A Look at Global Warming

I had fun writing about the Bill Nye and Ken Ham debate, and I realized just how much I’ve been wanting to start a sort of series of notebook posts. Since graduation, I’ve been trying to stay sharp by compiling personal research, and I thought I would share some.

I would like to tackle a number of subjects, particularly involving pseudoscience or debates about science.  These would be informative, both for me, and for any readers. While I can’t give a specific time frame, I now intend to make at least four other posts, addressing climate change, energy production methods, GMO’s, and vaccines. Additionally, I might make a larger more comprehensive post on young earth creationism, since that particular brand of pseudoscience seems to be my mortal enemy.

On its face, global warming is pretty simple. Most people can recite the basic mechanism easily enough. CO2 doesn’t stop sunlight, so it allows heat in. However, once this light strikes the Earth, excited molecules scatter infrared light off of the planet’s surface. This long-wave light is absorbed by CO2, preventing the escape of heat.  Some will point out that all infrared light in the CO2 absorbance spectrum is already currently being absorbed by CO2, claiming that this means the greenhouse effect is “saturated.” This supposedly means that adding more CO2 will have no further effect. There is some truth in this. One common info graphic shared by both sides of the debate (1)  appears to show that 100% of the infrared light in the CO2 absorbance range is already being absorbed. So if we add more, what difference will it make?

This argument makes a number of assumptions however. One is that all of the infrared light currently absorbed by CO2 just vanishes. If this is what you visualize, then visualize again. A CO2 molecule absorbs infrared light, then re-emits it. (2) So instead of picturing a solid wall that stops infrared light from escaping, picture a bunch of pegs slowing the progress of little metal pinballs (representing infrared light.) The pegs make the balls bounce around between them, but eventually, they will allow them to escape. So if you add more pegs, then it takes even longer for the balls to bounce their way through them. However, the pegs cluster more close to the ground, and are less dense at high altitudes where the air is thinnner. In effect, this means that as you add more CO2, the height at which infrared can freely escape the atmosphere climbs higher and higher, allowing more heat to build up. Skeptical science actually explains it better than I just did. (3) If the warming region of the atmosphere climbs higher and higher, that effects convection. If there is less cold air in the layer of the atmosphere adjacent to ours, then heat will not be sucked up from ground level as quickly.

For a more credible albeit more difficult source describing these dynamics, see this paper published in 1931. (4) Yes, it’s old news.

Another, more simplistic argument against global warming is that CO2 exists in very small quantities. It’s true that CO2 is currently only about 395 parts-per-million (ppm) of the atmosphere, up from the pre-industrial  280 ppm. However, the major issue with CO2 is that it absorbs light in the infrared spectrum, and small concentrations of things can drastically influence light absorbance. This is the basis for spectrophotometry, which is used in laboratories all across the world to measure compounds at both high and low concentrations. It does this by bombarding a sample with a spectrum of light that is absorbed by the compound of interest.  In fact, if we look at one such device sold by Wilks Enterprise Inc. (5) we can see that it is capable of detecting CO2 levels as low as 3 ppm, purely based on its ability to absorb light at the 4.25 µm wavelength.

However, there is a much simpler example of this phenomenon. This video (6) demonstrates the difference between water containing 0 ppm, 280 ppm, and 560 ppm of ink. Just as CO2 absorbs infrared light, ink absorbs visible light (that’s why it’s black).  You can clearly see that even hundreds of ppm drastically impact the water’s ability to absorb light in the visible spectrum.

Now that I’ve written a bit about the mechanism, I think I should go over the history of global warming, about which many people have major misconceptions. Many will claim that global warming is a recent speculation that came only after the supposed “global-cooling” scare of the 1970’s. I bought into this myself at a younger age, because of the massive misinformation I was exposed to. Later, I found that this was not the case at all. It has long been acknowledged that aerosols can scatter sunlight, and cause “global dimming”, and some have suggested that this might overpower the greenhouse effect and cause net cooling. However, this is not the same as denying the greenhouse effect altogether. It is only a debate over which of two man-made pollutants has more influence. Even in the 1970’s, more scientists favored CO2 as the stronger influence, and predicted warming being the end result. (7)

I was further shocked to learn that the origins of global warming goes back much further than this though, starting with Svante Arrhenius, who predicted warming due to CO2 in his 1895 paper (8), “On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground.”

