Failure to share vaccines around the world could jeopardise the success of the Cop26 climate summit because countries still battling Covid-19 will be less capable of launching green initiatives.
The UK is hosting Cop26 in Glasgow in November and wants countries to come forward with ambitious targets to slash greenhouse gas emissions by 2030.
But while the pandemic eases in Europe and North America, many developing countries are “still in a state of an immediate health emergency that overshadows climate concerns”, the Stockholm Environment Institute said.
This means developing countries are less likely to be ready to submit ambitious targets for Cop26 or to have the necessary funds available.
Some African nations were forced to divert climate funds to deal with the economic fallout from the pandemic.
A recent burst of initiatives by wealthy countries "raises the question of whether planning for the long term in the time of a pandemic is in itself a privilege", the SEI said.
The institute said that countries desperate for vaccines might back down in negotiations on climate funding in order to obtain Covid vaccination doses.
“The gulf in vaccination rates between poor and wealthy countries reduces the bargaining power of developing countries on climate issues,” it said.
On top of that, diplomats from poorer countries may not have been vaccinated and could struggle to take part in Cop26 in person.
The UK’s Cop26 president, Alok Sharma, said last month that he had “always championed the need for a physical Cop” rather than online talks.
He said the UK and Scottish authorities were “exploring every possible Covid security measure”, including testing and vaccines.
But the SEI called for spending on digital infrastructure that would allow poorer communities to take part online.
“The pandemic offers sobering lessons for handling global crises,” it said. “The climate crisis is the next looming global crisis. Cop26 could be the forum for a new start.”
The UK is pushing a green agenda at next week's G7 summit in Cornwall, the first in-person meeting of G7 leaders since the outbreak of the pandemic.
But G7 nations will face pressure to share vaccine supplies around the world after immunising large proportions of their own populations.
Rich countries are donating to the global Covax scheme but this is not expected to bring about herd immunity in developing countries.
So far, about 0.2 per cent of global vaccine supplies have gone to low-income countries.
Experts say that the disparity leaves the whole world vulnerable to new variants that can emerge in countries where the disease is rampant.
World Health Organisation chief Tedros Adhanom Ghebreyesus and the heads of other global bodies called this week for rich countries to donate more doses.
They called on G7 leaders to support plans to boost donations and financing for developing countries.
“Increasingly, a two-track pandemic is developing, with richer countries having access and poorer ones being left behind,” they said.
The called for a "pragmatic solution" on intellectual property after Washington last month signalled its support for waiving patents on Covid-19 vaccines.
But the EU is sceptical and German Chancellor Angela Merkel last week spoke out against the idea.
