Ocean Cooling with Expansion?

While visiting Robert Bidinotto's Blog, I found a note he had written on an account called The Mystery of Global Warming's Missing Heat by Richard Harris of NPR. This article discusses the Argo buoy system finding that the oceans are not only not warming, but they are if anything cooling slightly. But, Harris goes on to note that in the last 4 years in which these measurements were made, the oceans also rose about 0.5 inches. It is said there that this is a lot. In general, the Global Warming alarmists have been cranking up the fear that there will be very great sea level increases due to man emitting more CO2 into the atmosphere. Certainly 0.5 inch is not a lot, except that those of this alarmist mindset have a tendency to project change at the rate measured over short times far into the future if it is consistent with catastrophe. Ofttimes, they will even assume positive feedbacks that amplify the rate of change in the future.

Wikipedia has an article called Sea Level Rise. There is a plot on the first page showing the rise in sea level since the last Glacial Maximum about 21,000 years ago. There has been a rise of sea level of about 125 meters since then. However, for the last 7,000 years, there has been little change in sea level, but there is a slightly positive slope to the data since then. Since about 1910, there has been a roughly linear increase in sea level of about 20 cm or a bit less than 8 inches, according to the first graph in the article, titled Recent Sea Level Rise. If you examine the fluctuations in that curve, you will see that in the mid-1980s to the early 1990s there is a sudden dip in sea level followed by a rapid increase. These changes were at least 3 cm, or about 1.2 inches. Still, the overall averaged curve before and after that time is approximately linear. With this perspective, a 0.5 inch change in 4 years is not a reason to throw industry and the automobile upon the scrapheap. They would love to tie humans down to propelling grind stones by walking in circles hour after hour and put horses back on our roads.

The NPR article mentions ice melting in Antarctica and Greenland as a possible reason for the sea level increase in the last 4 years, since there has been no thermal expansion of the ocean water due to increased temperature in that time. However, with most of Antarctica experiencing an increase in ice cap thickness, while only the western peninsula is losing ice, it is not clear that the Antarctica effect is very large or even a positive one. Greenland also has areas of receding glaciers and others with ice thickness increases. There has been recent growth of ice in western Greenland and in the interior regions, while there has been loss of ice near the sea on the eastern side. What is the net effect on the sea level?

There are other factors that affect sea level:

• Sediment washed into the seas
• Changes in the salinity of ocean water
• Changes in the amount of dissolved gases such as oxygen and carbon dioxide.
• Earth rotational variations or Chandler wobble
• El Nino/southern oscillation
• Tectonic plate movements
• Volcanic creation of new land masses in the ocean
• Earthquakes dropping land into the sea or opening new chasms undersea
• Atmospheric humidity
• Changes in water in lakes, rivers, soil, and minerals on land
  

These factors are not commonly going to be constant over any 4 year period of time. The Wikipedia article also notes that the TOPEX and JASON satellites making sea level measurements since 1992 have determined a 2.9 +- 0.4 mm sea level rise since 1992. This is an error of about 14% and the error over any four-year period is probably substantially larger. So, there is likely to be significant error in the 0.5 inch measurement.

It would be very interesting if a contributor to the sea level rise proved to be an increase in the amount of carbon dioxide dissolved in the oceans. Since the CO2 in the atmosphere has increased in the last 4 years and the ocean temperature has not, the equilibrium in the exchange of CO2 molecules between the oceans and the atmosphere will be shifted due to the present higher concentration in the atmosphere. This means that the oceans will dissolve more carbon dioxide and that will increase the volume of the ocean waters. I do not know the size of this effect and whether it is a substantial part of a 0.5 inch rise in sea level, however. It would be interesting to learn something about the magnitude of this effect.