Science & Environment

Our warming world and El Nino

Flood rescue in Cumbria Image copyright Getty Images
Image caption December's devastating floods in northern England

2015 was the warmest year on record, with global temperatures 0.75C above the long-term average, according to scientists at the UK's Met Office.

What does this mean for the UK?

December's devastating floods in northern England seem a world away from the Pacific Ocean but anyone embarking on a meteorological whodunit will inevitably have to stop off in the world's largest ocean and investigate further.

As well as being exceptionally wet, December 2015 was the UK's warmest December on record. Basic atmospheric physics tells us that warmer air can contain more water vapour and in December this translated into persistent rainfall that drenched the hills of northern England and caused the severe floods that swept downstream.

Image copyright Getty Images
Image caption Flooding in York

What's causing this?

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Media captionAccording to figures released by the Met Office, 2015 was the warmest year on record. Chris Fawkes has more.

Peter Stott, head of climate monitoring and attribution at the Met Office said "2015 was a record-breaking year for our climate. Global mean temperatures reached 1°C above pre-industrial levels for the first time and the year's average global temperature was the highest ever recorded."

In the search for the source of this warmth why are meteorologists pointing their fingers towards the Pacific? El Nino. It's the name given to a natural phenomenon, the occasional warming of waters in the central and eastern Pacific Ocean. In 2015 we witnessed this latest El Nino event becoming one of the strongest on record.

During El Nino a large expanse of Pacific water becomes warmer than average altering the usual heat exchange pattern with the air above it which goes on to influence weather patterns in a chain reaction around the world.

Image caption This map shows the patterns in precipitation over land favoured during El Nino events

Analysing the reasons for the December floods, the UK Met Office says El Nino contributed to a persistent weather pattern stretching from the Pacific across North America and the Atlantic that resulted in unusually warm, moist air reaching the UK.

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Media captionMeteorologist Matt Taylor explains what El Nino is

More than one player

As eye-catching as the effects of El Nino have been in the UK and elsewhere, the warming of the Pacific only reached its peak in the second half of 2015 and scientists say attributing all or even the majority of the year's global temperature increase to it would be like giving star billing to an actor who only appears in one scene of a movie.

More likely is that natural weather cycles such as El Nino are becoming aligned with man-made heating to boost global temperatures to new heights.

Image copyright Mauna Loa Observatory

Pushing up temperatures

The star of the heating show remains emissions from industry and agriculture adding to the greenhouse effect and trapping more of the sun's energy and heat within our atmosphere. The concentration of CO2 in the atmosphere is now higher than at any time in the last 800,000 years and reached a record high in May 2015.

El Nino's warming influence will be felt well into 2016 so the potential is very much there for this partnership with man-made heating to produce further global temperature headlines this time next year.

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