Short biography:
Sarah is a land-surface modeller focussing on permafrost regions. She came to this topic as a postdoc in 2013 (under the EU permafrost project 'PAGE21'). She is based at the University of Exeter in the UK, with close collaborations at the UK Met Office. Her interests lie both in developing process-based models, and also in a global perspective of changing permafrost and the carbon cycle.
Title of the seminar talk: A new constraint on the future of permafrost.
Abstract:
Permafrost, or permanently frozen ground, is a key component of the Earth system. It has major effects on the ground itself, and it also stores a lot of organic matter (dead plants and animals), which is frozen into the ground and cannot decompose. If the permafrost thaws, this organic matter will start to decompose, and this process could release large quantities of carbon dioxide into the atmosphere. Carbon dioxide is a greenhouse gas, and so the thawing of permafrost will increase global warming.
Due to its importance, models are used to find out what will happen to permafrost in the future. However, there are problems with using climate models for this, because the models don't represent permafrost very well and often have large biases. We have developed and tested a new approach where we look at measurements of how permafrost varies over the earth's surface, and how this varies with the air temperature (colder regions have more permafrost, and vice versa). We can then use this relationship to estimate what the permafrost would look like in a warmer world, without including any of the biases from the models.
Of course, we don't know what will happen in the future. Usually, climate models take one of a handful of different 'scenarios' for possible human activities in the future (e.g. how much fossil fuel will be burned). However, we use an approach that allows us to calculate the permafrost extent simply from the amount of global warming. So, for example, we can estimate how much permafrost will thaw if the climate is stabilised at 2ºC above pre-industrial levels, or alternatively at 1.5ºC, which are the targets in the 2015 Paris agreement.
Permafrost varies a lot even if the air temperature is constant, so our values provide a range rather than an exact number. We calculate that between 3 and 5 million km2 of permafrost will be lost for every 1ºC of global warming. Therefore around 8 million km2 will be lost if we stabilise at 2ºC above pre-industrial levels - this is approximately 50% of the pre-industrial permafrost area. Stabilising at 1.5ºC instead of 2ºC would save around 2 million km2 of permafrost, which could be significant for policy decisions.
Arranged date for the seminar talk: Feb 13, 2017