- We live in a world that has become so desensitised by
watching calamities unfold on global television - both natural and
human-induced
- that it takes something really spectacular even to get our
attention.
-
- And it usually has to be visually dramatic to register,
much less elicit a deep emotional response - such as the tragic events
of September 11.
-
- Recently, I came across a frightening report published
by the US National Academy of Sciences (NAS) - the nation's most august
scientific body. Yet, because there was no visually provocative content,
the report had received only a couple of short paragraphs tucked away
inside
a few newspapers.
-
- Here is what the academy had to say it is possible that
the global warming trend projected over the course of the next 100 years
could, all of a sudden and without warning, dramatically accelerate in
just a handful of years - forcing a qualitative new climatic regime which
could undermine ecosystems and human settlements throughout the world,
leaving little or no time for plants, animals and humans to adjust.
-
- The new climate could result in a wholesale change in
the earth's environment, with effects that would be felt for thousands
of years. If the projections and warnings in this study turn out to be
prophetic, no other catastrophic event in all of recorded history will
have had as damaging an impact on the future of human civilisation and
the life of the planet.
-
- A year ago the UN intergovernmental panel on climate
change (IPCC) issued a voluminous report forecasting that global average
surface temperature is likely to rise by 1.4 to 5.8 degrees centigrade
between now and 2100. If that projection holds up, we were told, the change
in temperature forecast for the next 100 years will be larger than any
climate change on earth in more than 10,000 years.
-
- The impacts on the earth's biosphere are going to be
of a qualitative kind. To understand how significant this rise in
temperature
is likely to be, we need to keep in mind that a 5 degrees centigrade
increase
in temperature between the last ice age and today resulted in much of the
northern hemisphere of the planet going from being buried under thousands
of feet of ice to being ice-free.
-
- The UN study predicts that a temperature rise of 1.4-5.8
degrees centigrade over the course of the coming century could include
the melting of glaciers and the Arctic polar cap, sea water rise, increased
precipitation and storms and more violent weather patterns, destabilisation
and loss of habitats, migration northward of ecosystems, contamination
of fresh water by salt water, massive forest dieback, accelerated species
extinction and increased droughts.
-
- The IPCC report also warns of adverse impacts on human
settlements, including the submerging of island nations and low-lying
countries,
diminishing crop yields, especially in the southern hemisphere, and the
spread of tropical disease northward into previously temperate
zones.
-
- The newly released NAS report begins by noting that the
current projections about global warming and its ecological, economic and
social impacts cited in the UN report are based on the assumption of a
steady upward climb in temperatures, more or less evenly distributed over
the course of the 21st century. But that assumption, they say, may be
faulty
- there is a possibility that temperatures could rise suddenly in just
a few years' time, creating a new climatic regime virtually
overnight.
-
- They also point out that abrupt changes in climate, whose
effects are long lasting, have occurred repeatedly in the past 100,000
years. For example, at the end of the Younger-Dryas interval about 11,500
years ago, "global climate shifted dramatically, in many regions by
about one-third to one-half the difference between ice age and modern
conditions,
with much of the change occurring over a few years".
-
- According to the study"An abrupt climate change
occurs when the climate system is forced to cross some threshold,
triggering
a transition to a new state at a rate determined by the climate system
itself and faster than the cause." Moreover, the paleoclimatic record
shows that "the most dramatic shifts in climate have occurred when
factors controlling the climate system were changing". Given the fact
that human activity - especially the burning of fossil fuels - is expected
to double the CO2 content emitted into the atmosphere in the current
century,
the conditions could be ripe for an abrupt change in climate around the
world, perhaps in only a few years.
-
- What is really unnerving is that it may take only a
slight
deviation in boundary conditions or a small random fluctuation somewhere
in the system "to excite large changes ... when the system is close
to a threshold", says the NAS committee.
-
- An abrupt change in climate, of the kind that occurred
during the Younger-Dryas interval, could prove catastrophic for ecosystems
and species around the world. During that particular period, for instance,
spruce, fir and paper birch trees experienced mass extinction in southern
New England in less than 50 years. The extinction of horses, mastodons,
mammoths, and sabre-toothed tigers in North America were greater at that
time than in any other extinction event in millions of years.
-
- The committee lays out a potentially nightmarish scenario
in which random triggering events take the climate across the threshold
into a new regime, causing widespread havoc and destruction.
-
- Ecosystems could collapse suddenly with forests decimated
in vast fires and grasslands drying out and turning into dust bowls.
Wildlife
could disappear and waterborne diseases such as cholera and vector-borne
diseases such as malaria, dengue and yellow fever, could spread
uncontrollably
beyond host ranges, threatening human health around the world.
-
- The NAS concludes its report with a dire warning"On
the basis of the inference from the paleoclimatic record, it is possible
that the projected change will occur not through gradual evolution,
proportional
to greenhouse gas concentrations, but through abrupt and persistent regime
shifts affecting subcontinental or larger regions - denying the likelihood
or downplaying the relevance of past abrupt changes could be
costly."
-
- Global warming represents the dark side of the commercial
ledger for the industrial age. For the past several hundred years, and
especially in the 20th century, human beings burned massive amounts of
"stored sun" in the form of coal, oil and natural gas, to produce
the energy that made an industrial way of life possible. That spent energy
has accumulated in the atmosphere and has begun to adversely affect the
climate of the planet and the workings of its many ecosystems.
-
- If we were to measure human accomplishments in terms
of the sheer impact our activities have had on the life of the planet,
then we would sadly have to conclude that global warming is our most
significant
accomplishment to date, albeit a negative one.
-
- We have affected the biochemistry of the earth and we
have done it in less than a century. If a qualitative climate change were
to occur suddenly in the coming century - within less than 10 years - as
has happened many times before in geological history, we may already have
written our epitaph.
-
- When future generations look back at this period, tens
of thousands of years from now, it is possible that the only historical
legacy we will have left them in the geologic record is a great change
in the earth's climate and its impact on the biosphere.
-
- http//www.guardian.co.uk
-
- Guardian Unlimited © Guardian Newspapers Limited
2002
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