There are several ways by which climatic change can be recorded and understood. Three of the most well known are quaternary subdivisions based on the terrestrial record, ocean sediment cores, and ice cores. These methods have been used in isolation and also in conjunction with one another. Of particular interest here is the growing body of data that has been collected from ice cores that is contributing to studies of environmental change and aiding correlations between polar, continental and ocean sediment records. ?The polar ice sheets and those of high tropical mountains are nourished by precipitation from the atmosphere, the composition of which is thus recorded as successive layers of ice accumulate. Such records provide information on environmental change over the past ca. 200K years and base line data from pre-and post-industrial levels for the biogeochemical cycling of metals such as lead.?
Over the past century, countless theories about climate change have been advanced and tested using the above techniques. First to be highlighted are those that look at climatic change as part of a system of internal adjustments within the climatic system. ?Several have emphasised changes in the quantity and quality of solar radiation, especially in relation to sunspot cycles…Currie?s (1995) identification of the 18.6 year lunisolar cycle and the 11 year solar cycles in Chinese dryness/wetness indices, for example.? Such phenomena have been associated with floods, draughts, poor harvests, and the like. A 1988 study by Labitzke and Loon made a connection between sunspot maxima/minima and quasi-biennial oscillation (QBO). ?The QBO is an oscillation of the zonal wind component in the stratosphere above the equatorial region with a periodicity of ca. 27 months.? Their study over a 36-year period pointed out a positive link between ?warmer winters during the Sun?s more active periods and between colder winters when the Sun is least active and when the QBO is in a westerly direction.? They found that the reverse conditions also applied. While this relationship has subsequently been criticised and generally disrespected, recent polar ice core samples have indeed shown correlations consistent with the study. Indeed, a 1990 study by Beer et al linked ?10Be deposition with the 11-year sunspot in Dye 3 ice core from Greenland. Beer et al. state that increased levels of 10Be occur when solar activity declines; and because the intensity of the solar wind is reduced there is an increase in the generation of cosmogenic isotopes such as 10Be and 14C.? Another 1990 study by Wigley and Kelly not only fortifies but also adds to these findings. ?Not only is there a relationship, albeit complicated by the effects of precipitation, between the 10Be in the Vostok ice core and temperature change, but there is also a possible relationship between the 14C concentrations and fluctuations in glaciers. The nature of this relationship and the way it varies have yet to be determined; for now, change in solar irradiance, alias sunspots cycles, remain as enigmatic as ever.?
Tree ring data has also been helpful in the study of natural climatic change. In addition to the variables just noted, there are researchers who believe that dust and sulphate aerosols, usually concomitant to volcanic eruption, mainly affect the quantity and quality of solar radiation that reaches the earth. ?The dust scatters and partially reflects incoming solar radiation whereas the aerosols act as cloud-condensation nuclei. Both cause reduced temperatures for short-lived periods unless the volcanic eruptions are very large.? Tree ring evidence has found that cool summers since the 17th century have indeed been primarily due to volcanic eruptions.
Volcanic eruptions can further influence climate by their pollution of the oceans. ?some of the dust will settle into the water body, providing nutrients such as iron and other cations, which may stimulate primary productivity in maine phytoplankton. Their uptake of carbon dioxide could reduce its concentration in the atmosphere and contribute to global cooling by diminishing the greenhouse effect.?
There can be little doubt that the combination of these, and various other factors, does induce a varying degree of cyclical climatic change. However, some suggest that none of them contribute sufficiently to create positive feedback that would effect changes in the magnitude of glacial-interglacial swing. ?It is now widely accepted that astronomical forcing, the Milankovitch theory, is the most important primary cause of Quaternary glacial-interglacial cycles and probably those of earlier geological periods….It is the change in the orbital eccentricity that is thought to drive the glacial interglacial cycle. These cycles influence the amount of solar radiation received at the Earth?s surface, especially in the high latitudes of the northern hemisphere.? However, these cycles have proven to have little effect on insulation. Other non-naturally occurring factors are therefore responsible for the climatic changes anticipated. Popular causes are the greenhouse gases, notably carbon dioxide and methane, whose changes in atmospheric concentration parallel global warming and cooling. Further, there may also be a relationship between ?ocean circulation, atmospheric concentrations of greenhouse gases and global temperature change. The production and dampening of North Atlantic Deep Water in particular is considered to be a mechanism whereby temperature change over the Arctic ice cap is translated into global change.?
