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Núm.
32 - september 2002
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Is
there a climate change? Biological
Symptoms of Climate Change The
Past is One of the Keys to the Future Resources
for studying climate change in Catalonia: An historic view Interview
with Richard Lindzen Editorial Views on Climate Change The Treaty on climate
change was one of the main benefits of the Earth Summit in Rio de Janeiro.
It springs to mind only a few weeks after the Johannesburg summit. This
document gave birth to the Kyoto Protocol, in which the principle nations
of the world became committed to reducing their greenhouse gas emissions.
The fact of the matter
has shown us that it is very difficult to implement the Kyoto Protocol
and that, within the European Union; some countries make efforts to do
their duty -Germany and Great Britain- while others really don't apply
themselves. The latter is the case of Spain. There are also sectors, such
as transport, which do not contribute to the reduction of greenhouse gases.
It is precisely these gases, emitted into the atmosphere as a result of human activities, that contribute to climate change. The subject of this issue is two-dimensional. One dimension is political and economic, since the current model of production and consumption aggravates the socio-environmental problem, while the other is scientific. It is worth mentioning that all scientists agree that the climate is changing, but while some attribute much of the responsibility to human activities, others argue that the climate is always changing and that the 0.5-degree increase in the planet's temperature over the past hundred years has more to do with natural variability -water vapour and clouds- than with man-made CO2 emissions. These are the diverse scientific views presented in this issue. The Chair of Physics at the Autonomous University of Barcelona (UAB), Josep Enric Llebot, gives us a review of the different attitudes towards climate change. Josep Peñuelas, researcher at the Centre de Recerca Ecològica i Aplicacions Forestals (CREAF) at the UAB explains how global warming is translating into significant modifications in the life cycles of plants and animals. The paleoclimatologist Antoni Rosell presents the main aspects of climate evolution over the past 500,000 years. Javier Martín Vide, Chair of Physical Geography at the University of Barcelona, goes over the tradition of studies on climate change carried out in Catalonia. These contributions are complemented by an interview with Richard Lindzen, Chair of Atmospheric Meteorology and Physics at MIT, Boston-Cambridge area. Professor Lindzen casts doubt on whether man-made greenhouse gas emissions contribute to climate change or not. A controversial perspective, no doubt. Finally, Ignasi Doñate analyses the Kyoto Protocol. Very different views, then, on a "hot" environmental problem. Lluís Reales
Is there a climate
change? Current thinking believes that human activities and today's life styles could notably alter the smooth running of planet Earth. The text looks at the scientific and socio-economic aspects of the controversy related to the climate. It wonders whether the climate really is changing, it reflects on the future and looks at whether the current situation is a threat or, in fact, an opportunity for new economic activities. The Dawn, the Sun and the Moon and the climate change In her book Relats
de mitologia. Els déus (1), Maria Àngels Anglada tells us
that Helios - the Sun, Eos - the Dawn, and Selene -the Moon were siblings.
The Sun drove a divine quadriga; four winged horses, in a golden chariot
that left the Ocean every day, in the east, crossed the vaults of heaven
and went back into the sea in the west. The Sun was so lovely that there
was not a nymph who refused to be his lover, and so he had a multitude
of children. Phaëthon was the son of Helios and Clymene, a daughter
of Oceanus. When he was an adolescent his father, on seeing him so handsome
and strong, promised to grant him a wish, Phaëthon asked him to let
him drive the Sun's chariot. Helios saw with concern that his son could
not manage the quadriga, but a god could not go back on his word. The
result was worse than even he had expected. Phaëthon knew nothing
about how to drive and control the chariot of flames and in the wild path
the four winged horses took him on, he dropped too close to the earth
causing fires in the forests and drying up rivers and lakes. Zeus, finally,
seeing the imprudent action of the runaway chariot, sent a saving thunderbolt,
killing Phaëthon. This story from Greek mythology tells us, in a
poetic and also exaggerated way, about the importance of the sun in the
climate system. Two thousand years after this story was imagined, Melutin
Milankovitch (2) suggests that the periodical variations of the characteristics
of the orbit of the earth around the sun were the cause of climate changes
in past eras, as if trying to justify, through the complicated compositions
of heavenly mechanics, what was represented in classical times by the
sun's chariot. However, it was not
until about seventeen years ago that we started to acquire a more or less
generalised form of awareness of the consequences of human activities
on the global behaviour of the atmosphere. Between autumn 1984 and spring
1985, articles by S. Chubachi (3) were published, corresponding to the
observations at the Japanese base at Syowa, and by Farman, Gardiner and
Shanklin (4) at the Halley Bay station, on the content of the stratosphere
in the Antarctic. The two teams of atmospheric scientists showed that
the content of ozone in the Antarctic stratosphere dropped spectacularly
between September and October. The fact that this phenomenon was measured
just above the continent that is furthest from the areas on the globe
where the majority of pollutants are emitted, produced, initially, signs
of scepticism, but soon after, once the measurements had been confirmed
and the phenomenon had been understood, it caused great concern. For the
first time there was evidence of a global environmental problem: the emission
into the northern hemisphere of chemical compounds known generically as
CFCs used in numerous consumer and industrial applications were spreading
throughout the atmosphere until they reached the stratosphere, and in
the Antarctic where, in spring, the low temperatures and the dynamics
of the atmosphere produced complex chains of chemical reactions, they
ended up eliminating the stratospheric ozone. As a result of the
scientific discovery and the importance of the problem, numerous groups
of scientists from around the world started to research the problem. There
was a great amount of activity and numerous congresses and meetings were
held to discuss and present the results of the latest pieces of research.
