The environment of the polar regions

The polar regions can be defined in a number of ways, based on geographical, topographic and even political factors. However, geometrically, the Arctic and Antarctic are considered as the areas of the Earth poleward of the Arctic and Antarctic Circles, which are located at latitudes of 66° 33′ 39″ north and south of the Equator (see maps on the end papers). These areas experience at least one day each year when the Sun does not set, and one day when the Sun is always below the horizon. At the poles themselves there is only one sunrise and one sunset each year, which occurs on the equinoxes of 21 September and 21 March. Together the Arctic and Antarctic comprise about 8% of the surface area of the Earth.

The regions of perpetual summer sunlight and winter darkness are present because the Earth is tilted away from the plane of its orbit around the Sun by 23° 27′, resulting in the high latitude areas having periods when they are orientated away from or towards the Sun. The tilt of the Earth's axis changes over long periods of time (millennia), resulting in variations in the latitude of the Arctic and Antarctic Circles. The change in the tilt, along with slow variations in the Earth's orbit about the Sun, alter the amount of solar radiation arriving at different parts of the Earth, which is a major factor in long-term, millennial-scale climate variability.

Introduction

In earlier chapters we have given a summary of our current understanding of past climate change at high latitudes and provided scenarios of how the climates of the two polar regions may evolve over the next century under different levels of greenhouse gas emissions. We are at a critical period in the study of the Earth's climate. Improved data sets providing insight into past climate variability are constantly appearing from new ice and ocean coring initiatives. In addition, we are getting superior observations from satellite systems that give us an unprecedented coverage of the atmospheric, oceanic and cryospheric conditions at high latitudes, which allow us to better understand the mechanisms that are important there. In recent decades our ability to model the environment of the polar regions has also improved. However, there are still many questions unanswered regarding the reasons for past and current climate change and significant doubt about what may happen over the next century.

Regarding future climate changes, perhaps the largest uncertainty is over how greenhouse gas emissions will change over the coming decades. With the release of the IPCC's Fourth Assessment Report, there has been a greater willingness to accept that human activities since the start of the Industrial Revolution, and particularly over the last 100 years, have altered the climate of the Earth.

The last few years have seen an unprecedented level of interest in the climate of the polar regions. The discovery of the Antarctic ozone hole, the reduction in extent of Arctic sea ice, the disintegration of floating ice shelves around the Antarctic and the high levels of aerosols reaching the Arctic have all been reported extensively in the media. This has been coupled with climate model predictions showing that the high latitude areas will warm more than any other region on Earth over the next century if ‘greenhouse gas’ concentrations continue to rise. Yet some have pointed to rapid climatic fluctuations that have taken place in the polar regions over the last few centuries and millennia and questioned whether the recent changes that we have seen are not simply a result of natural climate variability. Hence the time is right for a reappraisal of our understanding of recent high latitude climate change in the context of increasing anthropogenic influence on the Earth and our greater understanding of the reasons for past climate variability.

This book seeks to assess the climatic and environmental changes that have taken place over the last century and set these in the context of our understanding of natural climate variability in the pre-industrial period. We will draw on many of the new climate data sets that have become available in recent years and also make use of the results of modelling experiments.

Introduction

In this chapter we describe the main types of data available for the study of climate change within the polar regions. In comparison with most other regions of the Earth the time-series of ‘traditional’, in-situ instrumental observations is relatively short, particularly in Antarctica where most stations have only been operating for about 50 years. With short records it is more difficult to determine whether recent trends are significant, particularly for regions where there is high natural climate variability, such as the Antarctic Peninsula. One way of extending climate records is to use ‘proxy’ climate data; for example, the commercial whaling expeditions in both the Arctic and Antarctic provide historical data about the position of the sea ice edge, where the greatest amount of hunting took place.

The inhospitable nature of the polar regions means that conducting science in such areas can be very expensive. Thus, there are relatively few surface meteorological stations compared with the mid latitude and tropical areas. This is illustrated in Fig. 2.1, which shows the coverage of surface, ship and aircraft observations assimilated into the European Centre for Medium-range Weather Forecasts (ECMWF) model at 00 GMT 12 July 2010. In recent years advances in technology have allowed the deployment of autonomous automatic weather stations (AWSs) and these are particularly useful in the polar regions as they can be sited in very remote locations. The majority of the synoptic reports in Antarctica situated away from the coast are from such AWSs.

It is generally believed that the reduction of net emissions of carbon dioxide will be achieved more efficiently with tradable carbon credits than without. The subject is treated at length in Freestone (2009) and will not be explored here. The argument is that those organisations that can reduce carbon dioxide emissions or provide carbon sinks more economically than others will sell these benefits to others at a lower cost than the second party could produce the benefit themselves. This is a classic free-market argument.

This is supported by conventional economic discussion. However, the externalities are often neglected or ‘wrongly’ valued, and many socially undesirable consequences come from applying simple free-market concepts. Engineers in the future will take more account of externalities.

Just as there are climate models that, with the aid of many assumptions, predict the change in the global climate, there are global economic models that try and predict the change in indices such as GDP. The assumptions underlying these models are as uncertain as, or even more uncertain than, in physical models of the atmosphere. We would particularly like to identify the fact that assumptions must be made about social behaviour in the future. Predicting the reaction of people in the future must be considered most challenging, especially when one notes the social changes in large countries such as Russia that have occurred over the last few years.

Controlling the level of carbon dioxide in the atmosphere is a rapidly growing new commercial activity that did not exist a decade ago. It is predicted by Stern (2007) to rise in value to US$500 000 000 000 per year by 2050. This new activity is founded on the recognition that the threat of rapid climate change is a concern for future generations. Engineers are needed to exercise their skills to deliver economic solutions to this pressing problem. Greenhouse gases such as carbon dioxide trap heat in the atmosphere and their increasing levels threaten to bring about climate change. This is a global issue and its consequences are long term. At the same time, there is much uncertainty associated with a phenomenon that is not yet understood well enough to be reliably modelled.

Last century there was much political discussion on this topic, which culminated in the agreed text of the UN Framework Convention on Climate Change (UNFCCC). With the UNFCCC entering into force in 1994, the control of greenhouse gas concentrations in the atmosphere became an engineering problem. While debate continues both about the impact of greenhouse gas on climate and the role humans play in influencing its concentration, the engineer is faced with the less controversial questions of how to manage the uncertainty and how to control greenhouse gases at the least cost to society. The modern engineer must address the concerns of the populace and will need to engage with the economist and the social scientist.

In the previous chapter we looked at the concept of increasing the efficiency with which fossil fuels were used to produce work. However, this increase in efficiency will need to be taken up at an unprecedented rate under most of the scenarios discussed in Chapter 1 in order to stabilise greenhouse gas concentrations in the atmosphere. As an alternative, we could deploy technologies that emit near-zero greenhouse gas. This would also have the effect of reducing the carbon dioxide intensity.

About 20% of the world's primary energy at present comes from sources that emit no net carbon dioxide. Firewood is the largest component. Here carbon dioxide is extracted from the atmosphere by photosynthesis as the tree grows and is returned to the atmosphere during combustion. The primary source of energy for firewood is the sun, which radiates energy to the earth. The next most important low-emissions energy sources are nuclear energy and hydro-energy, which are about equal contributors to energy supply.

We need to recall the magnitude of the reduction in net carbon dioxide emissions required to stabilise the atmospheric concentration at some value. The emissions are shown in Figure 1.8. For example, if we assume the scenario IS92a is a business as usual scenario for the world without concern for greenhouse gas, then to achieve stabilisation of concentration at 550 ppm after 100years as per Figure 1.8, the world net emissions need to be held to about 9GtCyr−1 in 2030 and have a lower value thereafter.

The previous chapter discussed the 70% of the globe covered by the ocean, and in this chapter we consider the remaining 30% that is land. While the terrestrial ecosystem provides less than a tenth of the carbon storage of the ocean, it is about as active on a seasonal basis in terms of carbon flux in and out of the atmosphere. The upper 1m of soil contains some 2000GtC, while the present land vegetation stores about 750GtC, of which about 300GtC is stored above ground in forests. These are large stores of carbon which can be both enhanced as an alternative sink for atmospheric carbon or mobilised (unintentionally) to produce additional emissions. Most of the fossil fuel that is being burned to produce the rising atmospheric carbon dioxide came from the land. Remember that we estimated the recoverable fossil-fuel reservoir as 7000GtC. Logging of the forests for land clearance, and other changes in land use, add to the carbon dioxide emissions to the atmosphere at a rate of 2GtC per year. Vegetation grown for food is cycled once or twice a year and so does not hold much of the mobile carbon. In this chapter we will look at the three approaches to land storage of carbon.

