4 Questions with David Battisti on El Niño and Climate Variability

This year’s spring Houghton Lecturer is David Battisti, a professor of atmospheric sciences and the Tamaki Endowed Chair at the University of Washington. As the scientist-in-residence within MIT’s Program of Atmospheres, Oceans, and Climate (PAOC), Battisti has spent the semester giving a series of talks on natural variability in the climate system. Some of his main research interests include illuminating the processes that underlay past and present climates, understanding how interactions between the ocean, atmosphere, land, and sea ice lead to climate variability on different timescales, and improving El Niño models and their forecast skill—something that is becoming increasingly relevant in a warming world.

Credit: National Oceanic and Atmospheric Administration

The Pacific Ocean is primed for a powerful double El Niño—a rare phenomenon in which there are two consecutive years of episodic warming of sea surface temperatures—according to some scientists. It’s been a few years since the Pacific Ocean experienced one strong warming event, let alone an event that spanned two consecutive years. A double El Niño could have large ripple effects in weather systems around the globe, from summer monsoons and hurricanes to winter storms in the Northern Hemisphere. Meanwhile, some scientists think it may signal the beginning of the end of the warming hiatus. Oceans at MIT asked Battisti about this phenomenon and what it does and doesn’t tell us about climate change.

How rare are double El Niños and what are the expected effects?

[Double El Niños] are not unheard of, but the last time it stayed warm for nearly two full years was back in the early 80s. In the tropics, climate anomalies associated with a typical El Niño event will persists as long as the event persists. For example, El Niño warm and cold events explain the lion’s share of the variance in monsoon onset date: conditions in late boreal summer causes a delay in the onset of the monsoon in Indonesia, which greatly reduces the annual production of the country’s staple food, rice. If El Niño conditions persist for two years spanning the onset time for the Indonesia monsoon, monsoon onset will very likely be delayed for two consecutive years.

In the mid-latitudes of the Northern Hemisphere, where we live, El Niño affects the climate by issuing persistent, large scale atmospheric waves from the tropical Pacific to the North Pacific and over most of North America. These waves are most efficient at reaching the mid-latitudes during our wintertime. If El Niño conditions span two consecutive northern hemisphere winters, we should expect the winter climate in these regions to be affected similarly over two consecutive winters.
During an El Niño event, there is a greater than normal chance for an unusually warm winter in the Pacific Northwest and in the north central US, and for a colder and wetter than normal winter in southern Florida. Alternately, El Niño has little impact on winter weather in New England. It also greatly affects precipitation in Southern California and the southwestern US — El Niño years are reliably wetter than normal, but just how much wetter than normal is very unpredictable.

Why haven’t we seen a strong El Niño in nearly two decades?

A large El Niño event is characterized by exceptionally warm conditions in the tropical Pacific, or by very warm conditions that persist for 18 months or so – about nine months longer than normal. It’s been over 20 years since we’ve seen a very large warm event, but it is not known how frequently very strong and exceptionally long events happen.

We categorize El Niño events (and their cold event siblings) by measuring sea surface temperature and zonal surface wind stress along the equator in the tropical Pacific. Good data to construct these indices extend back to the early 20th Century. Unfortunately, we can’t answer this question by examining the behavior of the high-end climate models because about only two high-end climate models in the world feature El Niño warm and cold events that are consistent with observations. However, the observational record shows three El Niño events with exceptionally large amplitude that were exceptionally long lived since 1950s, so a 20-year gap since the last large warm event is not surprising.

What does the hiatus refer to, and is it related to the El Niño phenomenon? The whole hiatus idea is based on the expectation that as carbon dioxide increases, so to should the global average temperature. And indeed, the global averaged temperature has increased over the course of the 20th Century by approximately 0.85 degrees Celsius. And climate models support that the primary reason the 20th Century increase is rising concentrations of greenhouse gases associated with human activity. However, over the past dozen years or so, the global average temperature has not increased – hence the moniker ‘the hiatus’.

The decade long hiatus isn’t inconsistent from what we would expect from natural variability and human forced climate change. For example, a typical El Niño cycle features a very warm year, followed by a moderately cold year, and then nothing happens for a while. Somewhere between three and seven years later there’s another warm event followed by a cold event, but the duration between these events  is quite random. Selecting any single period—for example, the last 10 years—we would expect decades in which the global average temperature fluctuates by 0.15 degrees Celsius or so due to the randomness in natural climate variability. The regional patterns of temperature change and the hiatus in global average temperature over the past decade aren’t distinguishable from a superposition of the cold phase of natural variability with the expected warming due to human activity.

