“The severity of the ‘Big Dry’ has been exacerbated by recent warmer air temperatures over the past few decades…. In a warmer world, the severity of droughts would likely become far worse.” (Duh)
Australia is most definitely getting hotter, much as the entire planet has, much as climate scientists have been predicting would be the inevitable result of unrestricted emissions of heat-trapping greenhouse gases.
The figure is from the “Annual Australian Climate Statement 2009,” which notes:
2009 ends Australia’s warmest decade on record, with a decadal mean temperature anomaly of +0.48°C (above the 1961-90 average). In Australia, each decade since the 1940s has been warmer than the preceding decade. In contrast, decadal temperature variations during the first few decades of Australia’s climate record do not display any specific trend. This suggests an apparent shift in Australia’s climate from one characterised by natural variability to one increasingly characterised by a trend to warmer temperatures.
At the same time, parts of Australia are getting drier, much as as climate scientists have been predicting would be the inevitable result of unrestricted emissions of GHGs. And Dr. Bertrand Timbal, of the Bureau of Meteorology’s Centre for Australian Weather and Climate Research (CAWCR), concludes in his paper, “The continuing decline in South-East Australian rainfall: update to May 2009“:
The recent 12 year, 8 month period is the driest in the 110 years long record, surpassing the previous driest period during WWII….
This change in the relative contributions by the autumn and spring seasons now more closely resembles the picture provided by climate model simulations of future changes due to enhanced greenhouse gases.
So it was odd that Andy Revkin tweeted to disagree with the following statement in a recent guest essay by Auden Schendler and Mark Trexler (“The coming climate panic? Will U.S. conservatives usher in the era of permanently big government?“):
Meanwhile, that very planet is visibly changing””epic droughts, fires and dust storms in Australia; floods in Asia, alarmingly fast melting of land ice in Greenland and Antarctica; the prospect of an ice-free summer on the Arctic Sea; raging, unprecedented fires throughout the world; and mosquito-borne illnesses like Dengue spreading to regions previously untouched. Measurements show that the oceans are rising and becoming more acidic, while the Earth’s average temperature was higher in the past decade than at any time in the past century.
At some point, even climate change becomes teenager obvious: “Well, Duh, Dad! Look around you!”
The constraints of twittering turn that statement by Schendler and Trexler into this Revkin tweet (see “Why journalists should not twitter, Parts 87, 88, 89“)
UPDATE: Now aside from the misattribution from Schendler/Trexler to me, that study, “Nature and causes of protracted droughts in southeast Australia: Comparison between the Federation, WWII, and Big Dry droughts” doesn’t actual comment on whether the Big Dry is CO2-driven or not. But the authors of a similar study, “What causes southeast Australia’s worst droughts?” were concerned enough about the misreading of their work in the media that they issued a “Clarification,” which begins:
The implications of our work (Ummenhofer et al. 2009) have been misunderstood in some media commentary, with some reporters asserting we have discovered that south-eastern Australia’s recent “Big Dry” is not related to climate change. This is not correct.
Their study focused on the connection between negative Indian Ocean Dipole (IOD) events and drought. Their Clarification ends:
When taken in the context of other historic droughts over the past 120 years, the “Big Dry” is still exceptional in its severity. The last negative IOD event occurred in 1992. This is the longest period on record over the past 120 years without a single negative IOD event. Furthermore, the severity of the “Big Dry” has been exacerbated by recent warmer air temperatures over the past few decades (Figure 1). Warmer air temperatures lead to increased evaporation, which further reduces soil moisture and worsens the drought. While this work does not explicitly focus on the link between changing IOD frequency and recent regional and global warming, it does send a stark message: in a warmer world, the severity of droughts would likely become far worse.
In short, our paper does not discount climate change as playing a role in this most recent drought, the “Big Dry”. In fact, there are indications that climate change has worsened this recent drought. Refer to Abram et al. (2008) and Cai et al. (2009) and Nicholls (2004) who investigate changes in IOD frequency and south-eastern Australian drought due to climate change.
Here is part of Figure 1, “Historical record of … mean climatic conditions over southeast Australia”.
Timeseries of anomalous … (c) 5-yr running mean of temperature (°C), with a 15-year running mean superimposed in green, and (d) 5-yr running mean of Palmer Drought Severity Index (PDSI) over southeastern Australia during June-October. The grey shaded bars highlight periods of below average precipitation when the 5-year running mean falls below one standard deviation. The duration of three major droughts has been indicated in (d) with horizontal black bars.
So the work Aussie scientists cannot be used to argue that the “Big Dry” is not “a co2-driven event” (which in any case isn’t quite what had been asserted originally). Indeed, the scientists find that climate change has probably worsened this recent drought, which again is not new climate science (see “Must-have PPT: The ‘global-change-type drought’ and the future of extreme weather“). Warm-weather droughts are generally worse than cooler-weather droughts “” and this has been a hot-weather drought, which is perhaps the worst of all. Future droughts will increasingly be very hot weather droughts.
So I repeat again Journalists simply shouldn’t be twittering on science or other subjects that require more than 140 characters to discuss intelligently, which is pretty much every topic.