School of Physical and Chemical Sciences Te Kura Matū Seminar Series

The source and fate of fossil fuel CO2 emissions


Dr Jocelyn Turnbull


GNS Science, New Zealand and CIRES, University of Colorado at Boulder

Time & Place

Fri, 16 Mar 2018 11:00:00 NZDT in Room 531, level 5, West Building(formerly Rutherford)

All are welcome


Fossil fuel burning is the primary driver of increasing atmospheric carbon dioxide (CO2), which recently passed the landmark 400 parts per million mark. All nations have committed to reducing their emissions under the Paris Agreement, through a variety of United Nations Framework Convention on Climate Change (UNFCCC) prescribed mechanisms including reductions in fossil fuel emissions and credit for removal of CO2 by land carbon sinks.  To ensure that the promised emission reductions are achieved, an understanding of emission rates from individual sources, cities, regions and countries, and of the land carbon sink rate, is critical.  The land sink carbon accounting methods prescribed by the UNFCCC must match the actual real-world CO2 removal rates.

The UNFCCC currently relies on “bottom-up” economic information to determine fossil fuel emission rates, and on bottom-up biomass estimates to determine the land carbon sink.  In this presentation, I will discuss the use of a “top-down” approach that uses atmospheric measurements and modelling that complements the bottom-up method. 

Measurements of CO2 alone are usually not sufficient to determine sources and sinks, due to the large and varying CO2 background. Due to their extreme age, fossil fuels are devoid of radiocarbon (14C), whereas all other CO2 sources have 14C content close to that of the current atmosphere. Thus 14C is an ideal tracer for fossil fuel CO2.  Stable isotope and ancillary trace gas measurements can provide detail on the source sectors contributing to the fossil fuel emissions at a given location, and in the processes driving land carbon uptake. I will showcase how the method can be used to quantify fossil fuel CO2 emissions and land carbon uptake, giving examples from USA and New Zealand. 

I will discuss the broader context of radiocarbon measurements, including the Southern Ocean carbon sink, radiocarbon dating and forensic applications.