Temperatures According to Climate Models

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-

Science Matters

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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Climate Models Explained

Science Matters

A comment by Dr. R.G. Brown of Duke University posted on June 11 at WUWT.

noaa climate model Overview of the structure of a state-of-the-art climate model. From the NOAA website http://www.research.noaa.gov/climate/t_modeling.html

First about the way weather models work

That is not quite what they do in GCMs. There are two reasons for this. One is that a global grid of 2 million temperatures sounds like a lot, but it’s not. Remember the atmosphere has depth, and they have to initialize at least to the top of the troposphere, and if they use 1 km thick cells there are 9 or 10 layers. Say 10. Then they have 500 million square kilometers of area to cover. Even if the grid itself has two million cells, that is still cells that contain 250 square km. This isn’t terrible — 16x16x1 km cells (20 million of them assuming they follow the usual practice of slabs 1…

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