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The only way to get dangerous global warming is to assume stagnation

Here’s a version of the article I published in the Financial Post this
week with added links:


The debate over climate change is horribly polarized. From the
way it is conducted, you would think that only two positions are
possible: that the whole thing is a hoax or that catastrophe is
inevitable. In fact there is room for lots of intermediate
positions, including the view I hold, which is that man-made
climate change is real but not likely to do much harm, let alone
prove to be the greatest crisis facing humankind this century.

After more than 25 years reporting and commenting on this topic
for various media organizations, and having started out alarmed,
that’s where I have ended up. But it is not just I that hold this
view. I share it with a very large international organization,
sponsored by the United Nations and supported by virtually all the
world’s governments: the Intergovernmental Panel on Climate Change
(IPCC) itself.

The IPCC commissioned four different models of what might happen
to the world economy, society and technology in the
21st century and what each would mean for the climate,
given a certain assumption about the atmosphere’s “sensitivity” to
carbon dioxide. Three of the models show a moderate, slow and mild
warming, the hottest of which leaves the planet just 2 degrees
Centigrade warmer than today in 2081-2100. The coolest comes out
just 0.8 degrees warmer.

Now two degrees [above pre-indistrial levels] is the threshold
at which warming starts to turn dangerous, according to the
scientific consensus. That is to say, in three of the four
scenarios considered by the IPCC, by the time my children’s
children are elderly, the earth will still not have experienced any
harmful warming, let alone catastrophe.

But what about the fourth scenario? This is known as RCP8.5, and
it produces 3.5 degrees of warming in 2081-2100 [or 4.3 degrees
above pre-industrial levels]. Curious to know what assumptions lay
behind this model, I decided to look up the original paper describing the creation of this
. Frankly, I was gobsmacked. It is a world that is
very, very implausible.

For a start, this is a world of “continuously increasing global
population” so that there are 12 billion on the planet. This is
more than a billion more than the United Nations expects, and flies
in the face of the fact that the world population growth rate has
been falling for 50 years and is on course to reach zero – i.e.,
stable population – in around 2070. More people mean more

Second, the world is assumed in the RCP8.5 scenario to be
burning an astonishing 10 times as much coal as today, producing
50% of its primary energy from coal, compared with about 30% today.
Indeed, because oil is assumed to have become scarce, a lot of
liquid fuel would then be derived from coal. Nuclear and renewable
technologies contribute little, because of a “slow pace of
innovation” and hence “fossil fuel technologies continue to
dominate the primary energy portfolio over the entire time horizon
of the RCP8.5 scenario.” Energy efficiency has improved very

These are highly unlikely assumptions. With abundant natural gas
displacing coal on a huge scale in the United States today, with
the price of solar power plummeting, with nuclear power
experiencing a revival, with gigantic methane-hydrate gas resources
being discovered on the seabed, with energy efficiency rocketing
upwards, and with population growth rates continuing to fall fast
in virtually every country in the world, the one thing we can say
about RCP8.5 is that it is very, very implausible.

Notice, however, that even so, it is not a world of catastrophic
pain. The per capita income of the average human being in 2100 is
three times what it is now. Poverty would be history. So it’s
hardly Armageddon.

But there’s an even more startling fact. We now have many
different studies of climate sensitivity based on observational
data and they all converge on the conclusion that it is much lower
than assumed by the IPCC in these models. It has to be, otherwise
global temperatures would have risen much faster than they have
over the past 50 years.  As Ross McKitrick noted on this page
earlier this week, temperatures have not risen at all now for more
than 17 years. With these much more realistic estimates of
sensitivity (known as “transient climate response”), even RCP8.5
cannot produce dangerous warming. It manages just 2.1C of warming
by 2081-2100 [see table 3 in the report by Lewis and Crok here]

That is to say, even if you pile crazy assumption upon crazy
assumption till you have an edifice of vanishingly small
probability, you cannot even manage to make climate change cause
minor damage in the time of our grandchildren, let alone
catastrophe. That’s not me saying this – it’s the IPCC itself.

But what strikes me as truly fascinating about these scenarios
is that they tell us that globalization, innovation and economic
growth are unambiguously good for the environment. At the other end
of the scale from RCP8.5 is a much more cheerful scenario called
RCP2.6. In this happy world, climate change is not a problem at all
in 2100, because carbon dioxide emissions have plummeted thanks to
the rapid development of cheap nuclear and solar, plus a surge in
energy efficiency.

The RCP2.6 world is much, much richer. The average person has an
income about 16 times today’s in real terms, so that most people
are far richer than Americans are today. And it achieves this by
free trade, massive globalization, and lots of investment in new
technology. All the things the green movement keeps saying it
opposes because they will wreck the planet.

The answer to climate change is, and always has been,
innovation. To worry now in 2014 about a very small, highly
implausible set of circumstances in 2100 that just might, if
climate sensitivity is much higher than the evidence suggests,
produce a marginal damage to the world economy, makes no sense.
Think of all the innovation that happened between 1914 and 2000. Do
we really think there will be less in this century?

As for how to deal with that small risk, well there are several
possible options. You could encourage innovation and trade. You
could put a modest but growing tax on carbon to nudge innovators in
the right direction. You could offer prizes for low-carbon
technologies. All of these might make a little sense. But the one
thing you should not do is pour public subsidy into supporting
old-fashioned existing technologies that produce more carbon
dioxide per unit of energy even than coal (bio-energy), or into
ones that produce expensive energy (existing solar), or that have
very low energy density and so require huge areas of land

The IPCC produced two reports last year. One said that the cost
of climate change is likely to be less than 2% of GDP by the end of
this century. The other said that the cost of decarbonizing the
world economy with renewable energy is likely to be 4% of GDP. [See
fro example, this summary.] Why do something that you know
will do more harm than good?

By Matt Ridley | Tagged:  financial post  rational-optimist