One point worth mentioning is that despite the fact that the phenomenon
had been measured with scientific instruments at the time, there had already
been information available from satellites on the levels of ozone in the
Antarctic, for some years, but nobody had studied it. At the same time,
given the global dimension of the problem, the political representatives
of the governments of the countries met under the auspices of the UN,
to act against the problem and what we know today is that they reached
an agreement to limit the production and consumption of the chemical compounds
that were causing the problem, signing the 1987 Montreal Protocol, which
was extended, according to the increase in knowledge of the problem, in
later agreements. As a result of this, we can now say that the problem
of the stratospheric ozone is fairly well known from the scientific point
of view, and that politically there are international agreements that
have been drawn up with the aim of alleviating the problem. Therefore, the role
that the fast irruption of the ozone problem had on public opinion is
a paradigm: since then, there has been a change in the social conception
of environmental problems and their scope. Although there is still a more
direct perception of the local dimension of many environmental problems,
the possibility that human activities could significantly alter the function
of the planet is present in current thinking. While the conversations
that led to the Montreal Protocol were taking place, the World Meteorological
Organisation and the UN were preparing the setting up of the Intergovernmental
Panel on Climate Change (commonly known as the IPCC). The IPCC was finally
constituted in 1988, and since then it has been an important reference
point as far as scientific knowledge is concerned, as well as the impacts
of the climate change and of the actions of adaptation and mitigation
regarding this phenomenon. Therefore, in some ways, the IPCC represents
the opinion of the experts on the climate change associated with human
activities, their impacts and possible strategies of mitigation and adaptation.
The IPCC reports are used by those who are politically responsible as
a reference point for discussion and the eventual drawing up of international
treaties that try to deal with the problem of the climate change. When we talk about climate change today, we refer to the climate change on earth related to the effects of the emissions into the atmosphere of certain gases that are produced as a result of the activities of modern society. It does not refer to the climate changes that have occurred throughout the geological history of the earth, although knowledge of them is an important tool for getting to know the current climate and its development. It is also known as global warming, as the warming of the atmosphere is the first effect that the greater presence of greenhouse gases in the atmosphere seems to be producing. In this article, we intend to give a brief summary of the current state of the problem, basing it on a series of questions. The controversy associated with the climate change due to human activity has two aspects that are mutually related: the scientific and the socio-economic and political aspects. Traditionally, there was great emphasis on the first, as what was needed was to get to know the problem and its implications well, but at the same time as suggesting the actions to be taken it entered straight into the social, economic and political dimensions of our world that represent the starting point for any solution. The beginnings: what is the climate and what do we understand by climate change? An intuitive definition
what the climate is, can be resumed by saying that it is the average weather,
in other words, an average of the most important meteorological variables
that characterise meteorology: temperature, rainfall, humidity, etc. On
defining a time average, however, we must state the periods of time for
which it is calculated: days, weeks, months or years. Meteorology, therefore,
corresponds to knowledge of instantaneous weather, in other words, the
behaviour of the atmosphere for a period of less than ten days, whilst
climatology studies the average behaviour of the climatic system on time
scales that are greater than ten days, but that are normally seasonal
averages, or yearly ones or even averages for longer periods of time.
In fact, it is precisely this characteristic of climatology, regarding
the knowledge of the average weather that has meant that, until very recently,
it has not been a discipline of interest in the scientific community (5).
If we take a look
at recent history, the first person to talk in the current sense about
the question of climate change was Svante Arrhenius(6), a Swedish physical
chemist awarded the Nobel Prize, who in 1896 presented the Physics Society
of Stockholm with a document in which he argued that a reduction or an
increase of 40% in the concentration of carbon dioxide, a gas present
in very small concentrations in the atmosphere, could provoke disturbances
in the function of the climate which would explain the advance or withdrawal
of the ice fields. Arrhenius formulated a model that was simple but that
calculated the reflection of the radiation by the earth's surface and
by the clouds or the retroactions produced by the layer of ice and snow
in such a way that, taking into account current knowledge, we now consider
it to be naive or even maybe mistaken. Arrhenius (7) concluded that the
variation of the CO2 content and of the water vapour of the atmosphere
has a great influence on the energetic balance of the climate system.
He reached this conclusion after carrying out calculations without the
help of any mechanical instruments, or obviously, electric ones and he
did between 10,000 and 100,000 operations by hand, corresponding to what
we know today as different aspects of CO2 emissions. He also carried out
calculations for the four seasons of the year and tried to discriminate
the effects of the increase of CO2 depending on latitude. In the conclusions
to his work, we can read "...if the quantity of carbon increases
in geometric progression, the temperature will increase in arithmetical
progression". Arrhenius also worked out that the variation in temperature
would be greater in relation to a greater quantity of carbon dioxide,
that temperature would increase more if the latitude was greater and in
addition, that the increase would be greater in winter than in summer.
Overall, Arrhenius worked out that if the atmospheric content of CO2 doubled,
there would be an increase in temperature of between five and six degrees
Celsius. Luck and chance meant
that Arrhenius' predictions are very similar, from a quantitative point
of view, to the results obtained by current sophisticated climate models.
Probably, the consideration of the Swedish scientist as the person who
started the study of the climate change, is also due to this similarity.
However, Arrhenius would share an advanced vision with current experts,
as he did not just talk about the effects of the increase of carbon dioxide
on the physical system, but also about its environmental impacts. His
positivist view of progress together with the perspective of a person
who lived in a country subjected to the rigours of a long, hard winter
would have made him think about the positive impact of a less rigorous
climate that would probably facilitate the movement of certain agricultural
practices to higher altitudes, alleviating, to a degree, the deficit of
food at that time. If we take a huge
leap in time, research into climatology during the first half of the 20th
century was of interest to few scientists. It was only after the development
of the automatic weather forecasting systems during the second half of
the 20th century and particularly during the last quarter of the century,
that people started to think about methodologies for predicting the climate.
