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Politicians have forgotten the ‘dry’ in dry tropics and the change in the climate

Yes, it rains a lot in the north. But it’s also dry a lot. And variability could get worse. Kasi Metcalfe

**Northern futures, northern voices: It seems everyone has ideas about how Australia’s north could be better, but most of those ideas come from the south. In this six-part weekly series, developed by the Northern Research Futures Collaborative Research Network and The Conversation, northern researchers lay out their own plans for a feasible, sustainable future.

The most terrifying thing about political visions for northern Australian is the complete absence of consideration of climate change. The contrast between the Coalition’s 2030 vision and the climate change projections for 2030 couldn’t be more striking.

One number underpins plans to develop northern Australia. It is precise. It is astronomical. It is the annual average rainfall north of the Tropic of Capricorn.

But this number is so abstract and meaningless that citing it again here is pointless. The climate of northern Australia is far too variable across space and time for ideas like those of “northern Australian rainfall” to have any coherence. They should have no relevance to thoughtful policy.

Climate is commonly reduced to 30-year averages of certain weather elements: rainfall, temperature, and so on. This definition does capture some of the important dimensions of climate. Even a cursory glance at average monthly rainfall for Darwin (Jan 424mm; Apr 101mm; Jul 1mm; Oct 70mm), Broome (Jan 179mm; Apr 26mm; Jul 7mm; Oct 1mm), Kununurra (Jan 199mm; Apr 30mm; Jul 2mm; Oct 24mm), Cooktown (Jan 306mm; Apr 166mm; Jul 30mm; Oct 26mm), Cloncurry (Jan 182mm; Apr 20mm; Jul 2mm; Oct 21mm) and Weipa (Jan 484mm; Apr 101mm; Jul 2mm; Oct 24mm) reveals how climate varies across the north.

However, climate itself isn’t quite what we think it is. True climate also includes the extremes, frequencies and patterns of weather over several decades. For example, a brief history of Darwin rainfall shows that one year can vary markedly from another; one decade can scarcely resemble the next.

During the middle of the year little or no rain falls in the north. However, slicing time into Octobers, Januaries and Aprils (proceeding through The Wet) we see that between 1870 and 1942 rain volumes varied enormously between the years.

During these 72 years October rainfall ranged from 0mm (on three occasions) to 213mm, with fewer than 10mm falling on 10 occasions and over 100mm on 10 other occasions. The January extremes ranged from 68mm, in 1906, to 711mm, in 1895. Volumes exceeded 500mm 20 times and 600mm 8 times; yet failed to reach 250mm 14 times and 200mm on 10 occasions. During the driest April – 1897 – 1.3mm was recorded whereas 603mm were registered in 1891. There were 17 Aprils when less than 25mm fell and 11 with over 200mm falling.

Figure 1 Extremes of Rainfall, Darwin Post Office, 1870-1942 Bureau of Meteorology

Timing is also integral to variability. Twice during these 72 years rain fell every calendar month of the year in Darwin. In another six years rain fell during 11 of the calendar months. Yet, in 1896, no rain was recorded from April 24 till November 15. 1925 also saw one of the only other six-month periods without rain. Darwin experienced two “dry seasons” in 1926; one from May 10 till September 10, another from late September till early November.

Such variability demands nuanced thinking and planning. The vision to build large numbers of dams appears to solve the problem of rainfall variability, but assumes our current levels of rainfall will continue.Climate change projections strongly indicate the contrary is likely to be the case.

The core “vision” for both parties is investing in long-term, large-scale infrastructure. Yet doing this without factoring in the range of potential climate change impacts amounts to gross negligence that harms the financial interests and resilience of the nation rather than helping it.

With decreased rainfall and increased evaporation as a result of atmospheric warming, the ratio of horticultural output to dollars spent on dams and irrigation will be vastly reduced. We also need to factor in if, for how long and under what conditions cattle will survive the heat before we know if such an investment makes sense.

The other side of the northern investment plan is mineral resource extraction and associated booms in mine services, construction and populations. The dangerous combination of sustained high temperatures, combined with extreme humidity, already plagues these industries. Between 1982 and 2006, 20% of the year saw heat stress at “extreme” levels, where exposure has very serious to life-threatening health consequences.

Heat illness is common during the hottest period (September-November). Anecdotal evidence points to productivity declines of 20% in this period. Some exposed businesses traditionally roster-off staff or shut down entirely to avoid heat-stress related spikes in aggression and accidents.

Yet the number of dangerously hot days is set to increase. The number of “very hot” days above 35C is projected to rise from the current number - 11 per year - to 69 by 2030 and 308 by 2070. This measure doesn’t even take into account the significant effects of humidity. For Darwin, this means that, at some point between 2030 and 2070, almost every day of the year will be in the most extreme thermal-“comfort” range, radically reducing productivity, health and well-being.

Figure 2 The number of days over 35 Degrees. ‘Very hot’ days would increase in number if the thermal stress effects of high humidity were also factored in.

As temperatures continue to rise, serious adaptation measures will be needed. But there remains a dangerous absence of leadership on adaptation. There are very limited impacts projections for the Northern Territory, no NT adaptation strategy, and very broad-brush local strategies. Adaptation reviews sit around collecting dust.

At Territory and Federal levels, Liberal and Labor are engaging in short-term idealism that is spelling medium- and long-term disaster for businesses in agriculture, mining and construction.

Northern Australia needs investment, but it needs smart investment that takes into account the best scientific advice on climate change impacts already available. It needs to back its own findings with real leadership in developing adaptation plans.

Let’s trade-in “ideological delusion 2030” and “failure-to-adapt nightmare 2030” for a real vision, because 2030 is scarily close.

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