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CCfCS Lent Symposium: Time scales in Climate Science.

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If you have a question about this talk, please contact Dr Alex Archibald.

UPDATED: Start & end time is now 2:20-5 pm

Schedule:

Prof. David Beerling, University of Sheffield. The scientific case for avoiding dangerous climate change to protect future generations and nature.

This contribution will consider the observational evidence for the effects of the human- made imbalance in the Earth’s energy budget caused by the global carbonization of society over the past century. It will show why drastic mitigation actions to curb greenhouse gas emissions are required if we are to restore the Earth’s energy balance and avoid peak future warming of 2°C and loss of planetary biodiversity.

Dr. Dan Lunt, University of Bristol. Warm climates of the past – a lesson for the future?

The relevance of past climate research for future climate change is often cited as a motivation for palaeoclimate research. However, what is the reality?

There is very strong evidence throughout Earth history, over timescales from thousands to millions of years, that climate varies markedly, and can do so rapidly across key thresholds or when subjected to particularly strong forcing. Quantifying the climate forcings and responses is more challenging. However, past CO2 and temperature records can be combined to produce constraints on climate sensitivity, providing full account is taken of uncertainties in the forcing and response. Synthesis of past environmental change can be used to evaluate numerical models. Inconsistencies between models and data has been the stimulus to reassess both the data (through better quantification of uncertainties), and the models (through exploration of model sensitivities and experimental design), a process which has led to improved agreement. Indeed, this model-data comparison can be used to provide quantitative constraints on future climate predictions, through a Bayesian approach.

Although there has been significant recent progress in this field, many challenges remain. These include improved understanding and development of palaeo CO2 proxies, developing of non-temperature proxies, and integrating past climate test cases into the development cycle of climate models

Dr. Pierre Dutrieux, British Antarctic Survey. Large spatial and temporal variability of oceanic melting beneath the Pine Island ice shelf and implications for ice shelf-ocean interactions.

Thinning and acceleration of West Antarctic ice streams are presently contributing about 10% of the observed global sea level rise⁠. A primary source is from Pine Island Glacier, which has thinned since at least 1992, driven by changes in ocean heat transport beneath its ice shelf and unpinning from a seabed ridge. Details about the ice-ocean interaction driving this change, however, remain largely elusive, hampering our ability to predict the future behaviour of this and similar systems. Here, high-resolution satellite and airborne observations of ice surface velocity and elevation are used to measure patterns of basal melt under the ice shelf and the associated adjustments to ice flow, revealing a complex distribution of oceanic melting at kilometre-scales. In addition, ocean observations taken in austral summer 2012 show a 250-m lowering of the thermocline at the glacier calving front and a 50% decrease of basal melting since 2009. High-resolution simulations of the ocean circulation in the cavity beneath the floating glacier tongue demonstrate that the seabed ridge blocks the warmest deep waters from reaching the ice and strongly ties meltwater production to thermocline depth above the ridge. These results highlight the role of climatic variability in glacial ice loss and the fundamental importance of local ice shelf and seabed geometry in determining the ice sheet response.

This talk is part of the Cambridge Centre for Climate Science series.

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