leading climate scientists see on the very near horizon. Essentially X leads to Y, which then leads to A, B, C or any other letter in the alphabet, or perhaps, all of them. A warming average global temperature pushes certain aspects of the climate system past their tipping points, which result in a rapid and more irreversible change in the functioning climate system. Those anticipating abrupt climate change are looking hard at what is happening in the Arctic. Polar amplification has long been recognized, in that the Arctic has seen warming temperatures several degrees higher than the global averages, due largely to feedback loops related to the loss of sea ice and therefore albedo. As less sunlight is reflected (because there is less highly reflective ice around), more light is absorbed, which then warms the Arctic and melts yet more ice. There are suggestions that the Arctic may be more intimately influential in global climate than was previously suspected, and if the Arctic continues its death march towards a tipping point, it may take the whole world with it, quickly. There is precendent for the mechanisms of abrupt climate change in the paleoclimate record, abrupt climate change is in fact what has led the Earth into glacial periods, as well as to rapidly emerge from those same ice ages over a matter of decades.  

Over the past many many weeks and months we’ve spent most of our climate change energy focusing on the carbon, because quite simply, this whole thing starts with the carbon, it’s the crux of what is driving the warming of the climate. The parallel story is that while carbon is simple, climate is wildly complex and the system is massively difficult to describe quantitatively in terms of predicting behavior. That is why climate scientists are a strange mix of computer geniuses who build super computing climate models, and field researchers who drill cores in glaciers and ocean sediments trying to reconstruct past climate patterns. We look at the past to predict the future, and the past tells us that it is likely an abrupt shift, rather than a gradual stepwise transition, that we should be looking forward to.


Current effects of climate change from NASA, including several really good graphical representations of various effects:

IPCC home page, read the projections for your self:

Maine Climate Change Institute on Abrupt Climate Change

Book Review: WTF, Evolution?

Note: This program first aired January 17, 2015.

I read a lot of books, science and nature books mostly, and I am always on the lookout for new work that effectively translates heady science concepts into engaging understandable material for the public. 2005’s fabulously funny “How Animals Have Sex: A guide to the reproductive habits of creatures great and small” by David Strorm is a great example. It’s a small format, full color photographic book that surveys the amusing sex lives of a wide variety of animals. The heady topic in question? That life is incredibly diverse, and evolution has come up with an amazing array of ways for life to go on, that is, for animals to reproduce. It answers questions you’ve always wondered like, how do dolphins and whales mate? What about porcupines? And then titillates the reader with fun facts about animals you may have never heard of like Bean Weevils and Spoon Worms and Argentine Lake Ducks. I consider How Animals Have Sex to have set a high standard for this genre.

So it was with pleasure that I purused Mara Grunbaum’s “WTF, Evolution?! A theory of unintelligible design”, a 2014 release from Workman Publishing. WTF, Evolution?! follows the same small format, full color photographic design, with a sort of scrap book-y layout. The author imagines an ongoing conversation with Evolution, and the book is full of cheeky irreverent dialog, sharp enough to get your attention, smart enough to keep it. The narrator’s skeptical comments and dead pan retorts are contrasted by enthusiasm in the voice of Evolution. Each section is prefaced by a short explanation of some facet of the mechanisms of Evolution, highlighting how adaptations have given the world some very strange solutions to otherwise straightforward biological problems.

The main goal of the book is to showcase the diversity of strange adaptations that have evolved in the animal kingdom over the last 3.8 billion years on this planet. In doing so Grunbaum highlights  key misconceptions about evolution, that it has a goal in mind or some kind of intention, and that humans are the apex of evolutionary adaptation. Evolution is precisely not directional, and has no end goal in mind. As she says in the introduction “Like the rest of us, it’s basically just fumbling in the dark”. Genetic engineering aside, evolution is profoundly limited by its starting material. It can only work with the genes that are in the gene pool. The only source of new material is mutation, which happens with regularity yet doesn’t yield viable new genetic material all that often. Not every mutation is adaptive, but if it doesn’t have a negative effect, it can get taken along for the ride and persist along side genes that increase an individual’s fitness. And that makes the fact of the incredible diversity of animal forms (and they are almost entirely animals in this book) simultaneously bewildering and understandable.