Is this a sign that the warming hiatus is coming to an end?

El Niño does increase the global average temperature so we will see the average global temperature spike a bit this year compared to the last few years, which will bring us back up toward what the models say is the forced warming response. But El Niño events are not predictable more than a year or so in advance, so it is not possible to say what will happen over the next few years, or even the next decade.

On the other hand, if you view the change in global average temperature over the past thirty years as being a superposition of a steady increase due to human-induced forcing and decade-long periods of warm (the 1980’s and 1990’s) and cold (the 2002-2013) anomalies due to natural variability including El Niño, then decade-long periods of very large warming and very weak warming or even weak cooling should be expected. Exactly when these periods end is only obvious in retrospect.

For 25 years, Henry Houghton served as Head of the Department of Meteorology—today known as PAOC. During his tenure, the department established an unsurpassed standard of excellence in these fields. The Houghton Fund was established to continue that legacy through support of students and the Houghton Lecture Series. Since its 1995 inception, more than two dozen scientists from around the world representing a wide range of disciplines within the fields of Atmosphere, Ocean and Climate have visited and shared their expertise with the MIT community.

Originally posted: http://oceans.mit.edu

‘Substantial’ El Nino event predicted

The El Nino effect, which can drive droughts and flooding, is under way in the tropical Pacific, say scientists.

Australia’s Bureau of Meteorology predicted that it could become a “substantial” event later in the year.

The phenomenon arises from variations in ocean temperatures.

The El Nino is still in its early stages, but has the potential to cause extreme weather around the world, according to forecasters.

US scientists announced in April that El Nino had arrived, but it was described then as “weak”.

Australian scientists said models suggested it could strengthen from September onwards, but it was too early to determine with confidence how strong it could be.

“This is a proper El Nino effect, it’s not a weak one,” David Jones, manager of climate monitoring and prediction at the Bureau of Meteorology, told reporters.

“You know, there’s always a little bit of doubt when it comes to intensity forecasts, but across the models as a whole we’d suggest that this will be quite a substantial El Nino event.”

Aftermath of flooding in California put down to El Nino

An El Nino comes along about every two to seven years as part of a natural cycle.

Every El Nino is different, and once one has started, models can predict how it might develop over the next six to nine months, with a reasonable level of accuracy.

How can we predict El Nino?

In the tropical Pacific Ocean, scientists operate a network of buoys that measure temperature, currents and winds. The data – and other information from satellites and meteorological observations – is fed into complex computer models designed to predict an El Nino. However, the models cannot predict the precise intensity or duration of an El Nino, or the areas likely to be affected, more than a few months ahead. Researchers are trying to improve their models and observational work to give more advance notice.

A strong El Nino five years ago was linked with poor monsoons in Southeast Asia, droughts in southern Australia, the Philippines and Ecuador, blizzards in the US, heatwaves in Brazil and extreme flooding in Mexico.

Another strong El Nino event was expected during last year’s record-breaking temperatures, but failed to materialise.

Prof Eric Guilyardi of the Department of Meteorology at the University of Reading said it would become clear in the summer whether this year might be different.

“The likelihood of El Nino is high but its eventual strength in the winter when it has its major impacts worldwide is still unknown,” he said.

“We will know in the summer how strong it is going to be.”

Weather patterns

The El Nino is a warming of the Pacific Ocean as part of a complex cycle linking atmosphere and ocean.

The phenomenon is known to disrupt weather patterns around the world, and can bring wetter winters to the southwest US and droughts to northern Australia.

The consequences of El Nino are much less clear for Europe and the UK.

Research suggests that extreme El Nino events will become more likely as global temperatures rise.

Originally posted at: www.bbc.com

Atlantic, Pacific Fish Face Mixing as Arctic Warms

The gradual warming of the Arctic Ocean over the next century will weaken a natural barrier that has separated fish from the Atlantic and Pacific Oceans for millions of years, leading to a mixing of species that could make life difficult in fishing communities from Alaska to Norway.

