Some of the most common questions I get asked here on the channel are centered
around how our climate is changing and how quickly and what the most likely
outcomes are going to be for the coming decades.
Now I'm not a climate scientist as you know so I don't have any expertise to be
able to make those kinds of forecasts but there are thousands of incredibly
knowledgeable and intrepid researchers around the world seeking out more and
more information in an attempt to answer just those questions ever more
accurately with the help of advanced supercomputers running incredibly
complicated climate simulations and with processing speeds accelerating all the
time and more and more data being brought forward from field research all
around the world those models are becoming ever more sophisticated.
But of course nothing and no one can predict the future with 100 confidence can they?
So the best our scientists can do is to tweak the variables in the models based
on all sorts of things from obvious stuff like projected future human
greenhouse gas emissions to more elusive data like seawater salinity and the
Bearing Sea for example or the level of permafrost melt in the middle of nowhere
out in Siberia - you get the idea.
That leaves us with what can only be
described as a cacophony of different pathways that look like badly cooked
spaghetti on charts that grace the pages of periodic assessment reports published
by the Intergovernmental Panel on Climate Change or IPCC.
In December 2022 scientists at the Potsdam Institute for climate research
in Germany teamed up with the Washington Post to produce a fascinating analysis
of more than 1200 different scenarios in an attempt to establish whether any of
them might actually keep global warming below 1.5 degrees Celsius by the end of
the century.
And the conclusions were unsettling!
Hello and welcome to just have a think.
Before I get into the meat and potatoes
of this analysis I must just give a huge shout out to the journalists Chris
Mooney, Naima Ahmed, and John Muskyens, who worked alongside the folks at Potsdam to
produce the information and graphics for the Washington Post article.
I've left a
link to the report in the description section below here and I'd encourage you
to go and have a look at it if you get a chance, not only because it's a
brilliantly written piece of work in its own right but also because it contains
numerous links out to other sites and scientific research papers that help
explain some of their findings in more detail.
And, well, because supporting good
quality journalism is just a generally good thing to do in this day and age
isn't it?
So anyway, back in 2021 the Potsdam
Institute published this paper analyzing 414 emission scenarios set out by the
IPCC in their 2018 Special Report, SR15.
The Potsdam team applied five key
criteria to make their assessment.
Firstly the rate of acceleration in
future carbon dioxide removal technologies like direct air capture or
DAC and bioenergy with carbon capture or BECCS.
Secondly the rate of acceleration
in future carbon dioxide removal via changes in agriculture forestry and
other land use - a category that carries the catchy acronym of AFOLU in the IPCC
reports.
Then they looked at the potential future carbon intensity of
energy production and potential changes in the global level of demand for energy
itself.
And last but not least they looked at non-CO2 emissions,
predominantly focusing on methane.
Then in 2022 the IPCC published their
most up-to-date and comprehensive analysis of future scenarios in a
typically enormous document called the Sixth Assessment Working Group 3.
That
report contained no fewer than 1202 potential future pathways.
Now you can
clearly see that the vast majority of these spaghetti lines lead to
temperature increases far higher than 1.5 degrees Celsius by 2100.
Many of them
push us up to somewhere between two and three degrees of warming and the worst
case scenarios, where we effectively do nothing at all and continue on an ever
upward emissions and consumption trajectory, take the planet's warming up
above 5 degrees Celsius by the end of the century.
The overwhelming scientific and political consensus is that if we
allowed ourselves to stray into that territory then it would no longer be
possible to maintain global civilization as we know it today.
It's not impossible that we might turn out to be that suicidally stupid, but for
the purposes of this exercise any pathway that doesn't stay on or below
1.5 degrees Celsius by 2100 was immediately filtered out by the Potsdam
and Washington Post teams.
That left just 230 of the original 1202
scenarios remaining.
The next challenge is that some of those remaining
scenarios which were finalized in 2021 are already looking vanishingly unlikely
to happen based on the latest data available as we hurtle into 2023.
Global emissions fell by about five percent during the pandemic and there
was some hope that they might continue to do so, which is a lovely idea!
But as this graph, based on numbers from global
carbonbudgetdata.org, shows global emissions are now right back on the same
trajectory that they were following prior to the lockdowns.
And actually
China is not yet fully out of their draconian COVID restrictions which
means we can expect to see their emissions jump up significantly this
year.
So any scenarios predicting a dramatic
fall in emissions by 2025 now look hopelessly unrealistic and therefore
they were eliminated as well.
The Potsdam team also argued that other
overly optimistic developments like massive deployments of nuclear power by
2030 should also be removed.
That gets us down to 112 Pathways that then fall into
two distinct categories - those that predict what's known as a high overshoot
before temperatures drop back down again and those that predict a low overshoot
or even no overshoot at all.
The trouble with the high overshoot
pathways is that the world would have to spend several decades with average
surface temperatures significantly higher than 1.5 degrees Celsius above
pre-industrial levels and that risks setting off some of the major climate
tipping points that we've looked at in previous videos on this channel.
If you want to know more about what those tipping points are and you're
watching on a PC or mobile device then you can click up there somewhere to jump
over to one of those videos.
