Seán McDonagh reminds us that climate change is the most serious issue facing us. If we continue with a business-as-usual approach in relation to our use of fossil fuel, we will have set in train planetary changes like the melting of the Greenland ice sheet, which will make the world a more inhospitable place to live in for each succeeding generation.
200pp. Columba Press 2006. To purchase this book online, go to www.columba.ie
1. The Atmosphere
2. Climate Change and Extreme Weather
3. Climate Change, the Oceans and the Living World
4. Responses to Climate Change
5. The Kyoto Protocol
6. Is Nuclear Power the Solution to Global Warming?
7. Energy Efficiency and Renewables
8. Peak Oil and Transport
6. How the Churches have Responded to Global Warming
Websites on Climate Change
The atmosphere of planet earth is about 100 kilometres deep. The bulk of the gases which make up our atmosphere are found in the first five to ten kilometers. This very thin layer of gases sustains all life on earth. Energy from the sun, which is crucial for all life, reaches the earth through our atmosphere. If there was no atmosphere, life, as we know it, would not exist. The average temperature of the earth without its atmosphere would be around minus 18 degrees celsius. This would be too cold for life to thrive. It is because of the protective mantle of the atmosphere that the average global temperature of the earth is around plus 15 degrees celsius. (l)
The atmosphere also creates our climates, our clouds and our winds. The clouds produce rain which is a key element in our hydrological system, linking the atmosphere with the oceans. There are four distinct layers in the atmosphere. Starting at ground level, the troposphere extends 12 kilometres above the surface of the earth. It contains 80% of the gases in the atmosphere. The most important thing about this region of the atmosphere is its temperature gradient. This means that it is warmest at the bottom and cools by 6.5 degrees celsius at each kilometre above the ground. Above the troposphere we find the stratosphere. In contrast to the troposphere the stratosphere gets hotter as one moves up because it is rich in ozone which traps ultraviolet energy. The mesosphere lies 50 kilometres above the earth. The temperature here is minus 90 degrees celsius. It is the coldest part of the atmosphere. Above the mesosphere lies the thermosphere which consists of a very thin layer of gas. (2)
Glacial periods, followed by shorter warm periods, have been a feature of world climate history for at least two million years -long before human activity could be blamed for bringing about climate change. During the last period of glaciation, which began about 120,000 years ago, much of Ireland was buried under one kilometre of ice. In some places the ice was so heavy that it pushed the earth’s crust down into the mantle. Since the ice melted 12,000 years ago, the rebound of the earth’s crust is still happening in some places.
Scientists point to three naturally occurring phenomena which account for these regularly recurring warming and cooling periods. The first phenomenon flows from the fact that the earth’s orbit is more elliptical than circular. This means that, at certain times, the earth is closer or further away from the sun and this consequently impacts on the earth’s climate. This means that the intensity of the sun’s rays which reach the earth are markedly different throughout the year. Normally there is only a 6% difference in the sun’s radiation if one compares the figures.for January and July. When the orbit is fully elliptical the difference can range from 20% to 30% which is quite considerable. This phenomenon takes place about every 100,000 years.
The second phenomenon is related to the tilt in the earth’s axis of rotation. This tilt is normally at 23.4 degrees but can vary from 21.8 to 24.4 degrees. This cycle determines where the sun’s radiation falls and it takes 42,000 years to complete.
The third and final phenomenon is associated with a ‘wobble’ in the earth’s rotational axis which occurs every 22,000 years. During this cycle the axis of the earth shifts from pointing to the polar star to pointing to a star called Vega. This affects the climatic intensity of the seasons, bringing mild summers and harsh, cold winters.
These three natural cycles are called the Milankovitch cycles after the Serbian scientist Milutin Milankovich who was the first to use these naturally occurring phenomena to explain how ice ages and warm inter-glacial periods come about naturally. His theories were not well known because he wrote in Serbian. His writings did not become available in English until the 1960s.
One of the most interesting aspects of the Milankovitch cycles is that, even when they are synchronised, the annual amount of solar radiation reaching the earth may be less than one tenth of 1 % yet, it seems that such minute changes can stimulate the beginning of an ice age. (3) If we take these three processes working together, the earth’s climate should at this point in time be moving out of a warm inter-glacial period back into an ice age.
