In essence, scientific essays break down into three main sections: the introduction, the discussion and the conclusion.The introduction is analogous to the abstract that precedes most scientific papers. In the introduction, you should try to concisely summarise the key issues at stake and then sketch out how you plan to tackle these issues. Some authors use the phrase “in this essay I will….” (note that it is not sufficient to say, “in this essay I will answer the question”!) Rather, you should outline the lines of evidence that you will introduce and the argument that you intend to develop from this material.
The introductory paragraph can be a good place to include some basic definitions (see below). However, you also need to outline how you will tackle the question.
Below are some examples of introductions; two which could be improved, and three examples of good introductions. Review each and consider the pros/cons:
Q: How significant is volcanic activity in the context of the global climate system?
Volcanic activity, in forms such as magma eruptions, gas emissions and pyroclastic flows are a result of tectonic activity. Global climate is the combination of various meteorological elemental measurements, such as temperature, humidity and atmospheric pressure, on a worldwide scale. Wide ranging evidence shows that volcanic activity is extremely likely to be responsible for some changing patterns of climate on a global scale. This report will examine, using specific case studies, how volcanoes can affect the environment, the evidence behind this and how significant they are in comparison to other factors, such as anthropogenic CO2 emissions’.
In the example above, all the author does is to outline some key terms and say “this essay will answer the question”. Of course it will!
Note also how the ‘2’ in CO2 should be subscript. Small points like this can be disproportionately annoying to markers!
Q. Discuss the ways in which explanations of variations in sediment yield are scale-dependant.
Geomorphology must always be recognized as a dynamic subject matter, at no point remaining a passive framework, but instead describing a wide range of changeable processes that operate within a broad spectrum of conceptual bases (Summerfield, 1991). The landforms and processes conceptualized are palimpsests, continually being redrawn and redefined, prompting William Morris Davis in 1890 to apply a Darwinian evolutionary paradigm to morpho-geological study. He described the cycle of erosion theory as inevitably evolving, a continuous and irreversible process of change, producing an orderly series of transformations to the landscape (Chorley et. al., 1985).
All very interesting, but get to the point! The introduction does provide some context to the question, but don’t get too carried away with setting the scene.
The following examples are nice, concise introductions that define key terms, raise the main issues, and set out how the author is going to tackle the question:
Q: Discuss the ways in which explanations of variations in sediment yield are scale- dependent
Sediment yield can be defined as the total sediment outflow from a steam or river basin over a specific period of time (Knighton 1998) . Sediment yield is given as an average over a particular period of time but in fact varies significantly following individual storm or flood events . The quantity and type of sediment moving through a stream or river channel is as a result of denudation processes, and the extent to which these processes occur in certain areas can be greatly affected by several factors. These factors primarily involve the geology, topography, climate, vegetation and land-use of the catchment area in question. This essay will look at how these factors each contribute to and affect sediment yield. In doing this it will be possible to see that time and space are not simply passive frameworks within which processes occur, and instead can both be causes of change and variations in the relative significance of each of the above factors. This shows that looking at both temporal and spatial scale is of significant importance in determining and explaining variations in sediment yield (Chorley, Schumm and Sugden, 1984). The vast range of temporal and spatial scales often means that no one methodological approach or explanation is appropriate and that a range of scales, particularly spatially, need to be looked at in order to draw conclusions (Summerfield 1991).
Q: ‘Climate change during the Quaternary has been mainly driven by variability in the Earth’s orbit’ Discuss.
The Quaternary epoch encompasses the last 2.6Myr and is the culmination of 50Myr of global cooling. Despite this cooling being of a steady nature there is within it a clear signal of climate fluctuations with notable cyclicity. As has become apparent through the analysis of a wide range of climate proxies there have been 49 cold-warm oscillations to date during the Quaternary as periodic shifts from longer term glacial conditions switch to briefer interstadial phases of warmer and wetter conditions . It is this cyclicity which, for many, places changes in the Earth’s orbit as the primary means of climate change during the Quaternary. However it is not the sole driver and other forcing mechanisms undoubtedly have an influence. Climate change is driven by both internal and external forcing mechanisms, the latter including volcanic eruptions, changes in the solar output and anthropogenic influences; the former concerning changes in oceanic circulation, sea ice extent and tectonic processes. I will go one to assess the relative contribution of these other forcing mechanisms in relation to Quaternary climate change.
