Prepare For Weird Weather! An El Nino Is Bubbling Up…

El Nino is characterized by unusually warm temperatures and La Nina by unusually cool temperatures in the equatorial Pacific. This graphic based on data from 8 May 2014 shows temperature anomalies, deviations from normal temperature values, with unusually warm temperatures shown in red and unusually cold anomalies shown in blue.  Note the build up of warm waters off the western coast of the Americas. Courtesy NOAA

Click to enlarge. El Nino is characterized by unusually warm temperatures and La Nina by unusually cool temperatures in the equatorial Pacific. This graphic based on data from 8 May 2014 shows temperature anomalies, deviations from normal temperature values, with unusually warm temperatures shown in red and unusually cold anomalies shown in blue. Note the build up of warm waters off the western coast of the Americas. This is an El Nino brewing. Courtesy NOAA

California’s long drought may be about to end as Australia gets much drier and the rest of the world experiences some decidedly odd weather – as well as excitable press headlines – all thanks to a huge bubble of warm water that is building up in the Pacific Ocean.

This periodic warming of the surface waters of the eastern Pacific, known as El Nino, can affect weather patterns around the globe and two leading meteorological organisations have just issued warnings that they expect El Nino conditions to develop in 2014.

America’s National Oceanic and Atmospheric Administration (NOAA) issued what it called an “El Nino Watch” on 8 May while Australia’s Bureau of Meteorology (BoM) announced on 6 May that the chances of an El Nino developing in 2014 now exceed 70 per cent.

El Nino means The Little Boy, or Christ Child in Spanish. The phenomenon was named by seventeenth century fishermen who noticed the occasional appearance of unusually warm water in the Pacific Ocean off the coast of South America at around Christmas time.

El Ninos occur every few years as warm water in the western Pacific off the coast of Indonesia moves eastwards, rising to the surface and causing some distinctive changes in weather patterns. The resulting build up of warm surface water off the coast of the Americas drives evaporation leading to increased rainfall and flooding in the west of South America and as far north as California. The record breaking El Nino event of 1997/98 resulted in severe weather events in the US including floods in California, an ice storm in the north eastern US and tornadoes in Florida.

There is a cooling counterpart of El Nino called La Nina – the girl, in Spanish -which has been partly responsible for flooding in Australia in recent years, the ongoing Californian drought and reduced snow cover in the Rockies. La Nina conditions have dominated the Pacific Ocean for over a decade leading some climate scientists to expect a major El Nino this year that will help redress the balance. However, NOAA and the BoM are being cautious with their forecasts; NOAA stated on Thursday 8 May that there “remains uncertainty as to exactly when El Niño will develop and an even greater uncertainty as to how strong it may become”.

Expect drought in Australia and a cold winter in Europe…

If this warming does become a strong El Nino then Australia and India will face potential drought conditions and we might expect to see some monster bush fires in eastern Australia during January and February as a result. Trade winds in the southern Pacific will weaken and head east, cyclone tracks in the northern Pacific will alter and there will be more cyclones than usual forming in the eastern Pacific.

The affects of the El Nino will be felt far and wide. The countries of eastern Africa can expect wetter than usual weather next Spring while southern Africa is likely to get much drier as we move into the new year. El Nino’s impact on European weather tends to be stronger over the winter months as changes in the atmosphere ripple through the stratosphere. There is evidence that late winter during El Niño years is colder than normal in northern Europe and milder than normal in southern Europe.

UK Meteorological Office scientists Sarah Ineson and Adam Scaife wrote a paper that stated “The response in European surface climate to the El Nino signal is large enough to be useful for seasonal forecasting”. Now, this is not a weather forecast and there are other factors that feed into Europe’s weather apart from El Nino but don’t be surprised if our next winter turns out to be much colder than usual here in the British Isles – you have been warned.

It may be colder than usual in Europe next winter but globally average surface temperatures in 2015 will almost certainly be high as a result of the expected El Nino. They may even be high enough to end the so called global warming pause that has lasted since the late 1990s – and that some climate experts date to the major El Nino event that took place in 1997/98 and led to 1998 being reported as one of the warmest years on record.

Leading climate scientists Gavin Schmidt of NASA and Thomas Karl of NOAA, speaking at a press conference in January, explained that years with El Ninos tend to be slightly warmer and years with La Nina tend to be slightly cooler, but that the impact of El Nino and La Nina events do not hide the long term warming trend and that as a result future El Nino years are expected to get progressively warmer. Long term trends due to increases in greenhouse gases are apparent “regardless of whether it is an El Nino or La Nina year,” said Schmidt.

An end to the global warming pause?

Some scientists also expect El Nino events to become stronger as the world warms. We currently experience an unusually strong El Nino event every 20 years but this will double to one event every 10 years, according to Dr Agus Santoso of Australia’s Centre of Excellence for Climate System Science (CoECSS), co-author of a major scientific paper on this topic.

These strong El Nino events appear to be part of long term cycle in the Pacific Ocean that spans periods as long as 20 or 30 years and is known as the Pacific Decadal Oscillation (PDO). This is where the Pacific Ocean acts to alternatively warm the global atmosphere over periods of many years and then to cool it. The Pacific Ocean has been in a long term cooling phase of the PDO since 1998 evidenced by the dominance of La Nina conditions since then; some climate scientists believe that this cooling phase of the PDO may have contributed to the global warming pause.

It now appears that strong El Nino events may trigger changes in the PDO causing it to flip from a cooling to a warming phase and vice versa and that the major El Nino of 1997/98 was just such an trigger. Indeed, leading climate scientist Kevin Trenberth of the US National Center for Atmospheric Research told me in December that he believes it is possible that another significant El Nino event will flip the PDO into a warming phase, end the pause and result in a return to rising global surface temperatures. Will this El Nino turn out to be that event?

Now, El Ninos may have played a role in the global warming pause and they might become stronger and more frequent in the future due to global warming but it is important to note that the weather patterns caused by El Nino and La Nina events are part of the natural and continuing cycle that drives global weather.

El Ninos and La Ninas have come and gone for centuries and these cycles will almost certainly continue for many centuries more. So when you read the inevitable newspaper headlines that we can expect over coming months blaming the floods in the Americas, the bush fires in Australia and the cold winter in northern Europe on climate change – please take them with a pinch of salt.

The coming El Nino and the weather havoc that it may cause is not due to global warming – just nature.

Sources

Australian Bureau of Meteorology reports here.

US NOAA reports here.

NOAA report on the El Nino of 1997/98 here.

Link to the paper that links colder northern European winters with El Nino here.

A news story based on my interview with Kevin Trenberth here.

Kevin Trenberth’s paper on the PDO, global warming and the pause here.

Links to papers on changes in El Nino due to global warming: a Nature paper here and a Nature Climate Change paper here.

News stories on stronger and more frequent El Ninos here and here.

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