Whatever the particular cause of climatic change, what interests many observers is how the changes will impact on human existence. It is reasonably safe to say that, in aggregate, the changes will be large and profound. Indeed, it is quite possible that human life and ecosystems in some parts of the world will not be able to survive. In all likelihood, the change is probably going to be a reasonably quick one, occurring perhaps within decades, and most certainly within a century. ?Across the globe, changes in temperature would be reflected, in complex ways, in the migration of rainfall patterns, with enhancement in some areas and drying in others. Short-term weather events might become more variable and severe and unusual storms occur more frequently. Forests, sensitive to temperature, might be severely damaged if the rate of warming exceeded the rate at which the forest species could migrate toward more suitable conditions, and such migration would be widely obstructed where other land uses stood in the way.?
Moreover likely is that the melting of the polar ice caps would cause the sea level to rise. While some credible arguments actually suggest that the sea level would decrease (due to increased precipitation in the polar regions), the mainstream logic does rather suggest a rise to the tune of several centimetres per decade. In time, this would surely flood very low-lying coastal areas, and increase erosion and stress on shorelines around the world.
This knowledge, however, is of little comfort or interest to most people. The only fact that can perhaps involve people and ease their tensions is knowing which particular locations will be affected, and how they can begin to prepare themselves. It is towards this difficult question that the following question turns.
VI. REGIONAL AND LOCAL EFFECTS OF CLIMATIC CHANGE
Making any specific or even generalised claims about regional and local climate changes is even more controversial than the effects of climate change at large. ?Existing lakes and inland seas do have some measurable effects on temperature and humidity in the ribbon of land along their shores, but no so large and so widespread as ordinarily to justify creating new ones as climatic generators.? The same type of controversy surrounds the desertification of land. Looking to the cases of the desertification of the middle east, northern Africa, and India, it is argued that ?overgrazing by livestock both raised the albedo of the surface and injected dust into the air; thus altering the regional heat balance by reflecting away more solar radiation. A net cooling from these processes then promoted atmospheric stability and suppressed rainfall; the vegetation withered under the lessened rainfall and more dust swirled upward, magnifying the original impact.? The example of the diminishing rainforests provides another good, though controversial, case. As has been witnessed in these regions to some degree, changing the earth?s physical landscape can have affects on microclimates.
Cities, too, have witnessed some significant climatic changes as a result of increased urbanisation. The well-known ?heat island? effect; i.e., a net elevation of temperatures above those found in the adjacent countryside, has been well documented. ?It stems particularly from changes in the land surface and the energy budget. Cities themselves generate much of the heat in which they bask or swelter. The roughness of the urban land surface retards the speed of the winds, and thus lessens the dispersion of heat; the impermeable and well-drained surface is less moist, and so less heat is lost through evaporation; and the structures and surfaces typical of the city absorb and retain heat at high rates.? This increased heat may in turn result in fog, storms, precipitation induced by convective heating and pollution condensation.
On a larger regional level, the distribution of species will be affected by climatic change, which is likely to have widespread consequences for human life. Agricultural pests will be displaced, and the incidence of ?disease vectors? through the spread of malaria carrying mosquitoes, for instance, will affect the health and well being of human populations.
Mannion makes the observation that ?areas of high altitude are those which have been most directly affected by the advance and retreat of glaciers and ice caps. Indeed, the Arctic and Antarctic zones are currently experiencing glaciations, and it is from these areas that much can be learned about glaciations.? Many others share this posit that higher altitude will be more affected, but how much more remains the question.
