
We all have that one friend who uses
localised weather, particularly cold snaps, as evidence climate change isn't
happening. This week, that friend was President Donald Trump.
He took to Twitter to ask
"whatever happened to global warming?" in reference to the record
cold Thanksgiving parts of the US are expected to experience.
Brutal and Extended Cold Blast could shatter ALL RECORDS - Whatever happened to Global Warming?— Donald J. Trump (@realDonaldTrump) November 22, 2018
This is the coldest weather in the history of the Thanksgiving Day Parade in NYC, and one of the coldest Thanksgivings on record!— Donald J. Trump (@realDonaldTrump) November 22, 2018
In Trump's defence, it's an easy and
very common mistake to make in science, taking a short patch of weather in a
localised region and using it to make broad statements about the long-term
climate patterns of the planet as a whole. It seems intuitive that if the
planet is getting warmer, winters should get warmer too.
But this idea actually has no
scientific backing, and it's a dangerous error that can detract and distract
from the real science on climate change.
In fact, studies actually show that
the opposite is true.
Warmer conditions in the Arctic
actually coincide with colder winters in far North America, a correlation that
demonstrates global climate change isn't as intuitive as many might otherwise
imagine.
A 2017 study by an international team
of researchers has found the consequences of these colder and drier winters go
beyond a need to rug up – they're reducing the productivity of crops in lower
latitudes.
More carbon dioxide in the atmosphere
plus warmer conditions should by many accounts be good news for plants,
especially as melting permafrost frees up new terrain. But this isn't entirely
incorrect, at least as far as northern climates go.
When it comes to more distant
regions, the impact of the Arctic's changing climate on temperate plant growth
isn't as well studied.
Separated by thousands of kilometres,
it might not seem all that important. But researchers know all too well that
doesn't make much of a difference when it comes to climate.
El NiƱo is a classic example of what
climatologists call teleconnection, where an anomaly in one part of the world,
such as a change in air pressure around the Pacific island of Tahiti, can be
linked with an anomaly thousands of kilometres away, such as air pressure
around Darwin, Australia.
In recent decades, the Arctic has
experienced more than its fair share of warming thanks to a phenomenon called
Arctic amplification.
A loss of sea ice, hotter ocean
currents, and increased atmospheric water vapour mean temperatures have risen
twice as fast around northern latitudes.
These changes have also been
associated with harsher winters much further south, a knock-on effect that
often confuses people who assume global warming means we can all ditch our
mittens.
This recent research has shown how
above average temperatures in the Arctic lead to lower plant growth and
decreased uptake of carbon dioxide in North American ecosystems.
The team confirmed the connection
between anomalous weather patterns in North America and Arctic warming.
They then used a set of detailed
models called Coupled Model Intercomparison Project Phase 5 (CMIP5) to identify
a link between the anomalies and a drop in gross primary productivity.
In other words, it seems as if a
warming Arctic produces colder winters with less precipitation, reducing the capacity
for plants to take up CO2 by about 14 percent.
"Even though we're talking about
the Arctic, it has immediate impacts on what we experience at lower
latitudes," Anna Michalak from the US Carnegie Institution for Science
told Sarah Gibbens at National Geographic.
What this ultimately means in terms
of carbon sequestration is yet to be determined.
More research will be needed to see
just how widespread this effect could be, but if we're hoping that more carbon
dioxide will automatically make for a greener planet, it's looking a little
more complicated.
It's also unlikely to be a simple
relationship between Arctic temperatures and North American weather patterns,
meaning more data is needed to shore up existing models.
In the meantime, the research could
imply a need to consider frost resistant and drought tolerant crops in
anticipation of plenty more cold, dry winters in the future.
With lower states such as California
already experiencing tough drought seasons in the wake of low snow falls, water
management strategies could be set in place during warm spells in the Arctic.
One thing is for certain – global
warming knows no borders. We're all in this together.
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