Scientific American - Robert Wilder | Daniel M. Kammen
If we do not plan, now, to limit carbon emissions beyond this century,
we will foolishly raise the oceans dramatically for thousands of years
It’s shocking for me (Robert) to accept that my home could be wiped
out by greatly rising seas. That’s because I live on a hill north of San
Diego, 45 feet above sea level and more than a mile inland from the
coast. Equally shocking to me (Dan) is that the current coastline of my
beloved Mendocino County, California, could largely disappear, a place
where I spend weekends with my daughters exploring rivers that run
inland, deep into wine country. These inundations won’t happen this
century, but that is little solace. At the rate the world is going, land
so dear to our hearts could slip under the sea and stay there for
thousands of years.
That hurts. Most of us believe our homes, our towns, our cities will
be here for centuries and millennia to come. And why not? In Europe and
across Asia millions of people live in cities that are thousands of
years old. Indeed, inspired by European permanence, Robert’s family
built garden walls from stone and fondly looked forward to passing on
the land to hoped-for-grandchildren, and theirs, and so on.
That idea, however, now seems flawed to both of us writing this
article. Strong, new research indicates that anyone or anything tens of
feet above the sea today may one day face an unbeatable force, whether a
country home near San Diego or a skyscraping condo in Miami. Although
shorelines are forever evolving, these changes can be predicted
directly, and are due to needlessly
excessive carbon dioxide (CO
2) emissions from a relatively brief, recent period of time.
How has the public not been made clearly and painfully aware of this?
Why does fierce debate over climate miss so glaring a threat? The
misperception, the widespread disbelief and the fallacy are rooted in a
grave error in our thinking about time.
An Artificial Horizon
The many models that have projected
scenarios about future climate change
generally forecast only to the year 2100, or at times merely to 2050.
As a result, public discussions have been mostly about “X degrees of
warming” or “Y feet of sea level rise” to the end of this century. We
have accidentally but notably limited our thinking, causing us to miss
striking impacts that arise beyond this limited and artificial, specific
time horizon.
It is fair to say that citizens and politicians intend for Miami, and
indeed the whole State of Florida, to exist well beyond 2100. Same for
New York City, Boston, Washington D.C., London, Shanghai, Amsterdam,
Mumbai and so on. Yet the same people discount staggering losses these
places face beyond 2100. That’s wrong, and immoral too.
That’s because a crucial fraction of airborne carbon from the
industrial revolution, plus that coming this century and next, will
persist for tens to hundreds of thousands of years. The CO
2
stemming from just 150 years ago to a mere two centuries ahead may
commit the world by inertia to tens of thousands of years of impacts.
Anything going on for tens of thousands of years ahead essentially
means “forever” on human time scales. These new data imply that we’re
creating a kind of forever legacy, one that potentially can’t be ever
forgotten, or fixed, no matter how far ahead we conceive of humanity.
We are doing ourselves a dreadful disservice by consistently framing
2100 as essentially the last, final year of impacts. We’re thinking in a
blinkered way decades out, while our foot is pressing hard on a warming
accelerator that has serious impacts centuries out.
How, then, can we think about climate and seas in truer time frames?
An admirable new paper by Peter Clark and colleagues in
Nature Climate Change, titled “
Consequences of Twenty-First-Century Policy for Multi-Millennial Climate and Sea-Level Change,”
illuminates the issue and helps point a way ahead. It addresses sea
level rise in a longer term from a scientific perspective.
The authors first analyze data that show how a major rise in CO
2
and warming from 20 millennia ago brought Earth out of an ice age. Air
temperatures continued to rise over a long period from the Ice Age to
the near-modern climate that began some 11 millennia ago. From that time
onward, CO
2 levels and air temperatures sharply leveled off.
Sea levels, which were 400 feet lower than today, did not stop
rising, however. They continued rising long past when air temperatures
reached their plateau, rising for another 8,000 years, climbing another
150 feet up to today’s height. The oceans did not achieve the
near-current state that we all know as modern coasts and maps until
roughly 3,000 years ago.
The mere sliver (in geologic time) of climate stability in the last
10 or so millennia has dearly helped human societies and cultures to
flourish. But the lesson is that seas are acutely sensitive to CO
2
and temperatures, and they can have inertia lagging the carbon cycle
and climate system. That means today’s oceans could go on rising very
long after CO
2 might be steadied—even if humanity takes determined action to slow rises in CO
2 worldwide, or even decrease emissions. This thorny fact is not widely appreciated.
