UK academic paper argues cost-benefit analysis remains challenging, but delaying emissions reductions only drives up cost of meeting Paris goals
Limiting global warming to 1.5C by the end of the century could soon become too expensive to justify despite the benefits of such action, according to a new analysis today by a group of UK academics.
The paper argues that stronger efforts to cut greenhouse gas emissions must be undertaken swiftly in order to avoid having to rely on more speculative, risky, and expensive emissions reduction technologies further down the line, such as direct CO2 capture systems or geo-engineering technologies.
Experts from Imperial College London, the University of East Anglia, and LSE's Grantham Research Institute on Climate Change and the Environment assessed almost 200 published academic papers on climate change and the feasibility of limiting temperature increases to 1.5C. They concluded that these analyses produce "inconclusive" results about the value of limiting global average temperature increases to 1.5C, which is the higher-ambition target included in the internationally-agreed Paris Agreement on climate change.
"Due to large uncertainties about the economic costs and, in particular, the benefits, there can be no clear answer to the question of whether the 1.5C target passes a cost-benefit test," states the paper which appears in the Annual Review of Environment and Resources journal.
The authors do emphasise there are large environmental benefits from limiting warming to 1.5C, compared to 2C, including lower levels of biodiverity loss and cora reef damage and the reduced risk of crossing climate 'tipping points'. However, they stress "the reduction in risk cannot presently be quantified".
Lead author Professor Simon Dietz from LSE's Grantham Research Institute explained that at present "the evidence we have simply does not give us a clear answer on whether the benefits of limiting warming to 1.5C exceed the costs".
"But if we want to keep the option open to limit warming to 1.5C degrees, then unless we discover a much cheaper way to remove carbon dioxide from the air, and if we want to avoid risky methods of blocking out sunlight, we have to pursue the goal of 1.5C degrees now," he added.
The remaining carbon budget - the amount of carbon we have left to safely emit - consistent with a 1.5C world is now very small and the global economy would need to be decarbonised "at an unprecedented scale to stay within it, entailing larger costs", the paper warns.
It points to studies showing a carbon price consistent with limiting warming to 1.5C would need to be at least $100 per tonne of CO2 emitted by 2020, and about three times higher than the price required to stop warming of more than 2C.
"Further delay in pursuing an emissions path consistent with 1.5C likely renders that target unattainable by conventional means, instead relying on expensive large-scale CDR [carbon dioxide removal], or risky solar radiation management", it warns.
The experts point out that CO2 removal measures, such as planting more vegetation, biomass energy carbon capture technologies or directly capturing CO2 and storing it, tend to be costly and present more challenges for agriculture, sustainability and biodiversity, than tackling emissions at source.
And solar radiation management, including propoals to reduce the amount of the sun's energy which reaches the earth by injecting aerosol particles into the atmosphere, is largely untested and has "significant associated risks", the paper argues.
Despite the various uncertainties, co-author of the paper, Imperial College London's Dr Ajay Gambhir, said the comparative benefits between a 1.5C world and a 2C world were still "striking".
"Even though it will be significantly more challenging to achieve the lower temperature goal, in terms of the required investments, strength of policy and greater reliance on measures such as carbon dioxide removal, we must not close the door on it," he said. "This means we need to step up the immediacy and pace of action."
Few governments and businesses have to date set out clear pathways or targets for keeping temperature increases below 1.5C, with experts advising most industrialised nations would have to achieve net zero emission status before mid-century.
But today's findings may further fuel calls for net zero goals to be adopted. They come ahead of the Intergovernmental Panel on Climate Change's (IPCC) hotly anticipated special study on how the world can limit global warming to 1.5C, which is set to be published early next month and is likely to further crank up pressure on governments and businesses to strengthen their emissions goals.
The UK government has promised to instruct the Committee on Climate Change to investigate the feasibility of the UK adopting a net zero emissions target following the paper's release.
It remains to be seen how the international community will react to the IPCC's findings, but it is clear the pressure, risks, and costs associated with missing the 1.5C threshold are mounting every day.
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