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In January 2018, something strange happened in the Sahara Desert: it
snowed. The Algerian town of Ain Sefra, named the “Gateway to the
Sahara”, reportedly received up to an inch, barely enough to get the average
North American out of bed early to scrape the car, but for North Africans,
the outlier snowfall would have been magical; it was only the third time in
40 years that the Sahara Desert, one of the hottest places on earth, has
received snow. (the desert gets very cold at night but even if it dips below
freezing, any precipitation that crystallizes to snow usually melts right
away)
A year later, extreme heat and cold were experienced in Australia and
Russia. Temperatures at Port Augusta, South Australia, shot up to 49 degrees
Celsius, on the same day, Jan. 7, as the mercury plunged to -56 in parts of
Russia. That’s numbingly cold, but not as bone-chilling as in January 2018,
when a blast of -67 cold air hit Russia’s remote Yakuta region -
low enough to freeze eyelashes.
Can these outlier weather events be explained by climate change?
Global warming theory posits that higher temperatures are bringing more
extreme weather and more frequent, high-intensity storms. Last summer in
British Columbia, more of BC was burned by wildfires than any previous
summer. Heat records were set in the United Kingdom, northern Siberia, the
eastern two-thirds of the United States and southeastern Canada.
The hottest temperature ever measured, 51.3 degrees C, was
in Ouargla, Algeria, in July 2018, shattering the previous record of
50.7C set in 1961 in Morocco.
This summer has only just begun in the northern hemisphere, but already
records are falling and residents are drooping from the relentless
heat.
European scorcher
Few could have missed the headlines about the early-summer heat wave that
blanketed most of Europe in June.
According to the EU’s satellite agency, Copernicus Climate Change
Service, last
month was officially the hottest June ever recorded. The data showed
that, while the average global temperature rose by just 0.1 degrees Celsius,
compared to June 2016, the last record - in Europe, temperatures
soared.
The heat wave on the continent meant temperatures of 2C above normal, but
in France, Germany and Spain, the thermometer climbed to between 6 and 10
degrees higher than normal, in the last few days of the month.
Records were blasted through in France (45C), Germany, Poland and the
Czech Republic. In Spain, the 40+-degree temperatures set forests ablaze,
burning at least 4,000 hectares. It reached 39 in Turin, Italy, 39
in Zarazoga, Spain, and 39 also in Avignon, France, a city normally
known for its gentle Mediterranean climate.
The four-day heat wave was intense enough to kill seven people. It also
led to flash floods, grounded planes, buckled train tracks, closed schools,
initiated warnings over air quality, and triggered water restrictions that
affected farmers and their crops - including widespread damage to grapes
grown to make wine in southwestern France.
Meteorologists blamed the dangerously hot weather on a weakening of the
jet stream, pushing super-heated air from Africa up to Europe. CBC
reported that five of Europe’s hottest summers of the last 500 years
happened in the 21st century, and quoted the World Meteorological
Organization saying that the heat wave was “absolutely consistent” with the
extreme weather linked to the impact of greenhouse gas emissions. Or was it?
More on that below. Also remember, the heat wave of 2003 in Europe, which
marked the hottest August on record, was many times worse than this past June
– 35,000 people died!
But for now, let’s keep going on what has already been a wacky summer,
weather-wise.
Perma-melt
A recent
scientific report found that Canada is warming twice as fast as the rest of
the world. Even worse is what’s happening in the Arctic, where the
temperature has risen 2.3 degrees C compared to 70 years ago. Add another
degree of warming during winter, states the report from Environment and
Climate Change Canada.
That has left southern Canadians with more rain in winter, and northern
Canadians with melting permafrost and less sea ice.
When sea ice is lost, the sunlight is no longer reflected
back to the atmosphere, but rather gets absorbed into the open ocean.
This exacerbates ocean warming, and forms a warming cycle. Warmer
water temperatures delay the growth of ice in fall and winter, and the ice
melts faster in the spring, exposing patches of open ocean for longer periods
during summer, and further warming the ocean.
Along with calving glaciers, shrinking ice caps and disappearing sea ice,
evidence of Arctic warming can also be seen in the thawing of permafrost.
Arctic permafrost in 2017 reached record warm temperatures. Over the past 30
years, the Arctic has warmed more than any other region on earth.
A scientific team from the University of Alaska, Fairbanks, found that
permafrost at outposts in the Canadian Arctic is thawing 70 years earlier
than predicted.
“What we saw was amazing,” Vladimir Romanovsky, a professor of
geophysics at the university, told
Reuters. “It’s an indication that the climate is now warmer than at any
time in the last 5,000 or more years.”
As the Arctic tundra thaws, it exposes methane, a greenhouse gas that is
about 30 times more powerful than CO2, in terms of its ability to trap heat.
This creates a feedback loop, which accelerates warming.
