hello and welcome to just have think I'm still working away at the old WTF board at the moment
and this week I've decided it's about time I got my head around this one ocean acidification and
that means yet another dose of dangerous Dave's DIY demonstrations so brace yourself for that
coming up in a minute now it's an emotive title isn't it ocean acidification makes me
think I can't go swimming in the sea without me face melting off but is it an example of gross
exaggeration to play up to the mainstream media or is it a precise description of what's actually
occurring to be honest I didn't have the answer to that so I thought I'd better go and find out quite
recently my dad bought a SodaStream which he's very pleased with and which is certainly helping
him to reduce unnecessary water and plastic waste but it occurred to me that there's another way you
can use it so I bought my own and here it is now this thing is a can of pressurized carbon dioxide
in fact the CO2 in these things is primarily a byproduct of other industrial processes that's
not to say that those processes shouldn't be moving to a carbon-free energy source of
course they should but at least in the meantime they've got some sort of carbon capture process
which is by no means the solution but it's better than nothing oh yeah and the irony of
Pepsi the world's second favorite sugary water producer having just bought SodaStream wasn't
lost on me either anyway these things work by forcing carbon dioxide into water at pressure
and that then dissolves in the water before bubbling up to try and escape and that's what
makes all fizzy drinks fizzy but it also causes a chemical reaction that we can measure using
one of these things a pH indicator and no I didn't have a pH indicator lying around the
house and yes I did go out and buy one just for this experiment and yes that is quite a
nerdy thing to do and no I don't care so there now I poured some water from this bottle into
this jug so that we can measure the pH value so let's have a look at it you can just see that on
the screen there it's measuring about seven which is bang-on neutral on the pH scale so
let's get that out of there pour it back in our bottle and give it some CO2 and see what happens
all right so if we pour some of that out into here again let's pop it back on here so you can
see what's going on and put our pH indicator back in you can see that on the camera and that comes
out to four point seven a pH of four point seven which is very acidic essentially that's what our
scientists are telling us it's happening in our oceans so here's how it works it turns out that
the oceans are extremely good at absorbing CO2 since about 1750 our industrial systems
have pumped enormous quantities of CO2 into the atmosphere and our oceans have absorbed about
30 to 40% of it which is just as well because without that our planet would be a lot warmer
than it already is now as the CO2 is absorbed in the oceans this happens carbon dioxide plus water
becomes H2 CO3 which is basic chemistry that I can remember from school in which I can just
about manage even now an H2 CO3 is carbonic acid now this next bit gets a bit weird so bear with
me apparently carbonic acid molecules can release one of their hydrogen ions to make a bicarbonate
so H2 CO3 goes to HCO3 with a little minus one at the top to show that it's lost to hydrogen
iron and not content with that the bicarbonate can then release another hydrogen ion to become
a simple carbonate which means HCO3 with a little minus 1 goes to CO3 with a little minus 2 to show
that it's lost both of its hydrogen ions I'm just saying at normal temperature and alkalinity levels
the simple carbonate can then combine with calcium that's also in the water to make calcium carbonate
and that is what coral and shells are made of anyway the surface of the oceans about a hundred
years ago had an average pH value of about eight point two five which is clearly on the alkaline
side of neutral but today's average pH is about eight point one four so that's a decrease of not
point one one which sounds pretty insignificant but the pH scale is logarithmic which means two
isn't one more than one it's ten times more than one and three is 10 times more than two
which means it's a hundred times more than one so our naught point one one reduction is actually a
30% increase in acidity and apparently that is significant but pH 8.14 is still well alkaline
isn't it so why is it so important well it turns out that the whole reaction we looked at earlier
is reversible it worked both ways depending on temperature and alkalinity and that means that
as the CO2 concentration increases and more and more of the free hydrogen ions start floating
around causing trouble the simple carbonate can recombine with the hydrogen ions and go back to
being a bicarbonate the science bods have of course created a graph to show how things move
backwards and forwards and because scientists appear to be pathologically opposed to using
simple words it's not called a graph it's called a Bjerrom plot but I'm still going to go through it
