Periodic Table of Videos

The Periodic Table of the Elements compresses an amazing amount of information into 118 boxes, one for each chemical element. The most stunning revelation of the table is the regularity of patterns formed by the similar properties of elements in each group (column), which has come to be explained by the quantum structure of the electron clouds around atoms of each element. More about the table here (Wikipedia).

Unfortunately the periodic table can be a bit dry and boring. So much information! But by combining the delights of chemistry with the enthusiasm of videojournalist Brady Haran we get The Periodic Table of Videos--one of the coolest science teaching projects I have heard of since Khan Academy.

Here is a sort of history of the Periodic Table of Videos on the main page of its YouTube channel. The project's official site is here. Click on any of the elements in the table and view a video about the element and its properties, often with hands-on demonstrations, the more explosive the better.

Concerned about the radioactive strontium-90 released from the damaged Fukushima Daiichi reactors, or showered on many of us during the era of above-ground nuclear testing? Here is strontium's YouTube video.

Did you enjoy Uncle Tungsten, Oliver Sacks's biographical celebration of his early interest in chemistry (and one of the most delightful introductions to the periodic table)? Click "W" on the table and watch this video.

What about the most important element, number 47? (The number 47 rules the universe.) See silver on the screen.

And then there's gallium, used in semiconductors and fancy solar cells. Or why don't we end with a bang with caesium (aka cesium)?

Have fun exploring these videos on your own.

[Hat tip to Grrl Scientist for mentioning Periodic Table of Videos in her Guardian blog Punctuated Equilibrium.]

[Image from Periodic Table of Videos homepage.]

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David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 

Show And Tell--Sharing Science By Video

The Journal of Visualized Experiments (JoVE) makes hands-on science available by video. Real scientists demonstrate their experiments on line to accompany their publications. A picture being worth a thousand words, and a video being worth at least a thousand pictures, this novel channel gives fellow researchers (and budding scientists!) around the world clearer access to experimental procedures. Now JoVE is offering free access to developing-country researchers.

Those of us who have tried to figure out just how research was done by reading the often-cryptic "Materials and Methods" sections of scientific publications can appreciate the value of this approach.

JoVE has teamed up with the Health InterNetwork Access to Research Initiative (HINARI) of the World Health Organization to provide this free access. Here is a press release about the initiative.

Many schools and libraries in developing countries cannot afford to subscribe to scientific journals, which are among the most expensive of periodicals (and highly profitable to their publishers). See this blog post by George Monbiot about the high cost of access to the scientific literature. I agree with his complaint that these very high pay walls prevent the wide dissemination of information that is essential to progress in science, and to its understanding by the public. "Secret" science is a sin, especially in our digitally connected world.

At least through programs like HINARI some researchers and students in some developing countries can avoid being completely cut off from current information. It is important that students of science and medicine, wherever they are, have the best possible access to current research if they are to understand the latest methods and developments. And if they can see that research being done, so much the better.

The contributions of researchers in developing countries are essential to the solution of many of today's most challenging technical problems in agricultural, public health, and environmental fields. On-line resources like HINARI, JoVE and the Public Library of Science will help.

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David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 

How Much Radiation Is Bad For You?

Putting Fukushima In Perspective

This excellent chart puts in perspective the various amounts of radiation we might be exposed to. I know you can't read the reduced version shown here, so click on the image or go to the xkcd site to see the full-sized image. That site also has links to supporting information.

Yes, too much ionizing radiation can be very dangerous. But "too much" is a lot. We all tolerate minor amounts every day of our lives.

Smoking Sieverts

The chart doesn't include the very significant additional radiation exposure that tobacco smokers expose themselves to. (Info at this EPA site. The U.S. Army Corps of Engineers has a pdf here with some exposure examples.) This University of Iowa site says someone who smokes a pack and a half of cigarets a day exposes himself or herself to a dose of 1300 mrem/year, equivalent to a chest x-ray for each cigaret. That's one of the green boxes in the chart above per smoke. Second-hand smoke is similarly radioactive.

Nobody who smokes should complain about radiation. They expose themselves to more than anyone living around Fukushima is likely to receive. No tsunami required.

The Sievert Measures a Radiation Dose's Effect on Us

The sievert is the SI unit used to compare the effect of doses of ionizing radiation on the body. Different kinds of radiation have different effects, and different parts of the body are affected differently. The sievert takes this into account so we can compare, for example, the effect of the extra radiation received during an airplane flight with the extra radiation received by visiting Chernobyl. [Wikipedia article here.] Sieverts (Sv) and microsieverts (μSv), millisieverts (mSv) and so on are used in the chart above.

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David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 

[Cross-posted from Doc's Green Blog.]

Climate Change--What We Know and What's Uncertain

The Royal Society has published Climate change: A summary of the science. It has the aim "to summarise the current scientific evidence on climate change and its drivers." It is focused on how Earth's climate is changing and what is making it change. "The impacts of climate change, as distinct from the causes," are not considered.

Although the summary tries to be as non-technical as possible, it is after all a summary of the science, so it incorporates some scientific terminology necessary to convey the facts. It also includes some numbers, such as "240" and "3.6".

The report attempts to clarify which aspects of climate change science are widely agreed, which others have achieved consensus but where further research is expected to give more clarity, and which are not yet well understood.

It begins with a dozen paragraphs of "some background science", explaining very broadly what the greenhouse effect is, what is meant by "climate forcing" and "climate change", and why what may seem like small forcings of a few Watts per square meter can create the profound climate changes seen over past millennia.

At the risk of offering a précis of a summary, here are some of the key points of the report.
 

Aspects of climate change on which there is wide agreement

• "Averaged over the globe, the surface has warmed by about 0.8°C (with an uncertainty of about ±0.2°C) since 1850."
• "Each decade since the 1970s has been clearly warmer (given known uncertainties) than the one immediately preceding it. The decade 2000-2009 was, globally, around 0.15°C warmer than the decade 1990-1999."
• Other changes include "increases in the average temperature of both the upper 700m of the ocean and the troposphere (the atmosphere up to 10-18km), widespread (though not universal) decreases in the length of mountain glaciers and increases in average sea level."
• "Global-average CO₂ concentrations have been observed to increase from levels of around 280 parts per million (ppm) in the mid-19th century to around 388 ppm by the end of 2009."
• "Present-day concentrations are higher than any that have been observed in the past 800,000 years, when CO₂ varied between about 180 and 300 ppm."
• "Various lines of evidence point strongly to human activity being the main reason for the recent increase, mainly due to the burning of fossil fuels (coal, oil, gas) with smaller contributions from land-use changes and cement manufacture."
• "About half of the CO₂ emitted by human activity since the industrial revolution has remained in the atmosphere."
• "The concentration of methane has more than doubled in the past 150 years; this recent and rapid increase is unprecedented in the 800,000 year record and evidence strongly suggests that it arises mainly as a result of human activity."
• "These additional gases have caused a climate forcing during the industrial era of around 2.9 Wm^-2 [Watt per square meter], with an uncertainty of about ±0.2 Wm^-2."
• "The net effect of all human activity has caused a positive climate forcing of around 1.6 Wm^-2 with an estimated uncertainty of about ±0.8 Wm^-2."
• "Changes in CO₂ can lead to climate change and climate change can also alter the concentrations of CO₂."