Q: Critically assess the assertion that oxygen isotope analysis above all else has revolutionized our understanding of Quaternary climate.
The Quaternary is the most recent geological period, stretching from the last 2.6 million years to the present day. It is the culmination of fifty million years of global cooling, dominated by lower temperatures and larger ice-sheets than previous geological eras (Lowe and Walker 1997). Different geological studies have concentrated on climatic fluctuations within the Quaternary ‘ice-age’ itself. Perhaps the most important discovery was the work of palaeoclimatologist Cesare Emiliani, and his reconstruction of oxygen isotope records using deep-sea sediment cores. These can be used to trace changes in global ice volume, and thus infer past climatic conditions (Shackleton 1978). The results opened a new window into the Quaternary, and the ocean floor has been defined the “Rosetta Stone of past climate” (Stringer 2006, p: 55). Nevertheless, oxygen isotope ratios remain a ‘proxy-record’ from which scientists can only infer an indirect image of past climatic variations •. This essay is a critical assessment of the importance of oxygen isotope analysis for the palaeoclimatologic reconstruction of the Quaternary. The first part will describe the geological information contained in the isotopic composition of both ocean-sediment and ice cores. We will then assess the limitations of the oxygen isotope record, and the inconsistency with other forms of geological data. Although it is an essential aspect of palaeoclimatology, oxygen isotope analysis alone cannot produce an accurate reconstruction of the Quaternary climate.
Activity: Comparing introductions
Below are three example introductions taken from genuine supervision essays. As you read each example, jot down a few notes on its effectiveness as an introduction to the question ' Explain the processes which drive global ocean circulation and discuss its relationship with meridional temperature distribution.'
Discuss with a friend if possible before accessing the feedback. The aim of this exercise is ultimately to strengthen your ability to reflect critically on your own writing by first evaluating other students' essays and then applying the same principle to your own. Consider how you might apply your supervisors' feedback to your next essay.
While the dynamic vicissitudes of the global ocean-atmosphere coupling system are complex, the basic principles behind them, while often over-simplified, can be explained in relatively simple terms. The interaction of the oceans with worldwide heat distribution is once again easier to over-simplify than it is to fully explain but discussed will be some of the major driving processes: the role of the thermohaline circulation, with reference to the West Antarctic and the North Atlantic Current, will be described and explained along with its interaction with surface winds, the Coriolis effect and temperature gradients caused by latitudinally-dependent solar heating. Their effects on meridional temperature distribution, in terms of trade winds, global continental structure and Ekman transport, will be further discussed and evaluated.
The global ocean circulation describes the movement of water through deep water, the thermohaline circulation, and surface currents around the oceans. Whilst the circulation of deep water is driven by contrasts in density resulting from differences in salinity or temperature, the primary driver for surface currents is the influence of the wind, which in turn is modified by the Coriolis effect. It is this which helps to determine the ocean surface circulation patterns. Water is transferred vertically through the depths of the ocean at areas of upwelling and subsidence. These processes connect the deep water flow to the surface circulation which together form what is often described as the ocean ‘conveyor belt’. The general purpose of the ocean circulation (in addition to the atmospheric circulation system) is to counter the latitudinal temperature imbalance that has been caused by differences in the level of solar radiation that are received at different latitudes. More solar radiation reaches and is absorbed by the planet at low latitudes than at high latitude, this can be seen through sea surface temperatures which range from -1.9°C near polar ice (at high latitudes) to over 30°C in July in areas of the Persian Gulf and the Red Sea (Linacre and Geerts, 1997) therefore there is a transport of heat from tropical regions to the poles. This essay shall examine each of the processes above, their role in the global ocean circulation and how they support the redistribution of heat between latitudes.
Global ocean circulation is ultimately the result of two forces: firstly, the radiation received from the sun, which accounts for the winds and density differences that drive most ocean currents; and secondly, the Earth’s rotation, which causes the appearance of the Coriolis force, which deflects currents and deviates them from their “natural” path. Ocean currents can, in their turn, be divided into two main categories: surface currents, which roughly follow surface wind patterns, and thermohaline or deep-water circulation, driven by density (and therefore temperature and salinity) differences.
Now click here to access feedback on each of the three introductions above.