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CLIMATE CHANGE - still
the unanswered question?
Peter F Smith, Chairman, RIBA Sustainable
Futures Committee
Charles Ives composed an orchestral piece
called 'The Unanswered Question. He could have been thinking
about global warming. For a correspondent to the journal
New Civil Engineer, (p.18, 20 Jan 2000) the question has
indeed been answered by stating that the current phase of
global warming is nothing more than a natural fluctuation
of the kind to which the Earth has been subjected for many
millennia. He concluded: 'Trying to stop global warming
is as futile as Canute trying to hold back the tide'.
This paper addresses the question of the futility
or otherwise of 'trying to stop global warming'.
But first we should remind ourselves that,
under normal circumstances the greenhouse shield increases
average global temperature by 33 deg C. Without it most
life would not be viable. Why there is now concern is because
gases that produce the greenhouse effect, notably CO2, are
increasing in the atmosphere, meaning that more long wave
infra-red solar radiation is being deflected back to Earth,
hence the warming.
There is still no definitive answer to the
question as to whether the current episode of global warming
is being driven by human activity or is a fluctuation due
to natural causes. What we have to go on is a balance of
probabilities. To make a risk analysis we have to consider
the evidence. First, what is the evidence for climate swings
in the past?
In June 1990 scientists were brought up sharp
by a graph which appeared in the journal Nature. It was
evidence from ice core samples which showed a remarkably
close correlation between temperature and concentrations
of CO2 in the atmosphere from 160,000 years ago until 1989.
It also revealed that present concentrations of CO2 are
higher than at any time over that period. Since then the
rate of increase has, at the very least, been maintained.
Ice core samples give a clear indication of
temperature fluctuations in two ways. First their melt layers
give a good indication of the extent to which ice melted
and refroze after a given summer. A linear measurement of
melt ice gives a good picture of the relative warmth of
a summer. The second indicator is the heavy oxygen isotope
O18 in air trapped in the ice. It is more abundant in warm
years.
Another source of what is called 'proxy''
evidence comes from analysing tree rings. This can give
a snapshot of climate going back 6000 years. Each tree ring
records one year of growth and the size of each ring offers
a reliable indication of that year's climate. The thicker
the ring, the more favourable the climate to growth. In
northern latitudes warmth is the decisive factor. Some of
the best data come from within the Arctic Circle where pine
logs provide a 6000 year record.
The Climate Research Unit of the University
of East Anglia is making a special study of the evidence
for climate changes from different sources and has concluded
that there is a close affinity between ice core evidence
and that obtained from tree rings. Instrumental records
going back to the 16th century are consistent with the proxy
evidence.
Causes of climate fluctuation
A major cause of climate fluctuation has been the variation
in the Earth's axial tilt. The Earth is subject to the influence
of neighbouring planets. Their orbits produce a fluctuating
gravitational pull on the Earth, affecting the angle of
its axis. As the Earth wobbles, vast ice sheets wax and
wane over a cycle. However, thanks to the stabilising pull
of the moon, the variation in tilt is contained within limits
which preserves the integrity of the seasons. Without the
moon, the axis could move to 90 degrees from the vertical
meaning that half the planet would have permanent summer
the other, endless winter.
Incidentally, the current orbital configuration
is said to be similar to that of the interglacial period
400,000 years ago. We may indeed be in the early stages
of an interglacial episode and the accompanying natural
warming. This offers no comfort because human induced forcing
of the greenhouse effect may cause catastrophic climate
changes to occur very much more quickly than under the normal
processes of nature.
A second factor forcing climate change is
the movement of tectonic plates and the resultant formation
of volcanic mountains. In themselves mountains add to the
stirring effect on the atmosphere in concert with the rotation
of the Earth. They also generate fluctuations in atmospheric
pressure, all of which affects climate.
But dramatic climate changes can be caused
by volcanic activity. The surface of the Earth is constantly
shifting. The collision of plates accounts for the formation
of mountains. A feature of plate tectonics is that, when
plates collide, not only does this form mountains, but also
one plate slides under the other; this is called subduction.
In the process rocks are heated and forced through the surface
as volcanoes, releasing vast quantities of debris and CO2
in the process. In the short term this can lead to a cooling
as the dust cuts out solar radiation. In the longer term,
large injections of CO2 lead to warming, since CO2 has a
relatively long life in the atmosphere.
