Winter hasn’t felt too wintry yet in much of Australia. Most of us have have had more sunshine, higher temperatures, and less rainfall than is normal for the time of year. In fact, Australia just had its warmest average daytime maximum temperatures for July since records began in 1910.
The north and centre of the continent saw the biggest temperature anomalies as Western Australia, the Northern Territory and Queensland experienced record warm daytime July temperatures. Only the southwestern tip of Western Australia and western Tasmania had slightly below-average daytime temperatures.
Southern Australia was again very dry as the frontal systems that usually bring rain remained further south than usual.
For most of us, warm and dry winter conditions are quite pleasant. But with drought starting to rear its head and a severe bushfire season on the cards, some cooler wetter weather would be helpful to farmers and fire services across the country.
What caused the unusual warmth?
Often when we have warmer winter weather in Australia it is linked to El Niño conditions in the Pacific or a positive Indian Ocean Dipole. Both of these Pacific and Indian Ocean patterns tend to shift atmospheric pressure patterns in a way that brings more stable conditions and warmer, drier weather to Australia.
This year, however, neither El Niño nor the Indian Ocean Dipole is playing a role in the warm weather. The sea surface temperature patterns in the Pacific and Indian Oceans are close to average, so neither of these factors is driving Australia’s record warmth.
A clear human fingerprint
Another factor that might have influenced the July heat is human-caused climate change.
To assess the role of climate change in this event, I used climate model simulations and a standard event-attribution method. I first evaluated the climate models to gauge how well they capture the observed temperatures over Australia during July. I then computed the likelihood of unusually warm July average maximum temperatures across Australia in two groups of climate model simulations: one representing the world of today, and another representing a world without human influences on the climate.
I found a very clear signal that human-induced climate change has increased the likelihood of warm July temperatures such as the ones we’ve just experienced. My results suggest that climate change increased the chances of this record July warmth by at least a factor of 12.
July heat is on the rise
I also wanted to know if this kind of unusual July warmth over Australia will become more common in future.
I looked at climate model projections for the next century, and examined the chances of these warm conditions occurring in periods when global warming is at 1.5℃ and 2℃ above pre-industrial levels (we have had roughly 1℃ of global warming above these levels so far).
The 1.5℃ and 2℃ global warming targets were decided in the Paris Agreement, brokered in December 2015. Given that we are aiming to limit global warming to these levels it is vital that we have a good idea of the climate we’re likely to be living in at these levels of warming.
I found that even if we manage to limit global warming to 1.5℃ we can expect to experience such July heat (which is record-breaking by today’s standards) in about 28% of winters. At 2℃ of global warming, the chances of warm July temperatures like 2017 are 43% for any given year.
Given the benefits of fewer and less intense heat extremes over Australia at lower levels of global warming, there is a clear incentive to try and limit climate change as much as possible. If we can reduce our greenhouse gas emissions and hold global warming to the Paris target levels, we should be able to avoid the kind of unusual warmth we have seen this July becoming the new normal.
This June was the seventh-warmest and second-driest on record for Australia. Parts of the southwest and southeast saw record dry conditions as frontal systems passed further south than normal and high pressure exerted its influence on the continent.
While many of us will have enjoyed warm, dry weather, farmers in the south of the country will be concerned at the lack of winter rain for their crops. Winter is the dominant season for rainfall, especially in the southwest of the continent, so a return to wetter conditions would be welcome.
There are already indications of drought developing across the west coast of Western Australia and in other areas of the country.
Did climate change play a role?
To deduce whether climate change had an influence on this particular event, I used two sets of climate model simulations: one representing the world of today and another representing a world without human influences (that is, with pre-industrial greenhouse gas concentrations).
I compared the likelihood and magnitude of dry Junes in the two sets of simulations to determine the net effect of human-caused climate change.
I looked at the climate change influence on very dry Junes (such as the one we’ve just experienced) both for Australia as a whole, and for the southeast, which had its driest June on record. Both of these areas received well below half of their average June rainfall in June 2017.
For Australia-wide June rainfall, I found a clear climate change signal towards drier conditions.
According to my analysis, climate change has increased the likelihood of very dry Junes by at least a third. The driest Junes now are about 12% drier than they would be in the absence of human greenhouse emissions.
When I looked at southeast Australia, however, I found that the influence of climate change is less clear.
My analysis suggested that climate change has probably increased the chance of dry conditions, although there is more uncertainty than for Australia as a whole.
