The possibility of abrupt changes in Earth Systems provides a unique challenge for the scientific and policy-making community. The current scientific processes, and the way in which new knowledge is created and becomes generally accepted, were developed during a time when Earth Systems could be assumed to be stable over timescales of decades and centuries. The emphasis was placed upon painstaking verification, and attempted nullification of a given hypothesis, rather than speed. The peer-review process utilized by academic journals may in itself take years, after many years spent in the field and constructing and validating hypotheses from the underlying data.
Earth System Science is still a relatively young area of study that requires the integration of many disparate disciplines. The sheer complexity of the natural systems involved, and the interactions between those systems, provides significant challenges to accurate and complete scientific understanding. In the area of climate science, politically motivated attacks upon individual scientists can only have served to increase the general conservativeness and thoroughness of the scientific process. With respect to the Arctic, an additional issue is the amount of time to both gain funding for, and carry out, required scientific work in remote locations with extreme temperatures and difficult meteorological conditions.
The current climate change policy-elite consensus assumes that incremental change is enough, rather than the emergency-style response proposed by such individuals as Kevin Anderson[1]. In the face of rapid reductions in sea ice volume (as opposed to the much less representative two dimensional measures of sea ice extent and area), the consensus continues to support the view that the Arctic could only be ice-free as early as mid-century under a high emissions scenario[2] (IPCC AR5, RCP 8.5). Under all other scenarios, the consensus is that the Arctic will not be ice-free even by the end of the century. Given the significant increase to the Earth’s heat imbalance that would result from the loss of reflective arctic sea ice, this assumption is critical to the validity of the Paris Climate Accord. Without it, the incremental approach of Paris would have to be replaced with a rapid emissions reduction footing that may require fundamental economic and social changes.
The inertial tendencies of both the scientific and policy processes create the conditions for a paradigm shift event, where the consensus becomes untenable in the face of actual changes in the Earth Systems, such as a an ice-free Arctic. The strength of this inertia is shown by a recently published analysis[3] that looked at the impact of an ice-free Arctic upon the Earth’s heat imbalance and the currently assumed carbon budgets. Although accepting that an ice-free Arctic could possibly be a reality within a decade, the analysis restricted itself to the possibility of that taking place in either 2040 or 2050. Restricting the analysis further, it was assumed that the Arctic would only be ice free in September and would not later become ice free in earlier months. Given that the level of the Sun’s energy that reaches the surface of the Arctic increases rapidly as the Summer Solstice is approached, this assumption greatly reduces the energy imbalance. Even this highly restrictive set of assumptions sets the paper apart from the mainstream scientific consensus.
As sea ice had been rapidly lost in the Arctic, some researchers have begun to look at the possible effects and call for much greater funding for research in the area. These effects include (i) changes to the Earth’s heat imbalance that may be greater than that created by anthropogenic greenhouse gas emissions (ii) substantial changes to the Northern Hemisphere climate systems (iii) a northward move in the Inter-Tropical Convergence Zone.
Increases In The Earth’s Energy Imbalance
The paper “Mitigation implications of an ice-free summer in the Arctic Ocean”[4] provides estimates for the effect of an ice-free Arctic (sea ice of less than 1 million kilometres2) in the month of September in 2050 and 2040. As the paper comments, the possibility of an early loss in arctic sea ice has not been included in any of the Integrated Assessment Models used to assess the societal impacts of climate change.
It has been previously estimated that the increased energy imbalance from the loss of sea ice between 1979 and 2008 was equal to 0.11 Watts / metre-2 on a globally annually averaged basis[5]. Assuming a linear trend between 2010 and 2050, the paper proposes that the radiative forcing would increase to 0.29 W m-2, if the arctic became ice free in September for the first time in 2040. If the forcing then stayed at that level (i.e. no further deterioration in sea ice area), the UN IPPC 20C carbon budge would be reduced by 28.7%.
Under a more realistic assumption of a further reduction, the carbon budget is reduced by 41.1%. Even this scenario assumes slow linear decline in sea ice in the balance of the century, never reaching a fully ice-free state (a complete loss of the Arctic sea ice would produce an increase in the global energy imbalance of 0.7 W m-2.)
Using the same assumptions, a 2040 ice-free September reduces the carbon budget by 34.7% (with no further reduction in sea ice) and 51% respectively. With a faster decline in sea ice after the first ice-free September, the carbon budget would be cut further. Given the current rate of emissions, if an ice-free September in the Arctic were to arrive between 2020 and 2030 it could be assumed that the carbon budget would be reduced to zero, or even a negative number.
Northern Hemisphere / Southern Hemisphere Differential Heating
Due to the thermal inertia of the oceans, the atmosphere above landmasses will increase in temperature significantly faster than that over the oceans. As the Northern Hemisphere has a much greater percentage of land to ocean that the Southern Hemisphere, climate models already forecast that the former will heat up at twice the rate of the latter[6]. This effect will be exacerbated by any extra energy imbalance being provided by an ice-free Arctic that resides within the Northern Hemisphere.
This raises the possibility that positive feedbacks that reside in the Northern Hemisphere, such as permafrost melt, may be triggered at a lower global temperature than previously assumed. Recent research is pointing towards a high level of sensitivity of the northern permafrost areas to increases in temperature, resulting in possible increases in natural emissions of carbon dioxide, methane, and nitrous oxide. One study observed significant increases in the release of greenhouse gases as a result of only mild increases in temperature[7].