Aspects of climate change where there is a wide consensus but continuing debate and discussion

• "Current understanding indicates that even if there was a complete cessation of emissions of CO₂ today from human activity, it would take several millennia for CO₂ concentrations to return to preindustrial concentrations."
• "Natural forcing due to sustained variations in the energy emitted by the Sun over the past 150 years is estimated to be small (about 0.12 Wm^-2)" but this remains an active area of research.
• "Particles have caused a negative climate forcing of around 0.5 Wm^-2 with an uncertainty of ±0.2 Wm^-2."
• "Climate models indicate that the overall climate sensitivity (for a hypothetical doubling of CO₂ in the atmosphere) is likely to lie in the range 2°C to 4.5°C," with this wide range due to "uncertainties in how much water vapour amounts will change, and how these changes will be distributed in the atmosphere, in response to a warming."
• "Unless [internal climate variability] has been grossly underestimated,
  the observed climate change must result from natural and/or human-induced climate forcing."
• "When only natural climate forcings are put into climate models, the models are incapable of reproducing the size of the observed increase in global-average surface temperatures over the past 50 years. However, when the models include estimates of forcings resulting from human activity, they can reproduce the increase."
• "The observed vertical and latitudinal variations of temperature change are also broadly consistent with those expected from a dominant role for human activity. There is an ongoing controversy concerning whether or not the increased warming with height in the tropical regions given by climate models is supported by satellite measurements."
• "The IPCC’s best estimate was that globally averaged surface temperatures would be between 2.5 - 4.7°C higher by 2100 compared to pre-industrial levels. The full range of projected temperature increases by 2100 was found to be 1.8 - 7.1°C based on the various scenarios and uncertainties in climate sensitivity."
• "Climate models tend to predict that precipitation will generally increase in areas with already high amounts of precipitation and generally decrease in areas with low amounts of precipitation."
• "Because of the thermal expansion of the ocean, it is very likely that for many centuries the rate of global sea-level rise will be at least as large as the rate of 20 cm per century that has been observed over the past century."

Aspects that are not well understood

• "Projections of climate change are sensitive to the details of the representation of clouds in models. Particles originating from both human activities and natural sources have the potential to strongly influence the properties of clouds, with consequences for estimates of climate forcing. Current scientific understanding of this effect is poor." [Or, as Joni Mitchell wrote in 1967, "I've looked at clouds from both sides now, From up and down and still somehow, It's cloud's illusions I recall; I really don't know clouds at all."] 
• "The future strength of the uptake of CO₂ by the land and oceans (which together are currently responsible for taking up about half of the emissions from human activity…) is very poorly understood, particularly because of gaps in our understanding of the response of biological processes to changes in both CO₂ concentrations and climate."
• "There is currently insufficient understanding of the enhanced melting and retreat of the ice sheets on Greenland and West Antarctica to predict exactly how much the rate of sea level rise will increase above that observed in the past century ... for a given temperature increase."
• "There is little confidence in specific projections of future regional climate change, except at continental scales."

The authors conclude

• "There is strong evidence that changes in greenhouse gas concentrations due to human activity are the dominant cause of the global warming that has taken place over the last half century. This warming trend is expected to continue as are changes in precipitation over the long term in many regions. Further and more rapid increases in sea level are likely which will have profound implications for coastal communities and ecosystems."
• "Like many important decisions, policy choices about climate change have to be made in the absence of perfect knowledge. Even if the remaining uncertainties were substantially resolved, the wide variety of interests, cultures and beliefs in society would make consensus about such choices difficult to achieve. However, the potential impacts of climate change are sufficiently serious that important decisions will need to be made. Climate science – including the substantial body of knowledge that is already well established, and the results of future research – is the essential basis for future climate projections and planning, and must be a vital component of public reasoning in this complex and challenging area."

A nice effort by the Royal Society. What we know is sobering. What we don't know is scary. The fact that we don't know everything is unsurprising. That we know so much is among the great achievements of science over the past few decades. That we are unable to deal with the problem, or that some even deny that it is a problem, is just human nature.

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The report is available in PDF here.

The Royal Society of London for the Improvement of Natural Knowledge, better known as just the "Royal Society", is one of the world's premiere national scientific organizations. It acts as the United Kingdom's "academy of sciences".

David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 

What Is The "Greenhouse" Effect?

This post will help you understand

1. Why the "greenhouse effect" has to do with gases in the atmosphere,
2. How these "greenhouse gases" in the atmosphere warm the Earth (and what that has to do with things that are "red hot"),
3. What this implies for future warming as we put more of these gases into the atmosphere.

The use of a toaster is not required, but it helps if you know how one works.

What Is The Greenhouse Effect?

The "greenhouse effect" refers to how gases in the atmosphere which absorb infrared radiation make the Earth warmer than it would be without them. (It has nothing to do with the way greenhouses work to protect plants by trapping warm air in an enclosure. That's just its name.)

There are two ways to understand this phenomenon:

1. Some gases in the atmosphere absorb infrared radiation emitted from the surface of the earth. This warms them up and they radiate energy, some of which heats the surface in turn.
2. Gases in the atmosphere that absorb infrared radiation from the surface make the atmosphere more opaque to that radiation, preventing transmission from the surface into space. (Radiation into space still happens, but from high in the atmosphere where it is colder and thus radiates less.)

Both of these ideas involve reduction in the flow of energy from the surface and lower atmosphere into space as radiation. The loss of radiation to space is less than it would have been if there were less of these "greenhouse gases". Since the flow of energy is reduced, the Earth is kept warmer.

Over time the Earth reaches a temperature that radiates away as much energy as it receives from the Sun. But when the amount of greenhouse gases in the atmosphere change for some reason it takes time for the planet to warm or cool enough to restore that energy balance. That is why the "greenhouse effect" is in the news so much today--the concentrations of these greenhouse gases in the atmosphere are changing at unprecedented rates.

The Physics of the Greenhouse Effect

 It is easy to understand the greenhouse effect if you comprehend these simple facts:

1. The Earth is a big warm rock
2. Warm things emit radiation
3. Other things absorb some of that radiation
1. In particular the "greenhouse gases" in the atmosphere strongly absorb the infrared radiation the Earth emits
4. When something absorbs radiation it heats up
5. Warm things emit radiation (2. again)
6. Other things absorb some of that radiation (3. again)
1. Some of the radiation from the atmosphere (see 5.) is absorbed by the Earth, which warms it (see 4.)
2. Some of the radiation from the atmosphere escapes into space, but less than if the atmosphere hadn't absorbed it on its way from the surface and sent some of it back down. 

