Page 4 - 2020-The-Climate-Turning-Point

OUR SHARED MISSION FOR 2020

PREFACE: WHY GLOBAL EMISSIONS MUST PEAK BY 2020
Authored by Stefan Rahmstorf and Anders Levermann
Potsdam Institute for Climate Impact Research

In the landmark Paris Climate Agreement, the world’s nations have committed to “holding the increase in
the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit
the temperature increase to 1.5 °C above pre-industrial levels”. This goal is deemed necessary to avoid
incalculable risks to humanity, and it is feasible – but realistically only if global emissions peak by the year
2020 at the latest.

Let us first address the importance of remaining well below 2°C of global warming, and as close to 1.5°C
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as possible. The World Meteorological Organization climate report for the past year has highlighted that
global temperature and sea levels keep rising, reaching record highs once again in 2016. Global sea ice
cover reached a record low, and mountain glaciers and the huge ice sheets in Greenland and Antarctica are
on a trajectory of accelerating mass loss. More and more people are suffering from increasing and often
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unprecedented extreme weather events , both in terms of casualties and financial losses. This is the situation
after about 1°C global warming since the late 19th Century.
Not only will these impacts get progressively worse as warming continues, but our planet also runs
a growing risk of crossing critical tipping points where major and largely irreversible changes to the
Earthsystem are triggered (see Fig. 1).

High emissions

Intermediate scenarios

Low emissions

Fig. 1 Tipping elements in the Earth system, in relation to past global temperature evolution since the last Ice
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Age 20,000 years ago as well as future warming scenarios . The Paris range of 1.5 – 2 C warming is shown
in grey; the bars show increasing risk of crossing tipping points from yellow to red. ENSO = El Niño Southern
Oscillation. EAIS = East Antarctic Ice Sheet

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