The climate system was defined in a document drawn up by the GARP (Global
Atmospheric Research Programme) of the World Meteorological Organisation
in 1975, as the system formed by the atmosphere, the hydrosphere, the
cryosphere, the lithosphere and the biosphere8. Later, the framework convention
of the United Nations on the climate change, signed in Rio de Janeiro
in 1992, which was also mythical because of its environmental matters,
and that started functioning in March 1994, defined the climate system
as the atmosphere, the hydrosphere, the biosphere and the geosphere and
their interactions. Whilst both definitions are obviously very similar,
the second emphasises the interactions. The atmosphere, the sun, the oceans,
the surface of the water, the surface of the ice and snow and the set
of plant life and other living beings in the ocean and the continents,
are closely related to each other, exchanging energy flows and material,
which makes it difficult to achieve a complete understanding of its function.
We also often assess the climate in an excessively simple way, asking ourselves how the temperature or the level of the sea will change. The answers that we try to give from the perspective of the climate model however, are also related to more social aspects of housing and of sustainability answering questions such as "Will we be able to breathe the air"?, "Will there be enough water for drinking and for agriculture?", "Will the environment be comfortable enough?". To be able to answer these questions, we do not only need to know the function of the climate system but also to draw up scenarios of development of the socio-economic system, in other words, to clearly establish the relations between the climate system and human society. The concentration in the atmosphere of the gases that cause the greenhouse effect increase and as a result of this, is the climate changing? The common characteristic
of the gases that cause the greenhouse effect is their ability to absorb
long-wave radiation emitted by the Earth. The number of these gases is
very great. However, in practice the ones that are analysed in detail,
given their radiational significance, are just six. On the whole, the
emissions of these gases are increasing, although there are some that
are decreasing. Apart from water vapour, of the greenhouse gases that
are most directly influenced by human activity, the most important ones
are carbon dioxide, methane, ozone, nitrous oxide, sulphur hexafluoride
and chlorofluorocarbons (CFCs). Other atmospheric components that also
need to be taken into consideration are aerosols, particles in suspension
in the atmosphere, of different sizes, of a natural origin and products
of combustion, the role of which is not totally clear in climate development.
On the whole, the emissions of gases and of aerosols into the atmosphere
grow in relation to the growth of the economy. Economic wellbeing traditionally
leads to high emission rates, and, on the other hand, economic crises
are characterised by fewer emissions.
Carbon dioxide in
the atmosphere, for example, has been measured since 1958, when an observatory
was installed in Mauna Loa, in Hawaii, an instrument that since then has
continually registered the content of this gas in the atmosphere. If you
look at the Keeling curve in figure 1, you will see that without a doubt,
the amount of carbon dioxide in the atmosphere increases year after year.
This trend is common in the case of most of the gases that are responsible
for the greenhouse effect, which currently have concentrations in the
atmosphere that are greater than in pre-industrial times (9). Therefore, the fact
that most greenhouse gases increase thanks to human activities is not
questionable. However, there is some uncertainty about where all the CO2
emitted into the atmosphere actually goes, as the amount that is measured
in the atmosphere is approximately half the amount that is emitted into
it. Nor is it totally clear what the global effect of aerosols is, in
particular sulphates and soot. It is thought that their ability to reflect
solar radiation creates a softening effect of the greenhouse effect, as
they act as a shield from the sun's radiation. It has also been observed
that the rate of growth of emissions is decreasing, in other words, it
is not growing as was expected. This could be the result of the transformation
of many systems of electrical energy production, of the transformation
that goes from the use of coal to other fossil fuels with fewer carbon
emissions and to the transformations of certain agricultural, stockbreeding
and industrial practices. To be able to affirm
that the climate is changing, we need to refer to the study of data from
the networks of stations that measure the temperature of the earth. The
instrumental register of the temperature in earth stations and in boats,
leads us to conclude that the global surface temperature of the air increased
by between 0.4 º and 0.8 ºC during the 20th century. The trend
of warming is general throughout the planet and is consistent with the
retreat of ice fields, the reduction of the snow area and the faster rhythm
of the increase in the level of the sea during the 20th century compared
to the last thousand years, for example. Phenomena derived from the warming
that, corresponding to biological systems, means an integration of the
changes of different climate variables, such as the lengthening of the
period of growth in some plant species, the earlier flowering and the
later falling of leaves, the northward movement of some species of butterflies
and towards higher areas of some species of trees and the arrival before
expected of some migratory species, have been observed and documented.
It also seems that we can confirm that the surface water of the ocean
has heated by 0.05 ºC over the last fifty years. The most significant
changes, however, were produced in the Polar Regions, especially in the
northern hemisphere. The analysis of data provided by the declassified
information from Russian and North American submarines, show that the
ice in the Arctic has become thinner since the middle of the 1970s. Information
from satellites also shows that the concentration of ice over the Arctic
in the summer has reduced by about ten percent. In the same way, the variation
of the temperature has not been uniform throughout the whole globe, nor
for all the years. The greatest warming occurred before 1940 and after
1980 to the end of the century. However, the northern hemisphere experienced
a slight cooling between 1946-75 and there are areas in which this cooling
was very evident, especially in the east of the American continent. The reasons for this
interruption in the warming are not clear. One possible explanation is
the increase in aerosols, which we mentioned earlier, as a result of the
use of coal as a fuel with a high sulphur content. To these, we can also
add natural causes, such as the variation of the luminosity of the sun
or volcanic eruptions that took place during this time. The IPCC report10
compares the average warming produced during the 20th century with other
disturbances in the climate from the past. To make this comparison, they
use instrumental data that covers the last two hundred years, together
with assimilated data that comes from the analysis of the rings of trees
and the study of air bubbles in the ice in Greenland. The results of the
analysis show that the warming we experienced in the 20th century was
probably one of the greatest in the last millennium. However, this statement
must be interpreted with care: the best data available has been used but
it is irregular in its distribution over time and space and therefore
the degree of confidence it provides in the statement above is relatively
small. Another question is
to find out whether the change in temperature is due to human causes or
not. The aforementioned IPCC report, attributes, with a high level of
confidence, the reason for the warming to the growth of the atmospheric
content of greenhouse gases, and in addition, it shows simulations of
numerical models which have managed to separate, over the last ten years,
the natural variability and the variability related to human activities
that are, obviously, very significant. Critics of these statements show,
and not without reason, that there is still a great degree of uncertainty
in the knowledge of the magnitude of the natural variability. It is said
that by doubling the amount of carbon dioxide in the atmosphere there
would be a radiational forcing of 4 wm-2 (of 2% with regard to the total
radiation that reaches the surface), a quantity that is very small compared
to the effect that the connection between the warming and the content
of water vapour from the atmosphere and cloud cover could have. Therefore,
they sustain that up until now it has been impossible to relate the climate
change observed to anthropogenic emissions, as there is a lack of precise
knowledge of the natural variability. How much and in what way will the climate change during the 21st century? To be able to project
for the near future about what the magnitude of the climate change will
be, requires on the one hand, knowing with a good deal of confidence the
function of the physical environment, in other words, having a reliable
model, and on the other hand, being able to project with precision what
the future emissions of greenhouse gases will be, and what the development
of the carbon sinks, in other words, how the use of the land, agricultural
and stockbreeding practices, forestry, etc. will change in the future.
