Friday, 29 January 2016
An examination by Dr. Sophie Lewis of Tony Abbott's climate change denialism first as a shadow minister, then as Opposition Leader and finally (albeit briefly) as Prime Minister
In addition to showing that the perception-based understanding of climate change and extremes adopted by Abbott (i.e., the Natural Variability Concept) is not fully consistent with the observed time series, I also show that it cannot be internally consistent….
It should however, be noted, that I have taken a subset of representative quotes by Prime Minister Abbott to constitute a simplified mental model of climate change, and Mr Abbott has provided many opinions of the physical science behind climate change in addition to the small selection of quotes used here.
[Lewis, S.C., Can public perceptions of Australian climate extremes be reconciled with the statistics of climate change? Weather and Climate Extremes (2015), http://dx.doi.org/10.1016/j.wace.2015.11.008i]
Some of the Abbott quotes discussed at length in the study and set out briefly here:
* During the record-breaking spring temperatures in Australia in 2013, Abbott said, "… the thing is that at some point in the future, every record will be broken, but that doesn't prove anything about climate change. It just proves that the longer the period of time, the more possibility of extreme events". Other public comments by Prime Minister Abbott about climate change and variability include that the argument behind human-caused climate change is "absolute crap", that "there doesn't appear to have been any appreciable warming since the late 1990s" and that the link between climate change and extreme Australian climate events is "complete hogwash" (Readfearn, 2014).
Former Prime Minister Abbott's understandings of climate change and variability are not unique. Rather, these provide an encapsulation of a widely held view that the longer the period of time under consideration, the greater the possibility of extreme events. Abbott's comments are selected here for exploration as they demonstrate a widespread mental model of understanding and are capable of being highly influential. These personal understandings of climate change arise from several causes. First, the manifestation of climate change in weather and climate is typically poorly understood (Trenberth, 2011). In general, people have difficulty perceiving changes in the physicals climate system above the natural variability of local climate (Myers et al., 2012)…..
* On October 30 2013, Prime Minister Abbott stated, "… the thing is that at some point in the future, every record will be broken, but that doesn′t prove anything about climate change. It just proves that the longer the period of time, the more possibility of extreme events".
A statistical interpretation of this statement is that the sequence of observed temperatures fails to satisfy the assumption of being identically distributed and independent. If the assumption of IID were the case, then the "possibility" of an extreme would be less likely in 2013, and in 2014, than in the early part of the observed sequence…..
* In October 2009 Prime Minister Abbott stated that the argument behind human-caused climate change was "absolute crap." Later in December 2009, Abbott stated that "there doesn't appear to have been any appreciable warming since the late 1990s" and in July 2007 that "there may even have been a slight decrease in global temperatures (the measurement data differs on this point) over the past decade".
That is, in these statements Abbott rejected that an increasing trend in temperatures has occurred in the sequence of observations in recent years. Hence, these particular statements by Prime Minister Abbott are in apparent contradiction in terms of explaining the increase in record-breaking in the later part of the observational record. If climate change is "absolute crap" and "there doesn't appear to have been any appreciable warming" then the probability of recent record breaking should be lower with an increasing length of temperature time series.
* Prime Minister Abbott concluded in October 2013 that the link between extremes (in this case bushfires) and climate change was "complete hogwash" and that "I'm not one of those people who runs around and says every time there's a fire or a flood, that proves climate change is getting worse. Australia has had fires and floods since the beginning of time. We've had much bigger floods and fires than the ones we've recently experienced. You can hardly say they were the result of anthropic [sic] global warming."
Hence, to hold an internally consistent viewpoint within the Natural Variability Concept, the increase in the rate of record-breaking requires either a change in the shape of the temperature probability distribution with time that can be attributed to natural climate mechanisms, or requires that record-breaking rates have increased because temperatures are auto-correlated due to natural physical climate mechanisms such as thermal feedbacks between the ocean and atmosphere, sunspots and volcanic activity (Bassett, 1992).
* This does not, however, suggest that understandings developed under the Natural Variability Concept can be readily changed by simply viewing this conceptualisation as a deficit of knowledge. For example, former Prime Minister Abbott said in July 2009 that he was "…hugely unconvinced by the so-called settled science on climate change".
Hence, this mismatch between an individual's perceptions of the climate change and extremes, and the physical evidence of the observed and modelled climate system, is undoubtedly complex and cannot be resolved simply with a singular approach…..
Interested readers can go to http://www.sciencedirect.com/science/article/pii/S2212094715300293 and view or download an open access full copy of the 10 page study with diagrams.
What the author1 said about this study in The Guardian on 23 January 2016:
The first way to understand Abbott's claim is that in any system, the longer you wait, the more often you will see records fall.
But Lewis points out that the exact opposite is true.
In a system without any sort of trend, such as a random string of temperatures, the first one will be a record-breaker, by default.
The second one will have a 50% chance of being a record-breaker.
The third has a one in three chance of being a record breaker … and so on.
In a very long temperature series, you should see very few records being broken, and they will break less often over time.
Unless, of course, there is a warming or cooling trend.
Alternatively, Abbott might simply have meant there was no connection between extreme heat records and climate change.
Instead, natural variability might be to blame: natural variability includes things such as the El Niño phenomenon, which push temperature around year-to-year.
To test if that might be the case, Lewis ran a series of climate models in which the greenhouse effect was removed – so all that was left was natural variability. Unsurprisingly, in those models, high temperature records were less common than they are in reality. In other words, the record-breaking that we have seen cannot be explained by natural variation.
"It drives me mental that these sorts of statements go unaddressed," Lewis says.
She says scientific literature generally tries to simply explain what is happening, ignoring misunderstandings in the public sphere.
"This was an attempt to bridge that gap."
1. Dr. Sophie Lewis is Research Fellow in the Geophysical Fluid Dynamics group at the Research School of Earth Sciences, as part of the ARC Centre of Excellence for Climate System Science. From 2011-2014, she was a Research Fellow at the University of Melbourne. Her PhD was awarded in 2011 from the Australian National University, this investigated long-term changes in the Australian monsoon system.