I was recently reading a 1975 paper “The Influence of Snowcover on the Atmospheric Circulation and Its Role in Climatic Change: An Analysis Based on Results from the NCAR Global Circulation Model”.
What was refreshing (in the paper) was simple models* to help understand the processes. Although the models have improved, increasing complexity and a CO2 control knob does not mean increased skill.
* by today’s standards. This image shows the evolution well-
In December 2014, Willis Eschenbach posted GMT series generated by 42 CMIP5 models, along with HADCRUT4 series, all obtained from KNMI.
The dataset includes a single run showing GMT from each of 42 CMIP5 models. Each model estimates monthly global mean temperatures in degrees Kelvin backwards to 1861 and forwards to 2101, a period of 240 years. The dataset from CMIP5 models includes 145 years of history to 2005, and 95 years of projections from 2006 onward.
The estimated global mean temperatures are considered to be an emergent property generated by the model. Thus it is of interest to compare them to measured surface temperatures. The models produce variability year over year, and on decadal and centennial scales.
These models can be thought of as 42 “proxies” for global mean temperature change. Without knowing what parameters and assumptions were used in each case, we can still make observations about…
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