A third factor may be a consequence of the
second. Paleo-climatic data show that there have been periodic
surges of ice flows into the north Atlantic which, in turn,
affect the deep ocean currents, notably the Gulf Stream.
To understand why the ice flows affect the Gulf Stream we
need to look at what drives this rather special current.
Particularly salty and warm surface water
migrates from the tropics towards the north Atlantic. As
it moves north it gradually becomes cold and dense, and,
as a consequence, near Greenland it plunges to the ocean
floor. This, in turn, draws warmer water from the tropics
which is why it is also called the conveyor belt or deep
ocean pump. It accounts for 25% of the heat budget of north
west Europe.
So, what is the relevance
of the icebergs?
As these armadas of icebergs melted as they came south they
produced huge amounts of fresh water which lowered the density
of surface water undermining its ability to descend to the
ocean floor. The effect was to shut down the conveyor belt,
As a result northern Europe was periodically plunged into
arctic conditions and scientists are concerned that there
is now evidence that this process is beginning to happen
due to melting ice in the southern tip of Greenland. After
the melted iceberg water had dispersed, the conveyor started
up again leading to rapid warming. This cycle occurred 20
times in 60,000 years, and the evidence indicates that cooling
was relatively slow whilst warming was rapid - 10-12 deg
C in a lifetime.
For some reason these forays of icebergs stopped
about 8000 years ago, creating relatively stable conditions
which facilitated the development of agriculture and ultimately
the emergence of urban civilisations.
A fourth factor may seem ironic, because ice
ages can be triggered by warm spells leading to the rapid
expansion of forests. This, in turn, leads to huge demands
for CO2 which is drawn from the atmosphere. The result of
this stripping of atmospheric CO2 is a weakening of the
greenhouse shield, resulting in sharply dropping temperatures.
Changes in energy levels emitted by the sun
are also implicated in global fluctuations. In June 1999
the Journal Nature (vol 399, p 437) published research evidence
from the Rutherford Appleton Laboratory, in Didcot, Oxfordshire
which suggests that half the global warming over the last
160 years has been due to the increasing brightness of the
sun. However, since 1970 the sun has become less and less
responsible for the warming, yet the rate of warming has
been increasing, indicating that increased greenhouse gases
are the culprit. Some of the best evidence for the climatic
effects of varying levels of radiative output from the sun
comes from Africa. Sediment in Lake Naivasha in the Kenya
Rift Valley reveals the levels of lake water over the past
1000 years. Periods of high water have higher concentrations
of algae on the lake floor which translates to a higher
carbon content in the annual layers of sediment. There were
long periods of intense drought leading to famine and mass
migrations, the worst being from 1000 to 1270. (Nature vol
403, p 410)
Finally, we cannot ignore wider cosmic effects.
The dinosaurs will testify to the effect on climate of meteor
strikes creating perpetual night. New sites of catastrophic
impacts are still being discovered on the Earth, but if
we want a true picture of the historic record of meteor
impact we can see it on Venus. The stability of that planet
- no plate movement or vegetation to hide the evidence -
ensures that we have a picture of meteor bombardment over
hundreds of millennia. The Earth will have been no different.
In the light of all this evidence of the extremely
eventful history of the Earth, are the changes we are now
seeing out of character with changes in the past?
This is the crux question, one being addressed
by the Climate Research Unit of the University of East Anglia.
A main objective of the CRU team is to examine patterns
past and present which have had a forcing effect on climate,
including events like volcanic activity and solar cycles.
The aim is to compare patterns of the past with those of
today to prove conclusively whether or not current temperature
changes are significantly different from patterns of natural
variability in the past. Climate models so far suggest that
anthropogenic global warming will reveal a distinctive pattern,
for example by predicting that warming will be greatest
in northern latitudes of the great continental land masses.
Already recent summer temperatures in Siberia are higher
than for 1000 years.
There are two facets to the argument which
could favour human responsibility for current warming. One
is the evidence of patterns which have no precedent in the
paleo-climatic record; the focus of the work of the East
Anglia team.