A feedback loop is what happens when one change causes another change to
occur, worsening the first change. NASA states that climate feedbacks could
double the amount of warming caused by carbon dioxide alone. States
NASA:
The impact of climate change on the land carbon cycle is extremely
complex, but on balance, land carbon sinks will become less efficient as
plants reach saturation, where they can no longer take up additional carbon
dioxide, and other limitations on growth occur, and as land starts to add
more carbon to the atmosphere from warming soil, fires, and insect
infestations. This will result in a faster increase in atmospheric carbon
dioxide and more rapid global warming.
Read
more at Climate Armageddon - Part 5
The photo below of a dog team splashing through a body of water atop a
thin layer of ice that melted too early, is a powerful image of climate
change in action. The shot was taken in northwest Greenland by Steffen Olsen,
a climate scientist at the Danish Meteorological Institute, and published
by The Weather Network.
The institute reported in May that the spring melt began a month earlier
than normal in 40% of the huge Arctic land mass, “adding up to an estimated 2
gigatons of ice lost in a single day.”
Flooded out
Across the Atlantic, problems of a different nature were mounting in
May.
We’re talking about long and intense deluges, causing widespread
flooding.
The central US and southeast were the worst-hit areas, with cities from
Minneapolis to New Orleans slammed by heavy rains and cresting rivers.
CNN
reported May 30 that some 70 river gauges along the Mississippi and
its tributaries were experiencing major flooding, with another 104 showing
moderate flooding. At one point over 100 million people were on flood watch
from Oklahoma into Kansas, Missouri and Illinois.
The Mississippi River rose to 46.02 feet at St. Louis, the second highest
crest in history, just beneath the record set in 1993.
According
to AccuWeather, one storm after another bashed into the region during
much of March, April and May: The storms packed a great deal of
Pacific and subtropical moisture. May 2019 went down as the wettest on record
for Nebraska, Kansas and Missouri, and Oklahoma recorded its second wettest
May ever.
The weather news site notes that until the rains arrived, parts of the
southeast were facing a sudden drought due to a dome of sinking air that
produced extreme heat and dry conditions into late May. It attributed this
phenomenon to El Nino, the episodic periods during which the waters over the
tropical Pacific Ocean help to boost the intensity of storms in the southern
United States.
However AccuWeather also points to the extremely wet May, over two
inches more precipitation than prior records set during strong El Nino
winters, as evidence something else was happening - climate change:
While it is likely that the weak El Niño is intensifying rainfall over
the Lower 48, increases
in heavy rain events are also among the most anticipated
and well-documented impacts from climate change.
May was
characterized by warm extremes in the Southeast and
simultaneously cold extremes in the north-central region. Such a contrasting
pattern, which
may become more common in a warming world, breeds
storminess.
High snow pack
As southerners were hunkering down against slashing rain, high winds,
tornadoes (between May 1 and 23, 340 spun across the United States, compared
to a May average of 276) and swollen creeks/ rivers, farther north the snow
was still flying.
In Colorado this past winter, it was cold. Along Colorado’s Front Range,
three inches of snow fell in May. That day, the temperature in Denver only
reached a high of 39 degrees F - the coldest the Mile High city has
been in 128 years.
A higher than normal snowpack in the Rocky Mountains is likely to boost
water levels in the drought-prone Colorado Watershed, in 2020.
Data
from the US Bureau of Reclamation states shows the snowpack in the Upper
Colorado River Basin at 138% of the long-term median. The amount of snow
hasn’t been that high in mid-March since 1997, and is good news for
residents and businesses who rely on the Lake Mead reservoir - America’s
largest store of fresh water - for their drinking water and irrigation
needs.
Although, as federal officials warn, one wet winter is unlikely to solve
the southwest’s water problems; Lake Mead is projected to be just
five feet higher than 1,075 feet at the end of this year, the level deemed to
indicate a shortage.
The blob off BC
El Nino may have been partially responsible for the wild US weather in
recent months. Up north in the temperate Pacific Northwest, our unseasonably
warm weather also has climate and weather watchers scratching their heads.
Turns out the mild winter we had in British Columbia was owing to
something called “the blob”. The
blob is a huge mass of Pacific Ocean warm water that parks itself
off the coasts of BC, Washington State and Oregon, bringing a steady pattern
of mild weather throughout the winter months. It was reportedly first noticed
in 2014, re-appeared in 2016 and most recently, last fall.
True to form, this past winter has been warmer than usual, and it
continued into March, breaking temperature records like a board of falling
dominoes. In mid-March, Squamish and Agassiz both hit 25.9 degrees C,
smashing records set in 1999 and 1960, respectively, during weather more
suited to summer.
More records were broken in May during a summer-like warm spell that saw
multiple high-temperature records broken, including Victoria and
Squamish.
Wandering polar jet stream
To sum up, we have multiple anomalous weather patterns
emerging unevenly throughout the earth, but occurring around the
same time.
The big question is, why?
To understand this we need to begin with the jet stream, a band
of air that flows like a river around the Arctic from west to east. Cold air
is generally kept in latitudes above the jet stream, and warm air below
it.
The swirling bands of jet stream air that influence weather in North
America and Europe, create a pattern known as “Rossby waves”.