This paper was dismissed early on for a number of reasons. One was that it was clear that water vapor already absorbed much more infrared light that CO2 did. At the time, it was believed that CO2 and water vapor both absorbed light around the same frequency, so this would mean that most of the heat energy that could be trapped by CO2 was already being trapped by water vapor. Also, it was understood even then that the greenhouse effect due to CO2 was logarithmic, not linear. In other words, doubling CO2 will not double the warming effect.  Proponents of global warming admit that doubling the CO2 content will only increase the temperature by about 2.3 degrees Celsius, give or take. (9) Because of the geometric rather than linear correlation between CO2 and temperature, some past scientists like Angstrom dismissed this as inconsequential.

However, this is not a claim that can be easily made. The term the “butterfly effect” is very apt when applied to climate and weather, where even a small change can have drastic effects. For instance, one degree on average can mean a 10% difference in tropical rainfall. (10) This is just one of many examples of how volatile and unpredictable climate can be.

By 1938, the engineer Guy Stewart Callendar had begun the movement to reevaluate the role of CO2. (11) In particular, he pointed to newer, more accurate data showing that CO2 and water vapor absorbed different wavelengths of infrared light. Some fraction of the earth’s infrared light cannot be absorbed by water vapor, but can be absorbed by CO2, so even if the atmosphere was totally saturated with water vapor, an increase in CO2 would still have a warming effect.  He also demonstrated a warming trend of about 0.005°C. per year over the past 50 years.

By the 1950’s, global warming was gaining support, and becoming somewhat popularized to the public, as shown by this old propaganda video. (12) This may surprise some people ,who have been lead to believe as I once did, that global warming was something invented fairly recently after the whole “global cooling” scare of the 1970’s didn’t pan out. In fact, the global cooling scare was largely manufactured by the media, not science.

Others have pointed to a number of other cycles that also effect climate. To be sure, there are other factors than CO2 at work, and all climate scientists are no doubt aware of them. Perhaps the largest impact on climate is caused by the sun. There’s an 11 year cycle of solar irradiance. Every 11 years, the sun enters a new cycle, which is generally of a different intensity than the previous one. The current cycle seems to be weaker than the previous one, so if anything, the sun should be causing the climate to be cooler right now. Additionally, the type of warming associated with increased solar activity is supposed to extend to the stratosphere, which the current warming does not.  (13)

In addition, there is the El Nino/ La Nina cycle, associated with hot and cold air over the pacific respectively. These alternate every two to seven years. So if you wanted to show that the Earth is not warming, you could  easily do what climate change skeptic Christopher Monckton (14)  did when he claimed the Earth was cooling: pick out a strong El nino year like 1998 for your start date, and then end it at the weak-end of a solar cycle. Climatologists take these cycles into account when calculating the climate trend, but most people will not.

When someone denies that the Earth is warming, they generally leave out the numerous factors that should be cooling the Earth, such as the cycles previously mentioned. However, if one removes the noise caused by el nino/la nina oscillation, solar activity, and aerosols, one finds an even more pronounced warming trend. (15) This may seem like chicanery at first glance. After all, how do we know that these adjustments for the solar and el nino cycles reflect reality? However, to treat all years equally regardless of other cycles is also doomed to failure, so attempts to account for them must be made. Also, accounting for the solar cycle and el nino/la nina is a double edged sword; it forces you to dismiss periods of abnormal warmth as well as periods of abnormal cold due to these factors, so it is essentially fair.

One might take issue with the way the impact of these cycles were calculated, but thankfully, there is another way to factor them into the climate calculation; focus on multi-decade long cycles. If you look at long term trends rather than short term trends, the “noise” from these additional natural cycles like el nino and solar activity cancels out. If you look at the long-term graphs, measuring from way back in the 19th century, the trend is very clear. (16) Notice that the most recent data points do not appear to be part of a linear trend. If you tried to plot the last five points, you’d get a hopeless zigzag. Only by zooming out, and looking at the big picture, does the trend emerge. This is not preferential data analysis; in almost all statistical analysis, larger sample sizes are less prone to random noise and other forms of natural interference.