If you are interested in evolution, find animal diversity fascinating, like to laugh and don’t take yourself too seriously, do yourself a favor and pick up a copy WTF, Evolution?! At a bare minimum you will see evolution from a new angle, and regardless of where you are standing, a new perspective is something that benefits us all.


Climate Change Part 14: Methane 2

Note: This program first aired January 10, 2015.
Last week we introduced a key non carbon dioxide green house gas, methane. There are several naturally occurring sources of methane, a gas that is produced by anaerobic bacteria when organic matter decays.

Methane is a fossil carbon based fuel, and is the main constituent of natural gas, so when we burn it, just like when we burn any carbon based fuel, one of the waste products is carbon dioxide. Carbon dioxide is a major green house gas, meaning as we increase concentrations of it in the atmosphere, we create conditions that prevent the escape of infrared radiation (also known as sensible heat) from Earth’s climate system (that being the atmosphere and the ocean). When more heat is trapped than escapes, then we have a system that is warming. That is the current climate change scenario in a nut shell, and the combustion of methane plays a role.

Methane plays a second, and more significant role in climate change by being a green house gas itself.  The methane molecule, just like the carbon dioxide molecule, the water molecule, the nitrous oxide molecule and various other fluorine containing and halogenated industrial compounds, absorbs specific wavelengths of infrared radiation. Water is by far the most important green house gas, in that it traps the widest range of infrared wavelengths emitted by the Earth back towards space. And remember, the green house effect that results from these various atmospheric gasses is what makes our planet livable, so it’s a good thing. The issue currently is that the proportions of the green house gasses in the atmosphere are changing, resulting in more radiation being trapped down here in the lower atmosphere, so things are heating up on the surface of the earth. I said that water vapor traps the widest range of infrared wavelengths, but it doesn’t absorb all of them. There are gaps, or windows in the water vapor absorption spectrum. In the absence of other green house gasses, it is through these wavelength windows that some heat escapes the atmosphere. Some of these gaps are partially filled by the other greenhouse gasses, including carbon dioxide, and methane.

On a per molecule basis, methane absorbs a large amount of infrared radiation, so you often hear that it is something like 40 times as powerful as carbon dioxide gas in terms of its greenhouse warming potential. Some studies have linked methane releases to major warming events like the PETM (or Paleo Eocene Thermal Maximum) or mass extinctions like the end Permian. Methane is different than most other non water vapor green house gasses in that it breaks down relatively quickly, usually within a decade of emission. In the atmosphere it is oxidized, which essentially does the same thing chemically as combusting it, so when methane goes away, carbon dioxide and water are left, and we already know those are both green house gasses.
In the big scheme of things, methane makes up a very small percentage of green house gasses, and because it oxidizes so quickly, some scientists down play its role in climate change. Others see it as a great place to start mitigation efforts, because the effect of reducing emissions of methane can be felt within a decade, due to its short lifespan. As we have learned, there are many natural sources of methane. However, at this point there are many more anthropogenic sources of methane emissions than natural ones. These sources are industrial and agricultural and are somewhat unavoidable components of modern society. Landfills, the end point for much of our waste stream, are a huge source. When land fills are created and then capped, they become anaerobic environments, full of organic matter—perfect incubators for the creation of methane. Some forward thinking land fill operators actually capture that land fill gas and burn it to create heat or electricity. Methane comes from a variety of agricultural sources, including artificial wetlands where rice is grown, and ruminant livestock as well as manure. The oil, gas and coal industry itself is a large source of methane emissions, coming mainly from leaks in infrastructure, and directly from wells and mines. The anthropogenic effects of methane emissions can be compounded by a positive feedback loop that was recently quantified; Methanogenic bacteria are strongly temperature dependent, so the warmer it gets, the more methane they will make. In other words the warmer climate gets, the more active wetland bacteria are, the more methane is emitted, the warmer it gets. It is this effect that causes some scientists to link methane emissions to specific rapid climate change events in the geologic record.

The consensus in the climate science community seems to be that issue is the carbon dioxide, and that is where we should be directing our energy. At the same time however, methane needs to stay on the table, with a particular eye to all those methane hydrates at the bottom of the ocean. Ocean temperatures are warming, particularly deep ocean temperatures, which means that things could get very weird very fast in the climate system. Methane remains the wild card here, one that bears watching in the years to come.


