The Drought program has had a busy few months engaging with industry, the public, and policymakers in Australia and around the world. Andy Pitman submitted detailed feedback to the Australian Prudential Regulation Authority on their draft CPG 229 Climate Change Financial Risks Practice Guide; and briefed Bloomberg/BNEF on the utility of climate models in assessing climate risk and the Network of Central Banks and Supervisors for Greening the Financial System (NGFS).
Meanwhile, Jason Evans presented to investment company the JARDEN group about climate change and future climate risks and also took part in the meeting National First Peoples Gathering on Climate Change, that brought together scientists and indigenous people from all around Australia to discuss the impacts of climate change on country, what changes we might expect in the future and how we might adapt to them.
Andrea Taschetto was very active in the agricultural sector delivering a talk on ENSO Modoki and Australian rainfall impacts to the 2021 Winter Cropping Climate Outlook Workshop organised by AgEcon, and presenting as part of The Forewarned is Forearmed (FWFA) Project Webinar Series on ENSO diversity and Australian rainfall variability directed at farmers and agricultural stakeholders.
While all this was happening Ben Henley aimed his public interactions to the climate scientists of the future, giving a talk, Science, wonder and the climate: an Introduction, to 150 English as an Additional Language (EAL) refugees and new immigrants at Western English Language School at Braybrook (VIC).
Our research has also broken into new arenas. CLEX researchers were the first in the world to examine flash droughts in climate models. Flash drought is a type of drought that is characterised by a rapid onset and intensification and with substantial impacts on agriculture. In a matter of weeks, regions with lush green and healthy crops can find themselves in a severe drought, jeopardising the annual harvest and livestock. Examining these events in climate models not only shows how these processes develop in models but also gives us the tools to understand how flash droughts may change in the future. The results showed that in the future all drought indices show a higher frequency of flash drought events, particularly those based on precipitation or evaporative demand alone compared to the models’ soil moisture. Precipitation deficits are the main contributor to flash drought in climate models, with evaporation playing a secondary role.
The key role of precipitation in drought is why recent Drought program research aimed to evaluate the uncertainties in satellite precipitation data, by comparing the data with a ground-based radar product using both location-based and storm-based approaches. The results showed the satellite data had better agreement in terms of the average precipitation intensity and area. However, the satellite observations tended to show storms with smaller areas compared to the ground-based observations, possibly due to the effect of light precipitation not being detected properly. The researchers were also able to distinguish what caused the reduced precision of satellite observations that led to a growth in precipitation area and a downward trend in average precipitation intensity compared to ground-based observations. They were also able to show, which satellite sensors were best at capturing observed characteristics, the average intensity of precipitation events, and precipitation area.
We have also been involved in cross-program research. Working with researchers from the Weather and Climate Interaction, Attribution and Risk, and Modelling research programs, we used Sydney, Australia’s largest city, as a test case for our new configuration of the Weather and Research Forecasting model run at a very high resolution of 800 m with a new urban classification scheme that describes the complexity of Sydney’s built environment. The research aimed to explore how heatwaves formed over the Sydney basin and how much urban infrastructure amplified this heat. We found the urban environment on average adds about 1˚C of heat in the lower atmosphere, but over heatwave periods this can exceed 10˚C and also impact the Blue Mountains area when sea breezes act to push the heat further inland.
Extreme conditions also form in rural regions and can impact agricultural industries. It is important to understand how these extreme events may change in the future and whether certain crops will be able to weather or even prosper under new climate regimes. Working with our colleagues in the Attribution and Risk research program, we explored the impact of climate change on the hazelnut yield in south-eastern Australia as the growing market for nuts is driving demand for new locations for hazelnut cultivation. Using high-resolution regional climate projections with a process-based hazelnut simulation model we found while there was some variation in future growth areas, in the southeasternmost part of Australia all projections indicated yield increases, providing the confidence to establish new hazelnut cultivation in this area.
Another area of growing interest to agricultural producers is the capacity of soils to store carbon therefore understanding what influences the terrestrial carbon cycle may be of importance in the future. We know global weather can influence vegetation, and therefore the carbon cycle. One of the biggest global influences for Australia are El Niño events. For this reason, CLEX researchers explored the long-term impacts on the carbon balance on land linked to two El Niño types – the central Pacific and the eastern Pacific. Using a dynamic vegetation model, they simulated what would happen if either a central Pacific or eastern Pacific El Niño event occurred. They found that the different expressions of El Niño do affect interannual variability in the terrestrial carbon cycle. However, the effect over longer timescales was small. This means the changing frequency of these two types of El Niño events may be of little importance in terms of robustly simulating the future terrestrial carbon cycle.
Because of its importance to Australian climate extremes, understanding how the El Niño Southern Oscillation (ENSO) interacts and are affected by other ocean basins is an important underlying component of our research. ENSO is known to affect sea surface temperature in the tropical North Atlantic via atmospheric teleconnections in the tropics and the extra-tropics. However, this influence seems to vary depending on the strength of ENSO. In this study, CLEX researchers and colleagues showed the North Atlantic sea-surface temperature response to ENSO is nonlinear with respect to the strength of the sea-surface temperature forcing in the tropical Pacific. For example, further increases in El Nino magnitudes ceases to create further increases of the tropical North Atlantic sea surface temperature anomaly. They also found that the tropical teleconnection pathway is more linear than the extratropical pathway.
Together this research is building a picture around the causes of droughts and their impact on Australia’s urban and agricultural areas that will inform future policies and adaption activities. To help us continue improving our understanding we have been able to welcome new Postdocs and PhD students. Even in the time of COVID-19 we welcomed Anjana Devanand as a new postdoc in the program, joining us from Adelaide, while PhD students Rachael Isphording, from the US finished her 2-week quarantine period to join CLEX and Megyuan Yu was returned to us after being stuck overseas.
We should conclude by acknowledging those individuals who have had personal successes. Ben Henley recently commenced as Executive Domain Editor at WIREs Climate Change in the domain of Paleoclimates and Current Trends, Andy Pitman, was elected as a Fellow of the Australian Academy of Science.