Scientists
warn world will miss key climate target
Grim
backdrop to vital global emissions talks as new analysis shows 1.5C
limit on warming is close to being broken
Robin McKie
Observer science editor
Saturday 6 August
2016 22.01 BST
Leading climate
scientists have warned that the Earth is perilously close to breaking
through a 1.5C upper limit for global warming, only eight months
after the target was set.
The decision to try
to limit warming to 1.5C, measured in relation to pre-industrial
temperatures, was the headline outcome of the Paris climate
negotiations last December. The talks were hailed as a major success
by scientists and campaigners, who claimed that, by setting the
target, desertification, heatwaves, widespread flooding and other
global warming impacts could be avoided.
Environmental
records shattered as climate change 'plays out before us'
Read more
However, figures –
based on Met Office data – prepared by meteorologist Ed Hawkins of
Reading University show that average global temperatures were already
more than 1C above pre-industrial levels for every month except one
over the past year and peaked at +1.38C in February and March.
Keeping within the 1.5C limit will be extremely difficult, say
scientists, given these rises.
These alarming
figures will form the backdrop to the Intergovernmental Panel on
Climate Change talks in Geneva this month, when scientists will start
to outline ways to implement the climate goals set in Paris. Dates
for abandoning all coal-burning power stations and halting the use of
combustion engines across the globe – possibly within 15 years –
are likely to be set.
Atmospheric heating
has been partly triggered by a major El Niño event in the Pacific,
with 2016 expected to be the hottest year on record. Temperatures
above 50C have afflicted Iraq; India is experiencing one of the most
intense monsoons on record; and drought-stricken California has been
ravaged by wildfires.
Stanford
University’s Professor Chris Field, co-chair of the IPCC working
group on adaptation to climate change, told the Observer: “From the
perspective of my research I would say the 1.5C goal now looks
impossible or at the very least, a very, very difficult task. We
should be under no illusions about the task we face.”
The Paris summit
first agreed to limit global warming to 2C above pre-industrial
levels and then decided to try to keep it below 1.5C. This latter
limit was set because it offered the planet a better chance of
staving off catastrophes such as the melting of polar ice, which
would no longer be able to deflect solar radiation and allow even
greater global warming. Similarly, coral reef destruction and extreme
sea level rises might be avoided if the 1.5C limit is achieved.
“If the world puts
all its resources into finding ways to generate power without burning
fossil fuels, and if there were international agreements that action
must happen instantly, and if carbon emissions were brought down to
zero before 2050, then a rise of no more than 1.5C might just be
achieved,” said Dr Ben Sanderson of the National Center for
Atmospheric Research in Boulder, Colorado. “That is a tall order,
however.”
Climate models are
accurately predicting ocean and global warming
Read more
The problem was made
particularly severe because moving too quickly to cut emissions could
be also be harmful, added Field. “If we shut down fossil fuel
plants tomorrow – before we have established renewable alternatives
– we can limit emissions and global warming, but people would
suffer. There would be insufficient power for the planet. There is an
upper limit to the rate at which we can move to a carbon-free
future.”
The Paris agreement
is vague about the exact rate at which the world’s carbon emissions
should be curtailed if we are to achieve its 1.5C target. It merely
indicates they should reach zero by the second half of the 21st
century, a goal that was accepted as being ambitious but possible –
until global temperatures increased dramatically this year.
“It means that by
2025 we will have to have closed down all coal-fired power stations
across the planet,” said John Schellnhuber, director of the Potsdam
Institute for Climate Impact Research. “And by 2030 you will have
to get rid of the combustion engine entirely. That decarbonisation
will not guarantee a rise of no more than 1.5C but it will give us a
chance. But even that is a tremendous task.”
Many scientists now
believe the most realistic strategy is to overshoot the 1.5C target
by as little as possible and then, once carbon emissions have been
brought to zero, carbon dioxide could be extracted from the
atmosphere to start to cool the planet back down to the 1.5C target.
In other words, humanity will have to move from merely curtailing
emissions to actively extracting carbon dioxide from the air, a
process known as negative emissions.
“Some negative
emission technology will inevitably have to be part of the picture if
you are going to keep 1.5C as your limit,” said Professor Jim Skea,
a member of the UK government’s committee on climate change. “There
will always be some human activities that put carbon into the
atmosphere and they will have to be compensated for by negative
emission technology.”
But what form that
technology takes is unclear. Several techniques have been proposed.
One includes spreading crushed silicate rocks, which absorb carbon
dioxide, over vast tracts of land. Another involves seeding oceans
with iron to increase their uptake of carbon dioxide. Most are
considered unworkable at present – with the exception of bioenergy
with carbon capture and storage. Under this scheme, vast plantations
of trees and bushes would be created, their wood burned for energy
while the carbon dioxide emitted was liquefied and stored
underground.
“It could do the
trick,” said Cambridge University climate expert Professor Peter
Wadhams. “The trouble is that you would need to cover so much land
with plants for combustion you would not have enough space to grow
food or provide homes for Earth’s wildlife. In the end, I think we
just have to hope that some kind of extraction technology, as yet
unimagined by scientists, is developed in the next couple of decades.
If not, we are in real trouble.”
Sem comentários:
Enviar um comentário