The most direct approach is to pump compressed carbon dioxide into depleted oil and gas wells and this is already done for the purpose of recovering more oil. Aquifers can also be used.

Introduction

The Holocene is the period of approximately the last 11.7 kyr and covers the time from the end of the last ice age up to the present. It therefore includes the so-called anthropocene, which is the period when humankind has influenced the climate system. For most of this latter period there are instrumental meteorological records, and this era is dealt with in the next chapter.

The Holocene marks the return of warmer and more humid conditions after the cold and dry period of the Last Glacial Maximum (LGM) (see Section 4.2.5). The start of the Holocene coincided approximately with the end of the Younger Dryas event (12.8–11.5 kyr BP) (see Section 4.2.5), an abrupt return to cold conditions (stade) during the gradual warming at the end of the last Pleistocene glaciation. Temperatures derived from ice cores collected on the Greenland icecap (see Section 2.4.2) suggest that the transition to the Holocene was a rapid switch of mode, with the Younger Dryas ending abruptly over a period of about 50 years. However, in other parts of the world the transition was not so rapid.

The Holocene can be split into a number of stages, and in this chapter we will divide it into the Early Holocene (11.7–5 kyr BP), the Mid Holocene (5–3 kyr BP) and the Late Holocene (3 kyr BP to present) (see Table 5.1).

Greenland ice core data suggest that temperatures during the Holocene have been about 12 °C higher than during the Pleistocene.

The Kyoto Protocol is an international agreement linked to the United Nations Framework Convention on Climate Change. The major feature of the Kyoto Protocol is that it sets binding targets for 37 industrialised countries and the European community for reducing greenhouse gas emissions. These amount to an average of 5% against 1990 levels over the five-year period 2008–2012.

The major distinction between the Protocol and the Convention is that, while the Convention encouraged industrialised countries to stabilise greenhouse gas emissions, the Protocol commits them to do so.

Recognising that developed countries are principally responsible for the current high levels of greenhouse gas emissions in the atmosphere as a result of more than 150 years of industrial activity, the Protocol places a heavier burden on developed nations under the principle of ‘common but differentiated responsibilities’.

The Kyoto Protocol was adopted in Kyoto, Japan, on 11 December 1997, and entered into force on 16 February 2005. To date, 182 Parties of the Convention have ratified its Protocol. The detailed rules for the implementation of the Protocol were adopted at COP 7 in Marrakesh in 2001, and are called the ‘Marrakesh Accords’.

The Kyoto mechanisms

Under the Treaty, countries must meet their targets primarily through national measures. However, the Kyoto Protocol offers them an additional means of meeting their targets by way of three international market-based mechanisms.

Introduction

The climates of the polar regions are characterised by long periods of continuous sunlight in summer and perpetual darkness in winter that lead to large annual cycles in many aspects of the environment. The temperatures are very low in winter and only moderate in the summer because of the low elevation of the Sun and the highly reflective nature of the snow and ice surfaces. In fact the cryosphere is a major factor in defining the climates of the high latitude areas and the interactions of the ice and snow with the ocean and atmosphere will be discussed extensively in the following sections.

Many factors are responsible for high latitude climate variability and change, which can occur on a range of timescales. On long timescales, major changes in global climate are driven by orbital and solar variability. These affect the seasonal and latitudinal distribution of energy received from the Sun. Oxygen isotope data from ocean floor sediments indicate periods when the polar ice sheets were significantly more expansive than at present, particularly in the Northern Hemisphere (glacials) and when they were of similar size to the present (interglacials). Changes in the output of the Sun can result in high latitude climatic fluctuations with periods of reduced irradiance, such as the Maunder Minimum of the seventeenth and eighteenth centuries, being detectable in some aspects of the polar climates.