Green Roofs - Living Architecture Monitor - Summer 2019 - 30

RESEARCH

RUNAWAY CLIMATE CHANGE AND
THE ROLE OF VEGETATION IN CITIES
BY DR. BRAD BASS

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.

H

owever, '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 and other threats to
biodiversity.
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

LIVING ARCHITECTURE MONITOR / SUMMER 2019 / 30

and Greenland ice has been
slowing down the movement of warmer waters from
the south northwards, 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.
"Feedbacks" occur in a system when the response to an
input, in and of itself, becomes
an input to the system. If the
new outcome dampens or
reduces the magnitude of the
original results, this dampening is called a virtuous or
negative feedback. A positive,
vicious or self-accelerating
feedback is the opposite and
therefore increases the magnitude of the original result.

In the global climate system,
the archetypical feedbacks are
that increased greenhouse emissions to the atmosphere gas lead
to a higher surface temperature.
Higher surface temperature
in turn increases evaporation,
resulting in more water vapour
in the atmosphere. Water vapour
itself, is a greenhouse gas, and
this in turn creates a positive
feedback leading to a greater
increase in temperature. The
other well-known feedback is
the melting of ice that reflects
sunlight. As the ice melts, the
reflectivity of the northern and
southern regions decreases, the
absorption of sunlight increases
and the amount of heat radiated
from the surface increases,
further increasing the surface
temperature. (see image on P. 31)
Similar to the self-accelerating
feedback from increasing water
vapour is the increase of methane.
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Green Roofs - Living Architecture Monitor - Summer 2019

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Summer 2019

Table of Contents
Green Roofs - Living Architecture Monitor - Summer 2019 - IP
Green Roofs - Living Architecture Monitor - Summer 2019 - Cover
Green Roofs - Living Architecture Monitor - Summer 2019 - Cover 2
Green Roofs - Living Architecture Monitor - Summer 2019 - Table of Contents
Green Roofs - Living Architecture Monitor - Summer 2019 - A1
Green Roofs - Living Architecture Monitor - Summer 2019 - 1
Green Roofs - Living Architecture Monitor - Summer 2019 - 2
Green Roofs - Living Architecture Monitor - Summer 2019 - 3
Green Roofs - Living Architecture Monitor - Summer 2019 - 4
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Green Roofs - Living Architecture Monitor - Summer 2019 - 36
Green Roofs - Living Architecture Monitor - Summer 2019 - M1
Green Roofs - Living Architecture Monitor - Summer 2019 - A2
Green Roofs - Living Architecture Monitor - Summer 2019 - A3
Green Roofs - Living Architecture Monitor - Summer 2019 - A4
Green Roofs - Living Architecture Monitor - Summer 2019 - A5
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