A CLOSER LOOK AT CLIMATE CHANGE (PART 6)

IS CO2 CAUSING CLIMATE CHANGE? OR IS CLIMATE CHANGE CAUSING CO2?

Revised 8/6/2011

Back in the 1950s when Roger Revelle was pondering the relationship between atmospheric CO2 and the oceans (CLCC - 1), he concluded that the oceans weren't an unlimited sink that would go on dissolving CO2 forever and keep atmospheric concentrations from getting out of hand. The so-called "Revelle Factor" is a measure of the resistance of the ocean's surface to dissolve CO2 because CO2, the gas, has to dissociate into bicarbonate ions (HCO₃^-).  and carbonate ions (CO₃⁼ ) at the water's surface in order to enter into solution. Thus, there's a chemical equilibrium established between the HCO₃^- and the CO₃⁼  ions at the

sea surface and the molecular CO2 in the air. The equilibrium of the current system is such that for every ten additional ppmv of CO2 in the air, only one ppmv of CO2 dissociates at the ocean's surface and goes into solution.   Now, the argument that proponents of Anthropogenic Global Warning (AGW) are trying to make is that CO2 is entering the atmosphere because of "human activity", which is true, but human activity may not be the whole story. Here's the argument some scientists are making: - Global warming is causing more CO2 in the atmosphere.  
As any high school chemistry class teaches, many chemical reactions are reversible. Anything that disrupts the equilibrium of a chemical system will drive the reaction either forward or in reverse until equilibrium is regained. So we have a system in which the dissolved carbonate and (predominately) bicarbonate ions in the sea are in equilibrium with the CO2 molecules in the air. If the oceans are heating up, which we're told they are, the equilibrium will be shifted towards dissolved CO2 (in its ionic forms) reconstituting into airborne CO2 molecules at the ocean's surface and entering the atmosphere. It's a two-step process that looks like this:

Warmer <--------------------------
(carbon dioxide molecule) CO₂   +   H₂O  ⇌  H₃O⁺ + HCO₃^-  (bicarbonate ion)
                     

 (bicarbonate ion)   HCO₃^-  +  H₂O ⇌ H₃O⁺ + CO₃⁼  (carbonate ion)
------------------------------> Cooler

So, in a nutshell, the CO2 in the atmosphere is in equilibrium with bicarbonate and carbonate in the ocean. A warm ocean tends to drive the whole reaction to the left to produce carbon dioxide from its water solution (a process known as outgassing). Cold water will cause the equilibrium to shift to the right, causing more carbon dioxide to enter into solution in the ocean.
It's easy to visualize this when you consider that 98% of the total CO2 on the planet's surface is dissolved in the oceans as carbon dioxide, bicarbonate, and carbonate. Only 2% is in the air, so it doesn't take a really big equilibrium swing to push some of that dissolved 98% CO2 abundance out into the air.


So how could the oceans be heating up by themselves - without any help from the man-made greenhouse effect? It would have to be the sun, according to many astrophysicists, one of which is Dr. Willie Soon of the Harvard-Smithsonian Center for Astrophysics, whom I referenced in my previous post. Let's have another look at the Hubert Lamb chart (the bottom one):

Let's compare that with a record of observed sunspots encompassing the same time period:

This chart tracks sunspot activity over the course of the last millennium. It's kind of a funny chart - it's read from right to left, with the recent past expressed on the left side of the chart. In other words, it's a backwards chart.
Now if you could flip this chart around and compare it to the climatic data from Hubert Lamb, you'd see a striking resemblance. Here's another sunspot chart that can be read the normal way - from left to right:
                              
This is a zoomed-in version - it only shows the last 400 years beginning with the Maunder Minimum - which coincides with the Little Ice Age. From about 1665 to about 1700 there were only about 1/800th as many sunspots as usual. Relatively speaking, the sun was taking a long nap.                 

According to astrophysicists, more sunspot activity means a more active, hotter sun. The connection between sunspots and the climate was cited by astronomer John A. Eddy in a paper he published in 1976. Historical records of sunspot observations were meticulously consolidated in the late nineteenth century by Gustav Spörer and Edward Maunder that included post-Galileo telescopic observations and pre-Galileo naked-eye observations of the sun when it was low in the sky. Eddy supplemented the Spörer - Maunder data with proxy data obtained from carbon-14  (¹⁴C)   levels found in tree rings. There's an inverse relationship between solar activity and the presence of  ¹⁴C that is, when ¹⁴C levels in tree rings were low, solar activity was high, and vise versa. Tree rings, by the way, are also a means in determining temperatures in the past, they can establish a direct link between temperatures and solar activity.  

