Showing posts with label weather. Show all posts
Showing posts with label weather. Show all posts

Saturday, February 3, 2018

Is warming in the Arctic behind this year's crazy winter weather?

Is warming in the Arctic behind this year's crazy winter weather?

File 20180111 101511 sa3hd1.jpg?ixlib=rb 1.1
Seriously cold: The ‘bomb cyclone’ freezes a fountain in New York City.
AP Photo/Mark Lennihan
Jennifer Francis, Rutgers University

Damage from extreme weather events during 2017 racked up the biggest-ever bills for the U.S. Most of these events involved conditions that align intuitively with global warming: heat records, drought, wildfires, coastal flooding, hurricane damage and heavy rainfall.

Paradoxical, though, are possible ties between climate change and the recent spate of frigid weeks in eastern North America. A very new and “hot topic” in climate change research is the notion that rapid warming and wholesale melting of the Arctic may be playing a role in causing persistent cold spells.

It doesn’t take a stretch of the imagination to suppose that losing half the Arctic sea-ice cover in only 30 years might be wreaking havoc with the weather, but exactly how is not yet clear. As a research atmospheric scientist, I study how warming in the Arctic is affecting temperature regions around the world. Can we say changes to the Arctic driven by global warming have had a role in the freakish winter weather North America has experienced?

A ‘dipole’ of abnormal temperatures

Weird and destructive weather was in the news almost constantly during 2017, and 2018 seems to be following the same script. Most U.S. Easterners shivered their way through the end of 2017 into the New Year, while Westerners longed for rain to dampen parched soils and extinguish wildfires. Blizzards have plagued the Eastern Seaboard – notably the “bomb cyclone” storm on Jan. 4, 2018 – while California’s Sierra Nevada stand nearly bare of snow.
A study in contrasts: Warming near Alaska and the Pacific Ocean are ‘ingredients’ to a weather pattern where cold air from the Arctic plunges deep into North America.
NASA Earth Observatory, CC BY
This story is becoming a familiar one, as similar conditions have played out in four of the past five winters. Some politicians in Washington D.C., including President Trump, have used the unusual cold to question global warming. But if they looked at the big picture, they’d see that eastern cold spells are a relative fluke in the Northern Hemisphere as a whole and that most areas are warmer than normal.

A warm, dry western North America occurring in combination with a cold, snowy east is not unusual, but the prevalence and persistence of this pattern in recent years have piqued the interests of climate researchers.

The jet stream – a fast, upper-level river of wind that encircles the Northern Hemisphere – plays a critical role. When the jet stream swoops far north and south in a big wave, extreme conditions can result. During the past few weeks, a big swing northward, forming what’s called a “ridge” of persistent atmospheric pressure, persisted off the West Coast along with a deep southward dip, or a “trough,” over the East.

New terms have been coined to describe these stubborn features: “The North American Winter Temperature Dipole,” the “Ridiculously Resilient Ridge” over the West, and the “Terribly Tenacious Trough” in the East.
While the eastern U.S. suffered very cold temperatures in the recent cold snap, much of the rest of the Northern Hemisphere saw higher-than-average air temperatures.

Regardless what it’s called, this dipole pattern – abnormally high temperatures over much of the West along with chilly conditions in the East – has dominated North American weather in four of the past five winters. January 2017 was a stark exception, when a strong El Niño flipped the ridge-trough pattern, dumping record-breaking rain and snowpack on California while the east enjoyed a mild month.

Two other important features are conspicuous in the dipole temperature pattern: extremely warm temperatures in the Arctic near Alaska and warm ocean temperatures in the eastern Pacific. Several new studies point to these “ingredients” as key to the recent years with a persistent dipole.

It takes two to tango

What role does warming – specifically the warming ocean and air temperatures in the Arctic – play in this warm-West/cool-East weather pattern? The explanation goes like this.

