Major changes in species distribution and
abundance in North Pacifi c marine ecosystems
are often correlated with climatic shifts
in the twentieth century. Species affected
in the past include halibut in the Gulf of
Alaska, sardine near Japan, and various
species along the Oregon/California coast
[Chen and Hare, 2006; Zhang et al., 2004;
Peterson and Schwing, 2003]. Because these
changes can affect the fi shing industry, we
have investigated possible future climate
patterns in the North Pacifi c based on the
evaluation of 22 coupled atmosphere-ocean
general circulation models (GCMs). These
GCMs were made available to the science
community for independent evaluation
in preparation for the Fourth Assessment
Report (AR4) of the Intergovernmental Panel
on Climate Change (IPCC).
This analysis of a reduced set of 10 models,
which simulate the variability of twentieth-
century North Pacifi c sea surface temperatures
(SST) reasonably well, fi nds that
anthropogenic impacts on future North
Pacifi c climate will be as large as those of
natural climate variability in 30–50 years
under a midrange greenhouse gas emissions
scenario. The spatial pattern of the future
warming trend will be more uniform than
the main pattern of climate variability from
the twentieth century, suggesting that existing
climate-ecosystem-fi sheries relationships
might not be robust long into the 21st
century. According to the models, the North
Pacifi c climate system will likely enter into
an unprecedented state with regard to nearsurface
ocean temperatures sometime during
the fi rst half of the 21st century.
In comparison with the IPCC Third
Assessment Report, both the spatial resolution
and physics of GCMs in AR4 have
improved. For example, there is less or no
reliance on prescribed ocean conditions,
mobile sea ice, and improved parameterizations
of clouds/radiation and land/atmosphere
fl uxes (www-pcmdi.llnl.gov/ipcc/
info_for_analysts.php). We consider a middle-
range IPCC greenhouse gas emissions
scenario, A1B, and note that there are small
differences between scenarios for the fi rst
half of the 21st century.

Last Updated: 2007-09-20