Tuesday, April 17, 2018

Heat Storm

[ click on images to enlarge ]
Arctic sea ice extent has been at a record low for the time of year for most of 2018, as illustrated by above image. In 2012, extent went below 3.4 million km². The question is what minimum 2018 extent will be.

Arctic sea ice could disappear altogether in 2018. Have a look at the progressive loss of sea ice volume depicted in the image on the right, from an earlier post. Zero sea ice volume by 2018 is within the margins of the trend line contained in the data going back to 1979.

What drives volume decline is the combination of extent loss and especially thickness loss. Sea ice thickness has declined particularly where the ice once was at its thickest, i.e. north of Greenland and the Canadian Arctic Archipelago.

The combination image below shows the decline of the thicker sea ice, by comparing sea ice thickness on April 15 (run April 14) for the years 2015 through to 2018, showing that sea ice this year is entering the melting season with little or no thick sea ice left north of Greenland and the Canadian Arctic Archipelago to cope with the influx of warmer water.


The image below shows how much Bering Strait sea ice is at a historic low and the associated International Arctic Research Center post describes that this is caused by higher ocean temperatures and frequent storms.


The influx of warm water from the Atlantic Ocean and from the Pacific Ocean is melting the sea ice from below, while sunlight is melting the sea ice from above. Furthermore, warm water from rivers that end in the Arctic Ocean also contribute to melting of the sea ice, and there are numerous feedbacks that can dramatically speed up melting.

Disappearance of the sea ice means that the buffer that until now has consumed huge amounts of heat, will be gone and that heat that previously went into melting the sea ice, will instead warm up the Arctic.

Sea ice can be expected to continue its downward spiral, given the continued rise of the temperature of the sea surface in the North Atlantic Ocean and the North Pacific Ocean, as illustrated by the image below.


The sea surface is not necessarily the place where the water is at its warmest. This is illustrated by the image below, showing subsurface ocean heat in the area most relevant to El Niño/La Niña events.


[ click on images to enlarge ]
Indeed, while we're currently still in a La Niña period, it looks like a new El Niño will arrive this summer, as illustrated by the forecast plumes on the right.

This could result in a heat storm in which heat waves could decimate the sea ice, while storms could push the remaining sea ice out of the Arctic Ocean.

This danger is further illustrated by the trend line in the image below, a trend that is contained in NASA LOTI data up to March 2018, adjusted by +0.79°C to better reflect the rise from preindustrial and surface air temperatures, and to better include Arctic temperatures.


[ click on images to enlarge ]
The temperature rise in the Arctic is causing decline of the sea ice extent as well as the extent of the snow cover on land.

The image on the right shows the progressive decline of the spring snow cover on land in the Northern Hemisphere.

A recent study shows that the amount of water melt from the glaciers on Mt. Hunter, Alaska, is now 60 times greater than it was before 1850.

Heat waves combined with strong rainfall due to storms could devastate the snow cover in 2018.

Decline of the snow and ice cover in the Arctic comes with a huge loss in albedo, which means that huge amounts of sunlight that were previously reflected back into space instead get absorbed by the Arctic.

The Buffer has gone, feedback #14 on the Feedbacks page
A rapid rise in temperatures in the Arctic will also accelerate changes to jet stream, which can cause huge amounts of heat from the Atlantic Ocean and the Pacific Ocean to enter the Arctic Ocean, further speeding up the temperature rise and threatening to destabilize methane hydrates in sediments under the Arctic Ocean.

The methane will initially be felt most strongly in the Arctic, further speeding up the temperature rise that is already accelerating due to the loss of the snow and ice cover in the Arctic, which makes that less sunlight is reflected back into space and instead adds to warming up the Arctic.

All this shouldn't come unexpected. In the video below, Guy McPherson warns that a rapid temperature rise will affect agriculture across the globe, threatening to cause a collapse of industrial civilization, in turn resulting in an abrupt halt of the sulfates that are currently co-emitted as a result of burning fuel, which will further add to a temperature rise that is already threatening to cause people across the globe to perish at massive scale, due to heatstroke, dehydration and famine, if not perish due to nuclear radiation and further toxic effects of war, as people fight over who controls the last habitable places on Earth.