Let's look at that process in more detail:

1. The Earth is a big warm rock. The average surface temperature is about 14.5 degrees C (287.5 degrees K). This is the near-surface atmospheric temperature (as would be measured by a thermometer at a weather station) averaged the seasons, over day and night, and over the geography of the earth. (See Wikipedia article Instrumental temperature record.) The Earth is warmed by radiation from the Sun that it absorbs, and by its own internal heat, some left over from its formation and some from radioactive decay of elements it is made from.

2. Warm things emit radiation. Any object radiates heat, in the form of electromagnetic radiation. Everybody is familiar with the idea of an object being "red hot". An object that hot emits enough light that we can see it, mostly in the infrared part of the spectrum but some at long visible wavelengths.  When an object is "white hot" it emits even more radiation, including a lot of visible light and a substantial amount of ultraviolet radiation.

2a. The warmer a thing is the more radiation it emits. This is known as the Stefan–Boltzmann law. (See Wikipedia article Thermal radiation.)

You can easily demonstrate this. If you hold your hand near a toaster (not in a toaster!), where the radiation from the toaster's coils can hit it, the radiation from the toasters coils will be absorbed by your hand. Your skin will be warmed by this radiation, and the more radiation there is the more it will be warmed.

When the toaster is off and the coils are at room temperature you won't feel the warming of your skin. The nerves in your skin don't do much when they are just at room temperature.

(Everything that is not at a temperature of absolute zero emits radiation. But hotter things emit a lot more radiation than colder things. Notice that the Stefan-Boltzmann law says that the amount of energy radiated is proportional to the fourth power of the temperature: j*=εσT⁴. So coils glowing red hot--about 1,000 K--are hotter than coils at room temperature of about 293 K, about 700 degrees Kelvin hotter. They are three times as hot, but they emit more than 100 times as much radiation.)

But when the toaster is on, and the coils are glowing red hot, they will emit a lot of infrared radiation (and a little visible radiation). Your hand would be warmed noticeably as it absorbed this greater quantity of radiation.  

At 287.5 degrees Kelvin (14.5 degrees Celsius) most of the radiation the Earth emits is infrared radiation. None of it is in the visible range. (Even at 45 degrees Celsius, a really hot day, none none of the Earth's radiation is in the visible range. This is why the Earth does not appear to glow on a really hot night.)

3. The atmosphere absorbs radiation. Molecules of the gases that make up our atmosphere absorb radiation. Obviously the atmosphere doesn't absorb all wavelengths of radiation equally. It doesn't absorb much in the range of visible light (it is transparent to visible light). This is why we can see the Sun, Moon and stars. The oxygen and ozone in the atmosphere absorb a lot of ultraviolet radiation coming from the Sun. That is why organisms can live on the surface of the Earth (UV kills microorganisms and causes skin cancer in people, for example).

The atmosphere is mostly oxygen and nitrogen, but it is about 0.035% carbon dioxide. Carbon dioxide absorbs infrared radiation very strongly. Since the warm Earth emits mostly infrared radiation (with a peak at wavelengths of about 10^-5 meters) and CO₂ absorbs infrared radiation (especially that with a wavelength longer than about 1.3x10^-5 meters) you can see that a lot of the infrared radiation from the surface of the Earth is absorbed by CO₂ in the atmosphere. (The situation is similar for other "greenhouse gases" such as CFCs, nitrous oxide, methane and water vapor.) (See Greenhouse Gas Absorption Spectrum.)

4. When something absorbs radiation it heats up. The photons of radiation can interact with matter. How they interact depends on the properties of the photon (wavelength) and the properties of the atom or molecule of matter. (At the wavelengths we are talking about these properties mainly have to do with the energy states of its electrons.) When substances absorb radiative energy they increase their thermal energy. They get warmer.

2. again: Warm things emit radiation (see above). The warmer they are the more radiation they emit. The warmed greenhouse gases emit more infrared radiation than they did when it was cooler (see 2a. above). Some of that radiation escapes into space. Some is absorbed by other parts of the atmosphere. And some if it is absorbed by the Earth below, making it a little warmer (see 4. above).

So that's how the "greenhouse effect" works:

• Radiation from the Sun warms the Earth and the atmosphere
• The Earth emits infrared radiation (the warmer it is the more it emits)
• The "greenhouse gases" in the atmosphere, especially CO₂, absorb some of that radiation from the earth, and this warms them up (the more of these gases there are the more they absorb)
• The warm gases in the atmosphere emit infrared radiation (and the warmer they are, and the more of them there are, the more they emit)
• Some of the infrared radiation from the "greenhouse gases" in the atmosphere is absorbed by the Earth, warming it a little more
• Loop back and repeat

So it doesn't work at all like a greenhouse. (Not that most people have much idea how greenhouses, also called glasshouses, work, or even what they are.) It isn't a result of the atmosphere "insulating" the Earth, like a blanket. It has to do with the gases in the atmosphere absorbing radiation, heating up, and warming the Earth below by their own radiation. But the names "greenhouse effect" and "greenhouse gases" are well established, so we might as well go ahead and use them.

The Net Result

The diagram below shows how all this works in terms of the Earth's energy balance.

As you can see, the net imbalance (energy in minus energy out) is only 0.9 Watts per square meter. (Other estimates give net forcing of approximately 1 to 3 Watts per square meter.) Whatever the actual figure, it is enough to warm the Earth significantly over time.

Consequences

Also note that the net absorbed is only 0.26% of the total incoming energy flux. It only takes a small change in the transparency of the atmosphere in the infrared to change the outgoing long-wave (infrared) radiation enough to affect the surface temperature. And of course the more greenhouse gases in the atmosphere, the greater the climate forcing.

How much will the Earth's temperature rise because of this 1 or 2 Watt per square meter forcing? That is the subject of urgent research. Current thinking is that the level of greenhouse gas in the atmosphere today, if we didn't put any more up there, might lead to a further increase in global temperature of one or two degrees Celsius or so.

But there are many difficulties with this estimate:

1. Feedback effects. As the Earth warms up there will be changes in the global energy balance that might make it warm faster or slower, such as
1. Melting of ice. Ice is highly reflective, so if it melts to expose bare ground or open sea less incoming solar radiation will be reflected back to space ("Reflected by Surface" in the diagram above).
2. Vaporization of methane in permafrost and undersea deposits. Methane is one of the most significant greenhouse gases, and there are vast amounts of it tied up in frozen permafrost or in deposits of methane hydrates on the sea floor. If warming of the sea causes melting and release of some methane hydrates this could vastly decrease the transparency of the atmosphere to long-wave radiation, keeping more heat on the Earth. It is thought that when this happened in the geologic past it led to an earth many degrees hotter than today's.
3. Warming seas. Cold water can absorb more carbon dioxide than warmer water. So as that 1 Watt per square meter radiative forcing warms the oceans, more carbon dioxide will be left in the atmosphere to act as a greenhouse gas.
4. Clouds. As the climate warms the weather will change. There might be more clouds, or less, or their distribution might change. Clouds are an important part of the "Reflected by Clouds and Atmosphere" component of the energy budget in the diagram.
5. Water vapor. Warmer air can hold more water vapor, and water vapor is a significant greenhouse gas.
2. Continued emissions.
1. We have already perturbed the planet's energy balance by putting around a trillion tonnes of greenhouse gases into the atmosphere over the past couple of centuries by burning fossil fuels and by land-use changes (burning forests). That is why the energy budget is out of balance by one or two Watts per square meter. But we continue to put about 35 billion additional tonnes of greenhouse gases into the air every year. And that annual emission figure continues to increase. So the concentration in the atmosphere will increase, the transparency of the atmosphere to infrared radiation will decrease, and the greenhouse climate forcing will increase. We are on course to put at least another trillion tonnes of greenhouse gases into the atmosphere by 2050, probably closer to two trillion.