Paleoclimatological studies have pointed to changes in the position of the Earth’s thermal equator[8], and the Inter-Tropical Convergence Zone, during periods of differential heating between the hemispheres. During periods that the Northern Hemisphere warms up relative to the Southern Hemisphere the ITCZ moves northwards. Such a move can have significant local climatic effects, as it redistributes the areas of rainfall and aridity. With an ice-free Arctic, and a more rapid relative heating of the Northern Hemisphere, regional climatic changes may occur much faster than previously assumed. Such changes may negatively affect already stressed areas such as the Middle East, exacerbating the possibilities for regional conflicts. As the above paper states:
“Therefore, we predict that a northward shift of Earth’s thermal equator, initiated by an increased interhemispheric temperature contrast, may well produce hydrologic changes similar to those that occurred during past Northern Hemisphere warm periods. If so, the American West, the Middle East, and southern Amazonia will become drier, and monsoonal Asia, Venezuela, and equatorial Africa will become wetter.“[9]
Northern Hemisphere Climate Instability
Arctic Amplification has already produced a reduction in the temperature differential between the Arctic and the rest of the Northern Hemisphere. Some researchers have proposed that this reduced differential is already disrupting the Northern Hemisphere climate by decreasing the strength of the Jetstream winds that separate the polar climate cell from the rest of the hemisphere. This creates a wavier jet stream that “allows cold air from the Arctic to penetrate southwards into mid-latitudes, and ridges transport warm air northward”[10] (exacerbating Arctic Amplification). In addition, there have been observed atmospheric blocking events that keep a given weather event in place for extended period of time. As the temperature differential decreases further, the level of climate disruption may be greatly intensified.
Policy Implications
Contingency plans should be put in place to deal with a possible climate paradigm shift. These should include both plans for rapid reductions in emissions and the identification of possible emergency measures to reverse the loss of Arctic sea ice. The latter should include discussions with other governments that share responsibility for Arctic governance and the investigation of policy mechanisms through which such interventions could be effectively governed. Funding for climate science related to the Arctic should be increased, as well as funding to investigate the possibilities for reversing sea ice loss.
Arctic sea ice loss is only one of a number of climate feedbacks that may trigger a climate paradigm shift that may need to be managed at the global level. Given this, global climate governance processes must be extended to allow for effective monitoring and management of such possible feedbacks.
As a climate paradigm shift could trigger a general acceptance of the need for very rapid cuts in anthropogenic greenhouse gas emissions, individual governments should study the impacts of such large emission reductions. The scale of such cuts may be extremely disruptive in themselves, as significant reductions in energy usage would be required. There would also be severe financial issues for energy corporations (with knock-on effects throughout the economy and the banking industry) and energy-dependent governments in individual countries (e.g. Saudi Arabia) and regions (e.g. Alberta, Canada).
References
[1] Kevin Andersen (2015), Duality In Climate Science, Nature Geoscience. Accessible at https://www.nature.com/ngeo/journal/v8/n12/full/ngeo2559.html
[2] Matthew Collins et. al. (2013), Fifth Assessment Report, Long Term Climate Change: Projection, Commitments & Irreversibility, United Nation International Panel on Climate Change. Accessible at http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter12_FINAL.pdf
[3] Mikel Gonzalez-Eguino (2017), Mitigation implications of an ice-free summer in the Arctic Ocean, Earth’s Future. Accessible at http://onlinelibrary.wiley.com/doi/10.1002/2016EF000429/full
[4] Mikel Gonzalez-Eguino (2017), Mitigation implications of an ice-free summer in the Arctic Ocean, Earth’s Future. Accessible at http://onlinelibrary.wiley.com/doi/10.1002/2016EF000429/full
[5] M. G. Flanner et. al. (2011), Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008, Nature Geoscience. Accessible at https://www.nature.com/ngeo/journal/v4/n3/full/ngeo1062.html
[6] Andrew R. Friedman (2013), Interhemispheric Temperature Asymmetry over the Twentieth Century and in Future Projections, American Meteorological Society. Accessible at http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00525.1
[7] Carolina Voigt at. al. (2016), Warming of subarctic tundra increases emissions of all three important greenhouse gases – carbon dioxide, methane, and nitrous oxide, Global Change Biology. Accessible at http://onlinelibrary.wiley.com/doi/10.1111/gcb.13563/abstract
[8] Wallace S. Broeker & Aaron E. Putnam (2013), Hydrologic impacts of past shifts of Earth’s thermal equator offer insight into those to be produced by fossil fuel CO2, Proceedings of the National Academy of Sciences of the United States of America. Accessible at http://www.pnas.org/content/110/42/16710.full
[9] Wallace S. Broeker & Aaron E. Putnam (2013), Hydrologic impacts of past shifts of Earth’s thermal equator offer insight into those to be produced by fossil fuel CO2, Proceedings of the National Academy of Sciences of the United States of America. Accessible at http://www.pnas.org/content/110/42/16710.full
[10] James E. Overland et. al. (2016), Nonlinear response of mid-latitude weather to the changing Arctic, Nature Climate Change. Accessible at https://www.nature.com/nclimate/journal/v6/n11/full/nclimate3121.html
Teaser photo credit: By Ansgar Walk – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=47497187