As Clark and his co-authors note, one-fifth to half of the airborne CO
2
released by human industry so far and in the next 100 years will still
be present in the atmosphere by the year 3000. Combine CO
2
persistence with the inertia of seas and it can mean sea level rise
might go on at least 10 or more millennia—the unimaginable. There is no
easy off switch to halt the rising of seas, no matter how much future
societies might wish it to end.
The opportunity to go on ignoring this basic dynamic is now
vanishingly small. There’s already been a well-accepted 1.5 degree
Fahrenheit increase in global temperatures since 1900. That change alone
seems to come close to the greatest variations that have occurred over
the previous 10,000 years.
The current rate of change is just as concerning. It had taken a long
period, from some 21 millennia to 12 millennia ago, for atmospheric
concentrations of CO
2 to jump by 80 parts per million (ppm),
from about 190 to 270 ppm. In that time span global temperatures rose by
an average of 7 degrees F. We are on track to repeat that kind of
increase over a much shorter period.
Keep in mind what that scale of change means. A difference of 7
degrees F separates today’s “ideal” climate from the extreme conditions
of an ice age. For a refresher, the Ice Age built ice sheets over
Canada, New England, parts of the Midwestern U.S., Northern Europe and
Northern Asia. The Great Lakes were born when those sheets retreated.
The meltwater retreat created Long Island in New York, and Cape Cod.
Huge impacts were thus wrought by 7 degrees F; ice stood two miles tall
over parts of North America, and shaped the elevations of a continent we
know today.
Just imagine if there’s another 7 degrees F of global warming ahead.
Certainly that would alter land, sea and ecology in scales and ways hard
to fathom.
By looking back to Earth’s more distant past we know that with a
temperature rise of “only” 2 degrees to 5 degrees F warmer, seas could
rise 15 to 65 feet, a level that would drown so much today. For a
thought experiment, adding 5 degrees F of warming is very imaginable,
given current trends of increasing CO
2. So it is reasonable
to imagine seas 60 feet higher. That would render all of Florida a
memory, almost all of New York City, much of the Eastern seaboard, parts
of the Western U.S. and Gulf Coasts—and (Robert’s) acre of San Diego
land that today is a mile from the present shore.
Mechanisms by which this happens are easy to fathom. Greenland’s ice
sheet stores only 22 feet of potential sea level rise, possibly ongoing
for some 10 millennia. However, the Antarctic ice sheet stores around
150 feet of potential rise in that same time frame. Ironically, over the
last dozen years, the East section of the Antarctic ice sheet annually
has gained some 175 trillion pounds of ice. But West Antarctic annually
has lost much more, some 275 trillion pounds of ice. (Greenland has
averaged 600 trillion pounds of ice lost yearly, which is equivalent
to10 billion trucks a year carting ice away).
We may be heading quite outside of conditions known in human recorded
history. Earth might even begin to exhibit changes of states that only
can be guessed at. A new study, for instance, shows that net melting is
causing Earth to slightly change how it moves on its polar axis. Days
are getting just very slightly longer as ice melts at poles and
redistributes that mass as water towards the equator. A very tiny change
in Earth’s spin may not be troubling, yet it helps to show the
magnitude of changes possible from CO
2. Even distant
earthquakes conceivably can grow in size or frequency, as unburdening
crust rebounds after losing trillions of tons of ice. That in turn also
could mean increased volcanism and tsunamis worldwide.
These threats may be on long timescales but there’s an acute need for
scientific knowledge, measured in and across millennia, to seep into
our global discussions.
August 2016 was the planet’s warmest month on record, by a lot. It
was the 16th month in a row that a monthly heat record fell, way beyond
any such streak in 137 years of record keeping. Arctic temperatures were
an eye-opening 20 degrees F above normal. With relatively extreme
levels of heat covering the Arctic, ice levels in the winter there were
the lowest ever recorded. Nights have stayed warmer worldwide, too,
making heat waves tougher to endure. This happened alongside the
largest, single-year jump in atmospheric CO
2 concentrations ever recorded. The level is now over 400 ppm and rising. And the global ocean reached record warmth as well.
So what does all this mean for sea level rise?
An international panel in 2013 had given scenarios for rise in this
century mainly based on straightforward expansion of warming oceans.
They only allowed for a small influence from marine ice-sheet
instability, known as MISI, primarily on the assumption that Antarctic
ice sheets were too stable and vast to irreversibly shrink this century.