Many stars show a variation of luminosity over time - they pulsate because of back-and-forth equilibrium shifts in their cores. The sun isn't a particularly large star - it's known as a "yellow dwarf", although it radiates strongest in the yellow/green frequency range (flash a glance up at the sun or at a reflection of the sun in a windshield and you'll see a pale green disc). Being a smaller star, the sun is more stable than the bigger ones, and its luminosity pulsations are much smaller in magnitude than massive stars. Moreover, the time scales of these variations are measured in decades and centuries rather than every few days as with the bigger stars. The Lamb chart, in fact, appears to show a roughly millennial cycle, with temperatures once again on the upswing after being cooler for more or less five hundred years since the end of the Medieval Warm Period, which itself began over a thousand years ago. These are general trends - on shorter timescales there appear to be hiccups of cooler or warmer trends within the longer millennial trends. In fact, since about 2000 we appear to be experiencing a leveling off or even cooler burp which coincides nicely with diminished sunspot activity since about 2000 (Revision: The decade 2001-2010 has turned out to be one of the warmest periods in decades. Some experts are predicting the current decade 2011-2020 will be cooler. They cite the PDO (Pacific Decadal Oscillation) and the AMDO (Atlantic Multi-Decadal Oscillation) compounding each other to influence global temperatures, that is, they reinforce each other at times and cancel each other at other times, that is, they establish a resonance which repeats roughly every thirty years. Thus, the period of 1980-2010 was warmer than the long-term average[similar to the warm period of 1915-1945, which peaked in intensity during the Dust Bowl years]. Moreover, the La Nina - El Nino phenomena plays a major role as well. The second or third strongest La Nina of the past 100 years is blamed for the extreme temperatures and drought conditions in much of the Continental US this summer. At the same time, the Pacific Coast has experienced much cooler than average temperatures.) 
On a mucher longer scale, proxy evidence holds that there have been warmer periods interspersed with cooler periods over several thousand years. There was a substantial warm-up during Roman times, and another one during the Minoan Civilization between the 15th and 20th centuries B.C., each warm period being followed by a cool one.

Many paleoclimatologists believe that, historically, CO2 concentrations follow the earth’s temperature up and down over time instead of the other way around. In other words, when the sun is more active and heats up the Earth, more CO2 enters the atmosphere, and when the sun takes a nap the Earth cools and CO2 dissolves back into the oceans and seas.


The paleologic record, however, is inconclusive on any hypothetical link between global temperature and CO2 concentrations - there are a lot of complex variables that determine climate over vast timescales, so the warming-leads-to-CO2 theorists will have to rely on sunspot records and historical anecdotal evidence going back centuries, or at the most, millennia, to argue their case. Nevertheless, here are some paleologic charts to illustrate how difficult it is to make a convincing argument one way or another. Note: these charts are laid out temporally from right to left - they're backwards.

ABOVE - a temperature chart covering the last 550 million years

ABOVE - a temperature chart of the last 600 million years – pretty much the same as the one above it. Note that today's temperature is the lowest global temperature in more than 600 million years. 

ABOVE: A chart of the CO2 concentration in the atmosphere during the last 600 million years

ABOVE - a composite chart of CO2 and temperatures over the last 600 million years. The temperature is the blue line, the CO2 is the orange one. Sometimes the temperature follows the CO2 down, sometimes it follows CO2 up, yet other times the temperature takes the lead and CO2 follows. And in several instances the temperature is skyrocketing when the CO2 is in virtual freefall. Of particular note: The earth was hottest at the beginning of the Mesozoic Era (about 251 Mya), a sizzling 22° C, at a time when the CO2 was at its lowest concentration of the distant past.

Finally, here's the chart I put up in Part 4 (CLCC - 4) - the one where the temperature readings are exaggerated. This is a very crude chart - with data points every fifty million years. The data points represent the average values of each parameter for each of the 12 periods from the Pre-Cambrian to the present epoch.
There is a vague resemblance to the more precise graphs above, especially the CO2.       Stay tuned.