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NOAA:
El Nino is Coming. Extreme Weather, New Global High Temperature
Records to Likely Follow.
6
March, 2014
In
the masterfully constructed fantasy world of Westeros, George R.R.
Martin’s characters have a saying — Winter
is Coming.
The
words are spoken with an air of dread as winters in this realm can
extend for years, starve entire cities, and push civilizations to the
brink. In a world impacted by human climate change, the words El Nino
might be uttered with a similar dread, as it foreshadows a dumping of
Pacific Ocean heat back into an already warming atmosphere.
The
result is that most moderate to strong El Nino years are record hot
years, pushing the global temperature average ever higher through a
cycle of natural variability warped toward hot by human greenhouse
gas forcing. And, in fact, even two of the recent weak El Nina years,
2005 and 2010, were both hottest years on record:
(NASA GISS temperature graph showing global increases since 1950 reflecting El Nino, La Nina, and ENSO neutral years. Image source: NASA GISS.)
These
new record high temperatures occurred during a period when cold water
upwelling in the Pacific was particularly strong. Driven by the most
powerful trade winds on record, this ocean surface and atmosphere
mixing dumped an unprecedented amount of heat into Pacific waters. It
is a period known as negative Pacific Decadal Oscillation and it
usually reflects a time of cooling for the atmosphere. But, despite
this rather intense period of heat transfer from atmosphere to ocean,
the atmosphere remained at or near record hot levels, only slightly
slowing in its rate of upward rise.
El
Nino is Coming
Now,
according to reports from NOAA, the waters just below the surface of
the Eastern Pacific are starting to warm and rise. This warm water
pulse, known as a Kelvin Wave, is proceeding from west to east even
as it is rising from the depths. The source of these warm waters is a
deep, hot pool in the Central and Western Pacific. A pool of warmth
that has been intensified over the last 14 years by a near constant
bombardment of above normal ocean surface temperatures. The hot ocean
waters evaporated, becoming more heavily burdened with saline and
eventually sank far into the depths.
Now,
as the trade winds have weakened and westerlies sporadically began to
emerge, this pool of hot water was drawn eastward by upwelling
currents near the South American Continent. Should these hotter
waters break the surface, the world will experience a moderate to
strong El Nino along with global atmospheric temperatures that are
likely to be the hottest on record.
From
the NOAA ENSO forecast:
While
all models predict warming in the tropical Pacific, there is
considerable uncertainty as to whether El Niño will develop during
the summer or fall. If westerly winds continue to emerge in the
western equatorial Pacific, the development of El Niño would become
more likely. However, the lower forecast skill during the spring and
overall propensity for cooler conditions over the last decade still
justify significant probabilities for ENSO-neutral. The consensus
forecast is for ENSO-neutral to continue through the Northern
Hemisphere spring 2014, with about a 50% chance of El Niño
developing during the summer or fall.
Meanwhile,
the latest Climate Prediction Center forecast now shows a 52% chance
that El Nino will form by the months of October, November and
December:
This
is slight increase of about 2% from even the late February analysis.
It’s
worth noting that though continued forecast agreement across agencies
through early March provides increased likelihood of El Nino’s
emergence later this year, spring forecasts are typically somewhat
unreliable due to atmospheric instability. In addition, the Pacific
Ocean remaining in a negative PDO state over the last 14 years also
produces some uncertainty in the forecast.
“Impressive”
Subsurface Warming
In
addition to models showing an increased chance of El Nino starting in
April and rising through November, projections imply that this El
Nino, should it emerge, may be the strongest in over a decade. As
noted above, a very large pool of warm water is rising up from the
depths. Meanwhile, model
runs show sea surface temperatures warming to an average deviation
above 1.25 degrees Celsius with some showing values above 2.5 C.
Such moderate to strong values, should they emerge, could produce the
warmest conditions for the Eastern Pacific since 1998, a powerful
event that spiked surface water temperatures for that region up to
2.9 C above normal.
(Strong Kelvin Wave spreads eastward and features subsurface temperature anomalies in the range of 4-6 C above average in a wide zone at 150 depth. Note the wave beginning to push above 60 meters in a region near the Eastern Pacific during late February. Image source: NOAA.)
Mark
Halpert, acting director at the Climate Prediction Center, noted that
subsurface warming was “impressive” and seemed quite confident
for early spring that this region of the world was developing toward
a substantial El Nino event later this year.
Globe
to Warm. Amped Hydrological Cycle, Sea Ice Loss to Play a Role in El
Nino Induced Weather Swings?
Should
the predicted El Nino emerge and be as strong as average model values
indicate, global surface temperatures could rise by between .05 and
.15 degrees Celsius, pushing climatology into a range of .85 to .95
degrees Celsius above 1880s values. This would be a substantial jump
for a single year, resulting in yet one more large shift toward an
ever more extreme climate.
Perhaps
also as concerning is the fact that El Nino often results in severe
weather shifts around the globe. With drought and flood events
already being amplified by a 6% increase in the hydrological cycle
since 1880 and with a massive reduction in Arctic sea ice coverage
playing havoc with the Jet Stream, adding an excess of heat over
hundreds of thousands of square miles of Eastern Pacific waters is
likely to further increase instability.
As
examples, the last, rather mild, El Nino of 2010 coincided with one
of the worst heatwaves and wildfire outbreaks ever experienced in
Russia, while the powerful 1998 El Nino battered California with a
winter-long series of extraordinarily intense storms.
(El Nino flattens and amplifies storm track while aiming it at the US West Coast. In combination with already excessive atmospheric moisture levels driven by human-caused warming, such a situation can result in an extraordinarily extreme progression of storms for California in the event that a strong El Nino combines with human-warming driven weather alterations. Image source: ZoomRadar.)
For
the potentially arising El Nino, farmers in California may experience
a switch from extreme drought conditions to extreme deluge. The
result of a flattening pattern in the Pacific Jet Stream that tends
to coincide with El Nino to funnel a river of Pacific moisture
directly over the US West Coast. With the hydrological cycle already
amped up by human-caused warming, such a large moisture dump could be
even worse than those previously experienced.
As
observed in 2010, high temperature anomalies over Central Asia that
typically coincide with El Nino can, in the current climate state,
result in severe droughts and wildfire outbreaks. This could result
in an expanding zone of drought and fire as well as produce a
troubling hot air pool that could occasionally spill into the Arctic.
If the pattern emerges during summer or early fall, the result could
be both record sea ice melt and severe heatwaves, wildfires and
droughts from the center of the Eurasian Continent all the way to the
Arctic Ocean.
It’s
worth noting that both increased rates of evaporation and very low
levels of Arctic sea ice could amplify some aspects of El Nino
induced weather extremes. So the combination of spiking global
temperatures and adding yet more weather instability to an already
amped up system could make a moderate to strong 2014 El Nino a severe
event indeed.
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