The Greenhouse Effect Part 3: Gas Amplifier

Transistor drawn on portuguese pavement on University of Aveiro, Portugal

Transistor drawn on portuguese pavement on University of Aveiro, Portugal. From the WIkipedia article on Transistors.

In part 1 of this series, I discussed the four laws of thermodynamics. These laws tells us that the total change in energy in a system,  dU, is composed of two parts:

dU = dQ – dW

where dQ is the heat energy added to the system and dW is the work done by the system. The Earth is such a system, and one not isolated from external heat sources (the Sun).  In part 2, we learned how atmospheric gases like water and CO2 trap heat near the Earth’s surface and prevent the Earth from re-radiating all energy received from the sun back out into space. This allows the surface of the Earth to remain at a temperature hospitable to life as we know it. That temperature is slowly increasing over time.

But in part 2, we also observed that CO2 is an inferior greenhouse gas when compared to water, which has a higher overall contribution to the atmosphere. What is the relationship between CO2 and Water in the climate disruption cycle?

Consider a transistor. Don’t know what that is? No problem – it’s pretty easy to explain. A transistor is a device that allows a large electric current to flow at the pleasure of a much smaller electric current, called the “base” current. The base current can be provided by a very low energy source. This allows for control of the much larger current. Being able to control a large current with a much more modest one is the basis of electric amplifiers. Such devices take a weak signal, such as the crummy sound from your tinny iPhone speaker, and instead use the weak signal to control a much stronger electric current. That larger current drives more energy through bigger speakers, and the result is that your puny little iPhone audio output can be AMPLIFIED by regulating a much larger current that drives more power through much bigger speakers. And voila! You have a dance party.

Weak signals that cause changes in strong signals can have a profound impact. Let’s consider that same principle applied to water vapor and CO2 in the Earth’s atmosphere.

The amount of water in the air, especially closer to the surface of the earth, varies a great deal over the course of a day or a season [1]. In a dry climate where there is little water vapor to evaporate into the air during the course of a day, the night will grow very cold very fast because there is so much less heat-trapping water vapor in the air. In a moist climate, humidity will trap heat at night and maintain a relatively high temperature, closer to the daytime temperature. We already have a lot of experience with the effect that water vapor has on a local climate.

Water changes phase very readily in response to the typical pressure and temperature conditions near the Earth’s surface. Condensation of water releases the heat of vaporization originally input the get the water to the gaseous state; this release of energy during condensation in a primary driving mechanism in placing large amounts of energy into the atmosphere, powering weather phenomena like storms. The freezing of liquid water in the atmosphere leads to formation of clouds. Gases like CO2 and CH4 (methane), however, DO NOT change phase readily during normal Earth pressure and temperature conditions; as a result, they remain in gaseous form, and thus in the atmosphere, unless taken up by biomass on the surface of the Earth or chemically converted in the air. Water, on the other hand, doesn’t remain in the gaseous state very long; water’s life cycle in the atmosphere is short – about 9 days, on average. By comparison, CO2 and CH4 can remain in the atmosphere for decades, even centuries.

So what is the amplifier here? We see that water, while a powerful greenhouse gas, has a volatility in the atmosphere controlled primarily by the local variations in temperature and pressure over the course of a day or a season. CO2 and CH4, also greenhouse gases, remain as gases and thus in the atmosphere unless consumed by biomass or other means. CO2 and CH4 are the “weak signals” – they don’t trap a lot of heat, but they do trap heat. More of these weak greenhouse gases traps a little more heat.

More heat causes more water to enter the gaseous phase as temperature increases. Adding a little more water to the atmosphere leads to a great deal more heat being trapped. While water vapor concentrations vary over the course of a single day or a season, as the average amount of CO2 and CH4 increases so does the average amount of trapped heat, and thus the average amount of water vapor concentration also trends upward. A small change in CO2 or CH4, trapping only a little more heat, can lead to more water vapor, which traps a lot more heat.

Global carbon emissions for different fossil fuels, as a function of time.

Global carbon emissions for different fossil fuels, as a function of time.

Prior to the industrial revolution, the concentration of CO2 in the atmosphere was between 260-280 ppm (parts-per-million). Measurements from Antarctic ice cores show that this range was steady for the 10,000 years preceding the industrial revolution. After the industrial revolution, the consumption of fossil fuels as an energy source began to introduce increasing amounts of carbon compounds, including CO2, into the atmosphere. See the graphic at the left, from the Department of Energy [2]. Since the industrial revolution, CO2 concentrations have increased from 280ppm to 380ppm. Half of that increase, 5o ppm, took place after 1973.

What about water vapor? Measurements of specific humidity (the ratio of water vapor to dry air in a volume of air) suggest that water has increased in concentration in air, globally, by about 0.1-0.2 g/kg-1. The data I was able to find go back to about 1975 [3]. This paper uses surface observations (on land and at sea). Other observations, such as satellite measurements of moisture content, confirm a similar trend.