I hope you can see why putting more CO2 into the atmosphere, more than the land and the seas can reabsorb, could make the atmosphere, and thus the Earth, warmer, perhaps much warmer.

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The toaster image is from Explain that Stuff published under a Creative Commons License.

The energy balance diagram is from this UK government site, and is protected by Crown copyright. Used by permission.

Here is another explanation of the greenhouse effect.

David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here.

484TFZMUEH2N

Latent Heat--Sweat, Storms and Cooling Towers

If you don't understand "latent heat" you can't understand how much of the biosphere or a lot of engineering works. The latent heat of water is the energy absorbed when water is evaporated, or released when it condenses. Weather, thermoregulation, global warming and industrial cooling all depend on the high latent heat of water and its ability to transform heat to work and vice versa, and to move energy from one place to another.

Water is Magic

Water is marvelous stuff and has many interesting properties. This is a good thing (for us) since these properties are necessary for life (as we know it) to exist.

(This is an example of the anthropic principle--we are only able to observe water's interesting properties because we exist, and we are only able to exist because of water's interesting properties. So it is unavoidable that in our world--in any world where we could have evolved-- water must have such interesting properties.)

Among water's most important properties is its high latent heat. This property creates much of Earth's most violent weather and drives the thermodynamics of climate.

What is "Latent Heat"?

To understand latent heat you first have to understand the idea of states of matter and phase changes.

Chemical substances can exist in several "states". The common ones that we encounter in everyday life are the solid state, the liquid state, and the gaseous state. When matter changes from one state to another we call it a "phase change". So liquid water can undergo a phase change to become the gas water vapor, and it can reverse that transition and condense from a gas into a liquid. It can undergo a different phase change from a liquid to become solid ice, and the reverse to melt from ice into liquid. See the diagram below.

The names of the various common states of matter
and of the phase transitions between them

The reason this is important (to us and our planet) is that it takes a lot of energy to change water from a liquid to a gas. This is because water molecules in a liquid are attracted to each other because of their polarity.

illustrative separation of
charges on water molecule:
negative red, positive blue

Water molecules are highly polar molecules. This means they have uneven distribution of their electrons, with more electrons bunching around the oxygen atom and thus creating lower electron density around the hydrogen atoms. So the molecule is more negative on one side (where the electrons are concentrated) and more positive on the other side. It is like a little magnet, a dipole. As you are no doubt aware, "opposites attract". So the negative side, or middle, of a water molecule will tend to attract the positive sides, or ends, of other water molecules. This is an example of "hydrogen bonding". Hydrogen bonding is extremely important in the machinery of life. This attraction tends to hold the water molecules in liquid water together. To evaporate water--to make some of those molecules break away from the liquid mass and fly off as a gas--takes a lot of energy.

To evaporate one kilogram of water by boiling it, changing it from liquid to gas at 100 degrees C, takes 2,260 kilojoules. That is about two and a half times as much energy as is needed to vaporize a kilogram of ethyl alcohol.

Latent Heat in the Kitchen

Pot of boiling water

You are undoubtedly familiar with the large amount of heat needed to bring about this phase transition of water from liquid to gas. Imagine a pot of boiling water. To keep it on the boil lots of heat has to be supplied. As soon as the heat is reduced it stops boiling and steam stops coming off. Consider the flame or other heat source that is needed to keep it boiling. You wouldn't want to contact such a concentrated heat source directly. (Warning: please do not put your hand on the stove to confirm this!)

The truly amazing thing about the latent heat of evaporation of water is that when the phase change is reversed, when water vapor condenses into liquid water, the same amount of heat is released. This isn't as obvious to us as the amount of heat consumed in boiling, but you may have experienced it if you have gotten your hand in the stream of steam escaping from a teakettle.

This is the reasons that burns caused by steam can be so severe. Besides the heat of the steam, some of the steam will condense on the skin, releasing its latent heat of condensation. This is equal to the latent heat of vaporization of the same amount of water. You wouldn't want to put your hand in the flame needed to vaporize even a small amount of water. But when that small amount of water condenses out of steam on your skin it releases just that amount of heat. This is why a burn from steam can be more severe than a burn by boiling water itself, if the quantity of steam is significant.

How Latent Heat Drives Storms

So when water evaporates it takes up heat (cooling the local environment). As water vapor it carries that heat around as latent heat. Then when that vapor condenses it releases that latent heat, heating up the local environment, usually the air.

This is what drives some types of storms, including thunderstorms, tornadoes, hurricanes and typhoons. Such storms are driven by "heat engines" based on water vapor. The key to such systems is rising warm air containing water vapor. As it rises it expands (because the atmospheric pressure is lower the higher you go) and as it expands it cools (the same amount of heat is spread through a larger volume--adiabatic cooling).

At some point the parcel of moist air has cooled enough that it cannot hold all the water vapor it contains. (The amount of water vapor air can hold is strongly dependent on its temperature.) So some of the water vapor condenses out as water droplets--clouds, rain or snow. As that water vapor condenses to liquid it releases heat (the latent heat of condensation or latent heat of fusion), warming the parcel of air. Because of this warming, the moist parcel of air will be warmer and more buoyant than neighboring air, so it will continue to rise.

As it rises and expands more condensation will occur, continuing the process. (This gives rise to towering "thunderhead" cloud formations.) Essentially this creates a strong updraft as water condenses out of the rising air. This updraft causes locally lower air pressure below it and sucks in surrounding air to fill the gap, creating surface wind--the storm as we experience it. (There may also be downdrafts associated with falling precipitation.)

Without the heat released by the condensation of water vapor these systems couldn't grow to their towering size.

Tropical cyclone driven by energy
released by condensation of moisture

In a tropical cyclone (hurricane or typhoon) more warm moist air is drawn into the cyclone as it moves over warm ocean waters, feeding and perpetuating the system. This is why hurricanes can grow so large, persist so long, and have such high winds. "A tropical cyclone's primary energy source is the release of the heat of condensation from water vapor condensing, with solar heating being the initial source for evaporation. Therefore, a tropical cyclone can be visualized as a giant vertical heat engine supported by mechanics driven by physical forces such as the rotation and gravity of the Earth. [source Wikipedia]"

Latent Heat of Evaporation and Climate Change

There are several processes where the latent heat of water becomes important in trying to understand climate change associated with global warming.

