Jökull - 01.01.2005, Blaðsíða 10

Wallace S. Broecker
Figure 7. Idealized cartoon depicting the ocean’s global conveyor system (Broecker, 1991). – Einfölduð mynd
af færibandakerfi úthafanna. Rauði hluti færibandanna táknar heitan yfirborðsstraum en sá svarti kaldan og
saltan djúpsjó.
out from our Sun’s dark spots (i.e., the so-called so-
lar wind). The more dark spots, the more ions shot
forth and the stronger the magnetic shield they create.
Satellite-based observations which show that during
the course of the last two full 11-year sunspot cycles,
the Sun’s luminosity has undergone tiny changes (see
Figure 8). Its output was one part in 1300 greater
at the times of the last two sun-spot maxima than at
times of the intervening sun-spot minima (Fröhlich
and Lean, 1998). Even though our visual observations
of sunspots date back only to 1604 when they were
discovered by Galileo, the proxy record provided by
radioisotopes allows it to be extended back through
the entire Holocene (i.e., the present interglacial). The
mystery is that no way has been found for changes
in luminescence on the order of one part in a thou-
sand to generate the observed one degree temperature
fluctuations. According to the models, luminescence
changes of this magnitude are capable of producing
swings in temperature of no more than one tenth of
one degree (Douglass and Clader, 2002). So, once
again, we have evidence that our Earth’s climate sys-
tem has hidden amplifiers which allow it to greatly
over respond to very small nudges.
The failure of models to produce the impacts on
climate resulting from the seasonality changes pro-
duced by cyclic changes in the Earth’s orbit or from
tiny changes in the output of radiation from the Sun
suggests that these models might also underestimate
the long-term impact of CO2 and other greenhouse
gases. Further, large and abrupt changes triggered
by reorganizations of ocean circulation warn us that
the ride into the greenhouse future may be punctu-
ated with large bumps! My read of the paleo record
leads me to believe that climate is akin to an angry
beast which responds violently when poked. Hence, I
am convinced that we should do everything we can to
minimize the greenhouse poke!
10 JÖKULL No. 55, 2005