Presented by three
mathematicians - Dr Hannah Fry, Prof Norman Fenton (Statstiician) and Prof
David Spiegelhalter - it hones in on just three key numbers that clarify all
the important questions around climate change:-
·
0.85 degrees (the amount of warming the planet
has undergone since 1880)
·
95 per cent (the degree of certainty climate
scientists have that at least half the recent warming is man-made)
I studied Mathematical Physics very many years ago and had a
career in computer engineering. I'm well aware that statistics and numerical
computational solutions can give misleading answers, therefore require testing
in the real world (which we can't do with climate) so was very interested to
view this programme.
It covered lots of uncertainties and issues that need working
around. The history of how the differing techniques were developed illuminated
the problems well. This is good because
far too often we get told simplified analogies about the science which numerate
and educated people can be deeply suspicious of – like I am.
My review covers a few issues about the presentation for
each number, and follows with a few more numbers that I would like investigated.
·
200-300% Amplification by water vapour of the carbon-dioxide
heating
·
0.2% of the total Carbon Flux in the atmosphere
·
the average amount that Minimum & Maximum
Temperatures have increased
The First Number:- 0.85 degrees Centigrade
Warming Since 1880
Question:- Is
0.85 deg. Centigrade unusual?
Answer:- No.
The previous 170 years also warmed at about the same rate. (I applaud the
presentation in explaining that, as we go back in time, the accuracy of known
temperatures declines so that we have talk in approximations.) Unfortunately,
noone knows why the warming of 300 years ago started, and continued in fits and
starts. Thus there's no way to show that the same natural warming isn't
happening now.
The Second Number – 95% Certainty that Human
Carbon-Dioxide Emissions Contribute at least Half of Recent Warming
As a statistician, Prof. Fenton
should have explained that just because 2 things happen at more or less the
same time, (i.e. in his example, winning and football club wage bill; for climatology,
carbon dioxide and temperature) doesn't mean one causes the other or even that
they have the same cause. In fact, in
the case of carbon dioxide, it's a 'confounding' variable which is expected to increase due to warmth. As the oceans get hotter, carbon-dioxide is transferred to the
atmosphere (and the sea holds correspondingly less carbon-dioxide, becoming
more acidic). Another number that would
be really interesting to look at is the % of the carbon flux that is due to humans. I understand it's tiny, ~0.04%
Prof Fenton's presentation used
a Bayesian Statistics approach which showed that the computer models depended
on human carbon dioxide emissions creating more than half of the recent
warming. The impression given was that observational data from the real world
supports this conclusion. There was no investigations into how good the models were at modelling past temperatures, nor of the methods of model 'tuning' that take place.
A Computer Model output of the
troposphere was shown indicating additional heat over the tropics is expected
from human carbon dioxide warming but not from natural variability. If observed for real, it would be decisive.
However, it's not present in the real atmosphere!
… I'm really disappointed that
it was unclear that the model results hadn't been checked against reality.
The Third Number – Total Amount of Carbon we
can burn to stay below 'dangerous levels' of climate change
First, you have to show that it
could be dangerous. A really important
number was omitted – an expected 200-300% amplification by water vapour of the
basic carbon-dioxide heating. This is unproven
and is probably the most contentious thing in climate science because, without
it there's no catastrophe.