Whilst we currently
have fairly reliable models, as far as the knowledge that includes the
functioning of the physical environment is concerned, the second aspect,
the emissions and the development of the carbon sinks, is a challenge
that has many imprecise aspects. In fact, the emissions have, up until
now, been related to variables of a current economic and demographic nature
linked to previsions that enable us to have a view of the development
of the world economy over the next ten, twenty or fifty years. However,
we do not know what the structure of energy production, industry or transport
of societies in the future will be. These uncertainties are, therefore,
too important to consider the results that are obtained from the models
as predictions on which the future climate can be based. To be able to compare
the different models, the IPCC has drawn up future emissions scenarios
based on forecasts made by the World Bank or the UN on demographic growth
and world economy. These scenarios contemplate a wide range of assumptions
on future economy and technological development. There is no need to mention
the huge number of uncertainties that exist regarding economic growth,
lifestyles, the use of different ways of producing energy, the growth
of the population or future technological changes. It is based on these
scenarios, and in particular on average forecast scenarios, that the graphs
mentioned below should be understood. A useful scenario
to use is the one that assumes a growth of emissions over the next 20
years of 1% a year and that stipulates that until 2050, the emissions
of greenhouse gases will be established at current levels. In the current
context, it is as if we were considering a minimum situation. In this
scenario, the temperature would increase by 0.75 ºC in 2050. If we take into account
the scenarios used by the IPCC, it envisages that in 2100, the temperature
of the atmosphere will have increased by between 1.4 ºC and 5.8 ºC,
which would be the greatest warming over the last 10,000 years. In addition,
all the models say that the difference between the minimum temperatures
and the maximum temperatures would decrease and that, on the whole, the
minimum temperatures would be higher, thus reducing periods of extreme
cold. On the whole, it is also thought that the rainfall would increase,
although its distribution over time and space would be different. In our
country, for example, it would seem that rainfall would increase in the
winter, however, in the summer, on the other hand, periods of drought
would be more intense and frequent. The models also envisage a general
decrease in the area covered by snow and ice, as well as an increase in
the level of the sea, mainly due to the dilation of water as a result
of the warming, of between 0.09 and 0.88 metres. This general behaviour
should not make us believe that everything will change in a uniform way
or in the same way. The climate variability we mentioned above is not
just a manifestation in time but also according to regions. There is proof
of the co-existence in past times and within a few hundred kilometres
distance, of opposed trends of natural variation of the climate. This
fact is also the case in climate disturbances of an anthropic origin.
In a short period
of time, agriculture and the forests would benefit from the fertilisation
of carbon dioxide and the increase in the temperature and the rainfall.
Regional studies are scarce and still not very conclusive. Nor is there
a univocal trend for all kinds of crops and activities. The optimum conditions
for some crops would change and, often, significant adaptations would
be needed at regional levels. In the same way, the relation between the
time scale of the regional climate change and the time that is characteristic
of the evolution and adaptation of the species would be important. The
effects on pests and plant diseases of the climate change are not completely
understood and therefore, on a regional scale, and long-term, there is
still a great deal of uncertainty and a lot more studies are needed. Some models project
the trend, in semi-dry regions, towards an increase in periods of drought.
It seems likely that the amount of snow on the mountains would decrease
and that the snow would melt as a result of the atmospheric warming, which
could affect the water balance and important aspects associated with the
availability of fresh water. At the same time, the increase of rainfall
in the winter, and the hypothetical increase of periods of heavy storms
could produce problems in controlling floods and changes in the habitats
of plants and animals. Another important
aspect to be considered is the impact on health. The increase in temperature
would, without a doubt, influence the frequency and transmission of infectious
diseases, the effect on the population of heat waves and cold spells and
obviously on the air and water quality. However, the guidelines these
changes could produce are unknown. The variations of the temperature and
the rainfall would lead to changes in the habitats of the organisms that
act as vectors transmitting diseases (mosquitoes, rodents, etc.) It would
seem likely, that if there were a lower frequency of certain cold spells,
certain types of mosquito could survive, that under current conditions
do not do so. Some studies envisage a possible incidence of the malaria
mosquito in the south of the Iberian Peninsula within 10 years because
of this. The same can be said about the impact of heat waves and cold
spells. Cold spells would have fewer effects, as they would be less frequent,
whilst there would probably be more periods of extreme heat, which could
produce health problems in people who are particularly sensitive. In any case, the weather
is an important factor. Each of the above-mentioned processes has its
own dynamics and in no case is it felt that there will be abrupt processes
or changes. The adaptation of the natural systems to environmental changes
could be gradual and the success or failure, or the vulnerability or sensitivity
of a system will depend on the time it needs to adapt to the changing
environmental conditions. Not all the changes will be negative. As Arrhenius
forecast, the changes in the environmental conditions will be favourable
for some processes and unfavourable for others. For example, whilst the
changes of climate in the Mediterranean region could have a negative effect
on the productive cultivation of certain cereals in a negative way, on
the other hand, it will probably favour the growth of vines and olive
trees, which are crops of great importance at the moment. This means answering
the question of whether there is a threshold concentration of greenhouse
gases in the atmosphere, above which there would be catastrophic changes
in the function of the climate system or whether we are sufficiently aware
of the consequences of warming due to the increase of greenhouse gases
in such a way that the scientific community is able to define an acceptable
concentration based on the analysis of potential risks and damages. One way of answering
these questions is to observe what has happened in the past. Palaeoclimatology
offers data about the variation of atmospheric CO2 during past periods
of time in the geological history of the earth. About fifty million years
ago there was between three and nine times more carbon dioxide in the
atmosphere and it would seem that it was much hotter than it is now. For
example, it would seem that there was abundant life in the Polar Circle
or that the temperature of deep water in the sea was high. In addition,
periods with sudden variations over thousands of years of atmospheric
carbon dioxide have been found, also related to changes in temperature.