Pacific Ocean temperatures fluctuate naturally owing to short-lived phenomena such as El Niño/La Niña and longer, decades-length patterns. Scientists have long recognized that those variations affect weather patterns across North America and beyond.
When a persistent area of atmospheric pressure stays in the western U.S., air from the Arctic pours into the U.S, causing a split between the warm and dry West and the cold East.
Mesocyclone2014 and David Swain, CC BY-SA

The new twist in this story is that the Arctic has been warming at at least double the pace of the rest of the globe, meaning that the difference in temperature between the Arctic and areas farther south has been shrinking. This matters because the north/south temperature difference is one of the main drivers of the jet stream. The jet stream creates the high- and low-pressure systems that dictate our blue skies and storminess while also steering them. Anything that affects the jet stream will also affect our weather.

When ocean temperatures off the West Coast of North America are warmer than normal, as they have been most of the time since winter 2013, the jet stream tends to form a ridge of high pressure along the West Coast, causing storms to be diverted away from California and leaving much of the West high and dry.

If these warm ocean temperatures occur in combination with abnormally warm conditions near Alaska, the extra heat from the Arctic can intensify the ridge, causing it to reach farther northward, become more persistent, and pump even more heat into the region near Alaska. And in recent years, Alaska has experienced periods of record warm temperatures, owing in part to reduced sea ice.

My colleagues and I have called this combination of natural and climate change-related effects “It Takes Two to Tango,” a concept that may help explain the Ridiculously Resilient Ridge observed frequently since 2013. Several new studies support this human-caused boost of a natural pattern, though controversy still exists regarding the mechanisms linking rapid Arctic warming with weather patterns farther south in the mid-latitudes.

More extreme weather ahead?

In response to the strengthened western ridge of atmospheric pressure, the winds of the jet stream usually also form a deeper, stronger trough downstream. Deep troughs act like an open refrigerator door, allowing frigid Arctic air to plunge southward, bringing misery to areas ill-prepared to handle it. Snowstorms in Texas, ice storms in Georgia and chilly snowbirds in Florida can all be blamed on the Terribly Tenacious Trough of December 2017 and January 2018.
Cold weather from the Arctic combined with warm tropical air fueled a storm that produced well over a foot of snow and spots of flooding in Boston.
AP Photo/Michael Dwyer
Adding icing on the cake is the tendency for so-called “nor’easters,” such as the “bomb cyclone” that struck on Jan. 4, to form along the East Coast when the trough’s southwest winds align along the Atlantic Seaboard. The resulting intense contrast in temperature between the cold land and Gulf Stream-warmed ocean provides the fuel for these ferocious storms.

The big question is whether climate change will make dipole patterns – along with their attendant tendencies to produce extreme weather – more common in the future. The answer is yes and no.

It is widely expected that global warming will produce fewer low-temperature records, a tendency already observed. But it may also be true that cold spells will become more persistent as dipole patterns intensify, a tendency that also seems to be occurring.

It’s hard to nail down whether this weather pattern – overall warmer winters in North America but longer cold snaps – will persist. Understanding the mechanisms behind these complex interactions between natural influences and human-caused changes is challenging.

The ConversationNevertheless, research is moving forward rapidly as creative new metrics are developed. Our best tools for looking into the future are sophisticated computer programs, but they, too, struggle to simulate these complicated behaviors of the climate system. Given the importance of predicting extreme weather and its impacts on many aspects of our lives, researchers must continue to unravel connections between climate change and weather to help us prepare for the likely ongoing tantrums by Mother Nature.

Jennifer Francis, Research Professor, Rutgers University

This article was originally published on The Conversation. Read the original article.

Saturday, April 23, 2016

More and more extreme weather

The weather is getting more and more extreme. On April 23, 2016, temperatures in India were as high as 47.7°C or 117.9°F. At the same time, temperatures in California were as low as -12.6°C or 9.2°F, while temperatures in Greenland were as high as 3.6°C or 38.6°F. Meanwhile, Antarctica was as cold as -60°C or -76°F.

The situation in India is most worrying. Temperatures are very high in many locations. India has been experiencing heatwave conditions for some time now, as reported in this and in this earlier posts.

[ click on images to enlarge ]
More extreme weather goes hand in hand with changes that are taking place to the jet stream, as also discussed in earlier posts (see further below).

As the Arctic warms up more rapidly than the rest of the world, the temperature difference between the Equator and the North Pole decreases, which in turn weakens the speed at which the north polar jet stream circumnavigates the globe. This is illustrated by the wavy patterns of the north polar jet stream in the image on the right.

