Is Geoengineering a Solution? A review of Cvijanovic et al, 2015.

The most likely tipping point and if not at least the most significant positive feedback mechanism in the Arctic system is the albedo feedback of sea ice. This article bypasses the assessment of feasibility and methodology and look at if we could whiten large areas of the Arctic Ocean, could we in fact counter this feedback loop and cause polar cooling.

The study utilises the CSEM global coupled climate model incorporating atmosphere, land, ocean, and sea ice models. The newer CESM model results in better representation of the meridional overturning circulation and sea surface temperature, in comparison to the CCSM3 model.

The method would operate by increasing surface albedo which would result in high latitude surface budget alterations and surface cooling which would spread aloft and southward. This method opposes the geoengineering projects that propose to block incoming radiation with injecting sulphates in to the stratosphere, as this aims to alter the total energy budget via the incoming radiation. Caldeira and Wood, 2008 and Tilmes et al, 2014 modelled these scenarios with reasonable success, although Tilmes concluded that currently the amount of aerosol needed to dim the Arctic is unrealistic and would most likely be blown to lower latitudes anyway so it instead would require extremely large reflects positioned in space above the pole.

The Important Part

The imposition of ocean albedo alterations in the Arctic resulted in the desired recovery of sea ice and decreased warming, with a trend or recovery over the first two decades and no discernible trend beyond. Its success operates with an efficiency peaking at 76% when albedo is enforced over 75-90 degrees North, lower than that proves ineffective in causing ice to recover as it is too far South, 80-90degrees also fails as the coverage of ice is already rather covered therefore little room to alter albedo.

Its success stabilises the ice cover at around 40% of the preindustrial value, which for context, is 37% higher than should nothing be done at all in the case of a 4xC02 climate with about 10degreesC in the Arctic. However, even the most extreme cases of the model have only a modest impact on sea surface temperatures and permafrost.

What this reinforces is that sea ice is a self-supporting system as this one feedback mechanism can cause sea ice to reform and stabilise. It also states that the effects of this reclaiming of sea ice effects the mid-latitudes and the precipitation pattern experienced there.

In essence then, this report serves to highlight that sea ice, although effecting precipitation patterns in the mid-latitudes is actually rather insignificant in terms of its ability to incite a change within the climate system.

Figure 1: "Annual surface air temperature anomalies (K) between 30° and 90°N in modified ocean albedo simulations relative to the control 4xCO2 simulation. Dashed areas indicate the anomalies that are statistically significant at the 95% confidence level. In addition to the Arctic cooling, altered albedo simulations also show notable warming off the West Coast of North America (less pronounced in alb70–80N but still present). This pattern of temperature response is found in all simulations with imposed albedo modifications. Thin and thick contour lines indicate the areas with annual mean sea ice fractions larger than 15% and 80%, respectively." (pg. 5). Credit: Cvijanovic et al 2015

On a Wider Note

The IPCC seems to think geoengineering is vital to restrain global warming, specifically carbon capture, so much so that the U.S. Department of Agriculture guaranteed a loan of $91million to build a carbon capture facility in Louisiana. However, it is most likely not enough to halt global warming. At best projects that block incoming radiation are a plaster that needs regularly refreshing in order to block further degradation while we find a solution to reduce the massive amounts of CO2 filling the atmosphere. CO2 removal from the atmosphere sets a dangerous precedent for producing CO2 I the first place and could just end up playing a continuous game of catch-up. The only real solution is to overhaul the global system and ‘turn the tap off’ instead of trying to widen the plug.