When carbon is irrelevant – vegetation and the glacial cycle

The net impact of the terrestrial biosphere on climate over the glacial-interglacial cycle has been speculated upon and modeled at low resolution (e.g. with only 51° longitude). Given the spatial heterogeneity of biogeophysical (e.g. albedo) effects, it is important to consider finer spatial scales and distinguish between biogeophysical and biogeochemical effects to fully understand the role of the terrestrial biosphere over the glacial-interglacial period.

In our Climate of the Past paper we present the first model analysis using a fully-coupled dynamic atmosphere-ocean-vegetation GCM over the last 120 ka that quantifies the net effect of vegetation on climate. This analysis shows that over the whole period the biogeophysical is the dominant effect, and that the biogeochemical impacts may have a lower possible range than typically estimated.

This is of particular interest from two research perspectives.

  • The net terrestrial biosphere contribution to climate is the opposite in these simulations to results of studies of the near past and future. This highlights how the balance of biogeophysical and biogeochemical terrestrial biosphere effects is very different depending on the timescale. This would be of interest to vegetation and climate modelers who work on the climate impact of the terrestrial biosphere in both the past and future.
  • The large range of low carbon changes from the last glacial maximum shown in our model challenges those who study this time period to think closely about assumptions that the terrestrial biosphere is a positive contributor to the carbon budget at this time.

This paper is currently in review for Climate of the Past.