The outlook for the next week shows the north polar jet stream move higher over the arctic, and to eventually disintegrate altogether, while merging with the subtropical jet stream over the Pacific Ocean.

The video below shows how a very wavy jet stream is projected to disintegrate over the Arctic Ocean over the coming week.

This makes it easier for warm air to move into the Arctic and for cold air to move out of the Arctic, in turn further decreasing the temperature difference between the Equator and the North Pole, in a self-reinforcing feedback loop: "It's like leaving the freezer door open."

Temperature forecasts for the Arctic Ocean are high, with anomalies projected to be above 4°C for the Arctic over the coming week.

The image on the right shows one such forecast, projecting a temperature anomaly of 5.31°C or 9.56°F for the Arctic on April 27, 2016, 1500 UTC, while an earlier forecast projected a 5.34°C or 9.61°F anomaly (hat tip to Mark Williams).

The danger is that the combined impact of high air temperatures and ocean heat will cause rapid demise of Arctic sea ice over the next few months.

On April 22, 2016, the sea surface was as much as 11.3°C or 20.3°F warmer than 1981-2011 (at the location off the coast of North America marked by the green circle).

High ocean heat is further accelerating Arctic sea ice demise, as the Gulf Stream keeps carrying ever warmer water into the Arctic Ocean. The image below, created with an image from the JAXA site, shows that Arctic sea ice extent was well under 13 million kmon April 19, 2016, and about 1 million km less than the extent in the year 2012 around this time of year.

Demise of the sea ice will cause even more rapid warming of the Arctic Ocean, with the danger that more heat will penetrate sediments that contain huge amounts of methane in the form of hydrates and free gas, threatening to trigger huge methane releases and cause runaway warming.

Methane levels are increasing strongly. This may not be as noticeable when taking samples from ground stations, but the rise is dramatic at higher altitudes, as also discussed earlier in this post and in this post.

Methane levels in ppb (parts per billion, at bottom of image)
The conversion table below shows the altitude equivalents in feet, m and mb.

57016 feet44690 feet36850 feet30570 feet25544 feet19820 feet14385 feet 8368 feet1916 feet
17378 m13621 m11232 m 9318 m 7786 m 6041 m 4384 m 2551 m 584 m
 74 mb 147 mb 218 mb 293 mb 367 mb 469 mb 586 mb 742 mb 945 mb

The situation is dire and calls for comprehensive and effective action, as described at the Climate Plan.


- What's wrong with the weather?

Monday, December 28, 2015

2015 warmest year on record

1.1°C or 34.1°F at the North Pole
The year 2015 is shaping up to be the warmest year on record. In the media, a lot of attention has been given to the many floods, droughts, wildfires and heatwaves that have battered the world this year.

Sadly, though, little attention is given to the situation in the Arctic. The image on the right shows a forecast for December 30, 2015, with temperatures at the North Pole above freezing point, as further illustrated by the image below, showing a temperature forecast of 1.1°C or 34.1°F for the North Pole. Wind speed at the North Pole is forecast to be 105 mph or 168 km/h on December 30, 2015, and 133 mph or 215 km/h closer to Svalbard.

As the image below illustrates, very high temperatures are forecast to hit the Arctic Ocean on December 30, 2015.

Above image shows temperature anomalies at the highest end of the scale for most of the Arctic Ocean, with a temperature anomaly for the Arctic as a whole of 2.4°C or 4.32°F above what was common in 1979-2000. The situation isn't likely to improve soon. For January 3, 2016, the temperature in the Arctic is forecast to be as much as 4.56°C or 8.21°F warmer.

How is it possible for such high temperatures to occur over the Arctic Ocean? The image below shows how the year 2015 is shaping up in terms of temperature anomalies.

Global warming is felt most strongly in the Arctic as warming continues, as illustrated by above image and by the image on the right.

Warming in the Arctic is accelerating due to feedbacks. One of these feedbacks is the way the jet streams are changing. Changes in the jet streams are becoming more prominent as the Arctic is warming up more rapidly than the rest of the world.

jet streams
As the difference in temperature between the Arctic and the equator becomes smaller, the speed at which the jet stream circumnavigates the globe is decreasing and jet streams become more wavy.

