New Delhi
Crowds relax on the beach during the summer bank holiday hot weather in Brighton, Britain on August 25, 2025. (Reuters)Climate scientists have proposed a new accountability mechanism for countries as 1.5 degrees Celsius of warming above pre-industrial levels becomes imminent.
The accountability system includes a carbon credit-based approach that assesses how much of each country’s fair share of the global carbon budget has already been consumed, scientists at the International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria; Potsdam Institute for Climate Impact Research; Others at the Grantham Institute — Climate Change and the Environment, London wrote in the journal Nature.
Scientists have emphasized the need for accountability, in the wake of the International Court of Justice’s advisory opinion on “state obligations in relation to climate change”, which states that the 1.5°C limit under the Paris Agreement is the primary agreed goal of countries.
“Exceeding 1.5 degrees Celsius marks our failure to prevent the least dangerous human interference with the climate system as established by the UN science-policy process,” IIASA Energy, Climate and Environment Program Director, Kewan Riahi, one of the co-authors, said in a statement Monday. The aim is apt to avoid careless support for backsliding.”
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This model of climate responsibility is particularly relevant to India’s position. India said in its intervention at the United Nations Climate Change Conference (COP30) in Belém, Brazil last year: “To leave the remaining carbon space for developing countries, they (developed countries) need to reach net zero, invest significantly more in negative emission technologies and meet their obligations under the Convention,” said Nchangma Climate Secretary (MoEFCC) during his speech.
Scientists have proposed that such an accountability framework could be created by adopting a carbon budget consistent with a 1.5°C warming limit (starting from a given year, such as 1990) and determining a fair share of the budget. Countries that have already emitted beyond this fair share are classified as ‘carbon debtors’ and each subsequent unit of emissions becomes a further unit of carbon debt. Using projections of countries’ emissions, estimates can be made of how much carbon debt each may accumulate in the future.
It can also identify potential liabilities for exceeding 1.5°C — calculated as a debtor country’s share of the sum of debt owed to all indebted countries. This can be predicted before the global 1.5°C residual carbon budget is exhausted, they said in the commentary.
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“The aim is to establish whether large emitters could potentially pursue more ambitious emission-reduction paths and help others do so by providing financial means. This can help people understand whether global emissions could have been lower — through their direct actions and the spillover effects, such as reducing technology costs. And it can help over-measure global emissions.” Such assessments can then provide the basis for assigning accountability for remedial measures through a corrective-justice lens. Remedial measures, according to the authors, include the establishment and adaptation of CO2 removal mechanisms (including net-negative emissions targets) and support for climate-related harm and community harm.
In 2024, the global average temperature exceeds 1.5 degrees Celsius for the first time. Going above 1.5°C in one year does not mean that the Paris threshold has been breached. This is defined as an average of at least 20 years for year-to-year variation, scientists said. With an overshoot likely to happen soon, they also cited an advisory opinion of the International Court of Justice that came in July last year. Judicial opinions have anchored 1.5 degrees Celsius as the Paris Agreement’s initial limit, reducing ambiguity about its goals. In the event of a temporary overshoot of 1.5°C, countries remain under an obligation to meet this temperature limit so that breaches of the 1.5°C threshold are reversed.
Countries must not only reach net-zero carbon dioxide emissions, but achieve and maintain net-negative emissions by removing billions of tons of CO2 from the atmosphere and sustainably storing them, the scientists write.
“Their further loss and damage and 1.5 deg Adaptation needs arising from crossing the Celsius threshold must be addressed. And governments need to ask why they failed to prevent dangerous human intervention and who is responsible,” they said.
“It’s important to look at what we need to do to get back below 1.5 degrees Celsius, but it’s equally essential to understand how we got here in the first place,” said Gaurav Ganti, IIASA Guest Research Scholar and postdoctoral researcher at Humboldt University in Berlin.