Of these oscillations, there are some in which the hot periods exceeded
the magnitude of the most radical projections of climate models. These
changes are sometimes associated with the extinction or redistribution
of species, but in no case with a complete disappearance of the biosphere.
The development of
the future climate will depend on the nature of climate forcing, in other
words, of the content of the greenhouse gases and the sensitivity of the
climate system. Therefore, determining a sustainable concentration of
greenhouse gases depends on the capacity to determine the sensitivity
of the climate system as well as the exact knowledge of the factors of
the forcing, and of risks and vulnerabilities. In addition, as has already
been mentioned, the climate would change with a marked regional character
and whilst all the models envisage a global increase in the temperature
and rainfall, their distribution in time and space vary from area to area
of the globe and from model to model. Therefore, with the knowledge we
currently have of the climate system, it is difficult, if not actually
impossible, to establish an atmospheric concentration of greenhouse gases
in which the risks and impacts are related in a balanced way to the technological
and economic efforts to achieve it. In addition, the latter
factors are not uniform for everyone. The problem with the climate change
is different depending on whether one sees it from the perspective of
a city in the European Union or the United States, with good technological
and economic ability to adapt to changes, or from the point of view of
an Eskimo who depends on the ice field for his food, or an inhabitant
of the Maldives, a set of 1600 coral islands, for whom the extension of
his country depends on the rising of the sea level. Therefore, considering
a realistic and pragmatic point of view, the action when faced with climate
change includes two kinds of fundamental actions: the mitigation of the
causes and the adaptation to the new climatic conditions. The mitigation
consists of decreasing the emissions: it is clear that under current conditions,
the technology is available for stabilising the atmospheric content of
carbon dioxide to 450 ppm, 600 ppm or 1000 ppm. Defining the level is
a question of an economic nature and of political and social desires.
With regard to the adaptation, this means preparing for the changing conditions,
from the point of view of economic activities, with the adaptation of
infrastructures, etc. Both strategies, adaptation and mitigation, will
be vital in order to alleviate the phenomenon. The only international agreement on reducing emissions that has been made to date, the Kyoto Protocol, still waiting to be ratified, establishes commitments that are the results of agreements between states, the ones that make up the so-called appendix B, that questions the technological ability to reduce emission and adapt itself to the economic cost this would involve. There are no scientific considerations for the reduction proposals, or what amounts to the same thing, the scientific recommendations were far removed from the ceiling of the reductions proposed. Greenhouse gases remain in the atmosphere for a long time, in other words, they degrade with difficulty. This means that the actions that are taken will have long-term effects, over tens or hundreds of years. This is an important coincidence with other environmental problems, such as the degradation of the stratospheric ozone content to which we referred at the beginning of the article. The time scale of the origin of the disturbance is very much smaller than the time scale for the system to recover. Therefore, it is important to apply the precautionary principle, which consists in acting now, although there are still no complete certainties about the magnitude and scope of the phenomenon. What we do know, however, is that any action will have to be maintained for a long time and that it will come into effect far beyond our generation. This is a complication that is added to the management of the problem. Climate change, an opportunity for new economic activities? To be effective, the
actions for alleviating climate change must be economically feasible but
there are also new business sectors that are currently starting to develop
as a result of the actions of mitigation and adaptation, which hope to
become economically feasible. The development of these sectors would be
a good tool for reducing the problem of climate change. Examples of these
sectors are the companies dedicated to the development of alternative
energy, such as the renewable ones, mainly wind and solar, or ones that
work on the use of hydrogen as a fuel, and that study methods of generation
and storage or develop fuel batteries or even those that are making renewed
efforts to rekindle the generation of nuclear energy. There are also incipient
economic sectors linked to the reduction of emissions, such as the actions
of buying and managing forests. In fact, forests and plants exchange huge
amounts of CO2 with the atmosphere. Plants collect CO2 through photosynthesis
and when they breathe, they release oxygen and a part of the absorbed
CO2 . As a whole they retain carbon in the form of organic matter. The
storage of carbon by plants is increasing as a result of the practice
of reforestation or as a result of the changes in crop waste management
practices. In Catalonia, and in many other developed countries, abandoning
agricultural areas has, on many occasions, led to their transformation
into forest areas, with the corresponding fixing of atmospheric carbon.
