Carbon offsetting can play an important role in achieving airlines' climate goals, says study, but finds low level of understanding

Carbon offsetting can play an important role in achieving airlines' climate goals, says study, but finds low level of understanding | Susanne Becken,Brendan Mackey,Griffith University

Fri 8 Sept 2017 – With the growth in air travel demand forecast to outstrip fuel efficiency improvements, the aviation industry’s CO2 emissions goals can only be achieved through the purchase of carbon offsets. However, says a new study, there is considerable misunderstanding about offsetting and the difference between scientific and policy perspectives. Through their customer carbon offsetting schemes, airlines have already built partnerships with offset providers but it is important they correctly communicate the climate change benefits, say researchers from Griffith University in Australia. A total of 139 airlines were analysed in a study to investigate what information they provided on their role in carbon offsetting and whether the option was offered to their customers, with 44 airlines found to be actively involved. The researchers provide a number of best-practice principles to help airlines improve the reporting of their offsetting schemes.


“The key message of our paper is really to understand that carbon offsets play an important role in addressing climate change, but not in the sense that they make emissions ‘go away’ in some miraculous manner, but that they help slow down the flow of emissions into our atmosphere,” said Professor Susanne Becken of the Griffith Institute for Tourism, who co-authored the paper with Professor Brendan Mackey of the Griffith Climate Change Response Program. 


“We argue that there is a lot of confusion about what offsets can achieve and the use of language is often inaccurate or scientifically wrong. Given the airline industry is going to engage even more with offsetting through ICAO’s global CORSIA scheme, it is essential we clearly understand offsets and how to use them.”


The key, they say, to assessing the aviation sector’s carbon offsetting schemes is to appreciate the difference between science and policy. From a scientific perspective, the benefits and limitations of such schemes can only be understood in the context of the global carbon cycle and the major stocks, flows and natural processes that regulate, among other things, the atmospheric concentration of CO2.  


For example, forest protection and restoration do not offset fossil fuel emissions in the physical understanding of the word. The influence on the global climate system of additional atmospheric CO2 from the combustion of fossil fuels is not neutralised by offsets in the land sector. However, both forest protection and restoration are important components of a comprehensive approach to greenhouse gas mitigation along with the deep cuts needed in fossil fuel emissions.


“Indeed, emissions from both sources must reduce to zero by the end of this century to meet the Paris Agreement global warming target,” says the paper, which is published in the Journal of Air Transport Management.


Climate change policy, on the other hand, reflects negotiated outcomes between national governments that are parties to the UNFCCC. As a consequence, the idea of carbon offsets has developed a meaning and usage that is not necessarily consistent with the scientific understanding of the word, argues the paper.


Carbon offset projects can be broadly classified into three categories: those that are energy related so that CO2 emissions are reduced or avoided from fossil fuel use; those that relate to forest management (forest protection and reforestation); and waste projects that reduce greenhouse gases other than CO2.


Purchasing an offset generated from an energy project results in the avoidance of an additional one tonne of fossil fuel CO2 that would otherwise have occurred. This achieves a relative reduction of one tonne of CO2 compared with the alternative of not buying the offset. So if the flight produced one tonne of CO2 the offset results in one instead of two tonnes of fossil fuel emissions. Offsetting therefore leads to a relative reduction of the carbon flow into the atmosphere, compared with the status quo scenario of two parties emitting one tonne each.


When purchasing an offset generated from a forest protection project, the credit is generated through changes in forest management that prevent deforestation and degradation and thereby avoid future biomass carbon emissions. As with the energy-related example, the forest protection carbon credit results in one not two additional tonnes of CO2 flow into the atmosphere. However, in this case the avoided emission of one tonne is biomass CO2 rather than fossil fuel CO2. Again, in absolute terms and from the perspective of atmospheric carbon stock, emissions in the atmosphere have increased by one tonne of fossil fuel CO2.


When purchasing an offset from a reforestation project, the credit has been generated by making use of previously deforested land that can serve as a sink to regrow biomass carbon stock. In this case, the one tonne of CO2 has been sequestered from the atmosphere and the offset has served to ‘repay the carbon debt’ from when the land was previously cleared and is therefore restoring a depleted biomass carbon stock.  The end result is the same as in the other two project types that in absolute terms, emissions in the atmosphere relative to pre-industrial levels have still increased by one tonne of fossil fuel CO2.