Tropical Cyclones
Increases in sea surface temperatures could affect the formation and behavior of hurricanes. As noted above, warm ocean waters put a lot of moisture into the air (the air can hold more moisture at higher temperature), and it is water vapor in the air that makes the hurricane heat engine work once one gets started. Wider areas of warm ocean waters could mean tropical cyclones will form in places they didn't form before.

There is a lot of scientific discussion about this because warming causes other simultaneous changes. For instance, hurricanes can't form if the local winds are too high--only where there are just light breezes. Will warming change the distribution of winds over warm areas of the seas?

There is some evidence that Atlantic hurricane numbers have been rising (previous post) but this is still in dispute.

If seas are warmer they might also contribute to the strength of tropical cyclones that do form. This previous post discusses research that suggests increased destructiveness of hurricanes associated with warmer seas. This question is still not settled though.

Cooling By Irrigation
Because of the latent heat of water, more evaporation means more cooling in some places, and more rain means more warming in other places. A recent article in the Journal of Geophysical Research (pdf here, New York Times Green blog post about it here) says irrigation may be causing cooling in some regions, locally masking the effects of global warming.

The model runs reported in this paper suggest that parts of norther India may have experienced several degrees of cooling due to all the heat absorbed by irrigation water applied to crops in the later part of the 20th century. Weather patterns may even have been affected enough to reduce the amount of rain in the Bay of Bengal branch of the Southwest Monsoon. (Other researchers got somewhat different or even contradictory results with different models.)

This is a bit scary because if groundwater depletion leads to reduction in irrigation in the future, the reduction of cooling effect could have both local an regional climate effects, including sharply higher temperatures and changes in rainfall amounts and distribution.

Evaporative Thermoregulation

Evaporation is used to cool the bodies of many animals. Sweat evaporating from the skin makes it possible for us to deal with hot weather. On a hot day in dry weather a person can lose more than a liter of water by evaporation of sweat (even several liters if it is really hot or you are exercising). Think of the amount of heat it would take to boil away a liter of water.

Other Uses of Latent Heat

There are many other uses of the latent heat of water for cooling, for example:

• Evaporative coolers, a kind of air conditioning.
• Some cooling towers at power plants
  
  

  

  Cooling towers at Didcot Power Station,

  and other industrial facilities use evaporative cooling. Steam turbines require a condenser to cool the steam after it leaves the turbine so that it condenses into water and can be pumped back through the cycle. Such condensers often use evaporative cooling by spraying or dripping water over coils carrying hot water from the system. At big power plants these may be enclosed in characteristic hyperboloid chimney-like structures to provide draft to move the moisture-laden air out of the cooling unit. Other systems use fans. [Here is a video of the inside of a cooling tower showing water being sprayed over cooling circuits.]

Understand latent heat and many phenomena will be less mysterious to you.

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The diagram of phase changes is a public domain image from Wikimedia Commons. Rights information here.

The illustration of charges on a water molecule has been placed in the public domain by its author, from Wikimedia Commons. Rights information here.

The picture of the pot of boiling water is from Wikimedia Commons, with the permission of the copyright holder under the terms of the GNU Free Documentation License.

Diagram of tropical cyclone by Jannev, placed in the public domain at Wikimedia Commons.

Picture of Didcot Power Station by Dave Price from Wikimedia Commons, used under a Creative Commons Attribution Share-alike license 2.0

David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 

Plants Unhappy About Global Warming

Rice field in Bangladesh

New science raises serious concerns about the negative impact of global warming on crop yields and plant productivity in general.

This could be one of the most severe social and economic effects of climate change.

Rice Yields Hurt By Warming

Researchers from the University of California, Duke, National Bureau of Economic Research, IRRI and FAO published a very revealing paper in PNAS. They studied 227 intensively managed irrigated rice farms in six important rice-producing countries over several years. Their findings "imply a net negative impact on yield from moderate warming in coming decades. Beyond that, the impact would likely become more negative, because prior research indicates that the impact of maximum temperature becomes negative at higher levels." Rising temperatures, especially nighttime temperatures, will hurt rice yields.

The paper is behind a pay wall, but there is a good BBC News article on their results. It says they "found that over the last 25 years, the growth in yields has fallen by 10-20% in some locations, as night-time temperatures have risen. ... Although yields have risen as farming methods improved, the rate of growth has slowed as nights have grown warmer." And "if temperatures continue to rise as computer models of climate project, Mr Welch says hotter days will eventually begin to bring yields down."

The question is whether rice improvement efforts (plant breeding) can get ahead of the negative effects of rising temperatures.

This EurekAlert release summarizes the results.

Net Plant Primary Production Down

Researchers at the University of Montana studied terrestrial net primary production. Net primary production (NPP) is the total net fixation of carbon by photosynthesis in an ecosystem. They found that "Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere."

These results were surprising since earlier studies had shown increasing plant carbon capture with rising temperatures in the 80s and 90s. However temperatures since 2000 have been the highest in modern records and accompanying droughts have apparently cut into global plant growth.

Again the Science article is not open access, but this EurekAlert release has some more information on the results and their implications.

While longer growing seasons and higher atmospheric carbon dioxide levels may favor more carbon fixation in some northerly regions, more of the globe is water-limited and more drought could hurt total carbon fixation more than warming trends would boost it. As the authors say in their abstract, "A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production."

Plankton Declining With Warming Seas

Researchers from Dalhousie University studied the concentrations of phytoplankton in the oceans. Writing in Nature report "declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year". "We conclude that global phytoplankton concentration has declined over the past century" and "long-term declining trends are related to increasing sea surface temperatures." Since phytoplankton, minute plants, "account for approximately half the production of organic matter on Earth" this could be bad news.

Marine phytoplankton

According to a Reuters story, "The study estimates the decline in marine algae has been approximately 40 percent since 1950." Half of all photosynthetic carbon fixation, cut by 40%!? That's significant and scary.

The story quotes study co-author Boris Worm: "I think that if this study holds up, it will be one of the biggest biological changes in recent times simply because of its scale. The ocean is two-thirds of the earth’s surface area, and because of the depth dimension it is probably 80 to 90 percent of the biosphere. Even the deep sea depends on phytoplankton production that rains down. On land, by contrast, there is only a very thin layer of production."

Here is an excellent release in Science Daily summarizing the report.

Yield Reductions in China?

A review paper in Nature by Shilong Piao et al. assesses "the impacts of historical and future climate change on water resources and agriculture in China. They find that in spite of clear trends in climate (especially temperature), overall impacts are overshadowed by natural variability and uncertainties in crop responses and projected climate, especially precipitation. In a best-case scenario, crop production is constant, whereas the worst-case scenario suggests that production could fall by about 20% by 2050." (From Editor's Summary.)

A Reuters article quotes further from the paper, "Countrywide, a 4.5 percent reduction in wheat yields is attributed to rising temperatures over the period 1979-2000," and says "They forecast that rice yields would decrease by 4 to 14 percent, wheat by 2 to 20 percent and maize by zero to 23 percent by the middle of the 21st century."

