Reading Passage 3
You should spend about 20 minutes on Questions 27-40, which
are based on Reading
Passage 3 below.
Reducing the Effects of Climate Change
Mark Rowe reports on the increasingly ambitious
geoengineering projects being explored by scientists
A
. Such is our dependence on fossil fuels, and such is the volume of carbon dioxide
already released into the atmosphere, that many experts agree that significant global
warming is now inevitable. They believe that the best we can do is keep it at a
reasonable level, and at present, the only serious option for doing this
is cutting back
on our carbon emissions. But while a few countries are making major strides in this
regard, the majority arc having great difficulty even stemming the rate of increase, let
alone reversing it. Consequently, an increasing number of scientists are beginning to
explore the alternative of geo-engineering
–
a term which generally refers to the
intentional large-scale manipulation of the environment. According to its proponents,
geo-engineering is the equivalent of a backup generator: if Plan A
–
reducing our
dependency on fossil fuels
–
fails, we require a Plan B, employing grand schemes to
slow down or reverse the process of global warming.
B
. Geo-engineering has been shown to work, at least on a small localised scale. For
decades, May Day parades in Moscow have taken place under clear blue skies,
aircraft having deposited dry ice, silver iodide and cement powder to disperse clouds.
Many of the schemes now suggested
look to do the opposite, and reduce the amount
of sunlight reaching the planet. The most eye-catching idea of all is suggested by
Professor Roger Angel of the University of Arizona. His scheme would employ up to
16 trillion minute spacecraft, each weighing about one gram, to form a transparent,
sunlight-refracting sunshade in an orbit 1.5 million km above the Earth. This could,
argues Angel, reduce the amount of light reaching the Earth by two per cent.
C
. The majority of geoengineering projects so far carried out
–
which
include planting
forests in deserts and depositing iron in the ocean to stimulate the growth of algae
–
have focused on achieving a general cooling of the Earth. But some look specifically
at reversing the melting at the poles, particularly the Arctic. The reasoning is that if
you replenish the ice sheets and frozen waters of the high latitudes, more light will be
reflected back into space, so reducing the warming of the oceans and atmosphere.
D
. The concept of releasing aerosol sprays into the stratosphere
above the Arctic has
been proposed by several scientists. This would involve using sulphur or hydrogen
sulphide aerosols so that sulphur dioxide would form clouds, which would, in turn,
lead to global dimming. The idea is modelled on historic volcanic explosions, such as
that of Mount Pinatubo in the Philippines in 1991, which led to a short-term cooling
of global temperatures by 0.5 °C. Scientists have also scrutinised whether it‟s possi
ble
to preserve the ice sheets of Greenland with reinforced high-tension cables, preventing
icebergs from moving into the sea. Meanwhile, in the Russian Arctic, geoengineering
plans include the planting of millions of birch trees. Whereas the regions native
evergreen pines shade the snow and absorb radiation, birches would shed their leaves
in winter, thus enabling radiation to be reflected by the snow. Re-routing Russian
rivers to increase cold water flow to ice-forming areas could also be used to slow
down warming, say some climate scientists.
E
. But will such schemes ever be implemented? Generally speaking, those who are
most cautious about geoengineering are the scientists involved in the research. Angel
says that his plan is „no substitute for developin
g renewable energy: the only
permanent solution‟. And Dr Phil Rasch of the US
-based Pacific Northwest National
Laboratory is equally guarded about the role of geo
engineering: „I think all of us
agree
that if we were to end geoengineering on a given day, then the planet would return to
its pre-engineered condition very rapidly, and probably within ten to twenty years.
That‟s certainly something to worry about.‟
F
. The US National Center for Atmospheric Research has already suggested that the
proposal to inject sulphur into the atmosphere might affect rainfall patterns across the
tropics and the Southern Ocean. „Geo
-engineering plans to inject stratospheric
aerosols or to seed clouds would act to cool the planet, and act to increase the extent
of sea ice,‟ says Rasch. „But all the models suggest some impact on the distribution of
precipitation.‟
G
. A further risk with geoengineering projects is that you can “overshoot”,‟ says Dr
Dan Lunt, from the University of Bristol‟s
School of Geophysical Sciences, who has
studied the likely impacts of the sunshade and aerosol schemes on the climate. „You
may bring global temperatures back to pre-industrial levels, but the risk is that the
poles will still be warmer than they should be and the tropics will be cooler than
be
fore industrialisation.‟ To avoid such a scenario, Lunt says Angel‟s
project would
have to operate at half strength; all of which reinforces his view that the best option is
to avoid the need for geoengineering altogether.
H
. “The main reason why geo
-engineering is supported by many in the scientific
community is that most researchers have little faith in the ability of politicians to
agree
–
and then bring in
–
the necessary carbon cuts. Even leading conservation
organisations see the value of investigating the potential of geoengineering.
According to Dr Martin Sommerkorn, climate change advisor for the World Wildlife
Fund‟s International Arctic Programme, „Human
-induced climate change has brought
humanity to a position where we shouldn‟t exclude thinking
thoroughly about these
topics and its possibilities.
Questions 27-29
Reading Passage 3 has eight paragraphs A-H.
Dostları ilə paylaş: