As countries step up borrowing to fund COVID-19 stimulus spending, few governments are paying attention to how climate change could limit their ability to repay the debts, researchers warned on Wednesday.

Increasingly severe climate shocks, such as hurricanes, and chronic pressures such as water shortages and drought are already hurting economies, and could worsen in the future, scientists say.

But researchers at Oxford University, who estimated national governments issued 193 long-term bonds worth $783 billion in 2020, reviewed investor prospectuses for 50 and found about three-quarters did not disclose any climate-related risks.

The findings suggest "governments do not understand the economic impacts of climate risks or are unwilling to report them", they said in a commentary published in the journal Nature.

"Without rigorous climate disclosures, investors and governments are flying blind," they added.

Of the 26 countries assessed, only three - Bermuda, the Dominican Republic and El Salvador - acknowledged that increasingly frequent weather disasters would create risks for their economies.

Only two - Bulgaria and the United Arab Emirates - identified the financial risks of transitioning their economies to cut emissions, and only Ghana disclosed the impacts of both types of risk on its ability to repay, researchers said.

They also warned that only 18% of total announced COVID-19 recovery spending had been directed to activities that would reduce global emissions, despite calls to "build back better".

India had earmarked nearly $7 billion for new coal infrastructure in India, and Germany had provided a $10-billion unconditional bailout for its major airline, Lufthansa, they noted.

"Rather than creating prosperity and facilitating debt repayment, investing in outdated fossil-fuel technologies leaves future generations with more debts, higher costs of capital, stranded assets and even greater warming," the commentary said.

Co-author Thom Wetzer, director of the Oxford Sustainable Law Programme, noted that countries - unlike companies - cannot just cease to exist when bankrupt, meaning their citizens "will bear the cost of debt burdens for generations".

Last year already saw a handful of casualties, with Zambia, Argentina, Belize, Ecuador, Lebanon and Suriname defaulting on loan repayments as the COVID-19 crisis exacerbated economic woes and left them unable to meet scheduled payments.

They now have troubled relationships with their creditors and might have to face austerity measures to manage repayments, the researchers said.

On Tuesday, African leaders told a dialogue on COVID-19 and climate change that the pandemic was making it harder for them to invest in climate action.

In turn, worsening planetary heating could inflict more damage on economies, restricting countries' ability to fund healthcare, education or other key services.

When Saudi Arabia's newly issued bonds mature in 2060, lower productivity as a result of higher temperatures and related impacts could slash its GDP by 60% relative to scenarios without climate change, Oxford researchers said.

And when Hurricane Maria hit Dominica in 2017, it caused damage worth an estimated 220% of GDP, leaving the government little room for spending other than on recovery.

On Wednesday, finance ministers and central bank governors from the world's 20 biggest economies agreed to boost reserves at the International Monetary Fund by $650 billion and extend a debt-servicing freeze to help developing nations deal with the pandemic.

But Global Justice Now, a campaign group calling for debt cancellation, said that while G20 ministers had urged private banks to participate in debt relief, the officials had not committed to legislation forcing banks to join relief efforts.

That in effect let private banks "off the hook", it said.

Separately, World Bank President David Malpass outlined measures his institution was taking to ease the debt squeeze facing the poorest countries, noting they accounted for only about 4% of global emissions but were "dramatically affected by climate change".

To avoid bequeathing a "credit crunch" to the next generation, countries should disclose their climate risks, use the COVID-19 recovery to build climate resilience and support the most vulnerable borrower nations, the Oxford researchers said.

"As a government, you are doing a disservice to your citizens - current and future - if you ignore this," Wetzer told the Thomson Reuters Foundation.