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Lytton burns
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The climate, globally, is warming. Everyone acknowledges that.
It’s not warming equally, or consistently, or evenly; I think
everyone acknowledges that as well. Rather, the atmosphere is a
heat engine: as you put more energy into it in the form of heat,
you get more work out of it, in the form of turbulence. Winds get
stronger, precipitation more intense, and heat waves hotter.
Human beings function in a fairly constrained temperature
band. The healthy body temperature is 37° Celsius, plus or
minus about one degree. The human body cools itself by
evaporation. If water can’t evaporate from your skin, you can no
longer cool yourself. Rather, you take on heat from the
environment. Body temperature above 40° Celsius is a life
threatening emergency, and above 42.3° denaturing of
proteins, especially in the brain, may occur rapidly. This is not
survivable.
But the operation of the human body generates heat
continually. The beating of the heart generates heat. The
movement of the chest cavity in breathing generates heat. Even
brain activity – thinking – generates heat.
So in order to survive we need to be able to dump a small
amount of heat into our environment continually. If the air is
humid enough that sweat can’t evaporate, we need a small heat
gradient to make that possible. So we need it to be actually
cooler than 37°, and the survivable number generally quoted is a
“wet bulb temperature” of 35°.
What does ‘wet bulb temperature’ mean? It’s the temperature at
which water (and sweat) evaporates, and that’s a function of the
absolute temperature of the air, and of the humidity: the
saturation of water vapour in the air. As the air becomes
increasingly humid, so the wet bulb temperature falls. In very
dry atmospheric conditions, you can easily survive air
temperatures well above 35° Celsius, provided you can drink
enough fluids to enable you to sweat.
So: there is a temperature and humidity at which everyone
exposed to the air just dies, and just dies pretty quickly. How
close are we to hitting those temperature and humidity
conditions?
The answer, of course, is that there are places on Earth which
regularly exceeded those limits even before the days of
significant anthropogenic warming, but that people don’t live in
those places. Examples include Death Valley in California, parts
of the Arabian Peninsula and of the Sahara, and Pakistan’s
northern Sindh province, in which a Victorian British Brigadeer
had the bright idea of building a city. What’s interesting is
that these are not generally humid places; on the contrary,
they’re exceptionally dry.
But the consequence of anthropogenic heating is that we’re
seeing both higher average temperatures and higher variations in
temperature. Which means we’ve been seeing a lot more exceptional
heat events than we’ve been used to.
Over the past decade,
ten places on Earth have recorded wet bulb temperatures at or
above the theoretical ‘everybody dies’ limit. So far, we haven’t
had an event in which very large proportions of the population
have died suddenly of heat stroke, despite the fact that three of
the places which have seen the highest wet-bulb temperatures,
Ras Al
Khaimah, Jacobabad and
Mecca have
significant populations.
But we cannot be very far away from an ‘everybody dies’ event,
and the first probably won’t be somewhere that’s accustomed to
very high temperatures.
Lytton,
in British Columbia, Canada, wasn’t, until this year, accustomed
to exceptionally high temperatures. Yes, it had frequently been
the hottest place in Canada, but Canada is not on the whole a
very hot place. The extreme heat event that hit Lytton in June
2021 – 49.6° Celsius – was fully 5° Celsius warmer than
had ever been recorded there before. This is, as I’ve said
before, because having more heat in the atmosphere makes it more
turbulent and thus more heterogenous.
Lytton is 50°13’52" North. For comparison, that’s about eleven
miles south of Plymouth in Devon, England, or about six miles
north of Prague, in the Czech Republic.
Lytton didn’t quite exceed the ‘everybody dies’ limit,
although it came very close. But it did exceed the ‘everything
burns’ limit, which is what it isn’t there any more. And what
Lytton proves is that, in an era of increasingly unstable
weather, extreme heat events do not only happen in the
tropics.
So:
-
We’re currently on 1.19° Celsius of anthropogenic
warming over pre-industrial levels;
- At 1.19°, we’re seeing local temperature records being
exceeded by 5° not only in the tropics but even in
temperate zones;
- At 1.19°, our margin of safety for ‘everyone dies’ events
in previously habitable zones appears to be completely
exhausted;
- If capitalism continues (SSP4),
we’re heading
for 3.2° Celsius of warming; even on the much more
optimistic
SSP2 track, we’re now heading for 2.7°.
So: if at 1.19° average warming, we’re seeing local
records broken by 5°, by what amount will we see them broken at
3.2° average? This isn’t going to be a simple linear curve;
it seems to me that it must be at least to some degree
exponential, because there are clearly accelerating effects and
feedback loops in there.
But let’s assume that it’s simply linear. Then we would be
looking at current local records being exceeded by fifteen
degrees, more or less anywhere in tropical or temperate zones.
Indeed, given what we saw in Siberia in 2020, we could easily see
‘everyone dies’ events happening as far north as the Arctic
Circle. Obviously, they will be more common in the tropics. But
no currently populous place on Earth will be immune.
So, just sit for a moment, and imagine. It’s 2035. It’s June.
You’ve seen ‘everyone dies’ events, covering thousands of square
kilometres, happening in other parts of the world already. Now
the weather forecast tells you that there’s a 30% probability of
an ‘everyone dies’ event in the area where you live in the next
ten days.
What do you do?
That weather forecast is going to trigger everyone who can
move, to move. It will cause gridlock on every means of
transport. It will cause mass civil unrest. A fortnight later
we’ll see news reports of ‘rescue’ workers – probably troops –
going into the places people have gathered in their last
desperate attempts to survive, have died in heaps. Those places
may be subway stations, or underground vaults; they may be public
buildings where there had been some hope the air conditioning
system would not fail.
And each such event will leave a dead zone behind it to which
– although we’ll know that these events will happen more or less
randomly, like lightning strikes – few people will want to
return.
Let’s be clear about this. 3.2° of warming isn’t
‘survivable’. 2.7° of warming isn’t survivable. We’re on the
very edge of seeing ‘everyone dies’ events, covering areas the
size of small European countries, now, at 1.19°. We cannot afford
any more warming.
Yet already we’re hitting cascade effects. As the Arctic
warms, so methane frozen in permafrost or beneath the sea thaws
and is released into the atmosphere, ratcheting up warming. As
ice melts, new, darker sea and land surfaces are exposed,
ratcheting up warming. As ocean circulation systems are
disrupted, their moderating effects break down, ratcheting up
warming. Even if we all stop burning fossil fuels today, the
temperature will still rise to about 1.6° Celsius above
pre-industrial levels.
We are already in the disaster zone. Every barrel of oil we
pump makes it worse. We have to just stop.
