NEWS
June 1991. You don’t often get vol-
canoes of a size big enough to cause
such a substantial sunscreen effect.
They only occur every few decades
at best. So it was quite an extraordi-
nary projection by Hansen. Certainly
the newer models have done a very
good job of predicting the warming we
would have expected back in the ’90s,
so that denialist talking point doesn’t
hold any water.
Q: So if denialism were my side-hustle
— which seems to be the case with
many of the deniers — how could I go
about poking holes in the trends?
A: Fluctuations caused by the energy
fluxes between atmosphere and ocean
are popularly used by the denialist fra-
ternity to cherry-pick and cast doubt.
When we get an El Niño event, which
changes the circulation of water in the
Pacific, it releases a lot of that energy
back into the atmosphere. During El
Niño years you tend to get above-av-
erage warm temperatures; during La
Niña years the ocean tends to absorb
energy out of the atmosphere.
In 1998 we had a strong El Niño, which
made it a very significant El Niño year
— and that was the hottest year on re-
cord at that time. Even without factor-
ing in El Niño, we’ve repeated the tem-
perature record many times since then.
But that’s where this idea of a “warm-
ing hiatus” between the end of the ’90s
and 2012 came from. To even have a
snowball’s hope of showing that, you
have to start your record in extremely
hot 1998 and trace it through to 2012,
where you had a bit of a La Niña. Tem-
peratures didn’t cool, they simply pla-
teaued for a while, but this “hiatus”
was still the warmest period since re-
cords began.
Q: Right, but that’s just one period.
Why fixate on that?
A: Looking at the long-term warming
trends by drawing a line through a 40-
or 50-year period, and considering the
trends since 2012 where we still have
most of the hottest years on record
since 1998, you can see the denialist-
supporting wiggle in all this, and that’s
not entirely surprising. Earth-system
science is such a complex and multi-
faceted area and there are all sorts of
tricks you can use to confuse people
— fossil fuel emission uncertainties
and clouds and ocean circulation and
model sensitivity.
But none of the sceptics will take the
record from 1991 to 1998 and say,
“Ooh, global warming’s accelerated.”
They’d rather take the period from
1998 to 2012 and say, “Ah! Global
warming has gone away!” We call
that “cherry-picking”. If somebody
makes that argument, either the per-
son genuinely doesn’t understand the
science, or they do understand the sci-
ence and they’re trying to fool you. For
both of those eventualities that person
is not worth listening to as an expert.
Discount it. It’s just junk. Mendacious.
Completely false. Puerile.
Q: Climate projections seem to do fair-
ly well when considering large swathes
of the planet, but struggle on a granu-
lar level. Why the gap?
A: On a broader scale it’s certainly more
feasible to come up with general con-
clusions about climate change risks.
For example, in the northern hemi-
sphere the preponderance of evidence
shows that wild species have been
shifting their geographic ranges — the
areas where they naturally occur — to-
wards the pole and upwards in eleva-
tion when that’s available to them, be-
cause they’re tracking their preferred
“climate space”; and that the quantum
of those range shifts matches the pre-
dictions from the climate models.
There are people who say the tempera-
ture records have been fiddled with to
show global warming and to argue that
point you have to argue that the wild
species in the northern hemisphere
have also been duped by that fraud
because they’re all responding in the
way they should [laughs].
Q: What happens when you get more
specific and local?
A: Then the uncertainties pile up so
much that it becomes hard to say any-
thing specific. To predict impacts at a
particular point climatically starts to
make little sense because there are all
sorts of things that could push that pre-
Figure 3: Climate scientist Professor Guy Midgley of Stellenbosch Univer-
sity. (Photo: Kerry Grey)
Grassroots
Vol 19
No 4
November 2019
32