Chair in Biosphere and Climate Impacts

Earth System models have contributed invaluably to our evolving understanding and awareness of climate change. Yet, fundamental limitations to these mathematical tools remain, not the least of which is their tendency to deliver contradictory results. Pointing the finger at their unnecessary complexity, Prof. Colin Prentice and a number of other world-renowned scientists have undertaken the mission to produce a new generation of models of the global land surface, resting on secure theoretical and empirical foundations. The overall objective is to develop robust, quantitative knowledge about the impacts of environmental variability and change on land ecosystems, and interactions with the atmosphere.

During his tenure of the AXA Chair in Biosphere and Climate Impacts at Imperial College, from 2012 to 2019, Prof. Prentice developed a new approach to the study of plant ecology and land-system modelling, focusing especially on the measurement and prediction of carbon uptake by plants.

Predicting carbon uptake by plants: a prerequisite of climate change research

The main achievement of the research program is the development of a satellite-based model to predict the total uptake of carbon in photosynthesis (aka "gross primary production" or GPP) across the ecosystems of the world. “The model is remarkably simple, explains Prof. Prentice. Yet, it performs much better than many models that are far more complicated”. Part of the reason lies in theory. During the course of the AXA Chair, he and his team showed, for instance, that the "light use efficiency" formulation (which means GPP is proportional to the amount of light absorbed by leaves) has a sound basis, and can be used to predict carbon uptake provided the way leaves change properties over time is taken into account. They have also demonstrated how the temperature of leaves (provided the plants have sufficient water supply) is buffered, so leaves in cold climates tend to be warmer than the air while those in hot climates tend to be cooler. This is crucial information in regard to climate change and predicting how vegetation will respond to the shifts in temperatures. Another accomplishment of the program is the development of a model that correctly predicts how the thickness of leaves (leaf mass per area, LMA) relates to their lifespan, and how this relationship shifts according to light intensity, the length of the favorable growth season, and other aspects of climate.

Capitalizing on evidence-based research to develop “next-gen” vegetation models

“These mechanisms are all cogs in the ecosystems machine, and what we are doing is reassessing them, finding simple ways to explain and predict them, to make sure that our vegetations models are based on sound information”, he summarizes. On the long run, the work of Prof Prentice will help encourage the general adoption of more reliable models for the impacts of climate change on ecosystems and how ecosystem processes influence the carbon cycle and climate. “With better models will come a new-found ability of science to deliver actionable information on climate-change adaptation in the context of the Sustainable Development Goals.” His research, he says, is all about the consolidation of knowledge. And data, now widely available, is the key ingredient. “What was impossible 20 years ago, now is, because of the availability of all kinds of precise measurements, at scales ranging from the single leaf to the whole globe”.

The need for reliable information, based on fundamental research on the consequences of climate change, is growing as an urgent, practical matter. By responding to this demand with evidence-based, basic science, the AXA Chair in Biosphere and Climate Impacts has played a central role in initiating a slow, but sure change in plant functional ecology and land ecosystem modelling. The international consortium Prof. Colin Prentice helped set up during his tenure – comprising members from UC Berkeley, Texas Tech, Reading University, ETH Zurich and Tsinghua University –, by perpetuating effort to develop “next-gen” vegetation models, is spearheading a new paradigm shift in Earth system modelling.

More information about the subject

Simplicity Yields More Powerful Predictions for the Biosphere Biodiversity at Risk : Preserving the Natural World for our Future