The management of these and other areas in third countries subject to
being managed, precisely for their ability to retain carbon dioxide, can
represent a business opportunity if an international emissions market
is finally established. We have talked a great deal about carbon sinks and about the trading of emissions as alternatives to the reduction of emissions, especially within the framework of the Kyoto Protocol. The difficulties regarding its use, are not so much knowing whether they will really be useful for absorbing or retaining carbon dioxide, but concern the ability and the confidence of having systems for measuring and checking the quantities of carbon dioxide absorbed or not emitted. Only if this point is resolved, will the mechanisms for reducing emissions, that are so tame for some, the only ones possible for others, be able to be put into operation, and then actions will be started on the greenhouse gases in the atmosphere. Conclusion The attempt to offer a panoramic, brief view of some of the points that characterise the analysis of the possible climate changes, should not hide the fact that there are still considerable areas in which important questions are being made in which we need to improve knowledge and foster research into it. On the one hand, we need to maintain and increase the observational network and promote the development of studies that reconstruct the climate of the past as indispensable elements for understanding its current variation. We still need to understand, both globally and locally, what the contribution of the natural variability and of the anthropic variability is to the climate changes, which would lead to an improvement in the models and predictions at a local level. Thus, the incorporation of clouds and a precise knowledge of the carbon, water and nitrogen cycles would also improve the capacity to predict climatology. However, there will still be a lack of ability to predict the future socio-economic growth of our societies that, after all, is the essential element for being able to predict the development of the future climate. Despite all these elements, in no way can we adopt a hopeful attitude. The problem exists and we need to act on it as quickly and effectively as possible. The advantage is that most actions that intervene to alleviate the problem of greenhouse gas emissions into the atmosphere are actions that, in absolute terms, manage the resources better. In fact, improving the efficiency, using renewable energies, correctly managing agricultural and stockbreeding activities are examples of actions that reduce the emissions, but in absolute terms, even if the problem of climate change did not exist, it would be positive to carry them out.
1 - Maria Àngels
Anglada: Relats de mitologia. Els déus. Edicions Destino, Barcelona,
(1996) |
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The Past is One
of the Keys to the Future From Palaeoclimatology -he study of the climate of geological and historical periods before the invention of meteorological equipment- the author describes the main aspects of the development of the climate over the last 500,000 years. He also shows how the climate changes without human intervention and also offers a historic perspective of more recent changes that are related to human activity.
All these questions
are difficult to answer. The reason is that we really know very little
about why the climate is changing. More to the point, we understand even
less the reason why we have the climate we have anywhere in the world.
I mean knowing precisely why, for example, the average temperatures in
Barcelona, or on the planet, aren't 2, 5 or 10 degrees higher or lower,
as they have been over several periods of the Earth's recent past. Or
why are Greenland and Antarctica almost completely covered by ice in such
a seemingly permanent way, when it hasn't always been like that? Or why
is the Sahara now a desert, when it wasn't over 6,000 years ago? Or why
is there a phenomenon like "El Niño" every few years,
when the temperatures in the ocean around Peru increase with consequences
that are felt around the world? Or why do we breathe air with a certain
quantity of greenhouse gases, and not half or double the concentration,
as it was thousands or millions of years ago? In other words, since the
Earth was formed, what has led the planet to be the way it is now, especially
to have the climate it has now? And if the climate has changed without
the help of humans, why can't it continue to do so? In fact, the climate
surely will change, but exactly why or when it will change is not fully
understood. In the words of Winston
Churchill: How the Paleoclimate is Studied First of all, what
is climate? Simply, the average weather in a certain spot on the planet.
Or, put another way, the weather we should expect over a month, year,
decade, century, etc. For example, variations in temperature, atmospheric
pressure, humidity, wind, precipitation and other meteorological variables
over the past 50 years in Catalonia would define the climate of the region.
Changes in the values of these variables yesterday, or last week, do not
represent changes in the climate; rather they are variability in the atmosphere
or the weather. It is worth distinguishing between a variable that characterizes
the climate, such as temperature, and a factor in climate change, or forcing,
such as the composition of greenhouse gases in the atmosphere. Changes
in temperature give us signs that the climate could be changing. Changes
in atmospheric carbon dioxide do not necessarily indicate a change in
the climate. The relationship between cause and effect must first be established.
One way of doing so is to look at the relationship over time of variables
that characterize climate directly (i.e. temperature), or indirectly (i.e.
the presence of ice in the continent depends in part on the temperature,
but also on variables such as precipitation), with factors of change such
as the composition of the atmosphere. Due to the fact that these types
of measurements have been taken for only a few years, the time series
available are too short to show real variability in the climate, especially
for the whole planet. By studying the climate of years past, thousands
or many millions of years, we can extend these time and space series,
and we can also try to search for eras analogous to the current one, and
see how the variables of the climate system have been evolving while diverse
factors of change have varied. For example, 400,000 years ago, during
the so-called isotopic stage 11, conditions of the climate system are
believed to have been very similar to those of the current period. Alternatively,
an attempt can be made to identify a period of the past in which values
for carbon dioxide were the same or higher than current levels, in order
to see what the values of climatic variables were in greenhouse worlds.
It is believed that these conditions have occurred several times during
the Phanerozoic period (the past 550 million years), the last of which
was probably during the transition between the geological periods of the
Paleocene and Eocene Epochs, about 57 million years ago. Now then, this is
easier said than done, because it is very difficult to reconstruct past
climates, especially in a quantitative way. It's fine to know that in
the last glacial period it was colder than now (its maximum was 18,000
to 24,000 years ago), but it is more useful to inquire into how much colder
it was in different areas of the planet, since not all of them respond
in the same way to factors of change. For example, a volcanic eruption
in the area of the Equator could contribute to cooling in both hemispheres
of the Earth due to the effect of the aerosols that are formed, scattered
about and reflected by sunlight. However, if there is an eruption in Iceland,
to a great extent it only affects the Northern Hemisphere because, due
to atmospheric circulation, volcanic aerosols do not reach the Southern
Hemisphere. Quantitative paleoclimatic reconstruction is, in fact, a very
new research field that has developed rapidly since the seventies. Because
devices measuring temperature, humidity, etc. were invented a relatively
short time ago, indirect methods had to be found (proxies) in order to
estimate these variables in the past. What is first necessary is to find
a temporal record from which some sort of climatic information could be
extracted, such as marine or lake sediments, which have been constantly
deposited over thousands or millions of years. But studies are also done
on the growth rings of trees, coral, glacial ice and ice caps, among other
more or less exotic materials or deposits. In my opinion, the prize for
imagination is taken by a study for measuring chlorine isotopes in fossil
urine remains from rat lairs in the Nevada desert in the United States,
in order to reconstruct changes in cosmic rays, used to date sedimentary
records (Plummer et al., 1997). It must be said that
the further back in time you go, the harder it is to study, because it
gets more dificult to find continuous valid records from which to interpret
properties in a precise way, for example, due to the dynamics of Earth,
which eventually destroys paleoclimatic records while creating new ones.