Meanwhile, most of the extra heat caused by global warming goes into the oceans, and the Atlantic Ocean is warming up fast. At the same time, meltwater is accumulating at the surface of the North Atlantic, lowering sea surface temperatures there. With such large differences between high temperatures over North America and lower temperatures over the North Atlantic, the speed of the jet stream between those places can increase dramatically.

The result is that huge amounts of warm air are being pushed high into the Arctic. The image on the right shows the jet streams on December 27, 2015, when speeds as high as 263 mph or 424 km/h were reached at the location marked by the green circle. Also note the jet streams crossing the Arctic at the top of the image, while crossing the equator at the bottom of the image.

The image below shows sea surface temperature anomalies on the Northern Hemisphere in November.

For over a month now, storms over the North Atlantic have been pushing hot air high up into the Arctic. The video below uses surface wind content by Climate Reanalyzer (selected daily averages and sequences of forecasts) to cover the period from December 5, 2015, to January 8, 2016.

Best wishes for 2016
Above video stops at January 8, 2016, when two cyclones are visible, one in the North Atlantic and another one over the North Pacific, prompting me to create the image on the right.

What causes these storms to grow this strong? Waters keeps warming up dramatically off the east coast of North America. Emissions from North America tend to extend over these waters, due to the Coriolis effect, and this contributes to their extreme warming.

The image below shows carbon dioxide levels as high as 511 ppm over New York on November 5, 2015, and as high as 500 ppm over the water off the coast of coast of New Jersey on November 2, 2015. 

Emissions contribute to warmer waters - click to enlarge
The top panel of the image on the right shows that on December 11, 2015, carbon dioxide levels were as high as 474 ppm (parts per million, surface concentration) at the location marked by the green circle in New York.

The bottom panel of the image on the right shows that the water off the coast was warmer by as much as 10.3°C or 18.5°F at the location marked by the green circle on December 11, 2015.

The NASA video below shows carbon dioxide emissions over the year 2006.

It's not just CO2 off the North American coast that contributes to further warming of the Gulf Stream, many other emissions do so, including methane, CO, etc. Carbon monoxide (CO) is not a greenhouse gas, but it depletes hydroxyl, thus preventing oxidation of methane, a very potent greenhouse gas. The animation below shows a carbon monoxide level at green circle of 528 ppb on December 28, 2015, 0900z, while the sea surface temperature anomaly there was 15.8°F or 8.8°C on that day. 

Carbon monoxide reached much higher levels recently over land, as illustrated by the image below that shows a CO level of 2077 ppb in New York on January 6, 2016. 

These emissions heat up the Gulf Stream and make that ever warmer water is carried underneath the sea surface all the way into the Arctic Ocean, while little heat transfer occurs from ocean to atmosphere, due to the cold freshwater lid on the North Atlantic.

feedback #28 at the feedback page

The image on the right shows that it was warmer by as much as 9.6°C or 17.2°F near Svalbard on December 25, 2015, at the location marked by the green circle. The same anomalies were recorded on December 26, 2015, when the temperature of the water there was 11°C or 51.9 °F.

This gives an indication of how warm the water is that is being pushed underneath the sea surface into the Arctic Ocean.

Strong winds and high waves can cause more sea ice to be pushed along the edges of Greenland out of the Arctic Ocean, into the Atlantic ocean, expanding the cold freshwater lid on the North Atlantic, in a self-reinforcing feedback loop.

The image below shows the impact of these storms on sea ice speed and drift on December 31, 2015 (left) and a forecast for January 8, 2016 (right).

The danger is that, as warmer water reaches the seafloor of the Arctic Ocean, it will increasingly destabilize sediments that can contain huge amounts of methane in the form of free gas and hydrates.

Methane levels over the Arctic Ocean are already very high. Above image shows methane levels as high as 2745 ppb over the Arctic Ocean on January 2, 2016. High releases from the Arctic Ocean seafloor are pushing up methane levels higher in the atmosphere, as discussed in earlier posts such as this one.

So, while the extreme weather events that have occurred in the year 2015 are frightening, even more terrifying is the way the water of the Arctic Ocean is warming up. Sadly, this is rarely even discussed in the media. So, let's once more add the image below that should have been given more media attention.