A new study by scientists in Denmark combined current models of climate change, and the biological water temperature and food requirements for 520 fish species native to the two oceans. The report forecast changes in the range of these fish in five-year increments from now until 2100, when the world’s oceans are expected to heat up globally by an average 4 degrees Celsius (7 degrees Fahrenheit).

“There will be an interchange of the fish communities between those two seas,” beginning as soon as 2050, said Mary Wisz, lead author on the report in Nature Climate Change and a senior ecosystem scientist at Aarhaus University in Denmark. “We know from historical examples that this kind of interchange, when biotas have been separated over long evolutionary time scales, can have huge consequences.”

In this warmer future, fishermen based in Kodiak, Alaska, could be pulling up Atlantic cod, a prized species normally caught off New England and Northern Europe. A similar change has already started off the coast of Greenland, where fishermen in the last five years have been catching larger numbers of Atlantic mackerel, which prefers more temperate water.

Wisz and colleagues say that by 2100, up to 41 species could enter the Pacific and 44 species could enter the Atlantic, through Arctic water passages over Canada or Russia. This interchange will have ecological and economic consequences to ecosystems that at present contribute 39 percent to global marine fish landings.

While some fishermen may benefit from the new catches, scientists warn that it’s hard to predict exactly what kind of fish will take over, and which will be driven away by the newcomers. It’s also possible that several kinds of fish could compete for the same food source – smaller fish, marine shrimp or larvae, for example, leading to a big reshuffling of the existing marine food chain.

“Some species when they come together they get along,” said Peter Moller, curator of fishes at the Natural History Museum of Denmark and another author on the new report. “But of course the Atlantic cod has the potential to become extremely numerous and dominating if it has the right conditions. There is speculation if it gets to a new place, it can be a real game-changer.”

Moller said the cod is an especially voracious predator of smaller fish, and could impact commercial landings of Alaska Pollock, for example. Around 3 million tons of Alaska pollock are caught each year in the North Pacific from Alaska to northern Japan. Alaska pollock is the world’s second most important fish species in terms of total catch.

Jason Link, senior scientist for ecosystem management at the National Oceanic and Atmospheric Administration, agreed that the mixing of species will cause changes in the food web in both oceans, but it’s hard to predict exactly how it will shake out.

“Another issue not noted in this paper is what happens in the ecosystem that these fish move out of, do they remain there or do other species replace them from the south?” Link said via e-mail.

Another thorny issue is how to manage fishing boats who will likely be plying the rugged Arctic Ocean once commercial harvests become feasible.

“This work raises important ramifications for fishes in response to changes in sea ice,” Link said.

Wisz and Moller say their next task is to look at realistic scenarios of predators and prey in the new warmer Arctic ecosystem.

Read original post here.

El Nino predicted to return this year with implications for weather and fisheries

A warming of the central Pacific Ocean this year will change weather worldwide, US forecasters predict.

The warming, called an El Nino, can mean an even hotter year coming up and billions of dollars in losses for food crops.

Australia and South Africa should be dry while parts of South America become dry and parts become wet in an El Nino. Peru suffers the most, getting floods and poorer fishing.

But it could bring good news for some parts of the planet, leading to fewer Atlantic hurricanes and more rain next winter for drought-stricken California and southern US states. It could also bring and a milder winter for the frigid US north next year, meteorologists say

The National Oceanic Atmospheric and Administration issued an official El Nino watch today. An El Nino is a warming of the central Pacific once every few years, from a combination of wind and waves in the tropics. It shakes up climate around the world, changing rain and temperature patterns.

Read the full article here.

Has There Really Been A Sardine Crash?

Sardines have been a hot news topic in recent weeks. Environmental groups and others have claimed that the sardine population is collapsing like it did in the mid-1940s.

The environmental group Oceana has been arguing this point loudly in order to shut down the sardine fishery. That’s why they filed suit in federal court, which is now under appeal, challenging the current sardine management.

So what is the truth about the state of sardines? It’s much more complicated than environmentalists would lead you to believe. In fact, it’s inaccurate and disingenuous to compare today’s fishery management with the historic sardine fishery collapse that devastated Monterey’s Cannery Row.

Read the full story here.

El Niño may make 2014 the hottest year on record

Hold onto your ice lollies. Long-term weather forecasts are suggesting 2014 might be the hottest year since records began. That’s because climate bad-boy El Niño seems to be getting ready to spew heat into the atmosphere.

