NEWS
Putting deniers on ice:
Inside the mind of a climate
geek (Part One)
Current Address: Independent Economist PhD Candidate, University of Cape Town
Reprinted From: http://bit.ly/2XgGcvC
Tiara Walters
N
ew findings released this month
by the journal Nature Commu-
nications reveal that English-
language digital and print media
give 49% more coverage to bush-
league climate contrarians than top
scientists. We asked Professor Guy
Midgley, a Stellenbosch University
expert on how biodiversity responds
to the climate crisis. With the odds
in favour of ‘at scale climate change
disinformation’, as the study puts it,
what’s the best way for ordinary peo-
ple to make sense of this wilderness?
Q: Climate modelling is full of uncer-
tainties — how do these affect the sci-
ence community’s ability to nail its pro-
jections to the mast?
A: The temperature projections made
back in the early ’90s were done with
somewhat rudimentary models. Now
it seems those early projections were
more extreme because they didn’t in-
clude all the necessary processes. That
means projections dating to the early
’90s — such as a likely 2°C increase for
the planet by 2050 — are now more
likely to materialise towards the latter
half of this century, if no action is taken
to reduce emissions. There’s a lot of
empirical support for what these mod-
els do and they’ve been quite exten-
sively reviewed, including by the Unit-
ed Nations Intergovernmental Panel
on Climate Change (IPCC).
More recently even, the latest set of
models from the IPCC have included
new work on improving estimates of
climate sensitivity. Early results suggest
that they’re projecting a warmer future
sooner than the previous round five or
six years ago.
Q: So what’s making the latest batch
of models more climate-sensitive, and
therefore, more useful?
31
A: As I understand it, the new mod-
els incorporate energy feedback from
clouds more efficiently and more real-
istically. The net effect is that a more
responsive warming to rising CO 2 is
being projected than before. In fact,
we have a good idea from hundreds of
thousands of years of ice core data that
there’s a good correlation between
CO 2 concentration and atmospheric
temperature.
So, that’s not very good news for us,
but it’s a moving target and climate sci-
ence is evolving. For instance, I think
it’s fair to say that we don’t fully under-
stand yet how responsive the atmos-
phere is to CO 2 , but we do know with
virtual certainty that rising CO 2 is caus-
ing warming.
Q: But surely all this is grist to the de-
nier’s mill — extreme projections in the
early ’90s, cooler projections around
2013/14 and now we’re looking at a
warmer future again. And yet, scien-
tific credibility is the key to whether or
not people acknowledge that nature
is dangerously close to ejecting Homo
sapiens from the mothership.
A: I don’t think any modeller would
claim their model is 100% spot-on.
Models try to simplify and synthesise
complex processes so that they can
come up with useful predictions. Mod-
els are either useful or not useful, but
they’re never perfect — the complexity
of nature is beyond what models can
capture in all details.
In the physics of climate, it’s under-
stood that we cannot precisely predict
the future because climate has a char-
acteristic called “deterministic chaos”.
To get a perfect prediction, you must
measure everything with absolute pre-
cision and, even if you’re out by, say,
0.000001% in the measurement of so-
called “initial conditions”, the model
will deviate from reality after a certain
amount of time.
Therefore, it’s not possible to model
the weather precisely over long pe-
riods — modelling hurricane tracks is
a lovely, real-world example. That’s
why we need to consider the issues
very carefully and take lessons from
the results. Models are getting better,
though. We’ve all experienced more
accurate predictions of weather over
the timescale of days and even weeks
— and that’s part of research to reduce
the uncertainties.
Q: How well are the models serving us
on the long-term outlooks?
A: Pretty well. Take the simple ’80s
models of, say, the former director
of Nasa’s space studies institute Jim
Hansen [today Columbia University cli-
mate programme director]. He came
up with three scenarios — high, middle
and low — and here’s an example of
how iniquitous the denialist fraternity
are, because they always highlight and
cite his high scenario and say, “Well,
he completely overestimated climate
warming.”
But his mid-level scenario has been re-
ally useful. Hansen even included the
assumption of an El Chichon-sized
volcanic eruption in the mid-’90s. He
wasn’t predicting a volcanic eruption,
he was simulating an uncertainty: What
if there was a significant eruption? How
would it affect the projections? How
much time might it buy us? After all,
big volcanic eruptions can cause hemi-
spherical or even global cooling for
a few years, because volcanoes emit
sulphate aerosols, which create a “sun-
screen effect” that reflects radiation
back into the atmosphere.
In fact, we did have an eruption —
Mount Pinatubo in the Philippines in
Grassroots
Vol 19
No 4
November 2019