A number of misconceptions also arise from the debate over whether or not the warming is statistically significant, and whether or not it is happening. To the average person, no statistically significant warming means no warming, but this is bad science. For one thing, it’s often claimed that warming has not been statistically significant since 1995, but as we’ve established, short intervals don’t really hold as much weight in statistical analysis. Go back to the graphs showing long-term trends (16), and observe how easy it would be to cherry pick a time interval that seems to disprove the obvious long-term warming trend.

Three graphics on skeptical science.com demonstrate this very well. (17) First, they show how easy it is to find a high peak, and simply draw a line to a low point in order to manufacture a “cooling trend”. Secondly, they show that the long term trend is one of warming. Thirdly, and most informatively, they show how you can isolate a series of fairly flat lines from that warming trend, if you slice it up just right.

Another point involves the meaning of “significant”.

First of all, you have to be careful with statistical analysis. In one of my biology classes, a classmate did statistical analysis on the effects of sulfuric acid on plant growth. They arrived at a p-value just beneath the statistical significant threshold. From this, they came to the ridiculous conclusion that sulfuric acid was not harmful of plants. In reality, the concentration of the acid was probably just below what would be necessary produce totally unambiguous harmful effects. The flaw here should be obvious; real world correlations can sometimes fall just below the line of what is generally considered “significant.” If they fall way short of the mark, that’s good evidence against a correlation, but if they fall just short, say p=0.06 instead of 0.05, that’s what any honest scientist would call an inconclusive result. However, when the results are this inconclusive, the context and variables involved can go a long way to influencing the interpretation of the result.

More importantly, time interval is a factor here. It is much more difficult to prove the statistical significance of a short time interval than a long one. If something strange happens once, that could be nothing. If it happens repeatedly for decades, you can claim an anomaly much more easily. As we have seen, a 15 year interval is not that long in terms of climate cycles, so solar activity or a la nina event could easily explain away any trend within this time range.

So don’t be surprised when you hear people claim there has been no statistically significant warming for “X” amount of years. They are just narrowing the time range because they know that subtle trends are less statistically significant over short periods than over long periods. Even if the trend is the same, shortening the time interval will decrease its significance, so cutting the graph into 15 year periods is cheating in a sense.

To be fair, there will always be some uncertainty as to how much of an effect we have on the climate. It is such an insanely complex system that even weather prediction is difficult. Most experts agree the the effect of man-made CO2 is nonzero, but we may not necessarily know how large it is. However, as I hope I have shown, the data is nowhere near as ambiguous as some people would like to claim, and the basic physics behind global warming is pretty hard to deny.

1)    http://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Atmospheric_Transmission.png/595px-Atmospheric_Transmission.png

2)      https://spark.ucar.edu/carbon-dioxide-absorbs-and-re-emits-infrared-radiation

3)      http://www.skepticalscience.com/saturated-co2-effect.htm

4)      http://journals.aps.org/pr/abstract/10.1103/PhysRev.38.1876

5)      http://wilksir.com/infraran-specific-vapor-analyzer-ordering-information.html

6)      http://www.youtube.com/watch?v=81FHVrXgzuA

7)      http://journals.ametsoc.org/doi/abs/10.1175/2008BAMS2370.1

8)      http://rsclive3.rsc.org/images/Arrhenius1896_tcm18-173546.pdf

9)      http://www.sciencemag.org/content/334/6061/1385.abstract?sid=a7ab01bf-f2e5-413d-bbf0-c2c5ac2362df

10)   http://thinkprogress.org/climate/2012/09/18/868661/mit-study-for-every-1-degree-c-rise-in-temperature-tropical-regions-will-see-10-percent-heavier-rainfall-extremes/

11)   http://onlinelibrary.wiley.com/doi/10.1002/qj.49706427503/abstract;jsessionid=C31A6DD4ACEA76E0FEC5B0FCDB6F3391.f02t01

12)   http://www.youtube.com/watch?v=T6YyvdYPrhY

13)   http://earthobservatory.nasa.gov/Features/GlobalWarming/page4.php

14)   http://www.concordy.com/section/article/on-global-warming-cherry-picking-and-publishing/

15)   http://iopscience.iop.org/1748-9326/6/4/044022

16)   http://data.giss.nasa.gov/gistemp/graphs_v3/

17)   https://www.skepticalscience.com/global-cooling-january-2007-to-january-2008.htm

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