143
PNA
Figure 30: lOOO-500hPa thickness anomalies associated with the PNA 500hPa height
teleconnection pattern; for winter months only. From Gutzler et al (1988).
predictability of climate change, but in my opinion it is symptomatic of
how climate may respond to weak imposed perturbations.
The original IPCC (1990) report notes an apparent discrepancy between
observations of decadal variability and GCM simulations of the impact of
doubled CO2. Fig 26 (reproduced from the IPCC report) shows observed
temperature anomalies in the troposphere and lower stratosphere based on
Angell (1988). IPCC notes that 'in the upper troposphere (300-100hPa),
Fig 26 shows that there has been a rather steady decline in temperature
since the late 1950s and early 1960s, in general disagreement with model
simulations that show warming at these levels when the concentration of
greenhouse gases is increased'.
To reiterate, the basic notion of the nonlinear paradigm in section 4 is
that the system response to a small external forcing will, to first order, alter
the residence frequency associated with naturally-occurring atmospheric
regimes. Changes to the geographical structure of the regimes would be
a second-order effect. This paradigm arises because the regions of phasespace in the vicinity of the regime centroids are relatively stable. The
dominant instabilities are, in part, likely to be associated with saddle points
PNA
Figure 30: lOOO-500hPa thickness anomalies associated with the PNA 500hPa height
teleconnection pattern; for winter months only. From Gutzler et al (1988).
predictability of climate change, but in my opinion it is symptomatic of
how climate may respond to weak imposed perturbations.
The original IPCC (1990) report notes an apparent discrepancy between
observations of decadal variability and GCM simulations of the impact of
doubled CO2. Fig 26 (reproduced from the IPCC report) shows observed
temperature anomalies in the troposphere and lower stratosphere based on
Angell (1988). IPCC notes that 'in the upper troposphere (300-100hPa),
Fig 26 shows that there has been a rather steady decline in temperature
since the late 1950s and early 1960s, in general disagreement with model
simulations that show warming at these levels when the concentration of
greenhouse gases is increased'.
To reiterate, the basic notion of the nonlinear paradigm in section 4 is
that the system response to a small external forcing will, to first order, alter
the residence frequency associated with naturally-occurring atmospheric
regimes. Changes to the geographical structure of the regimes would be
a second-order effect. This paradigm arises because the regions of phasespace in the vicinity of the regime centroids are relatively stable. The
dominant instabilities are, in part, likely to be associated with saddle points