and other climatic effects of warming. Concern is complicated by our recently
strengthened realization that climates cycle at periods from decadal to millennial, as
well as at the long-recognized glacial–interglacial period. We are trying to trace shifts
in the North Atlantic Oscillation, the Pacific Decadal Oscillation, and other
oscillations partially coupled to them worldwide. Fisheries appear to be subject to
climate-driven oscillations of as long as 60 years, with different phases termed
regimes. Several examples of such regime shifts will be considered in Chapter 17.
This complex, multi-decadal cycling interacts with and obscures the longer-term, but
rapid, general warming currently underway. Even if global climate change has
become a mantra, it is essential that we stay with the process of sorting it out, come to
understand it as thoroughly as possible, and take mitigating action – particularly
reduced use of fossil fuel. Some other proposed mitigations are sited in the oceans and
are biological in proposed mechanism. They do not promise moderation of warming
commensurate with their difficulty and cost. We must also prepare to live in a warmer
world; considerable heating is likely to be inevitable. Parallel to warming attributable
to fossil carbon in the atmosphere, the fraction of fossil-fuel CO 2 dissolving in the sea
is shifting the carbonate buffering system to greater acidity. That has acquired intense
interest more recently, since about 2000.
(^) Biological production and the subsequent redistributions of organic matter in the
oceans have a part in climate control, and we will examine that from several
perspectives. This is not a complete essay on global climate change issues. The IPCC
is attempting to keep abreast of both the data and the current best thinking on the
issues. For thorough coverage, see their most recent full report: IPCC (2007; a
summary is available on the worldwide web at http://www.ipcc.ch) and the occasional
updates posted there.
Global Warming and CO 2
(^) The weather is, on broad average (a definition of “climate”), getting warmer (Fig.
16.1). Available data since the mid-1800s are averages of distributed temperature
observations, the quality of which was good then and has generally increased steadily
(mostly because of added observing stations). In fact, the warming has been going on
since before the industrial era, but is now accelerating, albeit in intriguingly stepped
fashion. Warming in the 20th century occurred in two episodes: 1905–1940 and 1976–
present. Means were fairly steady from 1940 to 1976, followed by more warming.
The interval from ∼2000 to present was the warmest in the instrumental temperature
record (Fig. 16.1), although it was also intriguingly flat. It is considered by some
oceanographers that the heating in this “flat” period has been focused in the ocean,
where a great deal of heat ∼0.64 W m−2 was stored in upper layers from 1993 (mostly