Pakistan, Bangladesh, Afghanistan, and India are among four South Asian countries where children are at extremely high risk of the impacts of the climate crisis, with global rankings of 14, 15, 15, and 26.
Nepal is ranked 51, Sri Lanka is at 61st place. Bhutan is ranked 111, with children at relatively lower risk.
South Asian countries are among the most vulnerable globally to the impacts of climate change. Extreme climate-related events - heatwaves, storms, floods, fires and droughts - affect more than half of the region's population every year and continue to burden their economies.
Worse, before they can recover from one disaster, another one strikes, reversing any progress made.
Also, rising global temperatures and changing weather patterns have put the futures of millions of children living in climate-vulnerable areas in South Asia at constant risk.
Around 1 billion children live in one of the 33 countries classified as "extremely high-risk," including the four South Asian countries.
"For the first time, we have clear evidence of the impact of climate change on millions of children in South Asia. Droughts, floods, air pollution and river erosion across the region have left millions of children homeless and hungry, and without any healthcare and water," said George Laryea-Adjei, Unicef regional director for South Asia.
South Asia is home to over 600 million children and has the highest number of young people globally.
The report found that these South Asian children are in constant danger from riverine floods and air pollution, but also that investments in child health, nutrition, and education can make a significant difference to protect children from climate change.
"Together, climate change and the Covid-19 pandemic have created an alarming crisis for South Asian children. The time to act is now - if we invest in water, healthcare and education, we can protect their futures from the impacts of a changing climate and degrading environment," Laryea-Adjei said.
The report also reveals a disconnect between where greenhouse gas emissions are generated, and where children are enduring the most significant climate-driven impacts.
The 33 extremely high-risk countries, including four from South Asia, collectively emit just 9 per cent of global CO2 emissions. Conversely, the 10 highest emitting countries collectively account for nearly 70 per cent of global emissions.
"The frightening environmental changes we are seeing across the planet are being driven by a few but experienced by many in South Asia," Laryea-Adjei said.
"We must urgently reduce greenhouse gas emissions and work together as a community to build greater resilience in South Asia. Children and young people are at the heart of this change, with almost half of 1.8 billion people below the age of 24 in South Asia."
Compared to adults, children require more food and water per unit of their body weight, are less able to survive extreme weather events, and are more susceptible to toxic chemicals, temperature changes and diseases, among other factors.
Without the urgent action required to reduce greenhouse gas emissions globally, children will continue to suffer the most.
So, Unicef urged governments, businesses and relevant actors to increase investment in climate adaptation and resilience in key services for children and cut greenhouse gas emissions.
Countries must reduce their emissions by at least 45 per cent (compared to 2010 levels) by 2030 to keep warming to no more than 1.5°C, it said.
Also, the Unicef report suggested providing children with climate education and green skills, critical for their adaptation to and preparation for the effects of climate change and including young people in all national, regional and international climate negotiations and decisions, including at COP26.
It called on the stakeholders and actors to ensure that the recovery from the Covid-19 pandemic is green, low-carbon, and inclusive so that the capacity of future generations to respond to the climate crisis are not compromised.