Emission targets for avoiding dangerous climate change

Thesis

A number of recent studies have found a strong link between peak global warming due to anthropogenic carbon dioxide and cumulative carbon emissions from the start of the industrial revolution. This thesis builds on this work by using a simple climate model to apply the concept of cumulative emissions to emission floors, by comparing cumulative emissions with other types of emissions target, and by extending the work to apply to noncarbon dioxide (CO₂) greenhouse gases and short-lived climate forcers (SLCFs).

Though peak global warming correlates well with cumulative carbon emissions, the link to emissions over shorter periods or in the years 2020 or 2050 is shown to be weaker. It is also shown that the introduction of emissions floors does not reduce the importance of cumulative emissions, but may make some warming targets unachievable. For pathways that give a most likely warming up to about 4°C, cumulative emissions from pre-industrial times to year 2200 correlate strongly with most likely resultant peak warming in the simple model used, regardless of the type of emissions floor used. The maximum rate of CO2- induced warming is not determined by cumulative emissions but is shown to be limited by the peak rate of CO₂ emissions. A simple model of non-CO₂ greenhouse gases is also developed and used to investigate SLCFs. It is shown that emissions of SLCFs today have little impact on peak warming, and that delaying near-term reductions in SLCFs would not have a significant impact on peak warming. Only once CO₂ emissions are falling do SLCF emissions have a significant impact on peak warming. A global climate policy framework is presented as an example of how the work in this thesis could be used in policy. Future work is also discussed, particularly verification of these results in a more complex model.

Authors: Bowerman, N

• Publication date: 2013
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: carbon emissions; Climate change; emission floor; cumulative emissions; emission targets
• Subjects: Atmospheric,Oceanic,and Planetary physics