![\"Figure](\"http:\/\/rankexploits.com\/musings\/wp-content\/uploads\/2010\/01\/NewUncertaintyIntervals.jpg\" "\\"NewUncertaintyIntervals\\"")
<\/a>Inspection of the graph indicates that, when analyzed this way, the difference between observations and a multi-run mean from an ensemble of runs used in the AR4 is negative (suggesting the models over-project warming) and moreover, the difference is statistically significant if we happen to start our analysis in ’50, ’60, ’70, ’00, or ’01. However, the difference is not statistically significant if we begin analysis in ’80 or ’90. <\/p>\n
The result are such that currently, the data permit cherry pickers to decide certain “key” years are the ‘right’ ones to begin analysis. It is worth nothing however, that analyses beginning prior to 2001 include comparison of “predictions\/projections” to “observations” that were not only available prior to making the “predictions”, but also available prior to freezing of the Scenarios used to create projections into the future. So, the projection period after 2001 has a special status relative to the period prior to 2001. For this reason, I favor 2001 as a start year– though of course others are permitted to have their own favorite start year for reasons of their own.<\/p>\n
I’m will be deferring full discussion of analytical choices to later (fairly long) blog posts. However, the synopsis is that :<\/p>\n
- \n
- The analysis uses monthly values for observations and projections in surface temperature. This is because it can be shown that when both monthly and anual average data are available, analysis using monthly data almost always has lower Type II error at a given choice of Type I error. <\/li>\n
- The multi-run mean is based on an ensemble of runs used in the IPCC AR4, downloaded from the Climate Explorer. The selected runs were forced using modelers choice for the 20th century and extended into the 20th century using the A1B scenarios.<\/li>\n
- The analysis accounts for the effects of volcanic forcing on the temperature excursions in a more phenomenologically realistic way<\/i> than the rather unphysical linear regression of volcanic aerosols with time.<\/li>\n
- The analysis accounts for the correction due to ENSO using the MEI.<\/a> I don’t know if this choice minimize the uncertainty intervals– I selected it because…well… someone else did. \ud83d\ude42 <\/li>\n
- The analysis assumes the autocorrelation of temperature with time varies as it would if the residuals can be described using an ARMA(1,1) process.<\/li>\n
- Analysis uses all data from the ‘start year’ indicated through Nov. 2009. Most start years are January for decades beginning with ‘0’; this choice is modified for 1950, because the method for correcting for MEI does not permit starting in January.<\/li>\n<\/ol>\n
For those who are curious about the rankings of annual average temperatures basd on the same analysis, after adjusting for MEI and any nonlinear response due to exogenous forcings, I’ve reconstituted and plotted them below. <\/p>\n
![\"Figure](\"http:\/\/rankexploits.com\/musings\/wp-content\/uploads\/2010\/01\/AnnualAveTempeartures-500x341.jpg\" "\\"AnnualAveTempeartures\\"")
<\/a>Figure 2: Corrected Annual Average Surface Temperatures<\/figcaption><\/figure>\n After adjusting for MEI & etc. I find 2009 had the third warmest temperature on record– whatever that means. (I don’t like to compare adjusted years since the result varies according to the adjustment method. We should really include uncertainty intervals in any sort of comparison of this type; if we did, we could conclude that the MEI adjusted temperature has been quite flat this century.)<\/p>\n
Over the course of the next two weeks, I’ll be posting discussion of each important analytical choice to let you critique them. But, I thought I’d let all ‘a y’all see the almost-end-year results first. When GISS and Hadley post their December data, I’ll update the final results for the year. <\/p>\n","protected":false},"excerpt":{"rendered":"
It has come to my attention that a certain blog-climate warrior has now decided to get back to work adjusting analysis to include factors that will widen error bars while doing things in ways that do a poor job of incorporating explanatory factors that would narrow the error bars. So, I decided I might as … Continue reading Multi-Run Mean AR4 Projections: Statistically Significant from Observations from ’50, ’60, ’70, ’00 and ’01.<\/span>
- The analysis accounts for the correction due to ENSO using the MEI.<\/a> I don’t know if this choice minimize the uncertainty intervals– I selected it because…well… someone else did. \ud83d\ude42 <\/li>\n