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

Links

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• Feedbacks in the Arctic
https://arctic-news.blogspot.com/p/feedbacks.html

• How much warmer is it now?
https://arctic-news.blogspot.com/2018/04/how-much-warmer-is-it-now.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

• Ten Dangers of Global Warming
https://arctic-news.blogspot.com/p/ten-dangers-of-global-warming.html

• Methane Erupting From Arctic Ocean Seafloor
https://arctic-news.blogspot.com/2017/03/methane-erupting-from-arctic-ocean-seafloor.html

• Warning of mass extinction of species, including humans, within one decade
https://arctic-news.blogspot.com/2017/02/warning-of-mass-extinction-of-species-including-humans-within-one-decade.html

• In the coastal communities near the Bering Strait, a winter unlike the rest
https://www.climate.gov/news-features/features/coastal-communities-near-bering-strait-winter-unlike-rest

• A 400‐Year Ice Core Melt Layer Record of Summertime Warming in the Alaska Range 

Monday, April 2, 2018

How much warmer is it now?

The IPCC appears to be strongly downplaying the amount of global warming that has already occurred and that looks set to eventuate over the next decade or so, according to a leaked draft of the IPCC 'Special Report on 1.5°C above pre-industrial'. The 'First Order Draft of the Summary for Policy Makers' estimates that the global mean temperature reached approximately 1°C above pre-industrial levels around 2017/2018.

Let's go over the numbers step by step, by following the image below line by line (click on the image to enlarge it).

NASA's data for the two most recent years for which data are available (2016/2017) show a warming of 0.95°C when using a baseline of 1951-1980 and a warming of 1.23°C when using a baseline of 1890-1910 (left map on image below). In other words, using this earlier baseline results in an additional 0.28°C rise. When using an even earlier baseline, i.e. 1750 or preindustrial, it could be 1.53°C warmer, as discussed in an earlier post.


In other words, merely changing the baseline to preindustrial, as agreed to at the Paris Agreement, can show that we're already above the 1.5°C guardrail that the Paris Agreement had pledged we should not cross.

There's more! As a recent publication points out, most methods that calculate the global temperature use sea surface temperatures. However, doesn't it make more sense to calculate the temperature of the air just above the sea surface? Measuring air temperature at the surface is done in the case of temperatures over land, where one doesn't measure the temperature of the soil or rocks when telling people how warm it is. Since air surface temperatures are slightly higher than sea surface temperatures, the result of looking at air surface temperatures across the globe would be a temperature that is approximately 0.1°C warmer. Furthermore, many areas in the Arctic may not have been adequately reflected in the global temperature, e.g. because insufficient data were available. Since the Arctic has been warming much faster than the rest of the world, inclusion of those areas would add another 0.1°C to the rise. Adding this to the above 1.53°C rise makes that it's already 1.73°C (or 3.11°F) warmer than preindustrial.

Another question is over what period measurements should be taken when assessing whether thresholds have been crossed. When focusing on temperatures during specific months, the rise could be much higher than the annual average. So, does it make more sense to look at a monthly peak rather than at a long-term average?

When building a bridge and when calculating what load the bridge should be able to handle, it makes sense to look at peak traffic and at times when a lot of heavy trucks happen to be on the bridge. That makes a lot more sense than only looking at the average weight of cars driving over the bridge during a period of - say - one, two or thirty years.


Accordingly, the right panel of the top image shows numbers for February 2016 when temperature anomalies were particularly high. When looking at this monthly anomaly, we are already 2.37°C (or 4.27°F) above preindustrial, i.e. well above the 2°C guardrail that the Paris Agreement had pledged we should definitely not cross.

