Runaway Climate Change and the Role of Vegetation in Cities

Sourced from the Living Architecture Monitor

Climate change is the most important issue facing humanity this century. It is global, affecting everyone and every planetary system. And to some extent it cannot be prevented, only managed, minimizing the damage by controlling the rise in the planet’s average temperature through reducing greenhouse gas emissions. However, ‘runaway climate change’ threatens even this premise – that we can control the planet’s average temperature. This article reviews some of the basic science that underlies the concept of runaway climate change and provides ideas on how to reduce this threat.

Runaway climate change can occur if the positive feedback processes in the climate system are accelerated, such that the climate system is pushed beyond thresholds that are in fact tipping points. Once the system crosses these tipping points, it will not be possible, even with reduced greenhouse gas (GHG) emissions, to stabilize the climate at an acceptable temperature increase (Steffan et al. 2018). Even stabilization at 2oC, the current acceptable temperature increase, will require enormous investment in adaptation measures to protect coastal cities from sea level rise and maintain food production while coping with the destruction of most of the coral reefs.

Tipping points are thresholds that if crossed will lead to large, irreversible changes in the system. One such tipping point would be the loss of Arctic and Antarctic ice sheets. At some point, the loss of these ice sheets becomes irreversible. Another possible tipping point, noted by Intergovernmental Panel on Climate Change Chair, R. Pachauri is the collapse of the thermohaline circulation. This refers to the global circulation of warmer ocean waters driven by global density gradients created by surface heat and freshwater fluxes. Under this system, the melting of Arctic and Greenland ice has been slowing down the movement of warmer waters from the south that moderate the winter climate in eastern North America and western Europe. If the system reaches a tipping point, the warmer waters will fail to move north, and average temperatures in eastern North American and western Europe would likely drop dramatically.

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