Seminar – Prof. Dr. Christopher Jones – 16.09.2026 11:00-12:30 Uhr 
Konferenz Raum Atlantik  5-1.214

"The Zero Emissions Commitment: When will Global Warming stop?"

There is a (mis)conception that our climate will continue to warm up even if we stop adding greenhouse gases to the atmosphere. But this is not true – if we stop emitting, the world stops warming. Or at least approximately. This old idea of committed warming, or “warming in the pipeline” was based on asking what would happen if we kept CO2 levels constant in the atmosphere. But this is the wrong question – if we stop emitting CO2 then natural carbon sinks will remove it and CO2 levels drop. This means that we are not “committed” to ongoing warming after the point of zero emissions – hence it is known as the “Zero Emissions Commitment” or ZEC. The model evidence that ZEC is close to zero has existed for a while, but in CMIP6 an intercomparison activity, ZECMIP, explored it in more detail and allowed IPCC AR6 to make a more formal assessment of the science.

More importantly, the warming we will see depends almost linearly on the amount we emit up to the point of zero emissions. This relationship between global warming and cumulative emissions is known as TCRE (the Transient Climate Response to cumulative emissions). This is an incredibly useful result, but quantitative uncertainty is large enough to hinder its use for policy making.

In this seminar I will explain the science behind these concepts, their implications for carbon budgets and climate policy, and explore the “what next” questions as we are still trying to understand the mechanisms behind ZEC and constrain uncertainty in TCRE.


Chris Jones bio:
Chris Jones is a Research Fellow at the Met Office Hadley Centre, and Professor in Climate Science at the University of Bristol. He has over 30 years’ experience of climate modelling, with particular focus on climate-carbon cycle feedbacks – i.e. how natural systems respond to climate change but also affect it by absorbing CO2 from the atmosphere. He has led research into how this question can drive global climate policy and has been multiple times IPCC author. He is currently leading a WCRP assessment into TCRE: how sensitive the Earth System is to emissions of CO2 and how the climate system will respond if we either stabilise global temperature or remove CO2 in a way which can reverse global warming.