The second concerns the weight of probability
given the rate of occurrence of changes that are happening
world-wide. Individually these changes can be attributed
to natural causes, but the question is this: is the accumulation
of anomalous events itself so unusual as to lay the finger
of blame on humans?
There is widespread evidence that changes
in the Earth's climate are occurring at a rate almost unprecedented
in the paleo-climatic record.
It is the widescale evidence of anomalous
climatic events coupled with the rate at which they are
occurring that has persuaded the IPCC scientists that the
finger of blame points to human activity.
The evidence
- There has been a marked increase in the
incidence and severity of storms. One of the most reliable
indicators of this is the escalating amount being paid out
by insurance companies. It is no coincidence that these
companies are directing serious money to research into global
warming. In France the 1999 storms killed 90 and caused
£7.5 billion worth of damage.
- El Nino has produced unprecedentedly severe
effects due to the warming of the Pacific.
- Receding polar ice is resulting in the rapid
expansion of flora; Antarctic summers have lengthened by
up to 50% since the 1970s and new species of plants have
appeared as glaciers have retreated.
- Sea level has risen up to 250mm (10 inches)
since 1860. Four million radar measurements of the Antarctic
ice sheet between 1992 and 96 show that its thickness has
reduced by less than 1 cm. This means that, at this stage,
most of the sea level rise has been due to thermal expansion.
- Sea temperatures in Antarctica are rising
at 5 times the global average, currently 2.5 deg C increase
since the 1940s.The major threat lies with the potential
break-up of land based ice. The recent break-away of the
12000 sq km of the Larson B ice shelf has serious implications.
In itself it will not contribute to rising sea levels. The
danger lies in the fact that the ice shelves act as a bulwark
supporting the land based ice. It is this which poses the
threat of sea levels rising up to 6m. The latest suggestion
(April 1999) is that the ice shelf is breaking up 15 times
faster than predicted. (The Guardian)
- At the same time there has been massive
melting of glacier ice. The Alps have lost 50% of their
ice in the past century. The International Commission on
Snow and Ice has reported that glaciers in the Himalayas
are receding faster than anywhere else on Earth.
- In Alaska there is general thinning and
retreating of sea ice, drying tundra, increased storm intensity,
reduced summer rainfall, warmer winters and changes in the
distribution, migration patterns and numbers of some wildlife
species. Together these pose serious threats to the survival
of the subsistence indigenous Eskimos. (New Scientist 14
Nov 98)
- Global mean surface air temperature has
increased between 0.3 and 0.6 degrees C since the later
19th century. The average global surface temperature in
1998 set a new record surpassing the previous record in
1995 by 0.2 deg C - the largest jump ever recorded. Worldwatch
Institute in Scientific American , March 1999. The warmest
year on record was 1999. Global warming is increasing at
a faster rate than predicted by the UN IPCC scientists in
1995. They anticipated that temperatures would rise between
1 and 3.5 deg C in the 21st century. According to the Director
of the US National Climate Data Center, in only a short
time the rate of warming is already equivalent to a 3 deg
C rise per century. This makes it probable that the end
of century temperature level will be significantly higher
than the IPCC top estimate. (Geophysical Research Letters,
vol 27, p 719)
- NASA scientists report satellite evidence
of the Greenland land based ice sheet thinning by 1m/yr.
Altogether it has lost 5m in SW and E coasts. On the one
hand this threatens the Gulf Stream or deep ocean pump and
on the other, it leads directly to a rise in sea level,
threatening coastal regions. (Nature, 5 March 99) Over the
past 20 years the polar ice cap has thinned by 40%.
- Concentrations of CO2 in the atmosphere
are increasing at a steep rate. The pre-industrial level
was 590 billion tonnes; now it is 760 billion tonnes or
around 360 parts per million by volume (ppmv) with most
of the increase occurring over the last 50 years. According
to ice core evidence from the Vostock ice station in Antarctica
this is higher than at any time in the last 400,000 years.
The previous highest concentration was 300 ppmv 300,000
years ago. (New Scientist 29 Jan 2000 pp 42-43) At the present
rate of emission, concentrations will reach 800 ppmv by
2100. According to the IPCC scientists this could lead to
a temperature rise of 4.5 deg C. The current target of stabilising
emissions at 1990 levels would still mean that CO2 concentrations
would continue to rise for 100 years. It would seem that
a temperature rise of at least 4 deg C is unavoidable. Bearing
mind the observed rate of temperature increase as mentioned
above, the aim now should be to prevent the planet crossing
the threshold into runaway global warming - the Venus syndrome.