The situation is dire and calls for comprehensive and effective action as described at the Climate Plan.

The year 2015 is shaping up to be the warmest year on record. In the media, a lot of attention has been given to the...
Posted by Sam Carana on Monday, December 28, 2015

Saturday, November 22, 2014

How melting Arctic ice is driving harsh winters

by Nick Breeze

The very least 'global warming' could do for us is to give us warmer winters, right? Wrong, writes Nick Breeze, who met climate scientist and meteorologist Jennifer Francis in his attempt to understand the complex interactions of jet stream, polar vortex, the melting Arctic, and the extreme snowfall that's hitting the northeast US right now.

"Historic" snowfalls have the US northeast this week, with Buffalo, New York under an astonishing 2.4m (8ft) of snow - enough to cause some roofs to cave in under the pressure.

It's just the latest chapter in 2014 unprecedented range of weather extremes - from persistent storms that battered, and flooded much of the UK at the beginning of the year, before going on to record the hottest October since records began.

And in the US, extremes have ranged from California's record drought, to the early snows now under way in the northeast - and let's not forget the 'polar vortex' that hit much of the US in January, bringing Arctic conditions as far south as Texas and Florida, causing flights to be cancelled in Chicago as aviation fuel froze in the -38.3C (-37F) temperatures.

Scientists now have evidence that these persistent extreme weather patterns are increasing in their frequency, due to the rapid heating up of the Arctic that is changing the behaviour of the jet stream, and in turn, the polar vortex.

And Jennifer Francis of Rutgers University, one of the leading US scientists studying the relationship between Arctic warming and changes in the jet stream, believes that it's thanks to 'global warming' that northern hemisphere weather is becoming more extreme - and it's not about to get any better.

Screenshot from Youtube video further below

The 'vast river of wind' that makes our weather

"The Arctic is generally very cold", she told me, "and the areas farther south are warm, and that difference in temperature between those two areas is really what fuels that vast river of wind moving high over our head that we call the jet stream."

"The jet stream in turn creates most of the weather that we feel all around the northern hemisphere and the middle latitudes, so anything that affects this jet stream is going to affect weather patterns. So as the Arctic warms up much faster than the areas farther south, we're seeing this temperature difference between these two regions get smaller."

The result of that, she explains, is that the atmospheric forces driving the jet stream's circular motion are getting smaller - and that means the winds themselves in the jet stream are getting weaker, and moving more slowly.

"When that happens, the jet stream tends to take a wavier path as it travels around the northern hemisphere and those waves are actually what create the stormy patterns and the nice weather patterns. As those waves get larger because of this weakening of those winds of the jet stream, they tend to move more slowly from west to east."

"That means it feels like the weather patterns are sticking around longer, because those patterns are moving much more slowly and this then makes it more likely to have the kind of extreme events that are related to persistent weather patterns."

Are critical findings influencing policy?

These changes in climate have huge implications. As Dr Francis points out, there are "people who worry about whether there is enough fresh water to supply cities, whether there is enough snowpack on mountains to supply reservoirs, and for agriculture ..."

"Drought and agriculture is a big problem. Storminess in certain areas is another big problem. Yes, it has a huge impact for a whole range of issues that affect the way we live."

It's no wonder then that Dr Francis and her colleagues have attracted the attention of President Obama's chief science advisor, Dr John Holdren.

Dr Holdren has been reporting directly to the President on the real time effects of climate change and is keen to understand what this new research tells us about the future impact of changes to the jet stream.

Asked about this sudden interest in her work from the US Presidency, Francis muses thoughtfully. "Yes, we've had a lot of interest from policy makers", she acknowledges.

"I think we're starting to make a lot of progress now in getting policymakers to understand that this is a big problem they have to face ... I think decision makers and the policymakers at the local level get it much better because they're already seeing effects on their local areas.

"Sea level rise is an obvious one. They're already seeing changes in drought and agricultural problems and dealing with fresh water issues. It is really at the local level that we're having more success."

New research supports the case that Arctic sea ice loss is driving climate changes

So to understand the changes in the jet stream it's important to research how the vast atmospheric river of weather above our heads is connected to other climate mechanisms.