Should the temperature rise be calculated using a longer period? The IPCC appears to have arrived at its temperature rise estimate by using an extrapolation or near term predictions of future warming so that the level of anthropogenic warming is reported for a 30 year period centered on today.

The image below, from an earlier post, shows global warming for a 30-year period centered on January 2018, using NASA 2003 to January 2018 LOTI anomalies from 1951-1980, adjusted by 0.59°C to cater for the rise from preindustrial to 1951-1980, and with a polynomial trend added.


If above trendline is adjusted by a further 0.2°C, by shifting to air temperatures instead of sea surface temperatures, and by better reflecting Arctic temperatures, then the trendline looks set to cross the 2°C guardrail in 2018. So, will Earth cross 2°C in 2018?


Above images illustrate the importance of what's going to happen next. The temperature rise up until now may well be dwarfed by what's yet to come and the outlook may well be even worse than what most fear will eventuate. The image below, from an earlier post, shows a steep rise from 2016 to 2026, due to the combined impact of the warming elements listed in the left box of the image below.


Meanwhile, the rise in carbon dioxide levels appears to be accelerating, as illustrated by the images below.


Indeed, despite pledges made at the Paris Agreement to limit the temperature increase to 1.5°C above pre-industrial, the rise in CO₂ since preindustrial, i.e. 1750, still appears to be accelerating.


On March 18, 2018, the sea surface temperature near Svalbard (at the green circle) was 16.7°C or 62.1°F, i.e. 14.7°C or 26.4°F warmer than the daily average during the years 1981-2011.


On March 30, 2018, methane levels as high as 2624 parts per billion were recorded.


On April 1, 2018, methane levels as high as 2744 parts per billion were recorded.



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


Links

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

• How much warming have humans caused?
https://arctic-news.blogspot.com/2016/05/how-much-warming-have-humans-caused.html

• IPCC seeks to downplay global warming
https://arctic-news.blogspot.com/2018/02/ipcc-seeks-to-downplay-global-warming.html

• 2016 well above 1.5°C
https://arctic-news.blogspot.com/2017/01/2016-well-above-1.5c.html

• Interpretations of the Paris climate target, by Andrew Schurer et al.
https://www.nature.com/articles/s41561-018-0086-8


Saturday, March 3, 2018

Warning Signs


The Arctic is warming up more than twice as fast as the rest of the world, due to numerous feedbacks. At times, large areas over the Arctic Ocean can become 30°C or 54°F warmer than 1979-2000, as illustrated by the image below.


On February 27, 2018, large parts of the Arctic Ocean north of Greenland had turned into open water, as illustrated by the image below.


Yet, while the situation in the Arctic is desperate, with sea ice north of Greenland collapsing and more, mainstream media do not seem to care. If there ever were warning signs of what could eventuate, this is one. The sea ice north of Greenland is typically the thickest, as it is the least affected by melting and can build over many years. Early February 2018, sea ice north of Greenland was up to 5 m thick. To see sea ice this thick getting pushed away and open water emerging north of Greenland in the middle of winter is simply stunning.

For years, I've been warning about the situation in the Arctic, in particular the 'Open Doors Feedback', which is accelerating Arctic warming. Such feedbacks were taken into consideration in an earlier analysis that warned about a potential 1.6°C warming globally due to albedo changes in the Arctic, in combination with associated changes such as loss of the ice buffer (latent heat), more heat transfer from the Atlantic Ocean to the Arctic Ocean due to stronger winds along the path of the Gulf Stream, and more heat entering the atmosphere or remaining in the atmosphere, due to more open water in the Arctic Ocean and as oceans get more stratified and take up less heat from the atmosphere.

So, the current situation doesn't come as a big surprise, but it's stunning to see sea ice collapse north of Greenland.

Back in March 7, 2007, I posted the article 'Ten Dangers of Global Warming', describing events getting progressively worse, with one danger feeding and reinforcing the next one, culminating in panic. Then, I thought that reading that post could at least help people better understand what's going on, and thus help people avoid panicking, but right now, I wonder whether most people do want to understand at all. Anyway, here are some images and words describing what happened over the past few days.