An El Niño occurs when warm water buried below the surface of the Pacific rises up and spreads along the equator towards America. For nine months or more it brings rain and flooding to areas around Peru and Ecuador, and drought and fires to Indonesia and Australia. It is part of a cycle called the El Niño-Southern Oscillation.

It is notoriously hard to make a prediction before the “spring barrier” as to whether there will be an El Niño in a given year. “The El Niño-Southern Oscillation cycle more or less reboots around April-May-June each calendar year,” says Scott Power from the Bureau of Meteorology in Melbourne, Australia.

The problem is that there is so much background variability in the atmosphere and ocean that it is hard to see any signal amidst the noise, says Wenju Cai from the CSIRO, Australia’s national research agency in Melbourne. “Even if there is a developing El Niño, it is hard to predict.”

Read the full article here.

As sardines vanish from Southern California coastal waters, fishermen rely on squid and anchovy

Larry Derr was as prepared as any longtime Southern California bait fisherman for the disappearance of the Pacific sardines he has pulled up by the ton since the 1980s.

He can fish anchovies instead and, if those become scarce, there’s been a local surge in market squid to keep him in business.

But the fickle sardines have been so abundant for so many years – sometimes holding court as the most plentiful fish in coastal waters – that it was a shock when he couldn’t find one of the shiny silver- blue coastal fish all summer, even though this isn’t the first time they’ve vanished.

And the similar, but smaller, anchovies have proven a poor replacement since sardines became scarce. Fortunately, a boom in market squid has propelled Derr and other coastal pelagic fishers.

In three days of nighttime fishing last week, Derr barely cleared a measly 20 scoops of anchovies to sell.

“A couple days ago we caught a ton of anchovies,” Derr said, keeping a vigilant eye for the telltale red mass on the In-Seine’s sonar during a predawn hunt Saturday. The screen remained black with irregularly dispersed green dots representing schools too small to fish. “We want this to be solid red.”

Though sardines aren’t as valuable as tuna or rockfish, they’re an important food source for larger fish, marine mammals like sea lions, dolphins and whales, and sea birds that can spot them from the air and dive for them.

Some have attributed recent rashes of sea lion pup and pelican deaths to the sardine population decline, which began a few years ago and was officially recognized in December when the fishing quota was dropped to just 5,446 metric tons for all of California, Oregon and Washington from January to June. In the same time period last year, the quota was 18,073 metric tons.

The Pacific Fishery Management Council lowered the quota in November after years of sardine stock decline from 2006, when 1.4 million tons were estimated to be swimming around the north Pacific. This year, their numbers are believed to be less than 400,000 metric tons.

Read the full article here.

State-of-the-art fishery research vessel Reuben Lasker completed for NOAA to commission in 2014

SEAFOOD.COM NEWS [seafoodnews.com] November 13, 2013 – NOAA has taken delivery of Reuben Lasker, the agency’s newest high-tech fisheries survey vessel from Marinette Marine Corporation, a Fincantieri company. The 208-ft. ship will primarily support fish, marine mammals and turtle surveys off the U.S. West Coast and in the eastern tropical Pacific Ocean.

“Reuben Lasker represents a significant milestone in the agency’s efforts to provide world-class marine science platforms,” said Rear Adm. Michael S. Devany, director of the NOAA Office of Marine and Aviation Operations and the NOAA Corps. “This state-of-the-art ship will play a key role in supporting NOAA’s mission and serving the nation.”

Built at MMC’s shipyard in Marinette, Wisc., and funded through the American Recovery and Reinvestment Act, Reuben Lasker is the fifth in a series of Oscar Dyson-class ships built for the agency. The ship is equipped with the latest technology for fisheries and oceanographic research, including advanced navigation systems, acoustic sensors, and scientific sampling gear.

“MMC has a long, established history of delivering exceptionally crafted and complex vessels,” said Chuck Goddard, MMC’s president and CEO. “The talented and skilled workers of MMC are proud to deliver this high quality vessel to NOAA in support of its important mission.”

The ship is also engineered to produce much less noise than other survey vessels, allowing scientists to study fish populations and collect oceanographic data with fewer effects on fish and marine mammal behavior. The ship’s comprehensive environmental sampling capabilities will enable researchers to gather a broad suite of marine life data with unprecedented accuracy.

Read the full article here.