This means that, although the Antarctic has been covered in ice for many
millions of years, the maximum age of this ice is no older than a half
a million years, due to glacial dynamics, which makes the ice cap remain
in constant movement until it ends up in the ocean. Marine sediments are
also eventually "destroyed" or transformed in the subduction
areas of continental margins. Many large lakes have also been formed "recently",
such as the Baikal Lake in Siberia. Its sediments are probably no morer
than 25,000,000 years old. Furthermore, the older the samples studied,
the harder it is to date them precisely. The most widely used and most
precise method, carbon-14 dating, is applicable for dating samples containing
carbon, obviously, but for ages no older than 55,000-60,000 years. There
are diverse techniques for dating older materials, but they either do
not measure absolute dates, or their margin of error makes solving climate
changes possible for less than a few thousand years. Comparatively, the
margin of error of the carbon-14 method is around a few dozen years. Paleo-reconstruction methods also have intrinsic limitations. For example, one way of reconstructing air temperatures is to associate annual plant distribution and their pollen with climatic regimes and the Earth's dominating temperature margins. If an old pollen sample is analyzed, then an attempt is made to relate its composition to a similar current distribution in some area of the planet, and deduce from there the most likely temperature values where the plants producing this fossilized pollen lived. Nevertheless, when you go far enough back in time, there comes a point where no plant found on the planet today existed. Climatic proxies often respond to more than one environmental variable. One of those most used is the measurement of the relationship between the amount of oxygen isotopes (expressed as d18O) in carbonate skeletons of marine organisms. This measurement fundamentally represents two combined climatic signs. One is a local sign, which is the temperature of the ocean in which the analyzed organisms lived. The other is a global sign, which is the volume of continental ice and, therefore, the level of the ocean. So in interpreting data, both effects must somehow be resolved. This also means that another key point is that reconstructions are approximate, with margins of error that are sometimes unknown. For example, it is difficult to understand how ecological relationships can affect the distribution of pollen in a certain place, or how this pollen moved from the plant that produced it to the place where it was deposited, such as the bottom of the sea. Therefore, it is very important in paleoclimatic studies to use more than one paleoreconstruction method in order to confirm the results from one technique or another. Lastly, it must be kept in mind that the climatic variables reconstructed are mostly of a local scope. Changes in temperature in Harare, Tarragona or New York will usually be quite different, due to the location of these cities on the planet. This means that many records from around the world must be studied in order to get a precise idea of global climate changes. On the other hand, changes in carbon dioxide or in sea level do take place simultaneously, to practical effects, in a global way, since gases in the atmosphere mix relatively quickly, and of course seas and oceans are for the most part interconnected. Stability over the last 1,000 years and warming in the 20th century The past few years have provided great advancement in our understanding of the "global" evolution of changes in air temperature over the past 10 centuries. A study of reference is that done by Mann and colleagues (1999) shown in Graph 1, obtained thanks to the combination of temperature data derived from the study of tree rings, ice cores, coral and historic documents, as well as thermometers for the past 140 years (see others at http://www.ngdc.noaa.gov/paleo/recons.html). It seems quite clear that temperatures in the 20th century, in the northern hemisphere, were the highest in the past 1000 years, with the decade of the nineties being the warmest of all, and 1998 the warmest year of the millennium. Furthermore, the magnitude of warming in the 20th century is unique during this period (0.6 ± _0.2°C), especially during the periods from 1919 to 1945, and from 1976 to 2000, when temperatures increased at a rate never before experienced, at least from the 11th to the 19th centuries. Data for the southern hemisphere before 1861 (from which time there were instrument measurements) are very scarce and, therefore, it is not quite known how temperatures evolved from the year 1000 in the southern half of the world. The record from Graph 1 has become emblematic, and the Intergovernmental Panel on Climate Change (IPCC) mentioned it in their last report in 2001 (IPCC, 2001).