Jet Stream over Arctic Ocean on February 25, 2018

As Arctic warming keeps accelerating, there's ever less temperature difference between the North Pole and the Equator, and this slows down the speed at which the jet stream circumnavigates Earth.

Jet Stream over Arctic Ocean on February 26, 2018
The jet stream is getting more wavy and a more wavy jet stream makes it easier for cold air to move out of the Arctic and for warm air to move into the Arctic, so this 'Open Doors Feedback' is a self-reinforcing feedback that further accelerates warming in the Arctic.

During the northern winter, the Arctic is increasingly getting warmer than North America, Europe and Siberia. This increases the temperature difference between these continents and the oceans, which at times is causing winds to strongly speed up over the North Atlantic and the North Pacific, making an already wavy jet stream extend even further over the Arctic Ocean, reaching areas well beyond the North Pole.

Atmospheric river of heat reaches the North Pole; temperatures were as high as 1.1°C or 34.1°F on February 25, 2018
As the jet stream makes this detour, a huge amount of heat enters the Arctic from the south.

Temperatures above 6°C at Kap Morris Jesup, Greenland's northernmost weather station, on February 25, 2018

These events were preceded by the Polar Vortex splitting up. On February 9, 2018, the Polar Vortex was split up into 4 vortices and reached speeds as fast as 425 km/h or 264 mph.

Polar Vortex split up into 4 vortices
A Sudden Stratospheric Warming event occurred on February 16, 2018, with temperatures reaching as high as 8.9°C or 47.9°F over Hudson Bay.

Polar Vortex splitting up into 4 vortices with a Sudden Stratospheric Warming event occurring on February 16, 2018
The heat that has accumulated in the Arctic Ocean is further illustrated by the February 2018 NASA temperature anomalies image below.


Below is an animation of sea ice thickness, from the Naval Research Laboratory.


Arctic sea ice extent was at record low for the time of the year on February 26, 2018, at 14.159 million km². Arctic sea ice extent typically reaches its maximum in March, but maximum extent in 1991-2000 was reached on February 24. So, there is a chance that Arctic sea ice extent will go all downhill from now on this year.


Zero sea ice volume is within the margins of the trend depicted on the image above on the right. Decline of the snow and ice cover in the Arctic comes with a huge loss in albedo, which means that huge amounts of sunlight that were previously reflected back into space instead get absorbed by the Arctic. Loss of sea ice also means loss of the buffer that until now has consumed huge amounts of heat.

The Buffer has gone, feedback #14 on the Feedbacks page
Peak SST near Svalbard rose from
12.4°C or 55.4°F on Feb 23, 2018,
to 15.6°C or 60°F on Mar 2, 2018.
The danger is that a sudden influx of heat can no longer be absorbed by the sea ice and will instead warm up sediments at the seafloor of the Arctic Ocean that can contain huge quantities of methane in the form of hydrates and free gas.

Destabilization of hydrates can occur in a relatively small area as a result of a relatively small temperature rise. Destabilization comes with a 160 times expansion in volume of the methane, which will send out shock waves that can destabilize nearby hydrates, causing them to destabilize as well, resulting in an eruption of huge quantities of methane over a large area.

Here's another warning sign. Peak sea surface temperature near Svalbard rose from 12.4°C or 55.4°F on February 23, 2018, to 15.6°C or 60°F on March 2, 2018, as illustrated by the red line on the image on the right, with the blue line showing the 1981-2011 average.

And here's another warning sign. High methane releases followed this chain of events on February 27, 2018, pm, likely originating from the seafloor of the East Siberian Arctic Shelf (ESAS).

Methane levels as high as 2892 ppb on February 27, 2018
On March 1, 2018, methane levels as high as 3087 were recorded. Note the solid magenta-colored areas over the ESAS on the image below.


The image below, with measurement by another satellite, shows that methane levels were again very high over the ESAS the next day, i.e. March 2, 2018, confirming earlier indications that this is where the very high methane releases did occur.