So there is evidence that in our climate system, more trapped heat is leading to higher concentrations of water. The Clausius-Clapeyron relation predicts this behavior – hotter air can hold more water vapor. But water has a short life cycle in the atmosphere, condensing back to Earth as water (dew, rain) or freezing the winter into ice or snow. CO2 and other gases don’t get to do that in the Earth climate; it’s too hot, even at freezing temperatures, to condense CO2 and CH4 in liquid form. They remain in the atmosphere, free to trap more heat continuously over time.

So water is a positive-feedback mechanism for warming. A little more CO2 traps a little more heat, which puts a little more water into the atmosphere during the hottest part of the day. This traps even more heat. Water condenses out of the atmosphere at night, while CO2 remains, and the whole thing repeats the next day. Over time, less and less heat is able to radiate away from the Earth.

The consequences of this behavior on small regional scales are not completely predicted. But the cycle is there, and it begins with carbon. Breaking that cycle will take policy initiatives, not poor education. The greenhouse effect has made our planet hospitable to life as we know it. It is an inevitable by-product of the laws of physics and the chemical properties of elements and molecules. Our carbon feast, a by-product of our energy needs, feeds the greenhouse effect and increases its potency consistently over time. None of this is in dispute in the scientific community.

We all want easy answers to hard problems. Students in school just want to know the answer to problem 5, without any concern for how to solve the problem or what the answer means. When a tragedy occurs we seek to pour blame on a single cause, a single actor. We want easy answers in a complex world. But sometimes, problems like that of CO2 require us to execute a shared sacrifice alongside a difficult set of technological innovations. It’s doesn’t matter that we want a simpler answer; it matters that we have the courage to accept the true answer.



[3] Dai, Aiguo. “Recent Climatology, Variability, and Trends in Global Surface Humidity.” Journal of Climate, August 2006.

PoliSci: Huntsman on Romney and Perry

In a recent post, I noted that Republican candidate Jon Huntsman is one of only a few in the field of candidates who seems to have a clear grasp of basic knowledge about the world. Well, this week his campaign has come out swinging and reaffirmed his own excellent grasp of reality:

“We’re not going to win a national election if we become the anti-science party,” John Weaver, Huntsman’s chief strategist, said in an interview Wednesday. “The American people are looking for someone who lives in reality and is a truth teller because that’s the only way that the significant problems this country faces can be solved. It appears that the only science that Mitt Romney believes in is the science of polling, and that science clearly was not a mandatory course for Governor Perry.” [1]

Oh, snap. Too bad you’ll never win a meaningless straw poll with a basic command of the facts like that. And today he tweeted the following:

“To be clear. I believe in evolution and trust scientists on global warming. Call me crazy.” [2]

Bravo, sir, for having the courage to light a candle in the dark.



PoliSci: Perry on Science Education in Texas

Let me just give a big shout out to our Texas-sized Governor, who just set back public impressions of the Texas science curriculum about 75 years. Oh, and also thanks to our highest-ranking public official for saying that Texas public schools are in violation of several supreme court rulings that state that teaching creationism in schools is a violation of the U.S. Constitutions protection of religion from public institutions and public institutions from religion. You go, Governor – you are definitely ready for Federal government.

Also, that mother’s behavior actually makes me feel a little nauseous. Still doesn’t justify Perry’s comments, but boy do I need some ginger ale. This whole thing reminds me why I hate politics, and why I also can’t avoid politics. Soda crackers please.

As a physicist, I found his profound mischaracterization of the age of the earth both sad and disturbing. I guess I am glad he’s not a public school science teacher. Based on the best radioactive dating of rocks using their unstable isotope ratios, Earth has been dated to be 4.54 billion years old, plus or minus 1%. This measurement has been verified using different isotope ratios from different locations across the globe. That’s called science. It’s what we should teach our kids in science class.

PoliSci: Perry on Climate

Science is sometimes very helpful when trying to sort informed political candidates from uninformed ones; uninformed or misinformed candidates are likely to make bad decisions when it comes to crafting policy. America deserves the most qualified policy makers.

Today, Gov. Rick Perry got some press for his statement on Climate Change (we’ll get to that in a moment). This got me thinking about what we know about climate change and the human contribution to it, as well as what what are the different Republican candidates’ positions on Climate Change and Energy Policy.

Let’s start with the science. Here is what we know about climate change:

  1. The average global temperature has risen about 1.0 degree Celsius since the mid-1800s. This is only an average. Some areas have risen more, some less. To put this in perspective, if your body temperature increased by about 1.0 degree Celsius you would be running a fever of 101F and would require medical attention. A 1.0 degree Celsius rise  is about the same as a 2 degree Fahrenheit increase in your body temperature from 98.6F.
  2. CO2 has increased in concentration in the atmosphere since the mid-1800s, which coincides directly with the period when humans began burning coal and other fossil fuels to power the industrial revolution. CO2 is a greenhouse gas, which in larger concentrations traps more heat at the Earth’s surface.
  3. The CO2 which has been added to the atmosphere has a nuclear fingerprint that tags it as having come from sequestered carbon sources, such as buried coal and oil deposits. Carbon from near the surface of the Earth has a different fingerprint. The amount of sequestered-carbon-based CO2 in the atmosphere is the primary component of CO2 which is increasing.
  4. Increased CO2 causes heating, which causes more water to enter the vapor state. Water vapor is a much stronger greenhouse gas. The added water vapor amplifies the warming effect of the CO2. More heating and more CO2 continues to add more water vapor to the air, further amplifying the warming.
  5. The long-term climate outcomes of the added heat-trapping gases is an area of active research. Heating will be part of it, but in addition large volumes of melted arctic and antarctic ice  are entering the Earth’s oceans. Large amounts of cold water entering the oceans may have other disruptive effects on the transport of energy across the earth. Thus, while strong climate disruption is expected, it may not all be heating. What is clear is that regional climates will be disrupted; how that will happen is a matter of scientific study.

The above issues, which are the knowns in all of this science, are clearly described, detailed, and developed in hundreds of peer-reviewed papers and summarized in the last IPCC Report.

What do current contenders for the GOP Presidential nomination think about the science? Have they digested the uncontested scientific facts, or have they missed too many days of school? What are they doing with that understanding?

  • Jon Huntsman and Mitt Romney both appear to accept the scientific facts [1]. They have previously supported cap-and-trade measures to control the growth of CO2 in the atmosphere. Their heads are in the right place. Of late, since seeking the nomination, they have backed off their original statements supporting cap-and-trade. They claim they have changed their minds to protect the economy from higher energy prices. We can argue whether this is bad policy – fossil fuels cannot last forever and alternative energy will be needed to meet increased demand and decreased supply. But that is a substantive policy discussion, where the basic facts appear not to be in question. Tim Pawlenty, now no longer in contention for the nomination, also backed off of cap-and-trade.
  • Michelle Bachman has come out strong in denial of the basic facts of climate. In fact, her ignorance runs deep into ignorance of basic chemistry and physics. “Carbon dioxide is natural. It occurs in earth . . . Carbon dioxide is not a harmful gas. It is a harmless gas,” [1] she said during a floor debate in the House on cap-and-trade. Her policy choices will be necessarily ill-informed, if not reckless. She needs a good science advisor, somebody with backbone. Arguing that CO2 is harmless, in this specific case, is like arguing that putting a fence around your pool to keep your toddler from falling in is senseless because water is natural.
  • Ron Paul has command of some facts, but misses the whole picture. “There is clear evidence that the temperatures in some parts of the globe are rising, but temperatures are cooling in other parts. The average surface temperature had risen for several decades, but it fell back substantially in the past few years. Clearly there is something afoot. The question is: Is the upward fluctuation in temperature man-made or part of a natural phenomenon.” [2] He goes on a small sidestep, talking about previous warming periods (which had nothing to do with the causes of the current period). Then he finally gets around to saying, “It is clear that the earth experiences natural cycles in temperature. However, science shows that human activity probably does play a role in stimulating the current fluctuations.” Ron Paul advocates removing subsidies for oil and coal, allowing their prices to normalize in the market, and causing pressure to develop alternative energies. Again, here we reach a substantive policy discussion that is built on top of an acceptance of the scientific knowns.An addendum to the Ron Paul story. When climate researcher emails were stolen and released on the internet, this causes a false stir about scientists “making up” climate change. Four independent reviews of the people involved in the mails, and the wider scientific community, cleared all doubt about the integrity of the scientific process. Ron Paul, however, jumped on the bandwagon of people using this as a chance to ignore the science and try to take the cheap way out of a substantive policy discussion. “The greatest hoax I think that has been around for many, many years if not hundreds of years has been this hoax on […] global warming.” [2] Foo on you, Ron Paul.
  • Rick Perry has entered the race for the GOP nomination. On Wednesday, Perry called human-induced climate change “a scientific theory that has not been proven.” [3] Ironically, Perry seems to be a victim of the kind of very poor science education policies he tried to shove on the State through appointment of fundamentalist Christians as chairs of the Texas State Board of Education. First of all, scientific theories explain facts; they are better than facts. So by definition, a theory has been proven. “I do think global warming has been politicized. … We are seeing almost weekly or even daily scientists are coming forward and questioning the original idea that man-made global warming is what is causing our climate to change. Yes, our climate has changed. It has been changing ever since the Earth was formed. But I do not buy into a group of scientists who have, in some cases, been found to be manipulating data.” None of what Perry says is true. Not only is he in zero command of the basic science, he seems to be mis-leading his supporters. The debates in the scientific literature are about the severity of impacts and the kinds of impacts, not whether there will be impacts. Nor is there scientific disagreement about the existence or cause of warming trends. He uses mis-direction by noting climate has changed in the past; that’s smoke and mirrors, meant to distract you from the truth that humans have been leading this one since the industrial revolution.
Indeed, science provides a valuable litmus test for us in this early stage of the Republican primary. The question remains: will Republicans choose to nominate someone who cannot command a basic understanding of established scientific fact, or will they choose a leader and a strong policy maker?