"It appears that over the north Atlantic, and towards Asia, there's a mechanism that appears to be quite robust, and several groups have found this mechanism using completely different analysis techniques", says Francis referring to new research by colleagues at the University of Alaska that has emerged in the last couple of months.

"So what we're finding is that there's an area, north of Scandinavia in the Arctic, where the ice has been disappearing particularly rapidly. When that ice disappears ... there is unfrozen ocean underneath, and that ocean absorbs a lot more energy from the sun through the summertime. So it becomes very warm there."

"Then as the fall comes around, all that heat that's been absorbed all summer long, where the ice has retreated, is put back in the atmosphere and that creates a big bubble of hot air ... over that region where the ice was lost."

And in turn, that goes on to disrupt the circumpolar winds whose behaviour determines much the weather across the northern hemisphere.

The gigantic bubble of warm air "tends to create a northward bulge in the jet stream", and in turn, "that creates a surface high pressure area that circulates in the clockwise direction. That sucks cold air down from the Arctic over northern Eurasia, and that creates a southward dip in the jet stream."

The bulging jet stream disrupts the polar vortex

"So what we're getting is this big northward bulge up over Scandinavia and a southward dip over Asia ... creating, first the tendency for a larger wave in the jet stream, which tends to move more slowly, but also we're seeing this mechanism that creates these colder winters that have been observed over Central Asia."

"Once the jet stream gets into this wavier pattern, it sends wave energy up into the highest levels of the atmosphere, which is called the stratosphere, where we have the polar vortex, which is kind of similar to the jet stream but it's much higher up in the atmosphere and it travels much faster."

"So as that wave energy gets sent up from this larger wave below, up into the stratosphere, it breaks down that polar vortex so that it becomes wavier as well. That wavier polar vortex sends energy back down to the lower atmosphere and it creates an even wavier jet stream in February."

"So we're seeing this connection of mechanisms that starts with Arctic sea ice loss and it makes a wavier jet stream for different reasons all the way through winter."

Will the jet stream continue to cause changes in climate?

By identifying these mechanisms and linking them back directly to loss of the Arctic sea ice, Dr Francis and her colleagues are demonstrating how man-made global warming is creating feedbacks that are changing the climate conditions in the northern hemisphere - and not for the better.

It may be counterintuitive, and it when it first happened it took scientists by surprise - but now it looks like this is one of the most important ways in which 'global warming' is hitting North America. Melting ice in the Arctic Ocean is indirectly pushing frigid Arctic air south across the continent, creating the perfect conditions for massive snowfall.

Which is all very well ... but what's coming next? "We are using these climate models, or computer simulations ... to try and project what we're expecting to see happen in the future, as greenhouse gases continue to increase.

"The early indications are that these large wavy patterns in the jet stream are going to become more frequent in the future, as far as we can tell. It is preliminary research that I haven't published yet but it does look as if they are going to increase."

Nick Breeze is a film maker and writer on climate change and other environmental topics. He has been interviewing a range of experts relating to the field of climate change and science for over four years. These include interviews with Dr James Hansen, Professor Martin Rees, Professor James Lovelock, Dr Rowan Williams, Dr Natalia Shakhova, Dr Michael Mann, Dr Hugh Hunt, among others.

Additional articles can also be read on his blog Envisionation.

Jennifer Francis is a research professor at the Institute of Marine and Coastal Sciences at Rutgers University, where she studies Arctic climate change and the link between Arctic and global climates. She has authored more than 40 peer-reviewed publications on these topics. She was also the co-founder of the Rutgers Climate and Environmental Change Initiative.

Article earlier posted at


Wednesday, July 2, 2014

What's wrong with the weather?

Above map shows temperatures in NewFoundland and Labrador close to 30°C (86°F), compared to temperatures in Albuquerque, New Mexico of only 20°C (68°F), while temperatures seem to be even lower in Mexico City. What's happening with the weather?

Jet Streams are changing

World climate zones used to be kept well apart by jet streams. On the northern hemisphere, the polar jet stream was working hard to separate the Tundra and Boreal climate zones' colder air in the north from the Temperate climate and the Subtropical climate zones' warmer air in the south.

