Malala Yousafzai says millions of girls in developing countries will fail to complete their education this year due to the climate crisis.
Speaking at an online event, the rights activist said women and girls were more vulnerable to the effects of climate change, which causes many to drop out of school altogether.
This is because they are more likely to take on childcare and other family responsibilities following disasters caused by climate-related events.
Four million girls in poor nations could be prevented from completing their education, according to the Malala Fund. This figure could jump to 12.5 million girls by 2025.
"When families are affected by climate change disasters – such as floods, droughts – girls are the first ones to leave their homes, take on the household responsibilities or to get married," Malala said.
"The Malala Fund has estimated that this year, climate-related events could prevent up to four million girls from lower-income countries from completing their education."
Before the Covid-19 pandemic, about 130 million girls worldwide were already out of school, according to the UN cultural agency Unesco, which said more than 11 million may not return to classes after the pandemic.
"When we educate girls ... they can become farmers, conservationists, solar technicians, and they can fill other green jobs as well. Problem-solving skills can allow them to help their communities to adapt to climate change", Malala said
Girls who stay in school marry later in life and have fewer children. This helps to reduce the impact of climate change and population increases, she said.
"When women and girls are educated, that brings, you know, stronger, low-carbon economies and creates a more equal workforce."
The activist appeared alongside British parliament member Alok Sharma at the online event, The Role of Girls' Education in Climate Action, hosted by Chatham House.
Mr Sharma, chairman of the coming Cop26 climate summit in Glasgow, agreed girls are disproportionately affected by the climate crisis.
"This is a real issue that people are grappling with on a daily basis," he said. "In the UK, we are pushing the global goal to get 40 million more girls into school through our G7 presidency. We want to put women, girls at the centre of climate action work."
"We're calling on all countries to implement that gender action plan that was agreed at Cop25 and to make sure that gender is actually taken into account in all climate policies."
The Cop26 climate change conference will start in Glasgow on November 1 this year.