Rapid Arctic Warming is Scarier Than Geoengineering

The past

Vostok ice core records demonstrate a correspondence between temperature fluctuations and levels of greenhouse gases (GHGs) in the atmosphere. A sawtooth pattern of temperature ranges (+2 to -9^o C), concentrations of CO2 (280 to 190ppm), and methane (0.78 to 0.32ppm) from 160,000-year records.  A consequence of the Earth's orbit and for the absorption of CO2 from vegetation and weathering (fig.1). 

Fig.1 Fluctuating temperature, methane and atmospheric CO2 concentrations from air samples in ice cores taken from the Antarctic (adaptations of Sowers and Bender, 1995; Blunier et al. 1997; Fischer et al. 1999 & Petit et al. 1999). 

What isn't shown in Fig.1 is the rapid present day increases in GHGs, particularly CO2.  Professor Tim Lenton states, that plants  significantly reduce atmospheric CO2, cooling the planet, but this is inhibited by the rate of anthropogenic-induced GHGs. Natural sequestering cannot keep up with the rate of burning woodlands, fossil fuel processing and peatlands that release stored CO2 and methane (86 times greater than the warming potential of CO2), amplifying warming (fig.2).

- For the interests climate sceptics that argue that CO2 increases lag whilst temperature rises over Antarctica please watch this video.

Fig. 2 Illustration of two positive feedbacks as a result of warming temperatures in the Arctic. A negative feedback would be a cooling in temperature ie. promoting sea ice extent, increasing albedo, radiation reflected and hydroxyl production.

The present

Over recent years the Arctic has become less ice-solated, the body Snow, Water, Ice, Permafrost in the Arctic (SWIPA), reported that over the past three decades the total area of sea ice in the Arctic has declined by more than half, also predicting that by 2040 the Arctic will be free of sea ice during summer, 30 years earlier than previous estimations. 

Global populations would have to be carbon zero by 2035 if we want to avoid Arctic melting. - Dr Hugh Hunt

There is a growing consensus that geoengineering is necessary. Historical records suggest we may have passed the 'carbon tipping-point', accelerating unprecedented warming that isn't solved by stabilising and/or reducing GHGs emissions. SRM may, therefore, have a role to play.

Though SRM does not tackle atmospheric CO2 concentrations, multiple studies indicate SRM's massive cooling potential, that may reduce warming and in turn,  reduce the impacts on biodiversity in  tundra biomes. Supported by Applegate & Keller (2015), who state stratospheric aerosol stimulation mitigates the melting of the Greenland Ice Sheet, aiding the growth in sea ice and more importantly thickness during summer. It could, in theory, do the same for the Arctic.

Astrophysicist Steven Desch et al. (2017), proposed that wind turbines on the Arctic sea ice that pump water from below onto the surface, to thicken the sea ice during winter so that in summer ,sea ice does not retreat to the same extent. Simulations suggest that turbines covering 10% of the Arctic ice would result in a meter of thickening per year. And if implemented over the entire Arctic by 2030 a year of adding a meter of ice would revert the Arctic back to present day volume and size. But this simple idea is plagued with issues surrounding:

1. Freezing seawater and promoting growth of old ice and not new.
2. Estimated cost of  $500 billion (£400 billion).
3. Logistics of shipping 10 million wind turbine pumps and individual weight of 10 tonnes of steel.

It is important to understand that SRM albedo modification is not a new concept. These approaches are often not as extreme, large in scale or  as effective as the construction of solar reflectors or releasing aerosols. But they seem to be working, with minimal negative effects after implementation (Fig.3). 

Fig.3 Screenshot of examples of small-scale SRM methods being applied in real life Ming et al. (2014).

Source: Save the Arctic illustration.

The future

The imbalance between winners and losers, and the unforeseen consequences of environmental and governance issues, means SRM, cannot be used exclusively. Dr Hugh Hunt, states SRM is required if we urgently need to slow melting in the Arctic. But if we are too late and Arctic permafrost starts to thaw then we will need to implement other means to capture billions of tonnes of atmospheric methane released. The debate still exists concerning which geoengineering approach is better SRM or CDR?  Conclusions are blurred, and perhaps policy makers, scientists and societies need to consider a diverse approach to tackling climate change.