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Byron Ellis

If I had to guess, I'd say that the models were trained on data up to ~2000 on the EIA data from the top graph. Oddly, there seems to be a much larger range < 2000 in the junkart chart relative to that first chart?

Mike Anderson

The graph on the left shows that actual greenhouse gas emissions have exceeded the level predicted by the most pessimistic climate models.

One might THINK that's what the graph shows, but without prediction intervals around the model curves, how can you tell? Prediction intervals in time-series models expand FAST.


I looked for the source of the blog's figures for that bar chart, and found it, eventually, at http://www.panda.org/. It shouldn't have been so hard for me to find.

I discovered that either the blog or the newspaper got the figures wrong, especially for Japan (emissions up, not down) and Britain (emissions down, not up). I also found that the WWF report fails to give emissions either in 1990 or today. lots of normalised measures and percentage changes, but no actual number for emissions.

That's disappointing. I had wanted to turn the bar chart with its percentages into a "cat's cradle" line chart with 1990 and 2005 numbers on the left and right (Kaiser's favourite "bumps charts" :-)

I'm also not impressed by the WWF's fondness for speedometer gauges. A simple traffic light spot would have worked better.


Derek: For some reason, speedometers are all the rage, especially in the business / management world.

Mike: The variability of the forecasts is given by the range of estimates produced by different models. Of course, as you said, each model has its own prediction interval but as a proxy for those, I think the range of estimates is not bad.

Bryon: I eyeballed the range of estimates as I don't have the data for each model.

R Simmon

A little late to the party here, but the range of carbon dioxide emissions are technically scenarios, not models. IPCC researchers used the estimates of carbon dioxide emissions to feed models, which then predicted changes in climate, the results of which were published in 2001 in the Third Assessment Report. The raw data are here:

and the IPCC report is here:

as well as the PNAS paper from which the line graph published here was taken:

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