Why is this warming happening? It is not entirely clear, but it is likely that it is not caused by one single natural or man-made factor. Changes in the climate can happen due to internal variability of the climate system and to external factors. The influence of external factors can be compared by using the concept of radiative forcing (energy radiating from a factor of change). This would be positive if it makes the Earth's surface warm up, or negative if it makes it cool down. Changes in the increase in the concentration of greenhouse gases, solar energy, vulcanism and the concentration of atmospheric aerosols affect radiative forcing in a positive or negative way. For example, the concentration of greenhouse gases (see carbon dioxide in Graph 2) in the atmosphere during the past 1,000 years has increased in the past 200 years in a way similar to that of the temperature in the northern hemisphere (Graph 1). This increase reflects the progressive use of fossil fuel in our society. Greenhouse gases have a positive effect on the increase of radiative forcing. Therefore, in the past 200 years, there could have been a progressive increase in the capacity of the atmosphere to absorb energy from the sun, which could have led to the gradual warming of the planet's surface. But it must be said that there are many other factors of change that have also varied over this same period. For example, the concentration of aerosols in the atmosphere has increased in an analogous way to temperature, caused by the progressive use of fossil fuel and biomass combustion (i.e. woods, rubbish) (IPCC, 2001). Its effect on the climate, however, is to cool the surface, although this is less well understood than greenhouse gases, making it difficult to judge its relative weight in climate change. Since we are just beginning to understand the relative influence on radiant energy of diverse factors, it is difficult to demonstrate in a conclusive way that the warming of the 20th century is due only to the increase in carbon dioxide and similar gases. For example, with mathematical models simulating variations in the Earth's temperature, and comparing the results with changes that have been measured, the causes of the main changes can begin to be glimpsed. The IPCC's 2001 report makes special mention of a study that mathematically simulated the variability of temperatures over the past 140 years, taking into account only factors of natural change (solar variability and vulcanism), or only man-made factors (greenhouse gases and aerosol estimates), or both (Crowley, 2000). In some ways their conclusion is not very surprising: by including man-made factors in the model, a large part of temperature changes in the past 140 years can be explained, but the correlation between the results of the model and real temperatures is even better if natural as well as man-made factors are taken into account. Furthermore, they conclude that although the factors of change considered can explain most of the changes, the possibility is not excluded of their being others that also contribute to warming in the 20th century. And so the debate continues, especially in order to clear up the relative weight of different factors of change and the mechanisms by which they act on the system. For example, by how much exactly does the temperature increase when the carbon dioxide content in the atmosphere is doubled? Or how do ecosystems respond to changes in the climate and the composition of the atmosphere?
Instability over the past 400,000 years Regardless of natural
change, the IPCC predicts that average global temperatures will increase
between 1.4 and 5.8°C from 1990 to 2100. If this is the case, the
rate at which temperatures are foreseen to rise will be unparalleled in
the last 10,000 years. This is a geological epoch called the Holocene
Epoch, in which humans are having our golden age. Climatically speaking,
however, this period of time is quite unusual since it has been and continues
to be very stable and long. Some have noted that this climatic stability
is relative, and that there have been significant changes, so that human
civilizations have been able to flourish or have failed depending on whether
environmental conditions have been favorable or not (deMenocal, 2001).
The norm in the climate system is change and instability. Changes in local
or global temperatures of 2 or more degrees, on slow time scales (over
thousands of years) or very rapid ones (within which is the average life
span of a person or a couple of generations), have been very frequent
until now, and nothing leads one to believe that in the future things
will be any different. By studying fossil records, on any time scale,
it becomes quite clear that the Earth's climate is anything but stable.
This statement would have been heatedly debated a few decades ago. The study of ice cores in the Antarctic and Greenland, together with the detailed analysis of marine and lake sediment with high levels of sediment accumulation, revolutionized our way of understanding climate evolution. First, to prove the close relationship between an abundance of greenhouse gases and the climate on scales of thousands of years, and second, to reveal the frequency with which episodes of abrupt climate change occur, on scales of less than a century, which is a subject discussed in the next section. The ice in ice caps is, in fact, frozen atmosphere. In Antarctica, there are traces of the atmosphere from almost that last half a million years (Graph 3; Petit et al., 1999). In Greenland, recovered ice cores "only" go back 110,000 years. In part, this is due to the fact that it snows there more, which gives the ice records in Greenland higher resolution, making it possible to measure annual variability in the composition of the atmosphere. In records of the atmosphere of Vostok (in reference to the Russian station where samples were taken) in Antarctica, the highest values for greenhouse gases (carbon dioxide and methane) are found during the interglacial periods, and the lowest during the glacial periods (Graph 3). The correlation between values of methane and carbon dioxide with temperatures in Antarctica (estimated by measuring the hydrogen isotope ratio of the ice) suggests there is a close link between these gases and the climate, and it demonstrates the dynamics of oceanic and continental carbon sinks in response to climate changes. However, it is still not well understood how greenhouse gases interact with the climate system. The concentrations of gases increase for thousands of years before the great ice caps totally or partially melt. So it is not entirely clear whether it is the change in the greenhouse gases or sunshine, or both, which instigates passage from a glacial to an interglacial epoch and vice versa. Whatever the initiating mechanism, it is not clear either what makes methane and carbon dioxide fluctuate naturally over thousand-year scales. In any case, in the current context of the increase of greenhouse gases, Graph 3 clearly shows that current concentrations of carbon dioxide are the highest of the past 420,000 years and, therefore, without precedent in nature in all this time. The concentration of carbon dioxide is currently 365 ppm, while maximums over the last three interglacials did not exceed 300 ppm, even though values reached in epochs analogous to the current one are around 280 ppm, the same as pre-industrial concentrations of this gas. At the current rate of growth of the carbon dioxide content in the atmosphere, within a few years, the increase in this gas since the 19th century will have exceeded the increase observed between glacial epochs (200 ppm) and interglacials (280 ppm) by far. In reference to methane, its current values (1600 ppb) are already double the normal interglacial values (700 ppb), and its growth since the pre-industrial era has more than doubled (900 ppb) the normal growth from glacial maximum to interglacial (350ppb). Therefore, even though the consequences that may arise from this are not exactly understood, or they cannot be proven, it is not unusual that so many people around the world are worried about the growing level of greenhouse gases.
Surprising changes: for the climate, 2 plus 2 don't always make 4 One of the most widely known paleoclimatologists at an international level (Wallace Broecker, from Columbia University in the United States) has said that the mainly inoperative behavior of our society towards the increase in greenhouse gases is like "poking the angry beast with a stick" (http://www.earthinstitute.columbia.edu/library/earthmatters/spring2000/pages/page7.html). The stick would be the emission of greenhouse gases, and the beast would be the climate system: no one knows when or how it will react, but sooner or later it will. So, while scientists like Richard Lindzen of the Massachusetts Institute of Technology believe that concerns of global warming are a passing phase, according to some climate models (see his testimony b |
