https://www.independent.co.uk/voices/europe-heatwave-climate-change-europe-global-warming-science-a9018426.html
[links and video in online article]
Europe is burning just as new research offers a chilling truth about the
volatility of climate change
Cooler years mask the underlying behaviour of the system. As natural
variations move in the other direction, they can unleash a period of
supercharged heating
James Dyke
Jul 24, 2019
It’s not the fall that will kill you, but the suddenness of the
stopping. Just as it is with a plane crash, so it is with global
heating. Changes in the climate don’t in themselves represent a
significant risk – the Earth’s climate has been changing for billions of
years after all – but it is the abrupt changes that could spell disaster
for us.
New research suggests that climate models which predict greater global
warming in the future also have more volatile warming trends. If that is
the case, and the climate is as sensitive to our carbon dioxide
emissions as many of the latest models suggest, this will seriously
threaten our ability to adapt. And it is that which will put a
significant fraction of humanity in jeopardy.
Many scientists focus on how much warmer the Earth’s climate will become
because of the extra carbon dioxide humans have put into the atmosphere.
The technical term for this is Equilibrium Climate Sensitivity (ECS).
Equilibrium because it takes years, decades or centuries for the climate
system to respond to extra heating.
Think how much energy it takes to heat a bathtub full of water and how
long it can stay warm for. The amount of energy required to heat the
trillions of litres of the Earth’s oceans is enormous.
Consider that bath of water again. Imagine the tap is dripping because
it’s not entirely closed, so the water level in the bath is increasing,
but only very slowly. Trying to track changes in water level just by eye
would be as difficult as seeing the march of time in the hour hand of a
watch. Now picture someone is in the bath. Unless the person stays
absolutely still, they will have an impact on the water level as their
movements will make waves. Depending on how much they move, these waves
can be plain to see and would easily mask the very slow water level
increase.
ECS tells us where the climate system will end up – what the final water
level will be. But it may not tell us a great deal about how we will get
there. Will we have a smooth increase or a much bumpier ride? How much
will the climate fluctuate as it responds to being heated up? How big
will the “waves” in temperatures be? These are the answers that this
recent research has addressed and why on reading it my first response
was “Oh no. This isn’t good”.
Because what the team lead by University of Exeter PhD researcher Femke
Nijsse found, is that more sensitive climates have higher fluctuations.
Using extensive climate simulations, they discovered that if a climate
system reacts strongly to increased greenhouse gases, then it is also
more likely to have decades when temperatures are much higher or
sometimes much lower than the longer-term average. In fact, more
sensitive climates may have a run of years that are cooler than less
sensitive climates.
But these cooler years are masking the underlying behaviour of the
system. As natural variations move in the other direction, they can
conspire with the sensitive climate to unleash a period of supercharged
heating. OK, but why should we be worried about that?
Because the warming trend of the Earth’s real climate between 2002-2012
was a bit less than what it should have been given how much we have been
increasing greenhouse gases. Some people leapt at that as being evidence
that the climate is less sensitive than was initially feared. They
argued we shouldn’t decarbonise too rapidly, or even at all, because
there is no urgency to do so.
But this period of depressed warming is consistent with the Earth’s
climate having higher fluctuations. What this means is that at some
point in the future we may see temperatures swing across to much faster
warming trends. This period of hyper-warming could swamp whatever
adaptation measures we are currently putting in place.
When in the future? Perhaps now, as witnessed by the near continual
breaking of temperature records around the world and much faster rates
of glacier retreat than expected. Rather than a brief anomaly, this may
be the beginning of an acceleration of global heating; an acceleration
of a trend that is already greater than any warming trend for the past
2000 years.
Exploring the relationship between sensitivity and fluctuations is very
complex, and no single study can be considered to provide the last word
on the matter. But this new research has kicked away another support
against the collapse into despair about how we are affecting the climate.
Because, remember, it’s not the fall, but the sudden stop. And the mess
our civilisation will make if climate change sends us plummeting hard
and fast to the floor will not be pretty.
James Dyke is a senior lecturer in global systems at Exeter University
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