For years now, we have been deluged with the news that the
earth’s oceans are warming as a result of atmospheric changes due
to the combustion of fossil fuels.
Typical of these was a 2005 story titled “Where’s The Heat?
Think Deep Blue,” from United Press International, describing a
recent paper in Science by NASA climate modeler James Hansen. UPI’s
“Space Daily” wrote that “Over the past ten years, the heat content
of the ocean has grown dramatically.”
Hansen’s study covered more than just the ocean surface
temperature, which can fluctuate considerably from year to year.
Rather, by considering a much deeper layer of water (the top 2,500
feet), Hansen actually calculated the increasing amount of heat
being stored. According to the UPI story, this provided “a match”
with computer model projections of global warming.
The ocean is a huge tub that integrates and stores long-term
climate changes. Consequently, when computer models are based on
ever-increasing atmospheric concentrations of carbon dioxide, the
deep oceans warm, warm, and warm. Like a big pot on a small burner,
it takes time to start up, but once the process starts, nothing
should be able to stop it.
That’s the conventional wisdom of our climate models, but like
the conventional wisdom on so many other aspects of life, it’s not
true to nature.
In the next few weeks, John Lyman of the National Oceanic and
Atmospheric Administration will publish a paper in the refereed
journal Geophysical Research Letters showing that,
globally, the top 2,500 feet of the ocean lost a tremendous amount
of heat between 2003 and 2005 — in fact, about 20% of all the heat
gained in the last half-century.
Needless to say, Lyman’s figures have climate scientists
scratching their heads. No computer model predicts such behavior.
And further, the changes in surface temperatures haven’t
corresponded (yet?) to the average changes at depth, although
deep-water temperatures have also dropped some. Nor has the sea
level dropped by an amount commensurate with the cooling (water
volume varies slightly with temperature).
This last observation has led scientists to speculate that much
more ice must be melting into the ocean than they normally assume
— but no one has been able to find it, and it’s not for a lack of
looking.
There’s another hypothesis out there that has received very
little attention. It has to do with the amount of carbon dioxide
accumulating in the atmosphere.
If carbon dioxide increases at a constant rate, basic physics —
as understood since the 1860s — says that surface temperature will
rise, but that the rate of heating will become lower and lower. In
other words, in order for temperatures to increase at a constant
rate, as has been observed since 1975, carbon dioxide would have to
go up at an ever-increasing rate.
But the ocean is so vast and slow to change that it takes
several decades to realize the heating caused by carbon dioxide.
Consequently, a change in the rate of carbon dioxide accumulation
in the atmosphere wouldn’t be noticed for 30 to 60 years, depending
upon whose calculations one believes.
Between the time atmospheric carbon dioxide was first directly
measured, at Mauna Loa, Hawaii, in 1957, and 1975, it clearly
increased exponentially. And once the ocean temperature began to
rise, it did so at a constant rate.
Then, about 30 years ago, something very peculiar began to
occur. Since 1975, it has been impossible to tell whether the
amount of atmospheric carbon dioxide is increasing at an
exponential or simply a constant rate.
Because of the lag time required for the oceans to register the
change in carbon dioxide, it may not be a surprise that an interval
of cooling has been detected. The timing is about right: around 30
years.
But that’s just another climate change hypothesis that time will
test. Be forewarned, though. As we’ve learned from the completely
unexpected cooling of the deep ocean that began in 2003, we know a
lot less about climate change than we think.
