World Environment Day 2018

It is World Environment Day, 2018.  A perfect day to write my first blog.

To be perfectly honest, the rate of global warming gives me the willies.  I can't even discuss the topic with Natalie because just thinking about the ramifications of rapid climate change terrifies her so much.  She has said that she doesn't know what she can possibly do to make a difference, so why even talk about it.  I understand her reaction.  I really do.  But, for me, I need to know.  I need to know how climate change works and I need to figure out what I can do about it.

Some years ago, I had a back-and-forth email exchange with my brother, Mark, about climate change.  At the time, he believed it was a storm in a teacup.  As I recall, Mark accepted that global warming was occurring, but he didn't believe humans were responsible.  I'm sure he'll correct me in the comments if I've mis-characterised his point of view.

Mark also had the opinion that 'climate science' was an academic swindle perpetrated by researchers focused on winning grant money.  I'm not entirely sure why this argument seems so convincing to people.  To my knowledge, conspiracy theories rarely turn out to be true.  There are genuine conspiracies, of course.  Think of the Manhattan Project.  Think of Watergate where Nixon was caught in a conspiracy.  Think of the conspiracy perpetrated by Islamists on the World Trade Centre and the Pentagon, now known as 9/11.  These genuine conspiracies illustrate the fact that it is difficult to pull off a conspiracy that involves a large number of conspirators.  Also, the longer a conspiracy has to be maintained, the more chances there are of the whole thing unravelling.  The idea that thousands of scientists around the world are involved in a conspiracy is a real stretch.  I mean, aren't they the ones with the data?  The data is what it is.  If the data did not support the hypothesis that there was a human fingerprint on climate change, surely there would be a groundswell of young idealistic scientists speaking up about it?  Instead, what we see is a small group of mostly old or retired scientists, often speaking outside their area of expertise, denying the consensus view.

To improve my own understanding of the greenhouse effect, I decided to do my own study.  All the science sources say that CO2 is the most potent of the greenhouse gases.  Most of these sources provide a rudimentary 'kindergarten' version of the greenhouse effect, along the lines of 'CO2 acts like a blanket, trapping heat in our atmosphere.'  Sorry, but that's not good enough for me.  I need to know some detail.

What I learned:

CO2 is a molecule with one carbon atom and two oxygen atoms (see below).  As a structural engineer with research experience in dynamics, I know that structures vibrate at specific frequencies in response to applied loads.

It turns out that the CO2 molecule has the exact same response when it is hit by a photon which is vibrating at just the right frequency.  The CO2 will absorb the photon and vibrate for a little while at its resonant frequency (high energy state).  Then, the CO2 molecule will stop vibrating and emit a photon (low energy state).  The next image shows the four different vibration patterns of the CO2 molecule.  These patterns of vibration are known as modes.

The bending modes of CO2 (i.e., the two patterns on the bottom) are relatively easy to excite.  CO2 will capture photons vibrating at 20 TerraHerz (THz).  The symmetric stretching mode (top left) is excited when the CO2 is hit by photons vibrating at 40 THz and the asymmetric stretching mode (top right) is excited by photons vibrating at 70 THz.  All of these frequencies are in the infrared range.  Red light is visible to human eyes from about 384 THz, so all of this 'catching and releasing' of photons by CO2 occurs outside our visual range.

[ Here is a cool aside.  It turns out that the reason we feel heat from infrared light, but not from visible light is because our bodies are mostly made up of water H2O.  Much like CO2, H2O also absorbs light in the infrared range making our water molecules vibrate at a higher energy state for a while. ]

So, what does all this have to do with global warming?

Well, it's remarkably simple and straightforward physics actually.  Most of the light, and, therefore, most of the energy, that comes from the sun, which is about 5,800 Kelvin, is in the visible light range (see image below).  When this energy reaches earth's surface, some of it is reflected back into space off white surfaces such as snow and ice, but a lot of it is absorbed into the earth.

The earth is much colder than the sun (about 300 Kelvin) and radiates energy back out to space.  Most of the light radiated by the earth is in the infrared range (see below).

The CO2 and other greenhouse gases in the atmosphere capture photons that are vibrating at their resonant frequencies.  They vibrate at higher energy levels for a bit, then spit out new photons in any direction.  Roughly speaking, half of those photons shoot off into space and half of them shoot back down to earth, warming the earth just a little bit.

So, we have an idea we can test against observations.  If the greenhouse effect is actually causing more infrared radiation to be radiated down to earth's surface, then we should be able to measure an increase in surface downward longwave radiation.  What do we find?  Well, Wang and Liang (2009) used long-term meteorological data from 3,200 weather stations around the globe and found an average increase of surface downward longwave radiation of 2.2 Watts per square metre per decade.  The authors show that this increase in radiation is due to the increase in air temperature, water vapour, and CO2 concentration.

The greenhouse effect seems to be an accurate mechanism and explains all the data quite well.  Warming will continue for a long time after we are dead.  What world will be leaving for our descendants?

My indigenous ancestors, living on Worimi land, existed in harmony with their environment.  Their way of being was one of connection to country; being a part of their ecosystem.  Our modern society has gifted us with a richness of harnessed energy and technological innovation that has improved our lives in so many ways.  And yet, it feels to me as though we have been spiritually removed from our connection to country, our connection to this earth and the remarkable gift of life.  We view ourselves as masters of the earth; somehow set apart.  This is not a sustainable way of being.

Let's not cut the branch off while we are sitting on it.

We need our industries to plan for the ultra long term.  Can they sustain their business activities indefinitely?  How can they justify their business plans in an economy where the costs of greenhouse gases are accounted for?  What decisions can we all make as individuals to ensure that our descendants can enjoy the lifestyles that we have enjoyed?  Can we reduce our reliance on dirty power sources?  Can we reduce our consumption of meat?  Can we spend less money on material goods?  Can we direct our superannuation funds to invest our funds only in companies that behave ethically and are environmentally responsible?

I don't have answers and I struggle with some of these issues (particularly cutting down on meat).  But I think these issues are of fundamental importance.

Reference:
Wang, K., & Liang, S. (2009). Global atmospheric downward longwave radiation over land surface under all-sky conditions from 1973 to 2008.  Journal of Geophysical Research, 114, D19101.