There has been considerable activity in Variability and Teleconnections research program.

We’ve had some additions to the Variability and Teleconnections team with the arrival of new Associate Investigators Giovanni Liguori, Callum Shakespeare and Andrew Marshall. We also welcomed new students Nick Velzeboer, Callum Shaw, and Sebastian McKenna.

Prof Markus Jochum visited us from the University of Copenhagen and worked with Max Nikurashin at the University of Tasmania through February, as well as visiting ANU.

We have a few triumphs to celebrate as well. Congratulations to Julie Arblaster who this year made the Highly Cited list from Clarivate Analytics. The list captures researchers who place in the top one per cent of the consistently most highly cited researchers in their field over a 10-year period.

Congratulations also go to Dom Thorn who received the AMOS Melbourne Chapter Regional Award for his Masters.

Researcher Andrea Taschetto was made guest editor of a special edition, Weather and climate extremes: current developments, for the journal Atmosphere.

In the meantime Dr Helen Phillips and Prof Nathan Bindoff are currently on study leave in Woods Hole, US, where they are collaborating with Caroline Ummenhoffer and Kurt Polzin. Nathan is also working on the IPCC Special Report on Oceans and Cryosphere in a Changing Climate  (SROCC).

Despite their absence, research has been continuing apace. A mystery of particular significance to the southern hemisphere has been the dramatic drop in sea ice around Antarctica during the Austral summer of 2016/17. CLEX researchers and colleagues used observations and climate models to examine this rapid decline. They concluded that natural variability was likely responsible although climate change could not be ruled out. In an interesting update, the 2016/17 record was broken again over the 2018/19 summer.

Understanding natural variability and ocean processes plays a key role in getting to grips with the teleconnections that influence Australia and the global climate. Observations taken during a voyage into the Southern Ocean by CLEX researchers have revealed that cold eddies carried heat into the Subantarctic Zone at a rate 2.6 times greater than previously estimated. Combining these observations with satellite measurements they estimate that 21% of the heat carried across into this zone comes from these cold eddies.

Further research on heat transfer in the ocean has found that small diabatic processes, like small-scale turbulence, play an important role in moving heat from tropical regions towards the poles. Importantly, these smaller processes are not represented very well in climate models and they need to be more precisely represented if we are to project future changes accurately.

Along with modelled improvements, researchers from the Climate and Variability team have recently called for an improvement in the tropical observing system. This observing system is crucial in monitoring and forecasting the development of El Niño and La Niña events. A paper by CLEX researchers and colleagues call for four important changes to the system and looks ahead at future requirements. This is an investment that is vital for Australia and many other countries around the Pacific Rim and beyond.

The importance of this improvement was reinforced by a paper in Nature that brought together a wide range of models to determine if there was a consensus result on how El Niños may change with global warming. The results across multiple models indicated an increase in strength and impact of future El Niños. This suggests the likelihood of extreme weather events will increase and adds a compelling argument for the improvement of the tropical observing system.

Finally, as with the other research programs, we have been working on improving the use of climate models. Recent CLEX research has found that optimising a climate model ensemble to perform well in one variable not only degrades estimates in other variables, but results in uncertainty estimates that are too narrow. It is only when several variables are optimised independently, and the results from each optimisation are merged, that we can achieve both improved ensemble performance and improved uncertainty estimates. These investigations and model behaviour continue to inform how we use climate models, reduced biases and diminish uncertainty.