That said, the driest Junes appear to be drier in the world of today than they would have been without climate change, by about 8% in the case of southeast Australia.
It’s not surprising that the result for southeast Australia is less distinct. Generally speaking, the smaller the area, the harder it is to detect an influence of climate change, as there is more year-to-year variability.
What can we expect in future?
The Paris Agreement aims to hold global warming well below 2℃ and preferably at around 1.5℃ above pre-industrial average temperatures. For context, we have had a little over 1℃ of global warming so far, so we’re more than two-thirds of the way to the 1.5℃ target already.
Under either a 1.5℃ or 2℃ global warming target, I project that dry Junes in Australia will become more frequent. For the southeast of the continent the picture is less clear, with high uncertainty in the change we might see.
The trend towards drier Junes across Australia is related to the southward shift in the storm track, the prevailing westerly winds that bring frontal weather systems across southern Australia. June 2017 is a very clear example of this effect.
Scientists use the Southern Annular Mode (SAM) to describe the position of the storm track. It has been trending towards more “positive” conditions, reflecting a poleward movement in the frontal systems which typically causes them to pass to the south of the Australian landmass.
These positive SAM phases bring drier conditions to most of Australia, but wetter conditions to coastal New South Wales. This is precisely what we have seen in June 2017.
As the effects of climate change intensify in the coming years, scientists expect to see the frontal systems that bring vital rainfall to the south of Australia moving further and further south. This increases the chance of Australia experiencing more dry Junes like the one just passed. Increasing temperatures will cause greater evaporation when there is rainfall, further exacerbating drought conditions.
You can find full details of the methods used in this analysis here.
The 2017 federal budget has axed funding for the National Climate Change Adaptation Research Facility (NCCARF), an agency that provides information to decision-makers on how best to manage the risks of climate change and sea level rise.
The NCCARF received A$50 million in 2008 to coordinate Australia’s national research effort into climate adaptation measures. That was reduced in 2014 to just under A$9 million. For 2017-18, a mere A$600,000 will be spread between CSIRO and NCCARF to support existing online platforms only. From 2018, funding is axed entirely.
Despite a growing global impetus to address the risks of climate change, there is evidence that Australia is being hampered by policy inertia. A review of 79 submissions to the Productivity Commission’s inquiry on Barriers to Effective Climate Change Adaptation, published in 2014, found that:
adaptation first and foremost requires clear governance, and appropriate policy and legislation to implement change.
Earlier this year the World Economic Forum listed “failure of climate change mitigation and adaptation” as one of the top five risks to the world, in terms of its potential impact. Meanwhile, in Australia, local governments, professionals and community groups have consistently called for more national policy guidance on how best to adapt to climate risks.
The government’s decision to slash funding for climate adaptation research is therefore at odds with the growing urgency of the problem. The Intergovernmental Panel on Climate Change, in its most recent major assessment report, pointed out that Australia can benefit significantly from taking adaptation action in highly vulnerable sectors.
These areas of vulnerability include: the risk of more frequent and intense floods; water shortages in southern regions; deaths and infrastructure damage caused by heatwaves; bushfires; and impacts on low-lying coastal communities.
To put it simply, lives and money will be saved by strong climate adaptation measures.
Australia needs a coherent policy approach that goes beyond the current focus on energy policy, although climate adaptation is indeed an important issue for our electricity grid as well as for many other elements of our infrastructure. A coherent, whole-of-government, approach to climate risk is the economical and sensible approach in the long term.
Like it or not, the federal government has to take a leading role in climate adaptation. This includes the ongoing need to address existing knowledge gaps through well-funded research.
The federal government is the major funder of leading research in Australia, delivered through CSIRO, the National Health and Medical Research Council, the Cooperative Reserach Centres, the Australian Research Council and universities. This role should not be divested. Without climate adaptation research, Australia can expect significantly higher infrastructure damage and repair costs, more death and disease, and more frequent disruption to services – much of which would be avoidable with the right knowledge and preparation.
The damage bill from the 2010-11 Queensland floods alone exceeded A$6 billion. Since 2009, natural disasters have cost the Australian government more than A$12 billion, and the private sector has begun trying in earnest to reduce its risk exposure.
In response to these known risks, there is demand for robust policy guidance. Effective partnerships between government, industry and the community are crucial. One such example led by the NCCARF is CoastAdapt, an online tool that collates details of climate risks and potential costs in coastal areas.
For projects like this, success hinges on full engagement with all relevant spheres of government, industry, research, and the community. There is more to be done, and it needs leadership at the highest level.