The report presented an optimistic lower-end CO
2 scenario that assumed strong actions would be taken later this century to reduce CO
2
emissions, and which predicted an estimated 1 foot of rise (0.3 to 0.6
meters) by 2100. The higher-end estimate, based on current trends
continuing and little strong action this century to reduce CO
2,
led to 3 feet of rise by 2100, with the rate increasing rapidly to
between one third to over half of an inch (8 to 16 millimeters) per year
during the last two decades of this century. Such a rate only a century
hence could be up to 10 times the 20th century average rise and might
possibly approach what had occurred around end of the Ice Age, when seas
rose rapidly.
In the three years since that major report, three new papers on
ice-sheet dynamics have shown that our prior understanding was
incomplete, and that MISI mechanisms may be much more extensive across
the Antarctic. The enormous
Pine Island Glacier
in Antarctica, for example, is thinning and retreating at a quickening
rate. Mechanisms in newer models show that mass loss from unstable
retreat may potentially become significant, sooner than expected. Some
early collapse may be starting at the
Thwaites Glacier now.
Unexpected collapse of the Antarctic marine ice sheet could cause
previous upper estimates of sea level rise to be exceeded not long after
the end of this century. Although the timescale is uncertain, more
rapid collapse could occur in a relatively short time period of two to
nine centuries.
Furthermore, an
important paper
released in 2016 notes marine ice cliffs may be becoming instable,
another mechanism for yet more rapid retreat through 2100. A different
paper, out in March, shows sea levels could start to rise much more than
was forecast in the prior lower-end scenarios. It indicates that more
than 40 feet of rise may potentially come just from Antarctica by 2500,
in accord with higher-end scenarios for CO
2.
The point here is that 2100 shouldn’t be regarded as a terminal year.
To do so is folly, a fallacy in thinking. Life goes on, people do not
end there, and seas will not suddenly halt their rise then.
Scientists are natural skeptics, not prone to dramatize their
findings. But cause for abundant hope is fading. That ought to stretch
our thinking. Listening to the sea and this emerging science should mean
adjusting ideas about what’s wise. The paleoclimate record indicates
that in periods of meltwater, or termination of the last glacial period,
seas possibly might have risen at an astounding rate of a foot per
decade, or 10 feet per century. There is no reason to say it can’t
happen again, or rise by faster rates. Given aggressive CO
2 trends, it must be considered.
Will such ideas lead to sound policy decisions? They should, but probably will not. Consider that likely levels of CO
2
could make a folly of putting billions or trillions of dollars into
armoring coastlines. One can imagine an enormously long and expensive
wall, say 10 feet high, being topped in a century or two. And one can’t
even imagine seawalls able to handle oceans going 50 feet higher and
rising.
Costly walls might make slightly more sense if rising seas could be
counted on to stabilize, or retreat from knowable heights, and do so in a
year meaningful to our species. Since neither is the case, capital that
might be spent on armoring might instead be deployed in smarter ways.
Arguably, rather than spending enormous yet finite capital on costly
“hardening,” it would be better to put resources into avoiding CO
2
emissions, and growing renewable energy in the first place. Prevention
rather than cure. That brings up the next part of this story: What,
then, should we do?
Global Climate Policy: Where’s the Action?
One recently celebrated initial step was the Paris climate agreement,
spelled out in December 2015. Although pundits thought it would take
years to ratify the accord, by October 2016 the needed threshold of 55
nations that also represented 55 percent of global emissions had
ratified it, putting it into effect.
Moving from hope to real and difficult action has undermined prior
aspirational agreements, however, such as the Kyoto Protocol. Paris is
an important start, as is
a recent amendment
expanding the Montreal Protocol to cover hydrofluorocarbons, but the
world is critically short on time and the means to verify reductions,
and on finance for the necessary actions to achieve those reductions.
Paris, moreover, isn’t binding. It is no treaty, and it lacks
penalties. And perhaps most importantly the formal goal of 2 degrees
Celsius (3.6 degrees F) for an “upper limit” on “allowable” warming is
in truth a legal fiction, a mere balm for present leaders, since the
planet is on a clear path to blow right past it.
Furthermore, science suggests this 2 degrees C of warming is far more
dangerous than the negotiators seem to think. Warming with much higher
seas for millennia can be already baked in, even at a hoped-for 2
degrees. That is why the Paris Accord left many scientists shaking their
heads in despair. There is an enormous gap between how quickly the
science says carbon emissions must fall to stay within 2 degrees C, and
what global agreements like that from Paris may aim to require.
