August 17, 2021 | Published by | , ,

The Attribution and Risk program is taking shape with regular meetings on the fourth Wednesday of every month and has established focused questions around the processes that shape Australian extremes and the advanced machine learning/statistical approaches that will help produce the answers. Research ranges from the broad understanding of how large-scale processes and variability drive changes in climate extremes through to understanding the causes of individual weather extremes (event attribution) and how all of these things play out in the future to impact our extreme climate risk.

A key study that helps set the stage for future research on event attribution was recently published in Climatic Change. It looks at the choices taken at each step in the analysis of the role of climate change in extreme weather events and determines how these choices may affect the outcome and usefulness of climate attribution. It identified how each choice from model selection through to evaluation techniques could introduce bias into the results and the importance of choosing the right way to communicate what the study found. Overall, the authors suggested event attribution studies are most useful when they are designed carefully to account for the methodological choices that can be made along the way.

As that research shows, event attribution studies are dependent on high-quality data and that applies broadly to attribution and risk research. With this in mind, researchers from the Attribution and Risk program have created two new evapotranspiration datasets, DOLCE V2 and DOLCE V3 that combines several existing ET products and field measurements of ET from global flux networks. Independent field measurements have shown these datasets match measurements more closely than any other assessed dataset. Intriguingly, trends derived from DOLCE V3 show clear increases in ET since 1980 over the majority of the Earth’s surface.

Through this foundational research, we can explore the future risk climate change poses to certain industries. This was highlighted in a regional study of areas undertaking hazelnut cultivation in Australia. CLEX researchers and colleagues combined high-resolution regional climate projections with a process-based hazelnut simulation model to predict future hazelnut yield. Most regions in southeast Australia showed a wide range of projected changes with both increases or decreases in yield possible due to the balance of competing processes. However, in the southeasternmost part of Australia, all projections indicated yield increases, providing the confidence to establish new hazelnut cultivation in this area.

But our research doesn’t just apply to agricultural areas, it also gives us deep insights into the risks that extreme events may play in our major cities. Working with CLEX researchers from the Weather and Climate Interactions, and the Drought 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 800m. The model used a new urban classification scheme that describes the complexity of Sydney’s built environment. The results showed that heatwaves often start with a hot continental flow over the Blue Mountains descending into the Greater Sydney region and that this gets trapped, leading to temperature differences across the city exceeding 15 ˚C. The level of detail from the high-resolution simulation was so high that the researchers could interrogate the role of local breezes to either enhance or dissipate heat. This capability is the first step towards building an understanding of how our cities will need to adapt to climate change.

We have also been sharing our research with the general public. The Attribution and Risk program was the first research program in CLEX to take part in a new series of streaming video episodes for Climate Australia. Julie Arblaster, Lisa Alexander, and Gab Abramowitz discussed the research around the Attribution and Risk research program with host Lee Constable in the episode, Is climate to blame? Understanding attribution and risk in a climate crisis. The episode explores why we can detect climate signals in some extreme weather events and not others and the implications this has for understanding how these events may change. Finally, we must acknowledge the level of engagement of postdoc Nina Ridder. Nina was re-elected for the Young Earth System Scientists executive committee for the second year in the row. Nina was also accepted as a member of the Interim Coordinating Committee (ICG) of the new WCRP Home Regional Information for Society (RifS). The ICG is set up to coordinate the preparation of a draft science plan, governance and structure for RifS. As if that isn’t enough, Nina is also the new committee chair for the AMOS NSW Chapter.