As the Arctic is warming even faster than the Equator, the falling temperature difference between the two reduces the speed at which warm air is moving from the Equator to the North Pole. This in turn slows the speed at which the jet streams are circumnavigating the globe on the Northern hemisphere and it is deforming the jet streams in other ways as well.

NOAA image ]
As above image shows, the polar jet stream is typically located at about 60°N and the subtropical jet stream at about 30°N. The polar jet stream's altitude typically is near the 250 hPa pressure level, or 7 to 12 kilometres (4.3 to 7.5 mi) above sea level, while the weaker subtropical jet stream's altitude is higher, between 10 and 16 kilometres (6.2 and 9.9 mi) above sea level.

NOAA image
The polar jet stream used to travel at speeds of up to 140 miles per hour, while following a relatively straight track that was meandering only slightly, i.e. with waves that go up and down only a little bit. This fast and relatively straight jet stream kept climate zones well apart. Accordingly, the Northern Temperate Zone used to experience only mild differences between summer and winter weather, rather than the extremely hot or cold temperatures that we're increasingly experiencing now.

Polar jet stream (blue) & subtropical
jet stream (red) - NOAA image
Loss of snow and ice cover in the north is accelerating warming in the Arctic. This is decreasing the difference in temperature between the Arctic and the Northern Temperate Zone, in turn causing the polar jet to slow down and become more wavy, i.e. with larger loops, as illustrated by the animation below.

Imagine a river that at first rapidly runs down a narrow and straight path when its waters fall down from the top of a high mountain. Once that river flows through flat land, though, it becomes slow and curvy.

Similarly, the polar jet stream is now circumnavigating the globe at slower speed and along a wavier tracks. Its waves are now more elongated, more stretched out vertically, making that cold air can move more easily down from the Arctic, e.g. through the middle of North America, as illustrated by the animation below.

At the same time, warm air can move up more easily from the South into the Arctic. This is creating huge temperature anomalies in many places, as also illustrated by the animation below.

Friday, May 16, 2014

More extreme weather can be expected

The heaviest rains and floods in 120 years have hit Serbia and Bosnia this week, Reuters and Deutsche Welle report.

The animation below shows the Jet Stream's impact on the weather. Cold temperatures have descended from the Arctic to Serbia and Bosnia in Europe and all the way down to the Gulf of Mexico in North America, while Alaska, California, and America's East Coast are hit by warm temperatures. In California, 'unprecedented' wildfires and fierce winds lead to 'firenadoes', reports CNN.

Saturday, February 15, 2014

Extreme weather strikes around the globe - update

As the weather gets more extreme, disaster strikes around the globe. The Guardian reports three people killed as storms continue to batter southern UK. The Vancouver Sun reports that a U.S. Northeast snowstorm kills 25. And the Sacramento Bee reports Six dead and 1,000 injured in fresh Japan snow storm.

What is the story behind these extreme weather events? The image below tells the story. The Arctic has been much warmer than it used to be, due to numerous feedbacks that accelerate warming in the Arctic. This reduces the temperature differential between the Arctic and lower latitudes, which changes the Jet Stream and Polar Vortex, in turn making the weather at many places ever more extreme.

 earlier forecasts by
Above image illustrates the situation, showing an Arctic Ocean that is warmer than the higher latitudes of the Asian and North American continents.

Arctic sea ice has meanwhile reached record lows, as illustrated by the image below.

The situation can be expected to get even worse. The image below shows sea ice extent, as measured by the NSIDC, which is one day ahead compared to above image.

Below, two regular contributors to the Arctic-news blog comment on the situation.

Monday, February 10, 2014

Extreme weather strikes around the globe

  Editorial note: this post has meanwhile been updated as
Extreme weather strikes around the globe update.

As the weather gets more extreme, disaster strikes around the globe.

Here's a snapsnot from today's news. In London, the BBC reports, flooded homes along the River Thames are being evacuated and thousands more are at risk. In Japan, reports Reuters, eleven people died, more than a thousand were injured and tens of thousands lost power when the worst snowstorm in decades hit Tokyo and areas around the Japanese capital before heading north to blanket the tsunami-hit Pacific coast. Many countries in the Middle East were hit by snow. The BBC reports that heavy snow in northern Iran has left around 480,000 homes without power and some towns and villages cut off.