with you so have another sip of coffee and here we go right so the vertical axis shows another
logarithmic scale this one of concentrations of carbon dioxide bicarbonate and simple carbonate
the horizontal axis shows the pH values ranging from very acidic over here to very alkaline over
here so when the water is very acidic you get mostly carbonic acid with just a little bit of
bicarbonate action going on down here and when the water reaches pH neutral the bicarbonate combo is
the dominant version of the reaction then as the water moves into alkaline territory the
simple carbonate end of the reaction becomes the most prevalent which is good news for shells and
corals and all of that so if we draw a vertical line down at pH levels from around a hundred years
ago and another one at today's pH level you can start to see the direction of travel as more and
more CO2 gets dissolved into the oceans simple carbonate levels go down and bicarbonate levels
go up and that means less carbonate available to combine with calcium to make calcium carbonate and
that means that shellfish and corals are less able to grow and repair themselves now like
most things that go on in our oceans and our atmosphere the process involves loads of other
variables so it's extremely complicated and it's not black-and-white at all for example there's an
argument that says that as the sea gets warmer the metabolisms of all organisms get faster and that
includes phytoplankton and phytoplankton take in CO2 as they grow just like trees on the land
do so that's a good thing right but other studies like this one from the American Geophysical Union
suggest that the nutrients the phytoplankton need to grow are supplied from deeper waters
and that as the oceans get warmer you get more temperature separation between the different
depths and so there's less mixing of the layers that make these nutrients available the thinking
is that this causes phytoplankton growth and CO2 uptake to decrease which results in more available
CO2 in the water and of course different parts of the oceans have slightly different pH levels
anyway as these charts show so the effects will vary around the globe and what we really don't
know is how much more CO2 human beings are going to spew out across the course of the next 50 years
or so but if we stay on what the scientists call our CP 8.5 which is the worst case representative
concentration pathway otherwise known as the business-as-usual scenario which is the curve
we're following at the moment then according to the IPCC we can expect a further lowering of
average pH values of about 0.3 to 0.4 by 2100 and that will drop the pH level down to about
seven point eight which is very likely to have a negative impact on the overall ecosystem of
our ocean here's a pteropod swimming around in water at a pH of 8.1 pteropods are tiny little
marine snails which are really a type of plankton that they play a very big role in the oceanic food
and ecosystems but here's what happens when it's put in water at a pH of 7.8 which is what
we might get to in 2100 if we continue on the way we are now this has been speeded up a lot
it actually took a month and a half for this to happen but essentially the shell dissolves
as the carbonate reacts with the free hydrogen ions to make bicarbonate although we're on the
RCP eight point five businesses usual trajectory at the moment renewable technology is advancing
at breathtaking speed and social and political will is changing fast despite the noise coming
out of the White House so it's unlikely that we'll stay on that trajectory all the way to
2100 in fact we probably wouldn't get there if we did that's not an oxymoron but a study by the
Royal Society in 2014 which carried out a combined survey of the water and the pteropods along the
Washington Oregon California coast in August 2011 showed that large portions of the shelf waters
are already corrosive to the shells of these plankton they found 53% of the onshore pteropods
and 24% of offshore pteropods had what they called severe dissolution damage the Royal Society study
estimated that the incidence of severe pteropod shale dissolution owing to anthropogenic ocean
acidification has doubled in near shore habitats since pre-industrial conditions across this region
and is on track to triple by 2050 so what to make of all this complicated information well
ocean acidification doesn't mean that our oceans are all full of acid so I can park my irrational
fear of going swimming and melting my face but the science is telling us that the direction of travel
is towards a less alkaline composition and when a reaction like that takes place throughout a body
of water as vast and fundamental to life as our ocean system then it must surely be something that
we need to keep a very close eye on that's it for this week you can click on the subscribe button
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thank you very much for watching have a great week and remember to just ever think see you next week