Sunspots can also affect localised climate changes. A lack of sunspots is now thought to be responsible for the cold spell which hit Europe during the late 17th and early 18th centuries causing rivers like the Liffey and Thames to freeze regularly in winter. This period is known as the Maunder minimum, after the scientist who first drew attention to it. (4) Some scientists claim that a cessation of sunspots activity could temporarily cause the earth to cool. But they are quick to point out that it will only be a respite from the ravages of man-made climate changes. (5)
Human Induced Climate Change
However, there is now a consensus among scientists, especially those involved in the Intergovernmental Panel on Climate Change (IPCC), that the current warming of the planet is due to human activity. This is specifically attributed to the burning of fossil fuels over the past two centuries since the beginning of the industrial revolution. John Tyndall, a British physicist was the first person to do any significant research in this area. In 1859 he designed a machine called a spectrophotometer to study the heat trapping properties of various gases. He discovered that oxygen and nitrogen, the gases which comprise most of the atmosphere, are transparent to both light and infra-red radiation. He also found that gases like carbon dioxide and methane, though found in much smaller quantities in the atmosphere, trap infrared heat. Tyndall realised that it was these gases that were responsible for determining the earth’s climate. If these gases were not present, the average temperature of the planet would be around minus 18 degrees celsius. But because of the presence of the earth’s protective mantle, which includes carbon dioxide, methane and other heat-absorbing gases, the average temperature of the earth is plus 15 degrees celsius which makes the earth very suitable for living organisms to thrive.
It took almost forty years for the Swedish chemist Svante Arrhenius to build on Tyndall’s work. He asked whether the carbon dioxide which the industrial world was spewing into the atmosphere was adding to the carbon already there and what the consequence of this might be. In 1894, he set out to calculate what might happen to the earth’s temperature if the level of carbon dioxide doubled. Living in a time before the advent of calculators or computers, he spent one year working on the calculations involved in the project. Finally, in December 1885, he produced a scientific paper for the Royal Swedish Academy of Sciences. His basic findings were that if the carbon levels in the atmosphere doubled the earth’s climate would be affected and mean temperatures would rise gradually. He estimated that it would take 3,000 years of burning coal to double the concentration of carbon dioxide in the atmosphere.
During the following seven decades little work was done by scientists on whether human activity, especially burning fossil fuel, was changing the global climate. Some argued that the oceans would become a sink for any extra carbon in the atmosphere. Most scientists assumed that in recent earth history the proportion of gases in the atmosphere was more or less constant. However, great strides were made in forecasting weather, though usually in a fairly restricted area and forecasts were for shorter periods of time, no more than a day or so in advance.
Research on climate over the past 50 years has added significantly to our knowledge about climate change. Scientists have better sources of data. This data originates from satellites, ice-cores, seabed samples, weather records and dendrology, in addition to the data from the network of weather stations around the world.
One important source of knowledge is gleaned from the ice sheets which are found in both the Arctic and Antarctic regions. Scientists can now take samples over one mile deep from ice-sheets and discover all kinds of information about past climate patterns. These ice cores can tell scientists the percentage of the various gases in the atmosphere at any time during the past 400,000 years. This research has undermined one accepted tenet of climatology which is that climate change happens very slowly. One incidence of this is the rapid climate change which happened 12,000 years ago called Younger Dryas. This is associated with the beautiful artic plant called Mountain Avens (Dryas octopetala) which is found in the Burren region of Co Clare. The earth, which had been warming for the previous few thousand years, was snapped back into a very cold spell during the Younger Dryas which lasted 1,200. (6)
Temperature data can be gleaned from the composition of the ice sheet and the ratio of gases to each other in the small air bubbles that are found in the ice. Such data is pointing to the fact that the earth is almost as warm now as at any time in the past three and a half million years, a period known as the mid-Pliocene warm period. The ice cores tell us that for the past 10,000 years, right up to the beginning of the industrial revolution 200 years ago, the average parts per million (ppm) of carbon dioxide in the atmosphere was 280ppm. However, measurements taken at the Mauna Loa observatory in Hawaii in 1958 by Dr Charles Keeling and his team found that there were 315ppm of carbon dioxide in the atmosphere. In 2005, it was 378ppm and rising by 2ppm each year. It is estimated that there has been a 35% increase in carbon dioxide since the beginning of the industrial revolution (7) It is projected that by 2050 it will be over 500ppm.
