The health of millions will be damaged if world temperatures continue to rise as a result of climate change, says the World Health Organization.
Malaria could become an even larger problem, say experts
Increasing temperatures will aid the spread of water-borne diseases, and those carried by insects, it predicts.
Even a rise of a few degrees could expose hundreds of millions more people to the threat of malaria, say experts.
In addition, changes to rainfall patterns, could damage agriculture, plunging millions into malnutrition.
The WHO has published a study into the likely impact of climate change to coincide with the UN conference in Milan this week.
Some scientists have predicted that global temperatures could rise by a few degrees by 2030 as a result of the "greenhouse effect" created by emissions of gasses such as carbon dioxide into the atmosphere.
One effect of this rise in temperatures would be to extend the malaria "season" in many countries where the disease is already endemic.
It could also allow malarial mosquitoes to live in greater numbers in countries where the disease is not a problem at present - such as some European nations.
Other diseases spread by mosquitoes, such as Dengue fever, could also increase.
Kerstin Leitner, the WHO assistant director-general, said: "There is growing evidence that changes in the global climate will have profound effects on the health and wellbeing of citizens in countries around the world."
One of the biggest threats to children worldwide is diarrhoeal disease, and the spread of these illnesses is more likely if hotter, wetter conditions are more prevalent.
Countries are most likely to suffer increases in malnutrition in the event of further climate change are India, Bangladesh, Myanmar and Vietnam, which are heavily dependent on a predictable monsoon season for the cultivation of rice crops.
However, a few countries - such as China - might actually benefit from climate changes.
Other effects of the predicted shift in climate patterns could be worsening air pollution and allergens - not to mention the likelihood of further "extreme weather" episodes such as this year's European heatwave, floods, storms and droughts.