11 June 2022 | New Scientist | 9if we do collectively accept that
the prospects of meeting the goal
are “dead”, would that paralyse or
catalyse action on climate change?
To supply answers, it is worth
recalling the goal’s origins.
“The push behind 1.5°C did not
really come from the science
community,” says Robert Rohde
at US non-profit organisation
Berkeley Earth. Since 1996,
the broadly accepted goal in
political spheres was 2°C above
pre-industrial levels. From around
2008, small island states argued
that anything weaker than 1.5°C
meant oblivion. A growing cast of
allies agreed. Yet it still surprised
many people when 195 countries
signed off on aiming for 1.5°C for
2015’s historic Paris Agreement.
That political deal led to
a seismic IPCC report in 2018,
which starkly spelled out the
difference in climate impacts
between a 1.5°C fate and the more
intense heatwaves, flooding and
human suffering that would
accompany a 2°C future. In turn,
1.5°C became the world’s rallying
cry on climate change, from the
lips of politicians to the placards
carried by Extinction Rebellion
and Fridays for Future campaigners
on streets across the world.
Calculating the odds
Scientists have rushed to catch up
with this new political aspiration.
In 2018, there were 53 published
scenarios that reached 1.5°C with
little or no overshoot before
returning to that target (see
“Overshoot world”, page 10), says
Skea. By this April, there were 97.
But because global average
emissions have kept growing
instead of falling, the models
BJANK
A^ KADIC/
AL
AMYA Climate Justice
protest in London on
6 November 2021underpinning those scenarios
are creaking under the strain.
The IPCC’s reports only include
scenarios with a 50 per cent
chance of staying under 1.5°C,
compared with a 66 per cent
chance of meeting 2°C.
Given how the odds are stacked,
is it still helpful for scientists to
maintain that 1.5°C is technically
possible? “Well, here’s the thing:
whether we meet 1.5°C or not, is
not a scientific question. It is a
political and a policy question,”
says Katharine Hayhoe at Texas
Tech University. “We [scientists]
stay in our lane and say,
‘technically, looking at the amount
of carbon in the atmosphere and
the amount that we are producing
every year, if we did X and Y,
we would still have a Z per cent
chance of staying below 1.5°C’.”
Alison Ming at the University
of Cambridge says it is still helpful,
because a 1.5°C world remains
feasible. “I think it’s worth saying
that this future is possible,” she
says. However, she echoes Hayhoe,
saying that scientists are just
laying out scenarios rather thanmaking predictions. Ming says
the IPCC models everything up
to the worst-case scenarios, which
no longer look likely. “I don’t
really see it as scientists pushing
1.5°C of warming,” she says.
Nonetheless, Rohde says some
researchers are uncomfortable
with the narrative around 1.5°C
because they believe it is anunrealistic target. “It’s not the
message I tend to emphasise,
because 1.5°C is very hard,” he says.
“Even if we have scenarios that
get there, they involve very radical
changes of the energy system
happening very quickly. And
even if that works on paper, it
doesn’t seem like humanity is
making the necessary changes.”
For now, few public figures,
scientists included, will concede
that the temperature target is
out of reach. But with Skea giving
November as a deadline, and the“ Even if 1.5°C works on
paper, it doesn’t seem like
humanity is making the
necessary changes”Warming projected
by 21000102030405060701990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100Glob
algreenh
o
use^g
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e
missio
n
s^GtCOe 2
/year2100 warming projections
Expected warming given emissions changes based on pledges and current policiesHistoricalOptimistic scenario
+1.8°C2030 targets only
+2.4°C
Pledges & targets
+2.1°CPolicies & action
+2.5 – 2.9°C1.5°C consistent
+1.3°CHouses in Ilulissat,
Greenland, near the
Jakobshavn glacier
>Source: Climate Action Tracker