What is causing these extreme weather events? The image below tells the story. While at times it has been cold at many places around the world, when averaged over the past 30 days, temperatures around the globe have actually been several degrees higher than they used to be. The Arctic has been hit hardest, with anomalies as high as 21°C over this 30 day period. This affects the Jet Stream and Polar Vortex, which in turn is making the weather ever more extreme.

The situation is further illustrated by the forecasts below.

And while the sea ice didn't look too bad at the start of the year, growth has meanwhile stopped, as illustrated by the image below.

Added below are two videos by Paul Beckwith, further discussing the situation.

Editor's note: Reanalysis of temperature anomaly Jan 12 - Feb 10, 2014.
Meanwhile, I've added another image (above), created with NOAA's reanalysis, which compares temperatures to a larger dataset, and the colors look a lot different, so NOAA may indeed have mixed the colors up somewhat in the initial image, as Albert suggested at the Facebook discussion (click on image below).

Anyway, the point made in the post remains, i.e. that as global warming continues, warming in the Arctic accelerates more rapidly than at lower latitudes, which weakens the polar vortex and jet stream in a self-reinforcing feedback that causes the Arctic to warm up even further compared with lower latitudes.

As said, the situation calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Thursday, January 30, 2014

Forecast: America to be hit by temperatures as low as minus 40 degrees

The image on the right shows that large parts of North America, the Arctic Ocean and Siberia are experiencing low temperatures.

What many people may not realize is that temperatures in the Arctic are actually a lot higher than they used to be around this time of year.

Temperatures in the Arctic have risen due to feedbacks as described in the post The Biggest Story of 2013.

As a result, temperature anomalies above 20 degrees Celsius now feature in the Arctic. As the image on the right illustrates, the once-common temperature difference between the Arctic and lower latitudes has been shattered, and this is weakening the Jet Stream and the Polar Vortex, in turn making it easier for cold air to flow down to lower latitudes and for warmer air to enter the Arctic, as described in posts at this blog for years, e.g. this post.

This is illustrated by the image below, showing that the Arctic is hit by an overall temperature anomaly of 6.55 degrees Celsius, while some areas in the Arctic feature anomalies above 20 degrees Celsius.

Forecasts show that on February 2nd, 2014, 1200 UTC, the Arctic will be hit by a temperature anomaly of 7.85 degrees Celsius, while on February 6th, 2014, 1200 UTC, the U.S. will be hit by temperatures as low as -40 degrees, as illustrated by the image below.

The video below shows temperature forecasts from February 1to February 8, 2014.

The video below shows temperatire anomalies from February 2 to February 9, 2014.

Meanwhile, the Gulf Stream keeps pushing warm water into the Arctic Ocean, as illustrated by the image below.

Click on image to enlarge - view updated animation at 
The image below shows how high sea surface temperature anomalies stretch out from the point where the Gulf Stream travels at high speeds, off the coast of North America, all the way into the Arctic Ocean.

This has already resulted in methane eruptions from the seafloor of the Arctic Ocean that started several months ago and are continuing to date - ominous signs of more to come. The image below, which compares peak methane levels at two altitudes between January 2013 and January 2014, suggests that January 2014 peak levels have increased strongly, compared to January 2013 peak levels. Furthermore, that the rise in average peak readings has been most dramatic at the higher altitude.

This suggests that huge quantities of methane have indeed been released from hydrates under the Arctic ocean, and that much of the methane is rising and building up at higher altitudes. The increasing appearance of noctilucent clouds further confirms indications that methane concentrations are rising at higher altitudes.

Of course, the above analysis uses a limited dataset, but if verified by further analysis, it would confirm a dramatic rise in the presence of methane in the atmosphere due to releases from hydrates. Moreover, it would confirm the immensity of threat that releases from the Arctic Ocean will escalate and trigger runaway warming, as high methane concentrations over the Arctic are contributing to the anomalously high temperatures there. The risk that this will eventuate is unacceptable, which calls for comprehensive and effective action such as discussed at the ClimatePlan blog.