• Once our society collectively decides to respond to the climate emergency, it is
possible that major scientific breakthroughs will occur, allowing humanity to
rapidly remove greenhouse gases from the atmosphere in time to restore a safe
climate.
• At some point in the future, there is a risk that climate warming will cause the
irreversible release of highly potent greenhouse gases stored in Arctic methane
clathrates and land-based permafrost that could cause severe, abrupt climate
change and lock in even more severe, long-term climatic disruption. There is
evidence that relatively small quantities of greenhouse gases are leaking from
these sources, although it is not precisely clear when the tipping points could
occur.
• In 2010, the National Science Foundation warned that if even a “fraction” of the
methane stored in the floor of the shallow East Siberian Arctic Shelf in the Arctic
Ocean is released into the atmosphere, it could “trigger abrupt climate
warming.”
• About 1.4 trillion tons of methane are trapped below the shelf, and it was recently
estimated that around 10 million tons leak from the shelf annually, according to
researcher Natalia Shakhova of the University of Alaska at Fairbanks. It is not
clear when the shelf began leaking or if it is leaking because of human activities,
but Shakhova and her team are concerned that the shelf is beginning to
destabilize.
• According to Shakhova, an abrupt, decade-long release of 50 billion tons of
methane is “highly possible at any time,” and would trigger a “climate
catastrophe.” Methane is 25 times as potent a greenhouse gas as carbon dioxide
over a 100-year-period, and 72 to 100 times as potent during the 20-year period
after it is emitted. There is a great debate among climate scientists about
whether the methane clathrates pose such a grave and imminent threat.
• A 50 billion ton belch of methane would quickly raise global temperatures
+1.3°C from current levels and increase global atmospheric methane levels
twelve-fold, pushing temperatures far beyond the unsafe +2°C “guardrail” and
likely setting off a number of other climate tipping points. Most ecosystems
generally cannot adapt to more than +0.1°C of change over the course of a
decade. It has been projected that such a belch would cost the world economy
$60 trillion.
• At the moment, the only way known to prevent such a scenario is the deployment
of high-risk geo-engineering technologies that are designed to rapidly cool the
earth.
• In particular, humans could use rockets, aircraft, or a giant hose to inject sulfate
particles (aerosols) into the upper atmosphere and substantially cool the earth in a
matter of months. This technology, the most well-known “solar radiation
management” approach, is in development. It would mimic the effect of
volcanoes, which spew sulfate aerosols into the atmosphere, and have
demonstrably cooled the earth in the past by reflecting the sun’s rays back into
space.
• Directly cooling the earth using solar radiation management could theoretically
prevent both a general melt of the permafrost as well as a catastrophic, largescale, irreversible release of methane from clathrates. It could also theoretically
slow down or even halt the melting of the Antarctic and Greenland ice sheets,
and give humanity a window of time to restore atmospheric greenhouse gas
concentrations to safe levels.
• However, solar radiation management would likely disrupt global rainfall
patterns, causing floods and droughts that would adversely affect billions of
people across the planet, and possibly kill large amounts of people in the absence
of massive international assistance. As a result of these potentially horrific side
effects, the use of this technology could potentially lead to war between nationstates. There could also be other side effects that cannot be predicted before the
technology is deployed.
• There is no way to test these technologies at scale. We agree with writers, such as
Naomi Klein, who argues that using these techniques would make all humanity
and the natural world guinea pigs in an extremely dangerous experiment.
However, it is also true that this extremely dangerous experiment has already
begun, thanks to hundreds of years of planetary deforestation, greenhouse gas
emissions and aerosol emissions that have completely transformed the earth
system and initiated a new geological epoch called the “Anthropocene.”
Consciously attempting to direct the entire global climate system using a relatively
small, continuous atmospheric injection of pollutants would certainly constitute
an entirely new phase of the experiment, raising a host of moral dilemmas.
• The use, or planned use, of solar radiation management could also provide
governments with an excuse to further delay major greenhouse gas emissions
reduction and removal — both of which are scientific and ethical imperatives.
• Emissions must be drastically reduced soon, in order to both stabilize global
surface temperatures long-term, and to reverse ocean acidification, which is
killing off key components of the ocean food chain — specifically shelled
organisms — and therefore poses a threat to the entire marine food web. More
than a billion people across the world rely on marine species as their primary
protein source. Solar radiation management technologies do not reverse ocean
acidification, which is caused by carbon dioxide emissions and is known
colloquially as “global warming’s evil twin.” Only carbon emissions reduction
and removal can halt and reverse ocean acidification.
• If the process of aerosol sulfate injection was completely disrupted by depression
or war for several years, the cooling effect could wear off, leading to a sudden,
disastrous pulse of warming that could overwhelm the ability of ecosystems to
adapt. If solar radiation management was deployed in order to mask the global
warming from a business-as-usual emissions trajectory and was suddenly
interrupted, it would result in an extremely disastrous warming pulse. Even if no
interruption occurred, solar radiation management would need to somehow be
deployed continuously for hundreds of years on end if it was deployed as a
substitute for zero emissions and greenhouse gas removal — a truly horrible idea.
• However, it will ultimately be difficult to avoid a sudden pulse of warming, since
about half of the “global dimming” effect from aerosol emissions that is currently
cooling the earth by -1.2°C will wear off quickly if fossil fuel burning is rapidly
curtailed. The earth would suddenly warm by about +0.6°C. The sulfate aerosol
particles emitted in fossil fuel burning fall out of the atmosphere after 10 days, but
are continuously replenished as humanity continues to burn large quantities of
fossil fuels. This means that as we curtail fossil fuel burning (and therefore sulfate
aerosol emissions), the rate of global warming will likely accelerate as the shortterm aerosol cooling effect wears off, although this could be tempered by sharp
cuts in emissions of short-lived warming agents such as methane and black
carbon.
• Meanwhile, the majority of fossil fuel carbon emissions cause a powerful climate
warming effect for about 200 hundred to 2,000 years, while a substantial minority
of emissions continue to impact the climate for tens of thousands of years and
longer. Delaying the date at which we curtail fossil fuel burning (and thus end
the temporary global dimming effect) will not solve the problem, since fossil fuels
are a finite resource that would be exhausted long before the warming impact of
emissions wears off — even if we continue to burn fossil fuels at only a fraction of
current levels long into the future.
• Former NASA scientist James Hansen calls this conundrum humanity’s “Faustian
Bargain.”