The European Research Council (ERC) has awarded Utrecht University researcher Johan Weijers an ERC Starting Independent Researcher Grant 2012 (1.5 million Euros).

With this award, Weijers can start-up his own research team to investigate the continental climate history of the Pliocene (ca. 2 to 5 million years ago). In the Pliocene, concentrations of the greenhouse gas CO₂ were equally high as what is currently measured in the atmosphere. This time interval, however, is characterised by absence of ice ages, elevated sea levels and higher sea surface temperatures. With his research, Weijers aims at a better quantification of the continental climate during the Pliocene. This is much needed to better validate current climate models and to improve our understanding of potential changes in our climate under the current elevated CO₂ concentrations.

Geological thermometer

For his research, Weijers applies advanced analytical techniques to investigate fossil molecules of soil bacteria. He has shown before that the distribution of these molecules in soils is related to temperature and soil pH. Upon soil erosion, these molecules are transported by rivers to the marine environment where they will sink to the ocean floor. By analyzing marine sediment cores layer by layer for the presence and distribution of these molecules, estimates of continental air temperature at the time of deposition can be made. This novel technique thus provides the opportunity to reconstruct absolute temperatures, something that has been rather difficult so far for continental areas.

Stronger warming around pole

In his new research project, Weijers will reconstruct continental temperatures for the Pliocene at different locations from the equator towards the pole. Based on the continuous reduction of sea ice surface area in summer at the North Pole, it seems like the North Pole is warming faster than elsewhere on earth. This is a known phenomenon from greenhouse worlds. Also during the Pliocene, sea surface temperatures at high latitude seem to have increased more strongly than in the tropics. Weijers will investigate if similar enhanced warming occurred on high latitude land and if this effect might have been even stronger on land than on sea. At the same time the analysis of fossil leaf waxes  from plants will be used to see if the intensity of the hydrological cycle (precipitation vs. evaporation) during the Pliocene was substantially different from today.

Analogy for the future

The reason for investigating the Pliocene is that it is the most recent period in Earth history with atmospheric CO₂ concentrations about similar to what is expected for the coming years (ca. 400 part per million). Since the Industrial Revolution, atmospheric CO₂ concentration is rising at such a speed that climate change in fact can’t keep up with this pace; i.e. the climate is lagging behind. Investigating the Pliocene provides us with a window into a world that experiences a climate similar to what we may expect for the near future. The results of this project are therefore also of interest for validating earth system models that are used for projecting future climate.