In the next to last week of August, 2012, it became plain
that the first domino was falling.
In that week, every single measure of Arctic sea ice extent
and area reached a new record low simultaneously. By the end of that week, area – the best
measure available – had gone 8.5% below the previous record low (in 2011). And
this was four weeks before the point where Arctic sea ice would reach its
minimum for the year.
In that four weeks, the minimum continued its downward
slide. For the first time in either 20,000 or 5 million years, major parts of
the Central Arctic Basin above 80 degrees North were open water. Currents
carried ice that was in most cases less than three feet thick across the North
Pole and poured it steadily into the Fram Strait east of Greenland, where it
melted. Less than 5% of Arctic sea ice remained by year’s end to build on for
multi-year ice. And when October arrived, and the sun set permanently for the
winter over the Arctic Ocean, refreezing was delayed, as the warmer water
resisted the colder air.
And so it continued, until by 2018, in September, pretty
much all of the ice in the Arctic Ocean was gone. And then the period of no ice
widened, and widened, until somewhere between 2030 and 2045 there was no ice in
the Arctic Ocean year-round. The water was warmer, as the sun in summer beat
down and stored heat in that ocean to be released in the fall, and warmer
currents from the south no longer were combated by cold ice, and global warming
from the south increased the air temperatures to 20 degrees Fahrenheit and
above in the depths of winter. And that ocean heat, in turn, warmed the global
air by only 1 degree Fahrenheit. But that was only the first domino.
Domino Two: Greenland the Archipelago
Because, already, the first domino was tipping the second.
For 20,000 or five million years, Greenland had been surrounded on the north,
northeast, and northwest year-round by sea ice. In that time, it had become a
cone of ice perched on a plateau of ice to a height of more than 10,000 feet.
The plateau was mostly surrounded by mountains, and the fjords formed cracks in
the “bowl” of mountains through which glaciers forced their way. But the
removal of Arctic sea ice removed the plugs slowing down the flow of the
glaciers. They speeded up, faster and faster. Then, in July and August of 2012,
for the first time, a Northern-Hemisphere heat wave from global warming put
temperatures above freezing all the way to the highest point in Greenland, for
several weeks. Melting had doubled in the 1990s and in the 2000s; now it
tripled in the 2010s. And the removal of sea ice by the 2020s meant that the
glaciers had in some cases melted to the shore line, where melt-water running
under the rest of the glacier could “grease the skids” of the glacier as it
slid toward the sea. The rate of melt continued to climb, until by 2050 it was
releasing a foot of fresh water into the ocean every decade, or a total (with
melt from other Northern land sources) of 10-15 feet of increase in the sea by
2100.
Except that this was an underestimate. At the same time, fed
partially by increased temperatures, the upper ocean warmed, slowly but surely,
expanding and therefore adding another 5% of increase, to 11-16 feet by 2100.
And the melt continued, until by 2250 the melt was almost done and 25 feet had
been added to the oceans from Greenland and other Northern land sources. In the
process, we discovered that despite “springback” of land crushed under miles of
central-plateau ice, Greenland was actually not one land but an archipelago of mountains
rising in a rough circle around a central sea.
Again, this melting of ice decreased “albedo” (reflectivity
of the sun’s light and heat back to space), and therefore increased global
temperatures, by perhaps ½ degree Fahrenheit by 2100, especially since black
soot from human emissions helped to discolor the off-white of the melting ice.
It also increased the “area of ocean” by 10-20 feet beyond the actual sea level
rise, because the increased heat in the air allowed greater storage of energy
in storms, so that storm surges carrying salt water to poison water supplies
now reached 30 feet higher by 2100 than before. But that wasn’t the worst of
it. The worst was that dominoes one and two now began to tip dominoes three and
four.
Dominoes Three and Four: Clathrates and Permafrost
In fact, it was evident from inspection as early as 2011
that both the methane clathrate and the permafrost dominoes were beginning to
tip. Still, sensor readings of atmospheric methane and carbon did not clearly reflect
this until the late 2010s and early 2020s.
Since 15-5 million years ago, methane had been accumulating
in the Arctic Ocean in the sea floor 10-1000 feet below sea level. Below the
very cold arctic upper-level and lower-level currents lay ground that was
several degrees below freezing – the temperature that trapped methane in a “cage”
not of ice but of something called a clathrate. And this accumulation of
methane in clathrates had been going on for an unusually long time – perhaps,
in some places, as long as 20 million years.
Meanwhile, somewhat of the same thing had been going on in
permafrost – the frozen ground in the northern reaches especially of
Siberia. Here the problem was not so
much clathrates as the fact that the frozen ground contained large amounts of
both carbon and water. When the water thawed, swamps replaced the frozen ground
– and swamps produce large amounts of methane.
While no one could be certain, it appeared that melting the Siberian
permafrost would result in methane production from the resulting peat even
larger than that from clathrates. Meanwhile, the increased heat from global
warming, starting in 2011, began to set the peat and forests on fire, adding
significantly to global carbon emissions.
Put together, and added to global warming from carbon emissions,
the resulting methane production per year began to climb sharply, to the point
where, combined with human emissions, it had reached 3 times its 2010 level by
2020. But then it continued to climb, reaching 10 times its 2010 level by 2050.
And then things got really serious.
