The Bureau of Meteorology [BOM] has released its report for Australian climate during 2013. According to the BOM 2013 was the hottest year on record, in Australia. However both satellite temperatures, RSS and UAH, and a global surface temperature, GHCN, all found other Australian years to be warmer:
Naturally the pro-AGW people have been all over the BOM report claiming it as evidence for AGW, while ignoring the results from the other equally valid sources for temperature. But even if the BOM report is correct it is problematic whether AGW is the cause of the temperature. It is doubtful because during 2013 and for at least a decade the Diurnal Temperature Range [DTR] has not been decreasing but increasing.
The DTR is the difference between the maximum and minimum temperatures. AGW theory predicts that the minimum temperatures should increase more than maximum temperatures and the DTR should decrease. This is explained by the IPCC at Figure 3.2 of their 4th report, AR4. AR4 gives a variety of reasons why the DTR should decrease but the main one is that back-radiation, which is the radiation the extra CO2 in the air throws back towards the Earth, will have a more pronounced effect at night.
Given this a simple test of whether the hottest year in Australia was due to AGW would be to measure the DTR. Ken Stewart has done this:
Since 1979 it is plain the gap between the maximum and minimum temperature has increased. So, in fact the DTR in Australia has increased not decreased.
Still, there is no doubt 2013 was a relatively warm year for Australia. It was certainly warmer than the year in the Antarctic. Professor Chris Turney and team of fellow scientists and media, and as it turns out family members, hired a ship apparently at taxpayers' expense and sailed to the Antarctic to retrace Mawson's steps from 100 years ago.
There is a certain irony in an expert climate scientist being trapped in sea ice. Despite this Professor Turney and his supporters such as the well-known Professor Lewandowsky have maintained the sea ice which trapped Professor Turney's boat, the Akademik Shokalskiy, was due to AGW.
The 120km long ice berg B09B that is grounded in Commonwealth Bay broke away from the continent three years ago, very likely as a result of climate change.
B09B collided with the Mertz Glacier, smashing a large ice tongue that released the ice into that area.
It was a mix of this ice that was blown across the path of the Shokalskiy, which led to it being trapped and explains why much of the ice surrounding the ship is old ice.
All of this incorrect. As the Australian Antarctic Division notes:
B09B originally calved from the Ross Ice Shelf in 1987 and drifted round to the east of Mertz Glacier by 1992. It was grounded for many years and started moving in late 2009. - In mid-February 2010 B09B collided with the Mertz Glacier tongue – a section of the glacier that protruded about 100 km from the Antarctic coastline at about 145ºE. The collision precipitated the calving of another massive iceberg, C28, from the tongue, measuring 78 km long and between 33 and 39 km wide. This calving event removed about 80% of the tongue, leaving only a 20 km-long stub. The calving had been anticipated, as rifts cutting across the tongue had been developing over many years, but the timing and collision was not.
So the ice Turney says was from AGW in fact came from a calving event which occurred 26 years ago. This event had been well documented but there was no ice from this event in the area where Turney's expedition became entrapped in ice. Unfazed Turney continues:
I believe you are probably aware of a number of papers this year that show land ice on Antarctica is in decline and that only seasonal sea ice has been expanding, likely due to the increase in westerly winds and potentially because of the decrease in salinity.
This too is problematic. A 2012 NASA study by Zwally et al concluded that:
During 2003 to 2008, the mass gain of the Antarctic ice sheet from snow accumulation exceeded the mass loss from ice discharge by 49 Gt/yr (2.5% of input), as derived from ICESat laser measurements of elevation change.
This mass gain was notably in East Antarctic where Turney's expedition was heading.
In addition air temperature over the Antarctic has not increased since 1979:
Sea surface temperature [SST] has actually decreased during this period:
So we have sheet ice increasing, air temperature constant and SST declining; all ingredients likely to lead to an increase in sea ice which has been occurring for many years without any contribution from AGW.
The 3rd piece of AGW news of note comes from Professor Steven Sherwood from the University of NSW Climate Change Research Centre. Sherwood's new paper concludes that things are worse than we thought because climate sensitivity, the temperature reaction of the climate system to AGW, is actually higher.
Sherwood reaches this conclusion by looking at which of his climate models were best at modelling and predicting the mixing rate of clouds and water in the lower atmosphere. Sherwood found that those models which predicted the highest temperatures were best at predicting the mixing rates.
The fallacy of this conclusion has several ingredients. Firstly even Sherwood concedes that knowledge of clouds is lacking and is responsible for most of the uncertainty with AGW predictions. How clouds form and effect climate depends on much more than the mixing rates in the lower atmosphere.
Just because Sherwood's warming models can model one aspect of cloud behaviour doesn't mean they model well any other aspect of clouds or climate. For instance In a critique of Sherwood's study Michaels and Knappenberger note that Sherwood's models which predicted mixing best were worst at predicting temperature:
Figure 1. Observed global average temperature evolution, 1951-2013, as compiled by the U.K's Hadley Center (black line), and the average temperature change projected by a collection of climate models used in the IPCC Fifth Assessment Report which have a climate sensitivity greater than 3.0°C (red line) and a collection of models with climate sensitivities less than 3.0°C (blue line) (climate model data source: Climate Explorer).
This paper by Sherwood is only the latest in a long line of papers where he has used models to prove AGW. For instance in 2008 Sherwood produced a paper proving the existence of a Tropical Hot Spot [THS], an essential prediction of AGW. In this paper, concerned that the temperature instruments showed no THS, Sherwood repudiated the instrument data and developed a windshear model which showed if there was windshear there would be warming. The irony here was that the instruments which Sherwood thought were not good enough for temperature were used by Sherwood to establish windshear and the model predicted temperature.
Sherwood's new paper received headline coverage, as did the BOM report. The ice entrapment of the Turney expedition also did but mention of the AGW purpose of the ill-fated expedition in the media was muted at best. Like the weather itself supporters of AGW run hot when the weather supports them and cold when it doesn't.