New Delhi
Climate scientists have proposed a new accountability mechanism for countries as overshoot of 1.5°C warming over pre-industrial levels becomes imminent.
The accountability regime involves a carbon debt based approach where it is assessed how much of each nation’s fair share of the global carbon budget has already been consumed, scientists from International Institute for Applied Systems Analysis (IIASA), Laxenburg in Austria; Potsdam Institute for Climate Impact Research; Grantham Institute — Climate Change and the Environment, London among others write in Nature journal.
Scientists have stressed the need for accountability, in view of the International Court of Justice’s advisory opinion on “obligations of States in respect of Climate Change” delivered last year which held that the 1.5°C limit is the countries’ primary agreed target under the Paris Agreement.
“Exceeding 1.5°C marks our failure to prevent minimum levels of dangerous human interference with the climate system established by the UN science-policy process,” said IIASA Energy, Climate, and Environment Program Director, Keywan Riahi, one of the co-authors in a statement on Monday, referring to the joint comment in Nature published on January 26. “This failure should make us reflect on whether current scientific approaches are fit-for-purpose to inform overshoot policy and avoid inadvertent support for target backsliding.”
This model of climate accountability especially aligns with India’s position. India in its intervention at UN Climate Meeting (COP30) in Belem, Brazil last year said: “They (developed countries) need to reach net zero much earlier than projected to release the remaining carbon space in favour of developing countries, invest significantly more in negative emission technologies and fulfil their obligations under the convention,” said Tanmay Kumar, secretary, Ministry of Environment, Forest and Climate Change (MoEFCC) during his statement.
Scientists have proposed that such an accountability framework can be developed by taking a carbon budget that is compatible with the 1.5°C warming limit (starting from a given year, such as 1990) and assigning fair shares of the budget. Countries that have already emitted beyond this fair share are classified as ‘carbon debtors’ and each unit of subsequent emissions results in a further unit of carbon debt. Using projections of countries’ emissions, evaluations can be made regarding how much carbon debt each might accrue in future.
It can also identify potential responsibility for exceeding 1.5°C — calculated as a debtor country’s share of the sum of debt across all debtor countries. This can be projected even before the global 1.5°C remaining carbon budget is exhausted, they said in the comment.
“The aim is to establish whether major emitters could have feasibly followed more ambitious emissions-reduction paths and helped others to do so by providing financial means, for instance. It can help people to understand whether global emissions could have been lower — through their direct actions and spillover effects, such as reduced technology costs. And it can help to quantify the additional global emissions and climate harms that resulted,” they write. Such assessments can then provide the basis to allocate accountability for remedial measures through a corrective-justice lens. Remedial measures according to the authors include the deployment of CO2 removal methods (accompanied by net-negative emission targets) and support for adaptation needs and climate-related loss and damage to communities.
In 2024, global average temperatures exceeded 1.5°C for the first time. Going above 1.5°C in one year does not mean that the Paris threshold is breached. It is defined as an average over at least 20 years to account for year-to-year variations, scientists said. With overshoot likely soon, they also referred to an advisory opinion from the International Court of Justice which came in July last year. The judicial opinion anchored 1.5°C as the primary limit of the Paris agreement, reducing ambiguity over its aim. In the event of a temporary overshoot of 1.5°C countries’ obligations to meet this temperature limit remain so that the breach of the 1.5°C threshold is reversed.
Countries will need to commit not only to reach net-zero carbon dioxide emissions, but also to achieve and sustain net-negative emissions by removing billions of tonnes of CO2 from the atmosphere and durably storing it, scientists write.
“They will need to confront the further loss and damage and the adaptation needs that arise as a result of exceeding the 1.5°C limit. And governments need to ask why they failed to prevent dangerous human interference, and who is responsible,” they said.
“Looking ahead to what we need to do to get back below 1.5°C is important, but it is equally essential to understand how we got here in the first place,” said Gaurav Ganti, IIASA Guest Research Scholar and a Postdoctoral Researcher at Humboldt University of Berlin in a statement.