30 November 2019 | New Scientist | 7THE huge challenge of meeting
the world’s climate change
targets has been starkly spelled
out in a new report from the UN
Environment Programme (UNEP).
In 2018, annual global emissions
of greenhouse gases reached
55.3 gigatonnes – a new high. This
must fall by 32 gigatonnes by 2030
to avoid warming of more than
1.5°C by the end of the century.
That is a 7.6 per cent emissions
cut every year, says UNEP.
Climate scientists last year
outlined the stark impact of
overshooting 1.5°C and hitting 2°C,
including wiping out the planet’s
coral reefs, more droughts and
extreme heat days and exposing
hundreds of millions of people
to climate-related risks. Globally,annual emissions have never
fallen, though they plateaued
during 2014 and 2016, and have
previously plunged dramatically
at a country level, such as in Russia
after the fall of the Soviet Union.
Despite the impossible-seeming
cuts required, UNEP maintains it
is still feasible to stay under 1.5°C.
“How long can we keep 1.5°C alive?
We haven’t killed it yet. Even if we
don’t get to 1.5°C, 1.7°C is a hell of a
lot better than 2.5°C, or the 3.2°C
we’re looking at now. Every 0.1°C
counts,” says Anne Olhoff at the
Technical University of Denmark,
one of the report’s lead authors.The report comes less than a
week before international climate
talks resume at a summit in Spain,
when countries are due to lay the
groundwork for bolder carbon-
cutting plans next year.
One source of hope is the
decline of coal use in power plants,
set for a 3 per cent fall in 2019 – the
biggest drop on record – according
to analyst Carbon Brief. UNEP cites
protests by schoolchildren and the
falling costs of green technologies
as other reasons for optimism, but
it also concedes there is “no sign
of greenhouse gas emissions
peaking in the next few years”. ❚To minimise risks, the world must cut emissions by a staggering
7.6 per cent a year for the next decade, reports Adam VaughanMarine biologyBlue whale’s ultra-
low heart rate
WHEN blue whales dive for
food they can reduce their
heart rate to just 2 beats
per minute – well below
the resting rate of 15 beats
researchers predicted the
animals would have.
The finding is remarkable
given the whales use lunge
feeding, an energetic
method in which they engulf
vast volumes of prey-filled
water, says Jeremy
Goldbogen at Stanford
University, California.
From a boat in Monterey
Bay, California, Goldbogen
and his team used a 6-metre
pole to attach a heart rate
monitor to a single blue
whale. The monitor was
held in place with a suction
cup. The researchers were
then able to monitor the
whale’s heart rate for almost
9 hours. They detected heart
rates of just 2 to 8 beats per
minute hundreds of times.
The whale’s heart rate
was at its lowest when
the animal was diving for
food and shot up after it
resurfaced, reaching a peak
of 37 beats per minute
(PNAS, doi.org/dfwb).
The reduction in heart rate
during dives enables whales
to temporarily redistribute
oxygenated blood from
the heart to other muscles
needed for lunging, says
Goldbogen. Whales then
recover upon resurfacing
by increasing their breathing
and heart rate, he says.
The whales have a “quite
extraordinary level of control”
of heart rate, says Sascha
Hooker at the University of
St Andrews, UK. ❚
Layal LiverpoolUN climate warning
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