These waves help to move heat from the tropics toward the poles, and cold
air to the tropics, thereby keeping temperatures moderate. When the
temperature difference between the higher and lower latitudes is great, the
Rossby waves flow in a relatively straight line with little meandering. When
the waves meander, causing more pronounced dips and bulges, weather events
occur, at the intersection of warm and cold air masses.
Now factor in the warming poles due to climate change. Because the Arctic
is warming faster than the rest of the planet, the jet stream is thrown off
course, with increasing frequency of meandering pockets of air, which create
stormy weather.
This is particularly so when disruptions in the polar vortex come
into contact with the meandering Rossby waves flowing over North
America.
The
polar vortex is a seasonal atmospheric phenomenon whereby high winds swirl
around an extremely cold pocket of Arctic or Antarctic air. The winds are
like a barrier that contains the cold air, but when the vortex weakens, the
cold air “escapes” from the vortex and travels south, bringing with it a cold
blast of Arctic weather. An example of such weakening occurred in 1985 when
the northern polar vortex became so distorted that cold air pushed down as
far as Florida, destroying the normally balmy state’s orange crop. During the
winter of 2018, the northern polar vortex stretched its icy fingers towards
Eurasia, which saw temperatures plummet to -80° Fahrenheit (-62C) in
Siberia.
How does climate change affect the polar vortices? The answer is warming
oceans. As more ice melts during the summer, the Arctic Ocean warms. The
effect is less pronounced in Antarctica due to Antarctica being a land
form, not a polar ice cap. That heat gets radiated back to the atmosphere in
winter, which reduces the intensity of the northern polar vortex winds. The
polar vortex gets disrupted, allowing cold air in the center of the swirling
cyclone above the pole to migrate south. According to Scientific American,
data taken from the past decade prior to 2016 shows that in years when a lot
of Arctic sea ice disappeared, the vortex was more likely to weaken.
This past winter, the weakening polar vortex, made worse by more warm
water allowed to escape into the atmosphere due to thinning Arctic sea ice,
disrupted the polar vortex, “leading to enhanced waviness in the polar jet
stream,” according to Judah Cohen, Director of Seasonal Forecasting at
Atmospheric and Environmental Research.
This accounts for the wild weather in the United States from April through
June, explains
an article in Discover Magazine:
What’s going on? Cohen believes the cascade of events that has led to
this month’s weather mayhem is tied to the shrinking lid of floating sea ice
in the Arctic.
In particular, the autumn sea ice freeze-up has been occurring more
slowly than it once did. Then in spring, break-up and melting of the ice has
been happening earlier.
The result: The sea surface is now exposed to the air for longer than
it once was. This allows warmth and water vapor to escape from the open
waters into the atmosphere. Research has shown that this, in turn, can
disrupt large-scale circulation patterns in the atmosphere — including the
polar vortex.
This is exactly what happened in April, with disruption of the polar
vortex leading to enhanced waviness in the polar jet stream, according to
Cohen. Over Scandinavia, within one of the northward-pointing lobes of the
wavy jet stream, a broad area of abnormally high pressure formed.
And there it sat, stuck in place, helping to reinforce the jet
stream’s waviness in what meteorologists call a “blocking pattern.”
“I do think the wild weather that we have seen, with a highly
amplified trough and the anomalous cold and snow, and even the severe weather
upstream, is related to sea ice loss, a weakened polar vortex, the high
latitude blocking, and a more amplified jet stream pattern across the U.S.,”
Cohen says.
How about the extreme heat in Europe? The scientific evidence suggests the
same phenomenon is likely responsible. In June the regular pattern of the jet
stream changed, into the shape of the Greek letter omega, which resulted in
warm, dry air being pulled north from Africa, and settling above
Europe.
While the reasons for the changing pattern of the jet stream are still a
focus of research, Evidence is accumulating that suggests large
northward swings in the jet stream, like the one that is causing this heat
wave, will occur more often in connection with a rapidly warming Arctic, [ABC
News quotes Dr Jennifer Francis, senior scientist at the Woods
Hole Research Centre USA].
The theory is that as the Arctic
warms, the difference in temperature above and below the
jet stream will lessen, causing the jet stream to slow and its flow to become
more wiggly. Similar to how a slow flowing river has wider meanders
than a fast one.
This would result in the jet stream swinging north more often to bring
unusually high temperatures as well as swinging
south to bring unusually cold temperatures.
Climate scientists also believe that the overall warming of the planet is
more likely to cause warming situations such as the European heat wave. A
study done after the 2018 heat wave in the UK, mentioned by ABC News, found
the probability of a similar event was 30 times more likely than in 1750 when
there was less concentration of greenhouse gases in the atmosphere.
The
Independent quotes Peter Stott, an expert on climate change and extreme
weather, saying that a similar heat wave 100 years ago would have been about
4 degrees cooler, because the baseline temperature was lower. In other words,
because Europe’s average temperature has risen about 1.5C over the last
century, suddenly adding a warming event makes temperatures spike higher than
if the baseline temperature was cooler.
Heat waves therefore are likely to be amplified by a rise in global
temperatures, due to heat-trapping greenhouse gases, and occur more often.
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