- Spring in the northern hemisphere is arriving
at least one week earlier than 20 years ago. A 40 year survey
by Nigel Hepper at the Royal Botanical Gardens at Kew involving
5000 species indicates that Spring is arriving 'several
weeks earlier'. A study of European gardens found that the
growing season has expanded by at least 10 days since 1960.
Munich scientists studied 70 botanical gardens from Finland
to the Balkans (616 spring records and 178 autumn) The conclusion
was that spring arrived on average 6 days earlier and autumn
5 days later over a 30 yr period. ('Nature', Feb 99)
- Extreme heat episodes are becoming a feature
of hitherto temperate climate zones. The majority of heat
related deaths are due to a lethal assault on the blood's
chemistry. Water is lost through sweating and this leads
to higher levels of red blood cells, clotting factors and
cholesterol. The process starts within 30 minutes of exposure
to sun. The critical temperature is 20 deg C. In recent
heatwaves western Europe experienced thousands of heat-related
deaths with only one third of the victims being already
seriously ill. One of the predicted results of global warming
is that there will be greater extremes of weather, which
not only means higher temperatures but also more extensive
swings of atmospheric pressure. Research at the University
of Lille has indicated that when the pressure falls below
1006 millibars or rises above 1026 millibars the risk of
heart attacks increases by 13%. The study also showed that
a drop in temperature of 10 deg C increases the risk of
a heart attack by the same percentage. (reported at a meeting
of the American Heart Association, Dallas, Nov 1998)
- receding ice sheets are increasingly exposing
tundra thus releasing methane and carbon dioxide, at the
same time absorbing solar radiation which was previously
reflected into back into space by snow cover, leading to
greater melting.
- oceans are the largest carbon sink. As they
warm they are becoming less efficient at absorbing CO2.
The latest prediction is that the carbon fixing capacity
of oceans will decline by 50% as sea temperatures rise.
- greater extremes of the hydrological cycle
are leading, on the one hand, to increased area of desert,
and, on the other, greater intensity of rain storms which
increase run-off and erosion of fertile land. In both cases
there is a loss of carbon fixing greenery and food producing
land.
- methane emissions from natural wetlands
and rice paddy field are increasing as temperatures rise.
Methane is a much more potent greenhouse gas than CO2 and
levels are rising rapidly.
This is a sample of the evidence; what about
the future?
The predictions
- Historic sea levels are well recorded in
the Bahamas and Bermuda because these islands have not been
subject to tectonic rise and fall. Ancient shore lines show
that, at its extreme, sea level was 20m (70 ft) above the
present level during an interglacial period 400,000 years
ago. This would occur if all the world's vast ice sheets
disintegrated. There is a serious risk of this happening
to the West Antarctic and Greenland ice sheets and their
loss would mean a 12m rise in sea level. (Geology, vol 27,
p375)
- The latest suggestion from Antarctic scientists
is that sea levels could rise by 6m (20ft) within 25 years.
(Reuters) Many millions of people live below one metre above
sea level. For example, Singapore and its reclaimed territories
will be at risk if the sea level rises above 20 cm. The
Thames barrage is already deemed to be inadequate. Hamburg
is 120 kilometres from the sea but could be inundated. The
mean high tidal water level has increase between 40 and
50 cm since the 1970s. In the UK rising sea levels threaten
10,000 hectares of mudflats and salt marshes. But the most
serious threat is to the 50% of the grade 1 agricultural
land which lies below the 5m contour. Salination following
storm surges will render this land sterile. The University
of East Anglia Environmental Risk Unit predicts that the
1 in 100 year storm and related floods will show a return
rate by 2030 for:
Milford Haven3.5 yrs
Cardiff 5yrs
Portland 5yrs
Newhaven3yrs
Colchester4yrs
- The geological record over 300 million yrs
shows considerable climate swings every 1-2000 yrs until
8000 yrs ago, since when the swings have been much more
moderate. The indications are that relatively small changes
led to massive outcomes - the butterfly effect. The danger
is that increasing atmospheric carbon to double the pre-industrial
level will trigger catastrophic change. There seems little
chance of avoiding such a build-up of carbon. The paleo-climatic
record shows that generally cooling occurred at a slow rate,
but that warming was rapid, for example 12 deg C in a lifetime.
