Altitude dependence of atmospheric temperature trends: Climate models versus observation

Abstract

As a consequence of greenhouse forcing, all state‐of‐the‐art general circulation models predict a positive temperature trend that is greater for the troposphere than the surface. This predicted positive trend increases in value with altitude until it reaches a maximum ratio with respect to the surface of as much as 1.5 to 2.0 at about 200–400 hPa. However, the temperature trends from several independent observational data sets show decreasing as well as mostly negative values. This disparity indicates that the three models examined here fail to account for the effects of greenhouse forcings.

A comparison of tropical temperature trends with model predictions

“…The present study includes all available datasets, and an Intergovernmental Panel on Climate Change (IPCC)-sponsored model inter-comparison project using the 'Climate of the 20th Century' (20CEN) forcing includes models from almost all the major modelling groups [Program for Climate Model Diagnosis and Intercomparison (PCMDI, 2005)]. The number of observational datasets and models constitutes a significant increase over the Douglass et al (2004a) study, and thus, it is appropriate that a new analysis be made. Santer et al (2005) recently investigated the altitude dependence of temperature trends during the satellite era, emphasizing the tropical zone, where the characteristics are well-suited for model evaluation.…”

Iceland as a heat island

“…The maximum in Figure 4 around 45°N is due to the warming regions N1, N3 and N5. The shoulder, at latitude $60°, which has been observed before but not identified [Douglass et al, 2004b], is clearly due to Iceland. Because of the small area of Iceland these warming effects have a small influence on the global average trend.…”

Eos, Transactions, American Geophysical Union Volume 87, Number 43, 24 October 2006

“…Specifically, Figure 5.4G, which compares key observations with the calculations of major greenhouse models, shows a considerable disparity. There are other differences between observed and calculated 'fingerprints' of temperature trends [Singer, 2006], further demonstrated by more detailed comparisons [Douglass et al, 2004].…”