The Southern Annular Mode (SAM) influences climate in the Southern Hemisphere. We investigate the effects of calculation method and data used to calculate the SAM index and how it influences the relationship between the SAM and climate. We propose a method to calculate a natural SAM index that facilitates consistency between studies, including when using different data resolutions, avoiding distortion of SAM impacts and allowing for more reliable results of past and future SAM trends.

A Little Ice Age (LIA) hurricane was characterized using key storm intensity metrics from historical naval records. Its unusual intensity was driven by a higher temperature gradient between continental and coastal atmospheric circulation that drove intense midlatitude extratropical transition. Quantitative attributes embedded in historical records allow multidisciplinary research to extend our understanding of climate processes through the historical period.  

Radiocarbon proxies suggest that the deep waters are poorly ventilated during the Last Glacial Maximum (LGM). Here we use two transient simulations with tracers of radiocarbon and ideal age to show that the deep-ocean ventilation age is not much older at the LGM compared to the present day because of the strong glacial Antarctic Bottom Water transport. In contrast, the ventilation age is older during deglaciation mainly due to weakening of Antarctic Bottom Water transport.

The Pliocene (~ 3 million years ago) is of interest because its warm climate is similar to projections of the future. We explore the role of atmospheric carbon dioxide in forcing sea surface temperature during the Pliocene by combining climate model outputs with palaeoclimate proxy data. We investigate whether this role changes seasonally and also use our data to suggest a new estimate of Pliocene climate sensitivity. More data are needed to further explore the results presented.

We analyse simulations with idealised aerosol scenarios to examine the importance of aerosol forcing on mPWP precipitation and how aerosol uncertainty could explain the data–model mismatch. We find further warming, a narrower and stronger ITCZ, and monsoon domain rainfall change after removal of industrial emissions. Aerosols have more impacts on tropical precipitation than the mPWP boundary conditions. This highlights the importance of prescribed aerosol scenarios in simulating mPWP climate.

In 2018, a new 120 m ice core was drilled in a region located under the Antarctic ozone hole. We present the first results including a 1300-year record of snow accumulation and aerosol chemistry. We investigate the aerosol and moisture source regions and atmospheric processes related to the ice core record and discuss what this means for developing a record of past ultraviolet radiation and ozone depletion using the stable isotopic composition of nitrate measured in the same ice core.