- Global warming poses a serious threat to
health. Pests and pathogens are migrating to temperate latitudes.
It is already widely understood that illnesses like vector
borne malaria and Leishmaniasis (affecting the liver and
spleen) are predicted to spread to the northern Europe.
Other affects are less well known.
- A warmer atmosphere means greater evaporation
with a consequent increase in cloud cover. IPCC scientists
consider that the net effect will be to increase global
warming. Water vapour is a potent greenhouse gas.
- Historically relatively abrupt changes in
climate have been triggered by vegetation. For example,
average temperature rose by 5deg C in 10 years 14,000 years
ago. I mentioned earlier that the paleo-climatic record
shows that the explosive growth of vegetation absorbed massive
amounts of atmospheric carbon resulting in a severe weakening
of the greenhouse effect and a consequent ice age. Nature
could still be the deciding factor. The Hadley Centre forecasts
that global warming will cause forests to grow faster over
the next 50 years, absorbing more than 100 billion tonnes
of carbon. However, from about 2050 the warming will kill
many of the forests, thus returning the carbon to the atmosphere.
This will bring a high risk of runaway global warming.
- It is estimated that all the glaciers in
the central and eastern Himalayas will disappear by 2035,
which will be devastating for the populations that rely
on the great rivers like the Ganges which are fed by melt
ice. Another danger is posed by the rapid accumulation of
meltwater lakes. Meltwater is held back by the mound of
debris marking the earlier extremity of the glacier path.
These mounds are unstable and periodically collapse with
devastating results. It is predicted that the largest of
these lakes in the Sagarmatha National Park in Nepal currently
holding 30 million cubic meters of water will break out
within five years. (New Scientist p18, 5 June 1999) The
world-wide melting of glaciers and ice caps will contribute
33% of the predicted sea level rise (IPCC).
- We have to add to these natural events the
prediction that there will be a substantial increase in
world population, mostly in areas which can least accommodate
it. At present the greatest concentrations of population
are in coastal regions which will be devastated if sea level
rise predictions are fulfilled. The UN Population Division
estimates that the world figure will reach 8.9 billion by
2050 and will level off eventually at 11 billion. Even at
present 1.3 billion live in extreme poverty on less than
$1 per day, one third of the total world population.
It is difficult to avoid the conclusion that
there will have to be enforceable carbon limits imposed
on nation states with serious commercial and political penalties
for states failing to meet their obligations. There will
have to be a global shift from pure market economics to
eco-economics by 2025 if catastrophic consequences of global
warming are to be avoided. This inevitably brings us to
politics and international agreements.
Kyoto - the flawed
protocol
The Kyoto conference was the follow-up to Rio. It has still
to be ratified by many nations, but is it worth its weight
in paper?
At the last minute the US insisted that it
should incorporate a mechanism to enable states to buy the
right to pollute. A company can buy pollution rights from
another company which has cut its emissions above its agreed
target. So, the net effect is an improvement? Not necessarily.
Where are the industries most likely to have pollution credits
to sell? Russia and the Ukraine. In these countries since
1990 there has been a 30% cut in emissions due to the collapse
of heavy industry.
Yet the operative date for pollution levels
by nation is 1990 when Russia still operated its pollution
intensive industries. So, the US is purchasing the right
to do little or nothing about its pollution from countries
that have gone well beyond their targets due to economic
collapse. The effect of this has been to render useless
the anti-pollution laws in the US. It is dressed up as a
market solution but in effect negates the Kyoto agreement.
At the same time a country might obtain carbon
credits by growing trees either at home or funding them
abroad. This too is flawed since it is difficult to predict
the sequestration capacity of standing trees. Already the
US has used its financial muscle to outbid local farmers
for 14000 acres of rainforest in Belize. But this is not
new carbon fixing capacity. Commodity brokers predict a
market worth $ billions a year when it comes into force
in 2008. The prediction is that the US industry will be
able to generate enough credits to avoid 90% of its reduction
commitments under the Treaty. Yet the major part of this
will be spurious, based on purely paper savings.
