PI: Ray Bradley,
University of Massachusetts
Email: rbradley@geo.umass.edu
In the IPCC 2001 Working Group 1 Report, Figure 9.8 shows zonal mean temperature change, averaged over several models, for CMIP2 simulations. I am interested in this because in the upper panel, the result shows that maximum changes might be expected both at low elevations in the Arctic, and at high elevations in the Tropics. As you know, tropical ice caps have been melting at a phenomenal rate, yet our instrumental data from high elevations is very limited. I've plotted the distribution of GSN stations along the axis of the Cordillera, from Alaska to S. Chile and the mean annual freezing level. There is a clear gap between Colorado (Niwot Ridge!) and Chile at high elevations. I am pressing NOAA to include some stations in their expanded GCOS network to fill that gap. It would be most useful to extract a similar plot as in Figure 9.8, but just for this transect (as opposed to global zonal averages).
To do this I will require the CMIP GCM data (delta T, by pressure level for each grid box). The other issue involves where the signal/noise might be maximized. My gut feeling is that the variance of temperature at low elevations in the Arctic is much higher than in the mid-troposphere in the Tropics, so in terms of detection of a climate change signal, the observational gap in the Tropical zone becomes critical. But to get at that, I'd have to somehow evaluate control run variance versus the projected temperature change. Something like that was done in Figure 9.8 (lower panel) but it's hard to see what the patterns really are with the color scale that was chosen. I'd like to re-examine this for different models, and for the Americas transect.