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.

A CLOSER LOOK AT CLIMATE CHANGE (PART 1)

THE BIRTH OF MODERN CLIMATE SCIENCE



Roger Revelle was an oceanographer and earth scientist who was instrumental in advancing the field of oceanography as a leading earth science during the post World War II era. He helped to found the International Geophysical Year (IGY) in 1958, which led to the creation of NASA, and the establishment of a cluster of South Pole research stations staffed with scientists from all over the developed world. Other discoveries by earth scientists involved with IGY were the Earth’s magnetosphere and the Van Allen radiation belts, and the mid-ocean ridges, which in turn led to the confirmation of plate tectonics and the ability to map the positions of the continents throughout Earth’s history.


Part of Roger Revelle’s activities as an oceanographer was the study of ocean chemistry and the development of an understanding of the ocean’s role as a carbon dioxide (CO2) sink. He concluded that the speed of the ocean’s ability to dissolve atmospheric carbon dioxide was determined by its temperature and alkalinity, and that an equilibrium back pressure had to be overcome in order to dissolve the increasing amount of carbon dioxide accumulating in the atmosphere due to natural processes such as volcanism and to anthropogenic sources such as the increased burning of fossil fuels to support the burgeoning population of the world. Thus, in the late 1950s, was born the science of anthropogenic climate change. A further note: A young Al Gore took a course taught by Revelle at Harvard in the late 1960s when Revelle was a visiting professor there. The seed for the eventual movie An Inconvenient Truth was planted in Al Gore's mind back in that Harvard classroom some forty years ago. 

Under Revelle’s directorship and with IGY funding, the Scripps Institute of Oceanography (SIO) hired a young oceanographer and geoscientist named Charles David (Dave) Keeling in the mid to late 1950s to keep track of the build-up of carbon dioxide from a newly established SIO outpost on Mauna Loa in Hawaii. From this station high up on Mauna Loa far away from point sources of carbon dioxide emissions, such as smokestacks, factories, and power generating facilities, and upwind of the active volcano at Mauna Loa (occasionally wind shifts cause elevated readings of volcanic carbon dioxide, but these anomalous readings are filtered out of the permanent record). During the decades that followed the establishment of the SIO outpost the daily soundings for atmospheric carbon dioxide content have been entered into a continuous record known as the Keeling Curve. The curve consists of a red line (the mean) drawn through a wavy, up and down pattern that reflects the seasonal variations of CO2 over the course of each year. Over the decades since this project was initiated, the curve is clearly showing that the accumulation of carbon dioxide in the atmosphere is accelerating.

In addition to the long term increase in atmospheric carbon dioxide, Keeling’s equipment also registered some short-term phenomena which became apparent over the course or the first days, weeks, and months of the study -  the diurnal variation of CO2 in the air due to plants photosynthetically taking up the gas during the day and their discharge of it at night while respiring (breathing). A further seasonal variation appeared over the months that showed decreased CO2 level due to increased aggregate photosynthesis during the summer months in the Northern Hemisphere, where most of the Earth’s continental land mass (with its rain forests, jungles, farmlands, golf courses, etc.) is located. In Northern Hemisphere winters, where the nights are long, the days short, and many trees are devoid of leaves, photosynthetic activity decreases significantly as plants respire like animals and contribute their fair share of CO2 to the atmosphere. These are the little up-and-down grey squiggles you can see when you look closely at the Keeling Curve. The squiggles go up during the Northern winters and down after the Northern summers arrive. These phenomena were either unknown or rarely thought about by geoscientists before Keeling came along. 

Here is a look at the standard Keeling Curve: 

Note the red line superimposed on the squiggly grey seasonal variations of CO2. The seasonal CO2 variation over one year's time is presented in zoom view in the lower right corner of the chart.

Finally, there are some aspects of this chart I will discuss in more detail in an upcoming installment in this series. Stay tuned.