Science Daily digest here on the study that quantified the “the warmer it gets the more methane we get” positive feedback loop:

Even high school students preparing for their school exams need to know about combustion chemistry:

Old archived science blog, but it has good info:

More about the nitty gritty of the bond chemistry that makes green house gasses work:

Google “sources of methane” and take a look at the images. You will see a wide variety of pie charts, with huge variation in what they show. Most show anthropogenic sources as nearly ¾ of the methane emissions, the methane hydrates that make up the huge volume of fossil fuels on Earth aren’t being emitted, so they aren’t included on these tallies (except for where they are emitted, in thus far relatively small amounts in coastal oceans and some high latitude lakes).

Climate Change Part 13: Methane 1

Note: This program first aired on January 3, 2015.
We left off last time with the biogeochemical mechanisms by which oil is made. Briefly, oil and gas result from primary productivity at the ocean surface. Photosynthesis happens in the bodies of tiny phytoplankton. Those plankton die without being eaten, and then sink to the bottom, where they accumulate. Over a geologically relevant amount of time, they turn into oil.

Today we talk about the gas part of “oil and gas”. There are several simple hydrocarbons that can form from dead marine organic matter, and the shortest of these chains of carbon are gaseous. The shortest chain of all isn’t a chain at all, it’s a single carbon atom surrounded by hydrogen atoms, CH4, methane. Methane gets special attention in climate change circles because it isn’t just a fossil fuel (it’s the primary component of “natural gas” when it wears that hat), it is also a green house gas in its own right.

Methane forms when organic matter is decomposed anaerobically, meaning without oxygen. This form of decomposition is slow, and yields less energy than aerobic metabolism, but allows microbes exist in anoxic environments where other things can not live. Methane occurs naturally on earth anywhere we have anoxic conditions and organic matter. Wetlands are a major terrestrial source, where waterlogged soils quickly become anoxic, and methanogenic bacteria have plenty of raw material. Swamp gas is the result. Animals are another surprising source of methane, some more so than others. Our guts are anaerobic environments that house billions of bacteria, these bacteria do much of the heavy lifting of digestion for us, but depending on the raw material we provide these bacteria, they sometimes make methane as a byproduct, a phenomenon I am sure you are all familiar with. Animals that make a living eating difficult to digest food, like cellulose and related compounds make methane regularly. Domestic cattle and other ruminants eat hard to digest grasses, and as a result, give methanogenic bacteria plenty of feed stock. Termites make a living eating wood and other high cellulose organic material, and again, rely on gut microbes that can break down the difficult to digest cellulose. As a result, termites are another natural source of atmospheric methane.

Much methane resides in the permafrost areas of the high arctic and subarctic. Productivity is slow in those regions, but the organic matter that does form breaks down very slowly due to the cold conditions, thus the soils there are quite peaty, and high in partially decomposed organic matter. They also suffer poor drainage due to underlying impermeable frozen substrate, and tend to be waterlogged as a result. These conditions lead to a slow but steady production of soil bound methane, typically locked into permafrost.

The largest store of methane on Earth is at the bottom of the ocean. As a simple hydrocarbon methane forms relatively quickly from organic matter that makes its way to the ocean floor. Over the long term these deposits can be buried and become the oil and gas deposits we now search continental shelves for, but in the short term the methane gas can also be trapped in near ocean bottom sediments, held in place by the extreme pressure on the sea floor. These deposits are called methane hydrates, because due to the pressure, the methane molecules get trapped in a crystalline matrix of water molecules, and form solid that looks something like ice.  This methane is not only the largest store of the gas on Earth, it is also constitutes over half of all fossil fuels on Earth, which is why so many people are trying to figure out how to commercially access this this odd source of natural gas, for better or for worse. Next time we will look at methane’s role in climate change, and why it might be our best hope for mitigating the most severe potential impacts.


From the University of California San Diego:

Online text book from the University of Oxford (UK) Environmental Change Institute:

Interesting info from NOAA on non carbondioxide Green House Gasses

Data, including details on sources and proportions from the EPA:

About termites from the Arizona Sonora Desert Museum (be sure to read the bit about the baby termites eating the feces of their older siblings…)

Department of Energy take on methane hydrates: