What was done
The authors compared tropospheric temperature trends over the period 1979-1999 that were derived from 67 runs of 22 general circulation models of the atmosphere that had been developed by researchers working at a number of institutions located in ten different countries with concurrent measurements obtained from various surface, radiosonde and satellite data sets.

What was learned
In the words of Douglas et al., this work revealed that "model results and observed temperature trends are in disagreement in most of the tropical troposphere, being separated by more than twice the uncertainty of the model mean," and that "in layers near 5 km, the modeled trend is 100 to 300% higher than observed, and, above 8 km, modeled and observed trends have opposite signs."

What it means
The four researchers conclude that "if these results continue to be supported, then future projections of temperature change, as depicted in the present suite of climate models, are likely too high," and they suggest, therefore, that "projections of future climate based on these models be viewed with much caution."