Despite these machiavellian manipulations
the US congress has still refused to ratify the Kyoto treaty.
First Rio, now Kyoto have proved that there is no real will
to do anything about global warming that might harm industry
in the short term.
There should be no doubt in your minds by
now that the balance of probability is strongly in favour
of a continuation, even escalation of anthropogenic global
warming. Because CO2 survives in the atmosphere for at least
100 years the level we have already accumulated will lead
to appreciable climate change with its attendant social
and economic disruption. As scientists are now more seriously
embracing the doomsday scenario of runaway global warming,
there will have to be drastic action at all levels at least
to halt the inexorable rise in atmospheric CO2.
This accumulation of evidence should be of
special concern to all who have any kind of transaction
with buildings. The reason: because buildings in use or
in the course of erection are the biggest single indirect
source of carbon emissions. In industrialised countries
like the UK the in-use proportion is 46% of total CO2 emissions.
Add to this the carbon cost of construction and it exceeds
50%. There is no escaping the fact that it is not the energy
supply side but the demand side which offers the best opportunities
for significant reductions in CO2 emissions, and the built
environment within the demand side. This is the sector of
emissions in which things can happen relatively quickly.
And if we take the example of housing, tackling the problem
of its related emissions will result in a whole cluster
of interlocking virtuous circles. But that's a big subject
on its own.
PAPER 2: CONSTRUCTION WITHIN A CLIMATE
OF CHANGE
No other century has begun with such an awareness
of the potential for change and of the uncertainties that
underlie that perception. The best we can do is identify
the developing technologies and socio-economic trends that
are clearly discernible and extrapolate from them. There
are some predictions we can make with reasonable confidence
and consider the implications for architects and related
professions.
Climate Change
The first paper outlined the case for taking
seriously the prospect of severe climate disruption as a
result of global warming. It has now been confirmed that
1999 was the warmest year on record. A histogram produced
by the United Nations gives a snapshot of the core of the
problem, namely the disparity between the industrial and
developing countries in terms of carbon dioxide emission
per head. Despite Rio and Kyoto carbon dioxide emissions
from developed countries are showing little sign of abating.
The USA at twice the European average is still increasing
its emissions.
One purpose of this paper is to suggest how
global warming will trigger changes that affect architects.
Already the prediction that global warming will lead to
greater intensity and frequency of storms is being realised.
It is inevitable that, as heat is built up within the biosphere,
this results in the release of energy. The first paper contained
examples of the predicted rate of return of the 1 in 100
year storm as currently defined. Milford Haven headed the
list with a return rate of 1 in 3 years by 2030. In January
2000 winds reaching 125 mph were recorded in Scotland. The
immediate consequence for architects is that design wind
loads should be amended to cope with this progressive change
and the fact that buffeting will increase in intensity.
Another probability is that extreme heat episodes
with occur more frequently. This needs to be considered
when incorporating passive solar design and the design of
atria and conservatories. At present natural ventilation
and the omission of air conditioning is justified on the
grounds that cooling is only required for a short period
in a year. This may change and mechanical ventilation incorporating
ozone-friendly chilling will become a necessity. This will
also reinforce the case for installing ground temperature
cooling (c.12 deg C).
At the same time there are serious fears that
winters will become more severe due to the demise or re-routing
of the Gulf Stream. Much greater extremes of temperature
will have major design implications, both for the stability
of materials and the levels of insulation. As fossil fuel
prices rise, this will increase the appeal of active solar
heating and seasonal heat storage. One method is to install
water circuits just below the surface of tarmaced car parks
and access roads. The summer heat generated will be stored
in underground aquifers - natural or artificial.
The possibility of colder winters adds urgency
to the need to tackle the problem of the unacceptable numbers
of unfit homes in the UK. According to the 1996 English
House condition Survey, 4.3 million households are classified
as 'fuel poor'. Across the UK fuel poverty afflicts almost
8 million households, mostly inhabiting unfit houses. The
same survey states that 96% of all homes are below SAP 60
which is regarded as the minimum acceptable level of energy
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