Suffice to say none of the consequences is good and
they include things like irreversible loss of polar ice sheets that could
eventually lead to several metres of sea level rise.
The point being that straying
way above the crucial temperature limit and sort of hoping that we might get
away with it by employing some kind of as yet unproven silver bullet
technologies a bit further down the line is arguably delusional and perhaps
even disingenuous.
So unfortunately those lines have to come out as well.
That leaves just 26 Pathways that show either a low overshoot or no overshoot
at all.
And now we can start applying the five Potsdam Institute criteria that I
mentioned earlier.
When the expert researchers restricted
the pathways only to those that fitted what are regarded as reasonable
expectations about our ability to capture and permanently store carbon
dioxide at scale as well as reasonable expectations for the other four
assessment criteria they came to the conclusion that the world has most
likely run out of any easy options to completely avoid slipping over the 1.5
degrees Target at some point between now and mid-century.
So that means we need to consider how we can at least stay on very low overshoot
pathways, which moves us away from measures that the Potsdam team regard as
reasonable and into territory that they describe as challenging.
Those scenarios assume that the world will roll out carbon dioxide removal
technologies like DACCS and BECCS at vast scale while at the same time achieving
dramatic transformations in land use to draw even more carbon back down into the
soil.
And when I say vast scale I'm talking about the removal of something
like 7 billion tons of carbon dioxide from the atmosphere every year by the
time we reach mid-century.
Right now we've got the capacity to remove just
over 40 million tons per year, so we'd need to scale all that up by about 160 times
which would indeed be challenging!
We'd also need a fundamental transformation
in energy use via a widespread global move to renewables and huge improvements
in energy efficiency resulting in an 80% reduction in the carbon intensity of
global energy consumption by 2050.
The only way we get there is through the
near complete eradication of fossil fuel combustion in the next three decades or
preferably much sooner of course.
That means a global electrification of
transport and energy systems moving far more rapidly than we are right now.
The other option is to reluctantly accept that temperatures will
significantly overshoot 1.5 degrees this century, most likely getting up to
somewhere around 1.8 degrees during the 2040s 50s and 60s
1.8 degrees is the number that our political leaders managed to conjure up
at COP 26 in 2021 by offering new policy proposals that would stiffen up their
efforts via what are known as nationally determined contributions or NDCs.
That level of temperature increase would still make tipping points and unexpected
consequences much more likely, but the Potsdam team identified 16 pathways that
allowed for this kind of overshoot but which they considered reasonable based
on their five criteria.
We would still need a major ramp up in
carbon dioxide removal and storage by all available methods as we hurtle
towards mid-century and we would have left ourselves with a Herculean task in
the second half of the century to remove really very large amounts of carbon
dioxide in an effort to pull temperatures back down below 1.5 degrees
by 2100, according to the Potsdam team.
And of course we'd still need a massive
step forward in renewables and energy efficiency improvements to help reduce
the carbon intensity of our daily lives by as much as 74% by mid-century.
The trouble is there's really no sign of a genuinely globally coordinated effort
to really achieve those goals.
In fact if anything we've got conflicts, fuel crises,
and political polarizations all over the world that are taking us in precisely
the opposite direction.
As the Washington Post team points out
though, not everybody will agree with the cut-offs imposed on these models by the
Potsdam Institute researchers.
Some experts, like RethinkX for example, who I
featured on the channel a few months ago, are much more optimistic about
technology and humanity's ability to innovate.
But other less optimistic commentators argue that it's easy to imagine
countries failing to achieve what's necessary even to stay below 2 degrees
Celsius.
What we know for sure though is that if
we'd started doing all this back in the mid 80s when people like James Hansen,
Carl Sagan, and Al Gore were setting out the size of the problem in no uncertain
terms to members of the United States Congress then we could have implemented
extremely modest carbon reductions of only about one or two percent a year
and that would have been enough to have completely avoided the serious
predicament we now find ourselves in.
If you're wondering why we didn't do
that then I can highly recommend reading this book by Nathaniel Rich, which gives
a blow-by-blow account of how our global leaders fail to act during that critical
decade.
The Potsdam and Washington Post analysis
can only be as good as the information it's based on at the end of the day
though.
These things are only models of possible future scenarios of course and
there's plenty of debate about the accuracy and validity of predicting the
future in this way.
But the science of climate change is
clear and unequivocal and we're already seeing some of the consequences of our
warming atmosphere in extreme weather events all over the world, so regardless
of the accuracy of our predictions there's no doubt that our future way of
life is in our hands and the choices we make now will have profound consequences
for all of us in the coming decades.
I'm sure you've got your own views on
all this stuff so as always if you're chomping at the bit to express your
opinion then why not jump down to the comment section below and leave your
thoughts there.
And as I said at the start of the video do follow the link in
the description to the original Washington Post article if you get a
chance.
It's well worth a read.
That's it for this week though.
A massive
thank you as always to our amazing Patreon supporters who help me keep
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And if you
want to learn more about the climate challenges facing us in the 21st century
then you might find this video useful too.
As always thanks very much for watching.
Have a great week, and remember to just
have a think.
See you next week