Global Warming Science (Part 1)

Global warming is real, is caused by people, and its consequences are likely to be catastrophic.

The deniers favorite lie is that climate scientists are greedy nerds spreading a false alarm in order to get grant money.  You don't have to know anything about science or scientists to pop that bubble: the denialist side pays much better for almost no work.  Real easy money for anyone with have Prof in front of thier name or PhD after it, and a middling talent for lying.

Thanksgiving is coming and will be an angry time around many US dinner tables.  In preparation for the arguments about climate change, I am posting information about the basic science of global warming.  The science is not new.  It started in the 19th century and ended fifty years ago with a series of measurements that proved global warming's inevitability.  Those results have been validated again and again.

In 1896, Swedish chemist Svante Arrhenius published that described the potential for global warming due to the burning of fossil fuels.  Here is the first page of that scientific article.  Note that "Carbonic Acid" is carbon dioxide (CO₂).

That first page tells us a lot that Arrhenius and his contemporaries knew a great deal of sophisticated physics.  It is impressive to realized that they article was written during the era of Sherlock Holmes.  Telegraph was the dominant form of communications.  No radio.  Automobiles were rare.  Airplanes non-existent.  But, the scientists understood the key factors that influenced global temperatures.  They knew the obvious, that the Earth is warmed by the sun.  

They also understood how the Earth cools at night.  Everything glows with infrared light that is light that we cannot see.  Warmer objects glowing more brightly than cooler ones.  Nighttime cooling occurs because the infrared light streams up through the atmosphere and into outer space, taking away much of the daytime warmth.  

What about "the Influence of Carbonic Acid...?"  Arrhenius references an article by Charles Joseph Fourier published in 1827 that described the role of heat-absorbing gases in keeping the planet warm.  Not all of the infrared light that is emitted by the Earth makes it through the atmosphere and into outer space.  Some of the light is captured by trace gases that are part of our atmosphere.  The infrared light is absorbed by the gases just as white light is absorbed by black pigment in paint. Carbon dioxide is the most significant gas.  The infrared light heats the molecules of CO₂ that, in turn, heat up the surrounding air that then warms the ground.  This is the greenhouse effect.  More carbon dioxide in the atmosphere would mean less infrared light (less heat) escaping.  The globe would warm.   

In 1896, no one knew if carbon dioxide added to the atmosphere would stay in the air.  Other outcomes were possible.  The extra CO₂ might dissolve into the oceans or it might accelerate plant growth.  Carbon dioxide measurement technology was not good enough -- not precise enough -- to determine if the CO₂ concentration was changing.  

Charles David Keeling answered the CO₂ question by an series of careful measurements that began in the late 1950's.  Keeling had figured out how to measure precisely the amount of carbon dioxide in the atmosphere.  He made measurements day after day for several years.  The results were conclusive.  Carbon dioxide concentrations were going up, and global warming was inevitable.

Here are a half-century of data showing the carbon dioxide concentration increasing from 315 parts per million (ppm) to just under 400 ppm in 2010.  This type of graph is known as a Keeling Curve. The rapid, small up-and-down variations are due to seasonal variations caused by the different growing seasons in the northern and southern hemispheres.  The big upward trend is due to us.  

  

Modern climate research is not about whether or not global warming will occur.  That question is long settled.  Today's research looks as how high temperatures are likely to go, how quickly, which areas will get hotter, and which areas might even cool, and what are the consequences.  In nearly every case, the consequences are not good.