(Grist carries an AFP story about this research.)

What Does It Mean?

These results from several unrelated fields of research suggest that we should be concerned that continued warming will negatively affect both wild plants (which act as a carbon dioxide sink) and agriculture (fundamental to social stability).

If forests, grasslands, phytoplankton in the sea and other ecosystems absorb less of the CO₂ we release by unrestrained burning of fossil fuels, then atmospheric CO₂ levels may rise faster than models currently predict.

If higher temperatures and drought reduce agricultural output more land will have to be brought under the plow. Such land-use changes usually release significant additional carbon dioxide.

We should significantly increase spending on agronomy and plant breeding, especially in Africa, India and East Asia, if we want to maintain the yields we have.

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[Crossposted from sister blog A Very Different Earth.]

David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 


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Oil Spill Math: How Much Risk for How Much Oil?

How much oil has spilled?

Big quantities are sometimes hard to grasp. They are outside our everyday experience. When you hear that millions of gallons of crude are spilling in the Gulf, how much is that really? Professor James Corbett of the University of Delaware has done the math in a creative way.

Assuming the gusher is was gushing 50,000 barrels of crude a day (you can adjust this assumption on the site), "As of day 66 (today), if that oil had been refined to fuel in a typical US refinery, it would have produced gasoline, diesel fuel, and fuel oil capable of powering these vehicles:

• 118,000 Cars for a year, and
• 9,800 Trucks for a year, and
• 163 Containership days"

All the cars in Topeka

Most of us don't have a good feel for how many a hundred thousand cars are. So the U. Delaware site also shows the cities in the U.S. with 100,000 or more cars. This includes such cities as Pasadena, California, Buffalo, New York, Brownsville, Texas, Hartford, Connecticut and Alexandria, Virginia. All the cars in one of those cities could do all their driving for a year on the gas that could be made from the oil spilled so far. And the same crude would also provide diesel fuel for 10,000 trucks for a year, and bunker for ships.

If that's too hard to grasp, consider that you could drive your car on that gas for 100,000 years. (But what fun would that be?)

If the first Homo sapiens had started driving with that gas he or she could still be driving today (assuming fewer miles driven during the first 199,900 years, when there weren't any decent roads). Our species is only about 200,000 years old.

How risky was it to drill there?

And was that a risk worth taking? The U. Delaware site also provides a good discussion of how we try to quantify such risks. In fact, we can look at the environmental impact statement approved by the Minerals Management Service and see the probabilities BP assigned to the type of accident that occurred. The EIS "estimated the probability of a blowout in deep water drilling to range between 2 and 7 in a thousand".

If you had such a 0.2% to 0.7% chance of a disaster costing $100 billion (and the bill might be that high--not counting the damage which can't be repaired at any cost), then you would have to expect a proportionately huge upside potential to make such a well worth drilling. In fact you would have to expect to make about $500 billion in profit on the well to take such a risky bet. Since BP only makes about $30 billion in profit a year, the well would have to generate as much profit as all of BP's other activities put together every year for more than a decade, which seems unlikely. So why did they drill there?

Oil companies get special math

The reason oil companies will drill in the face of such odds is this: They know they won't have to pay the whole bill. Also, they probably told themselves that it couldn't possibly be this bad. (In fact we can read their EIS and see that they told government regulators it couldn't be this bad--and the regulators believed them!)

The Oil Pollution Act "limits the liability of responsible parties for offshore facilities, such as the Deepwater Horizon facility, to all removal costs (i.e., direct cleanup cost) plus $75 million and other language places a limit of $3,200 per gross ton".

This gross ton number tells you why BP has been so cagey about accurately quantifying just how much oil is spilling, has spilled, or will spill. Expect lawyers to argue about this for the next few decades. There's more detailed discussion on the site.

So even if the Gulf blowout ends up gushing two million barrels, as seems likely, that is about 300,000 tons of crude, for a total liability of around a billion dollars. (See conversion factors here.)

So the math for oil companies is not so bad. Downside say a couple of billion max, with a probability of 0.5%, so you only have to plan on making $10 million profit on the project to make it an even bet. The U.S. taxpayer and those who would have benefited from an undegraded environment bear the rest of the liability.

The severity and cost of the current spill may change that calculus, but they haven't yet.

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[This is cross-posted from the Doc's Green Blog.]

David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here. 

Is There Scientific Consensus on Climate Change?

Research Shows Scientists Agree on Global Warming

Researchers at Stanford and the University of Toronto noted that some people dispute whether there is "scientific consensus" on the reality and causes of climate change. They decided to find out how much consensus there really is.

The Intergovernmental Panel on Climate Change concluded that anthropogenic greenhouse gases have been responsible for "most" of the "unequivocal" warming of the Earth's average global temperature over the second half of the 20th century. But how many scientists who study the subject really believe that? And which scientists disagree?

They tried to "examine a metric of climate-specific expertise and a metric of overall scientific prominence as two dimensions of expert credibility in two groups of researchers", that is, those who agree with the IPCC's conclusion and those who do not.

They "compiled a database of 1,372 climate researchers based on authorship of scientific assessment reports and membership on multisignatory statements about ACC [anthropomorphic climate change]. We tallied the number of climate-relevant publications authored or coauthored by each researcher (defined here as expertise) and counted the number of citations for each of the researcher’s four highest-cited papers (defined here as prominence) using Google Scholar. We then imposed an a priori criterion that a researcher must have authored a minimum of 20 climate publications to be considered a climate researcher, thus reducing the database to 908 researchers."

Of those climate researchers, only a few percent were unconvinced of the IPCC's conclusion. The other 97-98% agreed with the IPCC that climate change is real and is mostly caused by human activities. The study also found that those researchers who published more and were cited more often in the field were more likely to be convinced by the evidence, and that those unconvinced by the evidence were generally those with fewer publications and citations.

"Not all climate researchers are equal"

They concluded that "the expertise and prominence, two integral components of overall expert credibility, of climate researchers convinced by the evidence of ACC vastly overshadows that of the climate change skeptics and contrarians. This divide is even starker when considering the top researchers in each group. Despite media tendencies to present both sides in ACC debates, which can contribute to continued public misunderstanding regarding ACC, not all climate researchers are equal in scientific credibility and expertise in the climate system."

The abstract of the PNAS paper is here, with access to the full paper as PDF. (Bless scientists and their grant providers who pay so that their papers can be open access, not restricted just to the academic community and other professional researchers.)

Dueling Experts

Often debates about climate policy come down to "My experts can beat up your experts". This research shows that there are objective measurements that can reveal which experts are more expert, and therefore should be given more weight in guiding policy. (Not that policy is driven by experts--it's politics.)

Science, after all, is substantially about measuring and quantifying. Even scientific expertise can be measured and quantified. This particular method is not the last word in such analysis. It is true that the lonely dissenter, out of step with the general consensus, who can't get a grant and therefore publishes less, may have a useful contribution to make. In fact she may be right and all the experts may be wrong. But this is not likely. When the skew is 881 to 27, the consensus is clear.