You see, methane is 7-20 times more potent a greenhouse gas per
ppm than carbon. At the rates of 2010, that had a miniscule effect on global
warming, because methane (CH4) would recombine to form water (H2O) and carbon
dioxide (CO2) in relatively small amounts, and so on average it would stay up
as methane only 8 years. But at the rates of 2050, the amounts of methane being
pumped into the atmosphere were enough to add another degree Fahrenheit to
global warming. And then, as the methane emissions from clathrates and
permafrost continued to climb, things got even worse.
You see, there is a saturation rate at which there isn’t
enough carbon (?) around in the atmosphere to combine with methane and so remove it. And so, methane
began staying in the atmosphere longer – and longer. By 2150, it was hanging
around for 15 years and longer, and it was adding 4 degrees Fahrenheit to
global temperature instead of 1.
But even that wasn’t the worst of it. Eventually, that
methane was going to convert to carbon dioxide, in the atmosphere; and carbon
dioxide hangs around for 100-200 years – with a significant fraction hanging
around for 1000 years and longer. So by 2150, the methane that was being pumped
into the atmosphere by clathrates and permafrost had ensured an increase in
temperature of 2 degrees Fahrenheit (compared to 1950) until about 5000 AD, on
top of the 2 degrees increase from carbon emissions up to 2012 and the probable
additional 2 degrees of increase at minimum from carbon emissions from 2012 to
2100.
Meanwhile, all that heat was already, in 2012, beginning to
tip domino five.
Domino Five: West Antarctica
It was hard to believe, in 2012, that Antarctica would start
melting significantly in less than a time scale of thousands of years. After
all, the sea ice surrounding Antarctica was, if anything, increasing by 1% per
decade (for complicated reasons having to do with indirect temporary effects on
currents of global warming); and Antarctica is mostly well under freezing
temperatures year-round, and surrounded by a “moat” of cold ocean.
Except that the signs were there. A long-time visitor to the
Antarctic Peninsula (the long arm that reaches up to South America) reported
that areas frozen year-round in the 1970s were now melting three or more months
of the year. Unprecedented “calving” of Peninsula glaciers was taking place by
2010. Under the cold ocean current was a warmer one, and this one was reaching
further and further south, until in about 2010 it began reaching the Peninsula
and points south – and helping to melt glacier ice now stuck in the middle of
the Ross Sea from beneath.
And so, sometime between 2015 and 2020, the ice in the Ross
Sea that had been blocking the slide of West Antarctic glaciers began to
weaken, and the removal of the “plug”, as in Greenland, began to speed the
glaciers’ slide into the sea. Then, in the 2020s, the warm ocean current began
to reach south of the Peninsula to the rest of West Antarctica, the Ross Sea
and the “bowl” of land surrounding it, and the “plug” began to erode from the
north as well. Now, as in Greenland, the rate of melt began to double every
decade. And by the 2050s, the warmth in the air and the sea began to reach
freezing even in winter, as in the Arctic Ocean, and now the rate tripled,
until by 2060-2070 West Antarctica began to contribute its own fresh water to
sea level rise. And so, by 2250, another 20 feet had been added to sea level,
and by 2450 another 25 feet beyond that, all from West Antarctica. And, of
course, add another 10-20 feet from yet greater storm surges – say, a total of
100 feet.
And, just as with Greenland, these decreased albedo and
raised temperatures by ½ degree Fahrenheit, while the removal of winter sea ice
around Antarctica added another ½ degree Fahrenheit. But that even that wasn’t
the worst. Yes, domino five falling inevitably led to domino six, the last
domino.
The Last Domino: East Antarctica
Mostly, East Antarctica is like a Greenland separate from
West Antarctica – except there’s a big crack at the end of the Ross Sea where
ice can flow directly from the central EA plateau directly down to the Ross
Sea. Once West Antarctica goes, that’s one source of EA melt; but the very
warming at the edges and loss of sea ice that caused West Antarctica to go also
meant that East Antarctica was going as well.
In fact, the signs were there in 2012, as well. Measurements
were showing that EA was already beginning to lose ice. On Christmas Day in
2011, the South Pole set a new high temperature record, some 10 degrees
Fahrenheit. Still, the measurements showed only slight melting.
By 2050, the melt was perceptible. By 2150, it was beginning
to rival West Antarctica. By 2250, it was clearly outstripping it. And we are
talking more than 100 feet of sea rise, here. By 2350, 50 feet. By 2550, 100
feet. By 550 years from 2000, the Earth had seen 170 feet of sea rise, with
perhaps 70 feet more to go before it all ended. Again, add on 10 feet of storm
surge. Places that in 2000 were 250 feet above sea level were uninhabitable 550
years later – including 60-80% of all agriculturally productive areas.
And still, that wasn’t the worst of it. The fresh water and
other sources were making the ocean more acidic, killing off most ocean life.
On the continental shelves, toxic “iron blooms” were growing periodically (this
may be avoidable), which when they died released sulfuric acid into the
atmosphere, killing those living near the sea who breathed it. Inland for many
miles from the sea was a zone of living only if you could afford a breathing
mask – assuming, at that stage, that you could afford one.
Envoi
I don’t claim that I have every detail right, or that these
things are unavoidable. But I am telling you, as I watch Arctic sea ice amounts
tumble, what gives me nightmares. For these things might, just might, already
be baked in by what we have already done. Note that, in my description, there
are very few if any places where major additional human-caused carbon emissions
beyond today’s rates are required to move from one domino tipping to the next.
I shall almost certainly be dead by 2050, when the effects
of dominoes two through six may start showing up. Still, I care. And I pray, not for a miracle,
but for enough others to care to make a difference in the outcome.