In sum, it must be said that ?the diversity of the earth?s surface translates into a diversity of physical impacts of global changes, different social impacts even of similar physical ones, different expectations of their impacts?which , of course, have often been wide of the mark?and different costs that any globally uniform change in behaviour would incur.? Based on this observation, it is quite likely that landlocked countries have nothing to fear in terms of rising sea levels, and areas that have traditionally experienced poor levels of rainfall may actually benefit from increased precipitation. Canada, however, as a nation that is very dependent on agriculture, forestry, and fisheries?and thus more dependent on climatic conditions?will likely be quite vulnerable to any climatic shifts. In general, however, it can be said that ?climate change may create opportunities for gain as well as for loss, but countries with different endowments of skills and capital will differ in their ability to exploit those opportunities.?
VII. CONCLUSION
As has been advanced throughout this paper, there is a considerable degree of uncertainty surrounding the climatic future of the earth. This, according to Mannion, ?highlights the complexity of the climate system and the inadequacy of current scientific understanding.? This vein of thought also ran through the Rio Earth Summit, which recognised the reality of global warming, but also the substantial scientific uncertainty with regard to its timing and magnitude. This lingering confusion has made the problem of global environmental change ?the largest single problem facing the world scientific community.?
But, while the precise impact of man?s footprint on the earth cannot be measured with great accuracy, there is no reasonable man who will argue that current rates of consumption are either beneficial or wholly necessary. Indeed, it is quite intuitive to conclude that increasing industrialisation and increased economic output is a step in the wrong direction, at least in terms of the environment?s well being. Given the state of present day research, it has reasonably been estimated that ?under a business as usual scenario of continued growth of fossil fuel use, and hence of greenhouse gas emissions, the global average temperature is estimated to rise at a rate close to 0.3C per decade?a rate which is probably greater than any that has occurred on earth since the end of the last ice age, some 10,000 years ago. Associated with the rise in global average temperature will be substantial changes in regional climate, especially in the intensity and frequency of droughts and floods.? Though impossible to prove, in aggregate it has been argued that the change will be large and greater than the earth has seen since the last ice age. If this is even close to the truth, it is very likely that human beings and the earth?s ecosystems will not be able to sustain the pace of change in their present surroundings. What will happen at the regional and local level, however, is much more difficult to predict though in some cases, will likely be even more devastating. From what has been shown in this paper, there is distinct reason to suspect that higher latitudes will experience greater overall warming than lower latitudes. If this is indeed the case, ?the release of vast stores of carbon from the tundra peat lands and boreal zone will reinforce global warming. Moreover, if there are further reductions in acidic emissions, which at current levels cause a counteracting effect, global warming will be accelerated.? Put simply, this is not a good thing.
Quantifying the extent of the potential damage is not only beyond the scope of this paper, but perhaps beyond human comprehension (at this point) and even worse, missing the point. The only certainty about future climatic change is indeed uncertainty of its extent. It might not be wrong, given such circumstances, to prepare for the worst.
The picture that this study has painted is, quite apparently, confusing and sombre. However, there is a faint stroke of optimism that can be added. E. G. Nisbet notes that ?despite our losses, we are intellectually and physically richer than any other generation of humanity. Our poverty is spiritual. It is well within our power to be optimists, if we can dispel the cynicism of the past decades. If we are optimists, most things are possible. The challenge to cherish the planet, to construct a new global economy, is far less than the challenge, in 1940, to defeat the last threat against human hope.? This strain of reasoning provides a welcome contrast to the depressing observation noted by Barrett at the opening of this study. And it is true, there is nothing to suggest that we are firmly locked into a future that is condemned. For the first time in history, it may well be possible for a balance to be found between man and nature.
BIBLIOGRAPHY
Archer, Eileen (1994) People and the Environment: Preserving the Balance, London: Association of Commonwealth Universities
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Mannion, A. M. (1997) Global Environmental Change: A Natural and Cultural Environmental History, New York: Longman Press
Meyer, William B. (1996) Human Impact on the Earth, Cambridge: Cambridge University Press
Nisbet, E. G. (1991) Leaving Eden: To Protect and Manage the Earth, New York: Cambridge University Press
Wackernagel, Mathis., Rees, William (1996) Our Ecological Footprint: Reducing Human Impact on the Earth, Philadelphia: New Society Publishers
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