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David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here.

Know Your Spills--Confusing Names and Oil Quantity Equivalents

Confused about the many names for the Gulf of Mexico oil spill? Here is a useful list of equivalents.

• Deepwater Horizon Oil Spill--This follows the convention that spills are named after the vessel involved. The semi-submersible floating oil drilling rig Deepwater Horizon was technically an oceangoing vessel, registered in the Marshal Islands. This term unfortunately suggests that the event is a "spill", an unintended release of oil from a container like a vessel, pipeline or tank. It is really a "blowout" or "gusher".
• Macondo Blowout--The Macondo Prospect is an oil and gas prospect in the Gulf of Mexico, in which the Deepwater Horizon was drilling when the blowout occurred. This was the codename applied to the field during early exploration. "BP is the operator and principal developer of the oil field with 65% of interest, while 25% is owned by Anadarko Petroleum Corporation, and 10% by MOEX Offshore 2007, a unit of Mitsui." [Source: Wikipedia.]
• BP Oil Spill--BP plc has been named the responsible party in the incident by the U.S. government. It has the majority interest in the field, was in charge of its development, had leased the Deepwater Horizon and had contracted with various firms to carry out the drilling.
• Mississippi Canyon 252 (MC‐252) Incident--The Macondo Prospect was referred to by the U.S. Minerals Management Service as "Mississippi Canyon Block 252" in its lease sale. This is the terminology often used by NOAA and other U.S. government agencies in official communications.
• Gulf of Mexico Spill--This imprecise name is sometimes used in the media. There have been many oil spills in the Gulf of Mexico, and there are probably several active ones there at the moment.

How Much Oil?

Press reports and official announcements about the quantities of oil, gas and other materials released from the blowout use various units. A million here, a million there, pretty soon you're talking about a real mess. Here are some handy equivalencies.

one tonne of crude oil

approximately 7.3 barrels of crude oil

about 307 U.S. gallons of crude oil

one barrel of crude oil

42 U.S. gallons of crude oil

159 liters of crude oil

10,000 barrels of crude oil

420,000 U.S. gallons of crude oil

1,590,000 liters of crude oil

about 1,400 tonnes of crude oil

60,000 barrels of crude oil

2.5 million U.S. gallons of crude oil

9.5 million liters of crude oil

about 8,200 tonnes of crude oil

The conversions between weight measures (tonnes) and volume measures (barrels, gallons, or liters) depend on the density of the oil, which varies considerably.

Further useful conversion factors are here.

Carl Sagen "Sings" of Science (with Dawkins, Hawking, et al.)

Can the coolness of science be conveyed by a sort of synthetic music video? You decide:

[If you can't see the video, watch it at YouTube here.]

This is one of several videos created by John Boswell and his collaborators at Symphony of Science. "Boswell uses pitch corrected audio and video samples from television programs featuring popular scientists and educators. The audio and video clips are mixed into digital mashups and scored with Boswell's original compositions." Symphony of Science "aims to spread scientific knowledge and philosophy through musical remixes" and to "deliver scientific knowledge and philosophy in musical form". [Source: Wikipedia article.]

How science works: Auto-Tune, the software that "bends" spoken phrases into song in these videos, "was initially created by Andy Hildebrand, an engineer working for Exxon. Hildebrand developed methods for interpreting seismic data, and subsequently realized that the technology could be used to detect, analyze, and modify pitch." [At least according to Wikipedia.] Everything is connected?

Don't Sign If You Can't Do The Math

A recent research paper found that there was a strong correlation between basic understanding of numbers and ability of subprime borrowers to keep their homes. People who understood percents, discounts, and compounding were much more likely to be able to avoid default, even compared to less numerate people in similar economic circumstances. Math skills pay.

Here is the first numeracy question they used:

1. In a sale, a shop is selling all items at half price. Before the sale, a sofa costs $300. How much will it cost in the sale?

The study was published by the Federal Reserve Bank of Atlanta (abstract and full study here). It found "a large and statistically significant negative correlation between numerical ability and various measures of delinquency and default." The authors even say "Our results raise the possibility that limitations in certain aspects of financial literacy played an important role in the subprime mortgage crisis."

People with limited math skills caused the global meltdown?? It might be fairer to say that by lending to people with unstable or inadequate income and bad math skills lenders were lending to people likely to default, and probably knew it. It should have been no surprise when those loans went bad. If the risk hadn't been multiplied by layers of collateralized debt obligations and credit default swaps we wouldn't have had a global financial meltdown. But that's another story.

The interesting thing is that similar subprime borrowers with somewhat more robust financial math skills were much less likely to default, even controlling for socioeconomic factors. "We find a large and statistically significant negative correlation between financial literacy and measures of mortgage delinquency and default, and the finding is robust to the inclusion of controls for income, education, risk aversion, and time preferences, thus ruling out a broad set of potential biases from omitted variables. Foreclosure starts are approximately two-thirds lower in the group with the highest measured level of numerical ability compared with the group with the lowest measured level." "20 percent of the borrowers in the bottom quartile of our financial literacy index have experienced foreclosure, compared to only 5 percent of those in the top quartile. Furthermore, borrowers in the bottom quartile of the index are behind on their mortgage payments 25 percent of the time, while those in the top quartile are behind approximately 10 percent of the time."

Same income, same mortgage provisions, same problems, but moderate math skills: much lower likelihood of default. Paying attention in math class, or maybe just having a half-way competent math teacher in 7th grade, really paid off for some borrowers. "We include as control variables measures of other aspects of financial literacy and a general measure of cognitive ability, but find that the correlation is highly specific to one aspect of financial literacy: numerical ability."

To see the degree of numerical literacy we are talking about, try this quiz put together by The Economist. It uses the same five questions posed by the researchers. Here is the Economist article on the research findings. The abstract of the study is here (with access to the whole paper in PDF).

A Hard Rain's A-Gonna Fall

Researchers at the University of New Hampshire have analyzed 60 years' worth of National Weather Service rainfall records in nine Northeastern states and found that storms that produce an inch or more of rain in a day are coming more frequently. An increase in the frequency of extreme precipitation events
is one of the predicted impacts of a world warmed by heat-trapping
gases.

The researchers looked at several indicators of changing incidence of heavy rain events:

• Frequency of 24-hour periods when one inch of rain fell at a particular weather station site (a "one-inch event")
• Similarly, the occurrence of "two-inch events" and "four-inch events", when two or four inches fell at a site in 24 hours
• The frequency of extreme precipitation events, defined as the top one percent of 24-hour precipitation measurements for each year. "Changes in the threshold of the 99th percentile of daily accumulations exemplify changes in precipitation intensity" (how much rain has to fall in 24 hours to put an event in the 99th percentile for the year?)
• A third method was to define extreme precipitation events using recurrence intervals. They looked at the change in the amount of time between storms of a given magnitude.

