Nino and La Nina Variability as Part of the Larger Warming Trend
a measure of natural variability, La
cooler conditions to a large portion of the Equatorial Pacific Ocean.
Since the influence of this ocean on the larger climate system is so
strong, La Ninas tend to generate periodic cooling in surface
temperatures across the globe.El
by contrast, generates periodic warming. The cycling between these
two states can be imagined as a wave form.
and 2016 were both strong El Nino years — producing new record hot
global temperatures when they occurred. Follow-on La Nina years
resulted in counter-trend cooling that was not great enough to
disturb the much larger overall global warming based trend. Image
cycle, however, should not be confused with the overall larger
climate trend — which has been for considerable and rapid warming
over the course of more than a century. That said, and despite the
larger and obvious warming trend, La Nina years have tended to be
cooler than El Nino years. This prevalence has resulted in years in
which global surface temperatures temporarily, but slightly compared
to the larger trend, back off from recent records. Meanwhile, El Nino
years have tended to bring on new record hot temperatures due to
their peaking influence on the greater trend of fossil fuel and
carbon emissions based warming.
2017 Second Hottest on Record; 2017 Also Tracking Toward Second
August of 2017 came in as the second hottest August in the 137 year
climate record. Overall August temperatures were 1.09 C warmer than
1880s averages. A measure that came in 0.14 C cooler than the record
hot August of 2016 and 0.05 C warmer than the third hottest August —
2014. This added heat to the Earth System continued a larger record
trend that has been in place at least since 2014 in which
temperatures near the Earth’s surface spiked to far higher than
previous levels (see image above).
to Back La Ninas Probably on the Way, But no Significant Cool-Off So
appears that 2017 is likely to hit around 1.11 C above 1880s
averages. This is a 0.11 C dip below the record hot year of 2016. And
it’s a dip enabled by the formation of a La Nina during fall of
2016 and a likely back to back formation of La Nina during the same
season of 2017. In contrast, the
strong La Nina following the 1997-1998 El Nino produced a much
greater relative global temperature drop of around 0.2 C.
An approximate 0.1 C return from the very strong 2016 spike is not
much of a variability-based fall back and could point toward a
stronger relative warming and a possible near term challenge to the
2016 global record in a likely El Nino during 2018-2020.
of the sole cooler than 30-year climatology regions in the Pacific is
the Equatorial zone stretching from the Central Pacific to the West
Coast of South America. Periodic cool water upwelling is driving this
cooling which is a signal for La Nina. NOAA presently identifies a 55
to 60 percent chance of La Nina developing during fall of 2017. If
this happens, late 2016 and late 2017 will feature back to back La
Ninas. Despite this development, global temperatures are still
hanging near record hot ranges. Image source: NOAA.)
a signal would likely firmly solidify 2017 as second hottest on
record. However, stronger than expected variable La Nina based
cooling could upset this trend and bring 2017 closer to 2015 values.
With so many months already passed, we’re looking at a possible
swing of 0.02 to 0.04 C on the lower end if La Nina is stronger and a
strong polar amplification signal does not emerge — which would
still result in less of a variable dip than we saw post 1998.
amplitude Jet Stream waves to again transfer prodigious volumes of
heat into the Arctic during fall of 2017? Watch this space. Earth
model based image from September 28, 2017 shows another larger ridge
forming over the Pacific Northwest and extending up into the Arctic.)
end result is that the world is now firmly in a 1 to 1.2 C above
1880s temperature zone. Such a zone is one that is well outside of
typical recent human experience. One that will tend to continue to
produce unsettling and harmful weather and climate extremes.
Furthermore, increasingly harmful climate change related events are
likely to more swiftly ramp up with each additional 0.1 C in global
temperature increase and as the world approaches the 1.5 C to 2 C