International equity is important, too. Western nations have already
burned through much of the world’s total allowable carbon budget—the
amount of carbon the world can burn before the planet is likely to cross
the 2-degree threshold. This is profound, and vexing. Developing
nations like China and India bear little blame for fuels burned for a
century till now, and they may unsurprisingly argue for growth based on
carbon-spewing industry of their own.
Yet repeating our same carbon-path is now unaffordable given the
global carbon budget. The physical carbon ceiling is wholly unyielding.
The chemistry and physics of warming can’t be bargained with or pled to.
Therefore, although the Paris climate accord is good as a first step,
the need now is for ongoing real action and a strong, continuing
commitment to progress to a 1.5 C target. If we act as if Paris and the
Montreal Protocol amendment are the major endpoints, not a beginning,
that will put off real solutions until it is too late.
There are also pitfalls along the way if we don’t make climate
solutions an ongoing process. “Cap-and-trade” systems for carbon
emissions in theory can begin a transition to market-based mechanisms
but they have already been gamed by many participants because caps are
not rigorous and diminishing. A very hard look is needed at how natural
gas is implemented: Can a plant be built today
and be
decommissioned by 2050? So-called “clean coal” is expensive, untested,
unwieldy and unworkable, yet it is raised as a panacea. (Lost coal jobs
are indeed a concern worthy of much attention, however). Nonstarters
like geoengineering are suggested in some desperation, at least in the
long term, yet they defy morality and could worsen a spiraling ocean
acidification.
Today, opportunity lies in implementing clean, green economies of
solar and wind power, and energy efficiency, and geothermal and
hydropower when ecologically friendly. The challenges of ocean
acidification, fragile ecosystems and climate-induced migration all
point to the need to scale up the truly clean energy economy at an
exceptional pace.
We suppose that possibly we all could close our eyes and hope that,
say, leaders in China go even bigger on clean energy while dropping coal
entirely. But China is cutting back on its ambitious solar goals.
We could hope for “negative emissions” by sucking CO
2 from
the air and sequestering it into stone far below ground. That's
technically feasible in certain basaltic rock regions, but the process
is extremely expensive, and it is difficult to see this being
implemented at a global scale. And that is where the rub is: CO
2 dumping is free, today, and CO
2 sequestration is costly.
There are steps that make sense. Carbon taxes—including revenue
neutral ones where other taxes are reduced—can work because they send
unambiguous economy-wide signals. Carbon accounting across the public
sector, and for companies wishing to do business with local to national
governments, can educate and start the movement to full carbon pricing.
Strong crossover policies, such as those linking car purchases to
low-carbon goals, also accelerate the process. Financial divestment
from fossil fuels—which has been a challenge to implement—is another
natural place to begin.
We must consider, then, opportunities that harness viable technology
and economics. For example, a simple, transparent carbon tax could be
key. It could help get us near where we’ve got to be and hasten green
energy. Even many big businesses are now calling for a carbon tax. A
simple tax that’s adopted widely could be very significant. But in the
U.S. a carbon tax goes unmentioned in political debates.
One way or another, if leaders are going to get real on climate, they
have to end fossil fuel subsidies, then phase out fossil fuel use, all
while implementing clean, renewable energy for electricity generation
and transportation. We should do this for our grandchildren and for
their grandchildren. And because it is patriotic, will make us stronger
and is far less distorting to our interests than fossil fuel dependence.
These moves are not burdens. They are opportunities. Getting closer
to 100 percent renewables could be achieved more readily than most
people say. It can make nations stronger and more resilient, and add
jobs. In some places like California, China, Denmark, Germany, Kenya and
Morocco, renewable energy is progressing faster than in others. But
nowhere is it fast enough.
We two authors have spent most of our careers advancing renewable
energy and sustainability, addressing climate both in theory and
practice around the world—in academia, the public sector, the private
sector and as entrepreneurs. Yet nothing currently gives us great hope
that very harsh scenarios for climate change and sea level rise, lasting
for millennia, will be completely avoided.
Looking at rates of CO
2 emissions, and at international
actions that lean toward lofty words about future cuts over real action
with teeth today, optimism does not spring to mind. In a mere couple of
centuries, humans will have committed Earth to new climate regimes and
higher seas never seen in our history, that will potentially last
millennia.
And we will have done it all, knowing the likely consequences.
Links