These examples show that the science of what carbon offsetting means for atmospheric concentrations of CO2 is not straightforward and different to the commonly held view that it ‘neutralises’ aviation emissions, say the researchers. Therefore, in all three cases the offsets result in there being one less tonne in the atmosphere and so a relative reduction of CO2 flow has been achieved but not an absolute one in terms of atmospheric stock. However, they add, offsetting aviation sector emissions through purchasing carbon credits, while not neutralising them in terms of concentrations in the atmosphere, can make a significant contribution to mitigation efforts by slowing the rate at which anthropogenic CO2 is emitted into the atmosphere and helping repay the carbon debt.


Until CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) gets underway in 2021, carbon offsetting in aviation has focused on airline voluntary schemes for air travellers. However, the practice is still at a very low level, possibly in the order of several per cent of travellers, with previous research showing widespread scepticism and uncertainty about carbon offset schemes. This is not surprising given the complexity around carbon offsetting, suggests the paper, and airlines play a key role in communicating and facilitating offsetting.


To find out to what extent this is currently the case, the researchers looked through 139 major airline websites and company reports and found 44 (or 31.7%) actively involved in carbon offsetting activities, with five others stating they did not support offsetting at all. Of the 44 airlines, 34 provide an offsetting option to their customers on their website, but only four feature a link to carbon offsetting on their home page (Iberia, KLM, Scandinavian Airlines and Thai Airways). The study found that additional information was relatively limited, with just 18 airlines giving detail on the certification of their carbon offsets. Similarly, airlines’ reporting of methods used to calculate emissions was found to be neither comprehensive nor consistent, with 11 not disclosing any information on their methods.


Ten airlines reveal how much carbon has been offset through their schemes but since the uptake by travellers is comparatively small, very few demonstrate adequate disclosure on the total amounts of carbon offsets in a given timeframe. On the other hand, most of the 44 airlines offer some information on the projects they support financially through offsetting purchases by customers, although the extent of detail and transparency varies.


Airlines are taken to task in the study over the lack of clarity or scientific accuracy when communicating what carbon offsetting achieves, noting one North American airline implying that purchasing carbon offsets results in reduced CO2 concentrations in the atmosphere. “Very few airlines correctly stated that the offset results in avoided emissions elsewhere, and still have a climate impact in that fossil fuel carbon is released into the atmosphere – just less of it,” it says.


Becken and Mackey propose five principles as best practice for airline customer carbon offset schemes:

  • The terminology and wording used by the sector to describe their schemes accurately portray the scientific realities and the mitigation benefits being achieved;
  • Customers have the information needed to understand what carbon offsets achieve in relation to the emissions from their flights;
  • Understand that the most credible aviation carbon offset programmes are those designed to genuinely help avoid emissions through funding renewable energy projects and forest protection and restoration activities, and have important co-benefits;
  • The projects supported are selected carefully, reported on regularly and communicated transparently; and
  • Carbon credits are third-party audited and information on the quality of the credit – including assurance that double counting does not occur – is disclosed.


As the Paris Agreement comes to be implemented, it will have profound implications for the operation of the voluntary carbon market under which the aviation sector funds project-based offset activities and how aviation offsets are related to national mitigation commitments and associated national greenhouse gas accounts. All industrial sectors, including aviation, will also come under careful attention on how the mitigation burden of limiting global warming will be shared.


“While the social licence under which the aviation sector clearly operates is unlikely to be revoked, its emissions, especially the international component, will come under increasing scrutiny,” say the authors. As it does not reduce atmospheric concentrations of CO2, carbon offsetting should be seen as a second or even third best option behind technological advances or demand reduction efforts to make the necessary deep cuts in aviation emissions over the long term, they argue.


“However, when pursued, the principles suggested here should be adhered to so to provide a credible basis on which airlines can develop their brand-specific approach to carbon offsets,” they conclude. “In addition, adoption of these principles as part of a sector-wide framework will facilitate the aviation industry’s reporting of credible aggregate mitigation statistics, enhancing its role as a Non-State Actor.”


A PDF of the paper is available by email from co-author Professor Susanne Becken.




‘What role for carbon offsetting aviation greenhouse gas emissions in a deep-cut carbon world?’ (scroll down page for full paper)



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