Special Scientific Institutes such as The Goddard Institute for Space Studies (GISS) in New York are providing other tools which are deepening our understanding of how climate operates and what are the dynamics of climate change. GISS is an outpost for NASA and began as a planetary research station. Today one of its main functions is to provide information about climate. The 150 scientists at GISS work on different aspects of climate forecasting. They study the oceans, global vegetation, the atmosphere, the movement of clouds and rainfall patterns. The results of these studies are expressed as mathematical formulae which can be fed into a supercomputer. Their recent climate change model, based on the results of their research, is called Model E. It has 125,000 lines of a computer programme. This is just one of the computer climate models in operation today. There are 15 other computer models in various parts of the world, like the Postdam Institute Impact Research in Germany. Institutes like these provide much of the data for UN’s Intergovernmental Panel on Climate Change (IPCC). (8)
In order to test the accuracy of these models in predicting the future of climate, the researchers run them backwards to see if the findings match the actual weather patterns of the past, which are determined from other sources such as written documentation, dendrology, ice cores etc. The climate model at GISS factored in data from the volcanic eruption at Mount Pinatubo on the island of Luzon in the Philippines in 1991, which injected over 20 million tons of gas into the atmosphere. This condensed into tiny sulfate droplets which reflected sunlight back into space. Model E’s calculations about the impact of this event on the global climate came within 900th of a degree of accuracy. (9) This is very accurate indeed.
Recent research on Arctic seabed samples indicate that 55 million years ago the climate was much warmer and had a year round average temperature of 74 degrees celsius. Scientists claim, from their analysis of the seabed samples, that until now the scientific community has underestimated the potential of heat-trapping gases to warm the Arctic. By examining the seabed samples the scientists can now understand the various cycles of heating and cooling that have occurred over the last 45 million years. This study would seem to support the theory that the cold and hot periods in climate history are as a result of greenhouse gases primarily. (10)
What has brought about the recent changes in the percentage of the various gases in the atmosphere? During the past two centuries and a half, humans have begun to utilise fossil fuel in a more extensive way. Initially coal was used to power the beginnings of the industrial revolution in England, Continental Europe and latterly the United States. After the discovery of oil in the 1880s, oil gradually replaced coal, primarily because it is more versatile. It was also the preferred fuel for powering the internal combustion engine in cars, trucks, trains, airplanes and ships. Natural gas, most of which is methane, is now used widely in industry and for domestic use. It will probably be the most important fuel in the early part of the 21st century.
As the 20th century progressed, particularly after World War II, human beings began to use more and more hydrocarbons as they bought cars and used fossil fuel to generate electricity. In fact there was a sixteen-fold increase in the burning of fossil fuel in the 20th century (11) As more and more fossil fuel was burned the change in the percentage of gases in the atmosphere became more pronounced and the atmosphere began to heat up.
A study carried out by scientists from the University of East Anglia in Britain found that the late 20th century was the hottest period in the northern hemisphere since the year 800 AD. The scientists used data from a variety of sources including tree ringdata, ice cores, the chemical composition of sea shells, and historical documents in this study. Dr Timothy Osborn, co-author of the study, wrote ‘the 20th century stands out as having unusually widespread warmth, compared to all the natural warming and cooling episodes during the past 12,000 years’. (12)
The reason why global warming is called the ‘ greenhouse effect’ is simple. Most of the solar radiation is absorbed by the earth’s surface. Some is reflected back and is dissipated into space. However, some long-wave radiation is captured by greenhouse gases like carbon dioxide, methane and others. These gases act like the glass in a greenhouse and retain the heat. All of the above are part of the normal global processes, which regulate climate conditions and maintain the warmth and moisture that are essential for life. As long as the percentages of the various gases in the atmosphere remain more or less constant, an equilibrium is established which ensures the continuity of the present living world.
There are a number of other gases responsible for climate change besides carbon dioxide (CO2). These include methane (CH4), nitrous oxide (N20), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexofluoride. Methane is produced by fossil fuel extraction, cattle farming, rice growing, landfills and more recently by melting permafrost. The average life time of methane in the atmosphere is about 12 years. This means it has a much shorter life time than carbon dioxide.
Nitrous oxide is a minor greenhouse gas. Its concentration in the atmosphere is O.3ppm and, its present level is about 16% greater than in pre-industrial times. However it has a long atmospheric lifespan of around 115 years. (13) Its main sources are from agriculture, the chemical industry and the burning of fossil fuels.
