Climate Change (Part 4)

In this post, the last of a four-part series on climate change, I’ll start with the conclusions reached so far:

1.            There is overwhelming data indicating that the planet is in a warming trend—at least up until the last 10 years or so.

2.            Warming trends are historically correlated with increasing levels of CO₂, with emphasis on “correlated with” (not “caused by”).

3.            Mathematical models of future global temperatures are now predicting less warming than previously thought.

4.            Natural “forcings” of climate are significant.

5.            How the various natural forcings will interact with increased CO₂ and other greenhouse gases is, of course, unknown.

6.            C0₂, which acts like a natural fertilizer, stimulates plant growth significantly in some species.

7.            Plant species differ in response to elevated C0₂, with some being stimulated more than others.

8.            Elevated C0₂ increases water-use efficiency in some species.

9.            Elevated C0₂ stimulates growth in some ocean plants (e.g., phytoplankton), while other species, such as corals, may be destroyed or depleted.

10.            Ocean acidification may dissolve shells, corals, and other structures built of calcium carbonate, though some phytoplankton can apparently overcome any dissolving of their calcium carbonate structures by increased photosynthesis.

11.            Overall, ecosystems will respond to climate change by modifications ranging from slight to great, but they certainly will adapt.

In the course of researching ocean acidification, I learned of a recent report** on ocean warming.  It is proving to be very controversial, and may be wrong, but then again, it may be right.  And it does present some anomalies—like most everything else in science.  Here is the critical graph from the paper:

The lefthand side of the graph is a measure of heat, so what we have is a historical view of ocean temperatures from 1960 through 2008.

What the scientists found is that since the late 1970’s, the ocean has been getting warmer as far down as 700 meters, with the warming trend punctuated by periodic cooling caused by volcanic eruptions and a significant heat spike in the late 1980s caused by an El Nino event.  The authors conclude that the reason there hasn’t been any appreciable warming of the atmosphere during the last 10 years is because heat has been absorbed out of the atmosphere into the ocean.  In other words, the ocean is where the “missing heat” has gone.

When you look closely at the data, you can see that the region below 300 meters has warmed MORE than the upper 300 meters.  And this is the source of some criticism, since other scientists can’t figure out how the heat “skipped” detection in the upper ocean while showing up in the lower.   As a result, questions have been raised about the temperature-detection methods used by the researchers, as well as the manner in which the missing heat was calculated.

I certainly can’t evaluate the scientific integrity of this study, but it does seem strange that the upper layers didn’t warm first.  I wouldn’t be surprised if this data becomes a central part of the global warming debate.

A related issue regarding the ocean is, of course, rising sea levels.  Now this is a pretty easy concept as far as global warming is concerned:  ice melts, water flows into the sea, and the sea rises.  And as water heats up, it expands and the sea rises.

But actually measuring the sea level seems daunting, as anyone who has been to the beach can appreciate.  Tides, waves—these all need to be “smoothed out” or averaged.  However, sea height has been measured since 1700 in places like Amsterdam, where it is a daily concern due to the fact that 20% of the Netherlands—along with 50% of its population—is below sea level, and half of its land is less than 3 feet above sea level (most of the area below sea level is manmade after centuries of peat extraction). 

Sea heights were, and still are, measured by “tide gauges.”  Early calculations were made by measuring the height of the water relative to a specific point, such as a marking on a cliff.  Modern tide gauges (about 1750 of them around the world) do essentially the same thing using electronic sensors and small computers.   And incredibly, satellite measurements—using satellite altimetry—are so accurate that changes in sea level of only a few millimeters can be detected.

In any event, from 1870 to 2004, global sea levels rose by 195 mm or 7.7 inches, with an average rise of 1.4 millimeters per year.  And sea level rise seems to be noncontroversial, making it yet another proxy that provides evidence of global warming.  And given the melting of glaciers and the ice sheets of Greenland and Antarctica, sea levels should continue to rise—although, surprisingly, the rate of sea level rise has not accelerated along with increasing temperatures.  Perhaps inaccuracies in measurement would account for this.

So the planet is warming.  Ecosystems will change.  Cropping systems may also change, but they will adapt.  Forests will change.  Ocean fisheries may change.  New regions may become habitable.  Others may become less desirable.  Sea levels are rising.  Coastal communities will probably be affected.  Populations may be dislocated—and new phrases such as “environmental refugees”, “environmental migrants” and “climate refugees” have entered our vocabulary.

Because it is believed by most people that manmade greenhouse gases are responsible for the rise in temperatures, many proposals have been made to slow down the release of these gases into the atmosphere.  Complex international agreements have been developed allowing countries to trade “carbon credits,” while other proposals such as the Kyoto Protocol have tried to get commitments from countries to limit greenhouse gas production.  Other proposals have been made to slow down global warming, including methods to “absorb” gases or reflect sunlight from the planet.

But these proposals for limiting greenhouse gases are far beyond my expertise to review, summarize, or even comment on.  All I can really say is that limiting greenhouse gas production or increasing its absorption/sequestration will probably have a minimal impact on the temperature of the planet.  In fact, since the recent global recession has had no apparent impact on atmospheric C0₂, I’d say we have actually done an experiment of sorts—and found it to be ineffective.  It seems very unlikely that Homo sapiens will voluntarily agree to limit greenhouse gases if the cost equals or exceeds that of the recent recession.  I suspect that we will simply learn to adapt to a warming planet.

Assuming that the climate does not reverse itself and start getting cooler, that is.

Reference:

**http://onlinelibrary.wiley.com/doi/10.1002/grl.50382/abstract