As the image below shows, methane levels on March 4, 2018, were still very high, i.e. as high as 2964 ppb.

The image below shows the highest mean global methane readings on March 10 over the years from 2013 through 2018, for selected altitudes corresponding to 945 mb (close to sea level) to 74 mb.

[ click on images to enlarge ]
The table below shows the altitude equivalents in feet (ft), meter (m) and millibar (mb).
57,016 ft44,690 ft36,850 ft30,570 ft25,544 ft19,820 ft14,385 ft 8,368 ft1,916 ft
17,378 m13,621 m11,232 m 9,318 m 7,786 m 6,041 m 4,384 m 2,551 m 584 m
 74 mb 147 mb 218 mb 293 mb 367 mb 469 mb 586 mb 742 mb 945 mb

An earlier analysis calculated that seafloor methane could cause a warming of 1.1°C within one decade. Given a possible additional warming of 2.7°C due to just two elements (i.e. Arctic albedo changes and associated changes, and seafloor methane), a further warming of 2.1°C due to extra water vapor in the warmer atmosphere does seem well possible within a decade. Add up the impact of all warming elements of this analysis and the rise in mean global temperatures from preindustrial could be more than 10°C within one decade, as illustrated by the images below.


A rise of a few degrees Celsius would be devastating, especially when considering that the speed at which such a rise could occur leaves little or no time for plants and animals to adapt, let alone in case of a 10°C rise.


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

Links

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• Feedbacks in the Arctic
https://arctic-news.blogspot.com/p/feedbacks.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

• Ten Dangers of Global Warming
https://arctic-news.blogspot.com/p/ten-dangers-of-global-warming.html

• Methane Erupting From Arctic Ocean Seafloor
https://arctic-news.blogspot.com/2017/03/methane-erupting-from-arctic-ocean-seafloor.html

• Warning of mass extinction of species, including humans, within one decade
https://arctic-news.blogspot.com/2017/02/warning-of-mass-extinction-of-species-including-humans-within-one-decade.html


Tuesday, February 20, 2018

IPCC seeks to downplay global warming

The graph below shows global warming for a 30-year period centered on January 2018, using NASA 2003 to January 2018 LOTI anomalies from 1951-1980, adjusted by 0.59°C to cater for the rise from preindustrial to 1951-1980, and with a polynomial trend added.


From: ECMWF Nino Plumes
Above graph shows that the 1.5°C guardrail, set at the Paris Agreement, was crossed in 2016 and that a 10°C (18°F) warming could eventuate within a decade or so.

The variations in above temperature data are strongly influenced by El Niño/La Niña. We currently are in a La Niña period, during which surface temperatures are suppressed, whereas surface temperatures in 2016 were much above the trendline, due to El Niño.

The ECMWF forecast from 1 February 2018 on the right indicates that we're heading for another El Niño, i.e. surface temperatures will be rising strongly over the coming months.

The IPCC seeks to downplay the amount of global warming that has already occurred and that looks set to eventuate over the next decade or so. A leaked draft of the IPCC 'Special Report on 1.5°C above pre-industrial' (First Order Draft of SR1.5 SPM) estimates that the global mean temperature reached approximately 1°C above pre-industrial levels around 2017/2018. The IPCC appears to have arrived at this estimate using an extrapolation or near term predictions of future warming so that the level of anthropogenic warming is reported for a 30 year period centered on today.

This 1°C IPCC estimate looks quite incredible when calculating the temperature rise using NASA's data for the two most recent years for which data are available (2016/2017), which shows a warming of 0.95°C when using a baseline of 1951-1980 and a warming of 1.23°C when using a baseline of 1890-1910.


Indeed, the temperature rise differs depending on which baseline is used, and when using preindustrial as a baseline, i.e. the baseline agreed to at the Paris Agreement, indications are that temperatures have already risen by more than 1.5°C, as also discussed in an earlier post.

