Droughts, erratic rains and frosts brought by a super-charged El Nino are severely impacting the Pacific, with Papua New Guinea worst hit, aid group Oxfam said in a report Monday.
Calling for an urgent up-scaling in relief to save lives, the charity said 4.7 million people faced hunger, poverty and disease in the Pacific region as a result of the weather pattern.
"This is a crisis on a huge global scale," the report, "Early Action on Super-charged El Nino Vital to Save Lives", said.
"The current El Nino is one of the strongest ever measured, which means there will be more extreme weather conditions that will threaten people's food security, lives and livelihoods."
El Nino is the name given to a weather pattern associated with a sustained period of warming in the central and eastern tropical Pacific which can spark deadly and costly climate extremes.
Last month, the UN weather agency warned the phenomenon, triggered by a warming in sea surface temperatures in the Pacific Ocean, was the worst in more than 15 years.
Oxfam said climate change was super-charging the effects of El Nino and despite a landmark global climate pact reached in Paris on the weekend, much needed to be done rapidly to cut emissions.
It said the result of the current strong El Nino would likely be 40–50 million people globally facing hunger, disease and water shortages in early 2016 as the slow onset crisis plays out.
The worst-affected places include Papua New Guinea in the Asia-Pacific as well as Ethiopia and Malawi in Africa and Guatemala, Haiti and Honduras in Latin America.
"Papua New Guinea has been severely affected, particularly in the Highlands, with widespread drought and frost affecting up to three million people and destroying crops and livestock," it said.
"Drought has also affected Vanuatu, Fiji, the Solomon Islands, Samoa and Tonga, damaging crops and water supplies."
Because El Nino also increases the probability of a longer tropical cyclone season in the southern hemisphere, countries in the eastern Pacific such as the Cook Islands and Samoa may also be at risk of strong storms, it said.
Across Asia monsoon rains have been limited, with Indonesia worst affected, while the forecast for the Philippines is also poor, with 85 percent of the country expected to be in drought by March 2016, it added.
Oxfam said in Ethiopia some 8.2 million people currently needed support due to a lack of rainfall while huge areas of southern Africa were also in drought.
In Central America and Haiti, small farmers and day labourers are the worst affected, with the potential for greater drought and major flooding in South America.
"The warning bells are deafening. We must act now to save lives and prevent people falling further into poverty," said Oxfam Australia's humanitarian manager Meg Quartermaine.