Post-Graduate Student Talks 2018

Date: Friday 19 January 2018

Time: 18:00 - 20:30


University of Edinburgh
Drummond Street
United Kingdom


SPEAKER| Christine Mckenna, British Antarctic Survey.

ABSTRACT | Contrasting Northern Hemisphere Impacts Of Regional Arctic Sea-Ice Loss.

Most climate models agree that Arctic sea-ice loss will continue throughout the 21st century in response to rising greenhouse gases. This has led to much research into the impacts of future sea-ice loss on climate in mid-latitudes. However, the spatial pattern of future sea-ice loss is uncertain and, as such, understanding the impacts of different regions of sea-ice loss is important.

In this study, we conduct climate model simulations with surface warming (representing future sea-ice retreat) imposed in either the Atlantic or Pacific sectors of the Arctic. In agreement with previous work, we find different impacts on the stratospheric polar vortex in winter. However, the tropospheric response resembles a negative Arctic Oscillation (AO) in both cases, implying limited stratospheric influence on the troposphere. Still, there are different surface impacts, with the negative AO only causing cooling across Northern Europe in the Pacific run. In the Atlantic run, the imposed surface warming is closer to northern Europe and balances dynamical cooling through warm advection.

These results may be useful for interpreting the different responses to future sea-ice loss predicted by different climate models. For a climate model predicting sea-ice loss that is more heavily weighted towards the Pacific (Atlantic) sector, we would expect relatively more (less) northern European winter cooling.


SPEAKER | Alexander Todd, University Of Exeter.

ABSTRACT | Relating El Nino-Southern Oscillation And Global Warming Shifts In Tropical Precipitation.

Despite recent advances in climate modelling, uncertainty remains in future projections of tropical precipitation change under global warming. Previous work has presented a simplified method, based on the weak temperature gradient (WTG) hypothesis, for predicting tropical precipitation shifts using changes in surface air temperature and relative humidity (RH). We examine El Nino-Southern Oscillation (ENSO) precipitation shifts to assess the prediction method performance. The WTG assumption is justified using observations (r = 0.66), and an ensemble of coupled climate model simulations (r=0.51 to r = 0.82). Using inter-model variability, a significant relationship is demonstrated between method performance over land for present day ENSO and projected global warming. Hence, the prediction method presents a plausible mechanism linking future changes in precipitation, temperature and RH. These results support our understanding of the sources of uncertainty in tropical precipitation change under global warming.

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The meeting will be held in the Institute of Geography, University of Edinburgh, Drummond Street, EH8 9XP, starting at 6 p.m., with tea and biscuits available from 5:30 p.m. Please mention this meeting to friends and colleagues, since non-members of the society are very welcome at our meetings.