Furthermore, when using a 30-year period centered on January 2018, the current temperature will have to be calculated over the past 15 years and estimated for the next 15 years, i.e. up to the year 2033.

To arrive at a 1°C rise for the 30-year period, the IPCC must somehow assume that temperatures will magically fall dramatically over the next 15 years, whereas indications are that temperatures will instead rise dramatically over the next decade or so.

The image on the right shows that 10°C (18°F) warming from preindustrial could eventuate within one decade when taking into full account the warming that could result from the elements depicted in the stacked bar. Each of these warming elements is discussed in more detail at the extinction page.

The image below shows the rise from 1750 to 2030, in surface temperatures (land+ocean), rather than in anomalies.


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


Friday, February 16, 2018

100% clean, renewable energy is cheaper

A new analysis by Stanford University professor Mark Z. Jacobson and colleagues shows that the world can be powered by 100% clean, renewable energy, with today's technology.


The analysis looks at different pathways, using different ways of energy generation (by wind, water and sunlight), in combination with storage, transmission, and demand response, concluding that the world can also be powered by 100% clean, renewable energy at a lower cost than a BAU (Business-As-Usual) scenario dominated by fossil fuel.

“Based on these results, I can more confidently state that there is no technical or economic barrier to transitioning the entire world to 100% clean, renewable energy with a stable electric grid at low cost,” says Jacobson.

Moreover, the price of fuel currently excludes the cost of health and climate damage caused by fuel. When including these costs, the cost of clean, renewable energy is ¼ the cost of BAU.

The price of fuel looks set to go up over time due to decreasing economies of scale for fuel and due to the cost of conflict associated with fuel. As an example, a 2017 report puts the cost of U.S. military intervention in Syria, Iraq, Afghanistan, and Pakistan over the period FY2001-FY2018 at $5.6 trillion, or $23,386 for the average taxpayer. The report adds that, unlike past US wars, these wars have been paid for largely through borrowing. The $5.6 trillion includes the interest the US has already paid on this debt, but it does not include projected future interest. Even if the US stopped spending money on these wars right now, cumulated interest costs on borrowing will ultimately add more than $7.9 trillion to the national debt over the next several decades.

Meanwhile, the price of clean, renewable energy looks set to keep coming down, in line with ongoing innovation in batteries, efficiency improvements in electrical appliances, lights, etc.

Local feebates can most effectively and rapidly achieve the necessary transition to clean, renewable energy. One example is to impose fees on sales of fuel, with the revenues used to fund rebates on local supply of clean, renewable energy. Another example is to impose fees on registration of vehicles with internal combustion engines, with the revenues used to fund rebates on registration of battery-electric vehicles. Local feebates can best help areas each get their preferred mix (of local supply/storage, of grid interconnection and imports/exports of electricity, and of Demand response).

For more on the benefits of feebates, see the Feebates page. The Climate Plan calls for dramatic cuts in emissions through such policies, while also calling for further lines of action.


Links

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

• Matching demand with supply at low cost in 139 countries among 20 world regions with 100% intermittent wind, water, and sunlight (WWS) for all purposes, by Mark Z. Jacobson et al.
https://www.sciencedirect.com/science/article/pii/S0960148118301526

• Stanford engineers develop a new method of keeping the lights on if the world turns to 100% clean, renewable energy
https://news.stanford.edu/2018/02/08/avoiding-blackouts-100-renewable-energy

• Costs of War project, Brown University’s Watson Institute for International and Public Affairs
http://watson.brown.edu/costsofwar/

• Rapid Transition to a Clean World
https://arctic-news.blogspot.com/2015/11/rapid-transition-to-a-clean-world.html

• Roadmap for Repowering California for all Purposes with Wind, Water, and Sunlight
https://arctic-news.blogspot.com/2014/06/roadmap-for-repowering-california-for-all-purposes-with-wind-water-and-sunlight.html

• Feebates
https://arctic-news.blogspot.com/p/feebates.html


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.
NOAA, CC BY

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.