Diseases such as malaria may spread under climate change, Unicef warns
Climate change is already affecting the prospects for children in the world's poorer countries, according to Unicef.
The UN children's agency says that increases in floods, droughts and insect-borne disease will all affect health, education and welfare.
While richer societies can adjust, it says in a new report, poorer ones do not have the resources.
It is asking western governments to reduce greenhouse gas emissions swiftly and provide money to help poor nations.
"Those who have contributed least to climate change - the world's poorest children - are suffering the most," said David Bull, executive director of Unicef UK.
"If the world does not act now to mitigate and adapt to the risks and realities of climate change, we will seriously hamper efforts to reach the Millennium Development Goals (MDGs) by 2015 and sustain development progress thereafter."
The report is launched in the UK 10 years to the day after the government signed the Kyoto Protocol on reducing greenhouse gas emissions.
The eight Millennium Goals include such targets as eradicating extreme poverty and hunger, reducing infant mortality rates by two-thirds and halting the spread of diseases such as HIV and malaria.
Progress has been good in some parts of the world, but earlier this month the World Bank warned some targets were likely to be missed; sub-Saharan Africa was likely to miss all eight, the Bank said.
Unicef concludes that climate change is already making achieving them more difficult.
THE MILLENNIUM GOALS
1: Eradicate extreme poverty and hunger
2: Achieve universal primary education
3: Promote gender equality and empower women
4: Reduce child mortality
5: Improve maternal health
6: Combat HIV/AIDS, malaria, and other diseases
7: Ensure environmental sustainability
8: Develop a global partnership for development
Agricultural productivity is forecast to decline markedly in most of Africa, South Asia and Latin America; countries such as Zambia are already seeing a significant reduction in rainfall; the threat of waterborne diseases such as cholera is projected to increase.
The 2006 Stern Review concluded that climate change could increase annual child deaths in sub-Saharan Africa and South Asia by up to 160,000 through GDP loss alone.
"All the essential effects we are seeing now are associated with a temperature increase since 1850 of less than 1C," Sir Nicholas Stern writes in a foreword to the Unicef report.
"Past actions and the likely trend of emissions... imply that another 1-2C will be hard to avoid.
"Rich countries' responsibility for the bulk of past emissions demands that we give our strong support."
The UN climate convention contains funds designed to help the poorest countries adapt to climate impacts, but critics say the sums are far too small to make a difference.