Missing News: climate models stuffed (again)

We know ABC is a deadzone for climate science. The only climate science news its activist reporters cover favours alarm and sensationalism. No surprise then that this new paper by Ross McKitrick and Timothy J. Vogelsang has not made it past the gate keepers:

HAC robust trend comparisons among climate series with possible level shifts
Ross R. McKitrick, and Timothy J. Vogelsang

Environmetrics

Abstract

Comparisons of trends across climatic data sets are complicated by the presence of serial correlation and possible step-changes in the mean. We build on heteroskedasticity and autocorrelation robust methods, specifically the Vogelsang–Franses (VF) nonparametric testing approach, to allow for a step-change in the mean (level shift) at a known or unknown date. The VF method provides a powerful multivariate trend estimator robust to unknown serial correlation up to but not including unit roots. We show that the critical values change when the level shift occurs at a known or unknown date. We derive an asymptotic approximation that can be used to simulate critical values, and we outline a simple bootstrap procedure that generates valid critical values and p-values. Our application builds on the literature comparing simulated and observed trends in the tropical lower troposphere and mid-troposphere since 1958. The method identifies a shift in observations around 1977, coinciding with the Pacific Climate Shift. Allowing for a level shift causes apparently significant observed trends to become statistically insignificant. Model overestimation of warming is significant whether or not we account for a level shift, although null rejections are much stronger when the level shift is included.

For visiting ABC reporters there is a good summary of the paper by McKitrick at Steve McIntyre's Climate Audit.

Bottom Line

Over the 55-years from 1958 to 2012, climate models not only significantly over-predict observed warming in the tropical troposphere, but they represent it in a fundamentally different way than is observed. Models represent the interval as a smooth upward trend with no step-change. The observations, however, assign all the warming to a single step-change in the late 1970s coinciding with a known event (the Pacific Climate Shift), and identify no significant trend before or after. In my opinion the simplest and most likely interpretation of these results is that climate models, on average, fail to replicate whatever process yielded the step-change in the late 1970s and they significantly overstate the overall atmospheric response to rising CO2 levels.

Marcott: Another Gergis moment

Search for "Gergis" on the ABC site through Google provides 2 pages of results. The first story is:
"Last 50 years were Australia's hottest: study". It's not until the very end of the article that the following editorial note appears in a smaller font:
Editor's note (June 21): Since this story was originally broadcast, errors have been identified in aspects of the data processing which may affect the results of this study. As a result, publication has been delayed and the research has been withdrawn from online publication. Professor Karoly says the data will be recalculated, peer reviewed and published in due course.

The world is still waiting for this deeply flawed study to be published. ABC ignored reporting on the manner in which the paper was found to be flawed. Those interested might like to re-visit relevant posts at Climate Audit. 

In the meantime in early March ABC uncritically re-published an AFP article that reported on a new study proclaiming:

"We already knew that on a global scale, Earth is warmer today than it was over much of the past 2,000 years," said Shaun Marcott, the lead author of the study, which was published in Science.
"Now we know that it is warmer than most of the past 11,300 years."

Through the tireless efforts of Steve McIntyre we now know that the specular uptick at the end of Marcott's temperature graph that lead to the alarming claims, is an artefact of an inappropriate statistical methodology, It seems the dates of sediments from cores used in the study were shifted in time up to 1000 years. This effectively shifted warming of the Medieval Warm Period into the modern period. Results that showed cooling were truncated from the period of the uptick. Anyone smell the cherries?

How long now to wait for the ABC to comprehensively report on the issue? 

Perhaps this time around rather than adding a footnote, ABC's "journalists" might take the time to fully investigate and report on the matter. However with activists in charge, we won't be holding our breath.