According to each of the indicators studied extreme rainfall events have increased over the 50-year period. For 11 stations the records go back far enough to track such events from 1900 to 2007. For all of the indicators the  increases at those stations since 1948 were faster than for the whole period 1900 to 2007.

The increase in more-intense rainfall was correlated with increases in temperature seen over the period. This suggests that further increases in temperature will correlate to further increases in the occurrence of heavy rainfall events.

They also found that over the whole 50-year study period rainfall in the Northeast has an overall increasing trend of about three-quarters of an inch per decade.

The study concludes that communities are likely to experience increased flooding due to intense storms (as they have this year, for instance) and that planning and expenditure to minimize the impacts of flooding will be increasing drains on the public purse.

The report, Trends in Extreme Precipitation Events for the Northeastern United States 1948-2007, is available in PDF here.

Weird Science Words

Science Dictionary

Here are some weird science words. Be careful how you use them.

Auscultation—Listening. Especially listening to the sounds of the internal organs, as with a stethoscope.

Borborygmus, pl. borborygmi—Rumbling and gurgling noises from the intestines. Stomach "growling".

Bromhidrosis—Body odor, B.O. From the Greek bromos, a stench, and hidros, sweat.

Cacophony—Jarring, discordant sound. Cacophonous: having a harsh, discordant sound. From the Greek kakophnos, kakos, bad+ phōnē, sound. Kakos goes back to one of the oldest words we still use, the Indo-European root kakka-, to defecate.

Cacodyl—The arsenic group (CH₃)₂As, or a poisonous oil (As₂(CH₃)₄) with a strong garlicky odor. Same root as cacophony.

Emesis, pl. emeses—The act of vomiting

Eructation—Belching, burping

Flatus—The gas that comprises a belch or fart

Formication—A sensation that feels like insects crawling on the skin, a type of paresthesia. From formica, Latin for "ant".

Googol—The number 10 raised to the power 100 (10¹⁰⁰), written out as the numeral 1 followed by 100 zeros. Not to be confused with "Google", a trademark of Google Inc.

Mastication—chewing

Micturation—Urination; needing to pee

Osculant—Intermediate in characteristics between two similar or related taxonomic groups. Closely adhering or joined; embracing

Osculation—Kissing; a kiss

Oscitancy—the act of yawning

Pandiculation—The act of stretching and yawning at the same time.

Radicle—A small root, specifically the part of a plant embryo that develops into the root. Not to be confused with "radical", meaning the root (e.g. of a word), at the root, the mathematical root sign (√) or a highly reactive atom, molecule or person. Nor with "ridicule".

Sternutation—Sneezing

Stertor—The sound of snoring

Syzygy—Lots of meanings in different sciences (and in poetry, rhetoric etc.) generally having something to do with being paired, joined, aligned or something. From the Greek zugon, yoke

Vomiturition—Forceful attempts at vomiting without bringing up the contents of the stomach; retching

Vomitus—Vomited matter

Wamble—To turn or roll (said of the stomach), an upset stomach, nausea


Your assignment: Use all these words in a sentence.

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This list is revised or updated from time to time.

Do Cow Farts Cause Global Warming?

Bovine Flatulence--Threat or Menace?

Cows can digest things we can't, especially including the cellulose in grass and grain. They do this by maintaining cultures of microorganisms in their complicated series of "stomachs" that can break down cellulose. The cows then digest the microbes and the sugars and fatty acids they produce.

(Brief overview of ruminant digestion here. If you are interested in delving into the digestive physiology of ruminants in more detail, start here.)

Some of these microbes produce methane (CH₄). Some of the other microbes can use that methane as food, but a certain amount of it escapes as belches or farts (mostly belches). (Some people have microbes in their guts which produce methane, and thus their farts also contain methane--but nothing compared to the amount cows produce.)

The publication Emissions of Greenhouse Gases in the United States 2006 (pdf) summarizes the total greenhouse gas output of the US:

Of the 605 million metric tonnes CO₂ equivalent of methane shown in the graph, about 115 million tonnes CO₂e is from "livestock enteric fermentation"--mostly cow burps and farts. That is less than 20% of the methane load, and less than 2% of the 7 billion tonne CO₂e total.

Of course raising cattle causes other greenhouse gas emissions.

• There are about 56 million tonnes CO₂e of methane and 55 million tonnes CO₂e of nitrogen oxides released from cattle wastes as they decompose. (Some of that methane can be captured and used to generate electricity or heat, while releasing carbon dioxide, a much less potent greenhouse gas.)
• About 227 million tonnes CO₂e of nitrous oxide is released from nitrogen fertilization of soils (30% of it from nitrogen fixed by the crops themselves, not from industrially produced fertilizers).
• Most of the nitrogen fertilizer used on crops (89%) is used on corn (maize). About half of the corn produced in the US is fed to livestock, a large fraction to cattle, especially dairy cows. So about 50 million tonnes CO₂e emissions associated with fertilizer use should be indirectly blamed on cows.
• (Another large fraction of corn is used to make ethanol as a motor fuel, indirectly causing the release of significant amounts of greenhouse gases in the corn production. But that's another story.)

So cattle are responsible for about 3.5% of US greenhouse gas emissions, on a CO₂ equivalent basis. To keep this in perspective:

• 2% of greenhouse gas production is in the form of methane from garbage decomposing in landfills.
• Roughly 2% is chlorofluorocarbons (CFCs) from air conditioners, refrigerators and industrial processes.
• Other industrial processes (especially cement manufacture) produce about 2%.
• Burning jet fuel accounts for more than 3%.
• 12% of greenhouse gas emissions are CO₂ emitted generating electricity which is used in residential applications like lighting, TVs, computers, and refrigerators.
• 17% came from burning gasoline in cars and trucks.

So cow farts and burps do contribute some to greenhouse gases, and thus to global climate change. But they are not a major cause. Nonetheless, improvements in fertilizer use and waste management in agriculture could reduce the cow-related burden on our atmosphere.

Reduced consumption of beef and dairy products would probably have little effect. (If half of US consumers cut their consumption of beef and dairy products in half -- and the resulting drop in prices didn't stimulate the other half to increase their consumption, or drive more exports -- it would reduce national greenhouse gas emissions by about 1%.) Maybe this will become more of an issue in the future.

Update 8 May 2012: If you think cow burps are bad, recent research suggests dinosaur flatulence was a lot worse. 

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David Wheat's Science In Action site has articles about science and math in the real world, weird science, science news, unexpected connections, and other cool science stuff. There is an index of the articles by topic here.

tags: global warming, climate change, carbon choices, greenhouse gas emissions, co2, methane, cattle, cows, farts, agriculture

Science on the Small Screen

Check out these science video sites

Several sites have been set up to allow research scientists and educators to post videos of their experiments, lab projects, or results. It's a chance to see real science in action.

Scivee
The Journal of Visualized Experiments
LabAction
DNATube

There's everything from an animation about how the lac operon works to preparing T cell growth factor from rat splenocytes with a French accent to a lecture on centripetal force.

Explore to see some real scientists doing real science, as well as a lot of science stuff lifted from TV, etc.