Britain's Met Office says the exceptional warmth in Britain and northern continental Europe is linked to the strongest El Nino ever recorded.
"What we are experiencing is typical of an early winter El Nino effect," said Adam Scaife, head of Met Office long-range forecasting.
The cyclical event, named after the birth of Christ because it traditionally occurs in Latin America around Christmas, sees temperatures in the equatorial Pacific rise several degrees. The consequences in years like this are dramatic. Monsoons and trade winds are disrupted, leading to cyclones, droughts, floods and food shortages across the world.
With the warm spell in Europe set to continue, it is almost certain that more records will be broken.
According to Scaife, "we cannot attribute the recent floods [in Britain] to the El Nino, but in early winter [during El Nino years] we tend to have a strong jet stream which brings us mild conditions. In late winter, January and February, we tend to get a weak jet stream which brings more wintry conditions."
Roger Brugge, a senior scientist at Reading University's atmospheric laboratory, said of Britain's weather this month: "The first 17 days of December have been the mildest on record by a remarkable 1.1C. The average temperature during this period, of 10.6C, is similar to what can be expected around the beginning of May."
Worldwide, November was the warmest recorded by the US government's National Oceanic and Atmospheric Administration, and the seventh month in a row where temperatures have been well above the 100-year average; 2015 is on track to be the warmest year and last week the Met Office forecast that the global average temperature next year would be a record 1.14C above pre-industrial temperatures.
So is the current spell of exceptional heat around the world a foretaste of life in a warmer climate, or just a temporary blip? Atmospheric scientists believe we are seeing climate change with an El Nino effect on top. The two combined are raising temperatures dramatically.
"We expect 2016 to be the warmest year ever, primarily because of climate change but around 25 per cent because of El Nino," said Scaife, who added that El Nino was not linked directly to climate change but exacerbates its effects.
The effects are already being seen worldwide, and nowhere more dramatically than in east and southern Africa, which is most vulnerable to climate change and extreme droughts. The El Nino effect has shifted rainfall patterns and led to severe drought. After years of good harvests and relative food security, Africa faces one of its biggest food emergencies in a generation with Ethiopia, Malawi, Eritrea, Somalia, Zimbabwe and other southern and east African countries all needing emergency food aid within weeks.
"The projections across Africa are shocking; 39 million people are expected to be affected," said a spokeswoman for the UK Department for International Development.
"Around 3.5 million people in Africa could also be affected by floods and subsequent disease epidemics. The situation in Ethiopia is particularly worrying, with 18 million people projected to require food assistance in the coming months."
This month the United Nations World Food Programme said 2.8 million people in Malawi needed urgent food aid as shortages had more than doubled food prices from 2014 levels. This year, it said, southern Africa's cereal harvest fell by almost a quarter, down to 34 million tonnes.
"Serious concerns are mounting that southern Africa will this coming season face another poor harvest, possibly a disastrous one," warned the UN's Office for the Co-ordination of Humanitarian Affairs. The UN has appealed for US$8.5 billion ($12.6 billion) for humanitarian aid for Africa. A further US$100 million has been requested for Central America, the Pacific region and northern South America, where a combination of intense rains and droughts has devastated crops.
The widespread El Nino effects are being felt in Latin America as well as Indonesia and Papua New Guinea, where it has led to some of the worst forest fires in decades. In Central America, one of the most severe droughts on record has led to 3.5 million people in Guatemala, Honduras and El Salvador needing food aid. The UN says that more than two million people have been affected in Peru and Ecuador.
The warm Pacific temperatures have also led to a record number of hurricanes and cyclones. According to the US Government's National Oceanic and Atmospheric Administration's Earth Observatory, there were 18 named storms this year, including 13 hurricanes, nine of which were category three or higher.
This is the greatest number on record since reliable measurements started in 1971.
Each El Nino is different, but this year is being compared with 1997 and 1998, when 21,000 people died and US$36 billion of damage was caused. Scientists say that El Ninos can add significantly to climate change. Because the phenomenon causes less rain to fall in many areas of the tropics, forests become vulnerable to man-made fires, which accelerate carbon dioxide build-up in the atmosphere and reduce air quality.
The tens of thousands of fires that engulfed much of Indonesia this year and led to serious air pollution across the region are believed to have emitted more greenhouse gases in one day than is generated from all US economic activity, according to the Washington-based World Resources Institute. The 1997 fires in Indonesia produced carbon emissions estimated to be the equivalent of between 13 per cent and 40 per cent of the world's annual fossil fuel emissions.
We are nearing "peak El Nino". The UN's World Meteorological Organisation said it expected the warming of equatorial waters in the Pacific to peak in a few weeks. But the medium-term consequences are hard to judge. Secretary-general Michel Jarraud said: "This event is playing out in uncharted territory. Our planet has altered dramatically because of climate change. So this El Nino event and human-induced climate change may interact and modify each other in ways which we have never before experienced. El Nino is turning up the heat even further."
In the flow
• El Ninos occur every two to seven years, when the waters along the equator in the eastern Pacific naturally warm up to 3C above average.
• Because this affects air pressure and atmospheric circulation, they can have large-scale impacts on weather around the world.
• They typically last for nine to 12 months and are followed by a cool phase, La Nina, which often affects the weather in North America and influences the Atlantic hurricane season.
• It was previously thought that El Ninos did not affect Europe greatly, but it's now known that they influence the jet streams and can lead to unusually warm weather around Christmas.
