Lewis and Karoly 2013: climate change is “likely” to blame for the hottest angry summer.
Did your air-conditioner make Australia the hottest angry summer ever? Could be. If we apply mystery-black-box-techniques to data from a few sparse thermometers averaged over thousands of square kilometers we can find a “record”. If we compare that “record” to models that are known to be wrong, voila — then the coal fired power stations heated more than just your home, they heated the whole country.
On the other hand, if we use thousands of measurements from satellites that criss cross the nation day and night covering every corner of the land, we didn’t have a hot angry summer, we had a normal one. The Lewis and Karoly study is moot. If we caused a normal summer, is that so bad?
The not-angry-summer is visible with no statistical analysis.
Satellite records only go back to 1979, but to answer the question “was this the hottest ever summer” we only need records back as far as 2010.
The peer reviewed, comprehensive, Lewis and Karoly paper does not contain the words “satellite”, or “UAH”. Lewis and Karoly apparently do not know about the UAH satellite program yet, otherwise they surely would have emailed John Christy or Roy Spencer (as we did) to ask for the data. We can only hope that they get enough government support, more funding, and better education in future so that they may discover what unpaid volunteers figured out on the Internet for free 3 months ago. Frankly it is shameful that the Australian Research Council (ARC) Centre of Excellence for Climate System Science is not connected to the world wide web and has not trained staff to use “google”.
How good are those surface records?
The AWAP records from ground based thermometers are based on a method that still has not been made public. What we do know is that there were 700-800 sites (strange how the actual number so hard to state). As far as we can tell, less than half of those were operating in the 1930s and 1940s when we had our last major heat waves, and hardly any were measuring the temperatures of the hottest bits central Australia (see the black dots on the map). There are gaps of 1,000km between thermometers. Lewis and Karoly compare the latest heat wave to the average for 1910-1940, yet in 1910 there are only 16 thermometers covering 7.6 million square kilometers. Half a million square kilometers per thermometer?
 Anthropogenic contributions to the record hot 2013 Australian summer are investigated using a suite of climate model experiments. This was the hottest Australian summer in the observational record. Australian area-average summer temperatures for simulations with natural forcings only were compared to simulations with anthropogenic and natural forcings for the period 1976–2005 and the RCP8.5 high emission simulation (2006–2020) from nine CMIP5 models. Using fraction of attributable risk to compare the likelihood of extreme Australian summer temperatures between the experiments, it was very likely (>90% confidence) there was at least a 2.5 times increase in the odds of extreme heat due to human influences using simulations to 2005, and a five-fold increase in this risk using simulations for 2006–2020. The human contribution to the increased odds of Australian summer extremes like 2013 was substantial, while natural climate variations alone, including El Niño Southern Oscillation, are unlikely to explain the record temperature.
If the satellites showed that the last Australian summer was hot, would Sophie Lewis and David Karoly have left them off the paper?
The graph data comes thanks to John Christy, Director, Earth System Science Center, Distinguished Professor, Atmospheric Science University of Alabama in Huntsville, Alabama State Climatologist and Roy Spencer. It was graphed by Ken Stewart at KensKingdom, and inspired by Tom Quirk at Quadrant.