Chlorofluorocarbons or CFCs are synthetically created chemicals which were widely used in refrigeration because of their safety and versatility until it was discovered in the 1970s that they were destroying the ozone layer of the atmosphere. Once released into the atmosphere the chlorine can take 5 years to reach the ozone layer. Once there it attacks and destroys the ozone. In 1985, the British Antarctic team lead by Joe Farman discovered that ozone had been stripped from huge areas of the atmosphere over Antarctica. Since ozone absorbs harmful ultraviolet radiation from the sun, ozone depletion would have enormous consequence for human welfare and the natural world. The serious nature of ozone depletion was recognised by many governments in the early 1980s and it led to the signing of the Montreal Protocol in 1987. CFCs are also greenhouse gases. Even though they have a miniscule presence in the atmosphere a single CFC molecule has 5,000 to 10,000 times more global warming effect than a carbon dioxide molecule.
Since the Montreal Protocol, CFCs have been replaced by other halocarbons, and hydroflurocarbons. Neither of these chemicals contain chlorine or bromine and therefore do not destroy the ozone layer. Their global warming effect is also much less than CFCs but if they continue to be manufactured in increasing bulk their impact as global warming gases will increase.
Under every current scenario put forward by the Intergovernmental Panel on Climate Change (IPCC) the average global temperature is expected to continue to rise. They estimate that the increase in surface temperatures will range between 1.4 and 5.8 degrees celsius over the 21st century. In May 2006, researchers at the Centre for Ecology and Hydrology in Britain, claimed that these figures are conservative estimates by at least 2 degrees celsius. According to Peter Cox, the director of the Centre, the initial calculations were made on the basis of the well-known fact that carbon dioxide warms the planet by insulating it like a blanket. What is less well known is that as the earth warms more carbon dioxide is released from both soil and oceans, thus increasing further the amount of carbon dioxide in the atmosphere. The knock-on effect of this is a further warming of the earth. (14)
Even if the changes in temperature are to be kept at the lower level of the scale, we still need to understand the dynamics of climate change, its potential consequence, and what we can do to mitigate its worst effects.
Some of these changes could mean that some places might actually become colder than they are at present. If, for example, the Gulf Stream is interfered with as a result of global warming, then Ireland, Britain and Northern Europe could be plunged into a mini-ice age. The Gulf Stream is responsible for bringing about one third of the heat of the sun to Western Europe. There are records that the Gulf Stream slowed down and stopped in the past and the processes which caused this are now better understood. As the warmer water from the Gulf Stream moves north into the colder regions of the Atlantic, it sinks because it is saltier and therefore heavier than the surrounding water. This in turn draws more warm salty water northwards. If fresh water from melting glaciers dilutes the saltiness of the Gulf Stream, its warming impact on Western Europe could be terminated or diminished. (15)
At present global warming in the Arctic is accelerating through a phenomenon known the Albedo effect. Albedo comes from the Latin word for whiteness. During the Arctic winter the area of sea ice expands and the increased white surface reflects the sun’s light back into space. The Albedo effect is measured around 0.8 or 0.9. When the ice melts the water absorbs the sun’s energy and the albedo drops down to less than 0.1 to 0.07. Commenting on this change, Elizabeth Kolbert of The New Yorker put it succinctly when she wrote that it is like ‘replacing the best reflector with the worst reflector’. (16) Here we encounter the notion of feedback loops. As more sea ice is lost to oceans, more energy is absorbed by them which, in turn, heats up the planet. According to Elizabeth Kolbert the albedo factor is the main reason why the Arctic ocean is heating up so rapidly. (17)
Despite a few remaining skeptics and the usual vested interest groups, especially those who have invested heavily in the fossil fuel industry, there is now a broad consensus among scientists that climate change is happening. We therefore need to understand what the consequences will be for humans, other species and the planet. Finally, we need to know what we can do to prevent the worst case scenarios from taking shape.
Time Scales Involved in Climate Change
As I wrote on page 16, until very recently it was assumed that the climate would not change abruptly; that it would take decades or even centuries for a major climate change to happen. This assumption has been challenged in recent times. Scientists from Trinity College, Dublin found that there was a profound change in the local climate in Glendalough, Co Wicklow about 11,500 years ago. Using pollen grains extracted from the sediment in the lakes, the scientists found that the climate changed from a tundra-like condition to a mild climate in a period of 7 years. Initially, there were no trees, merely grasses, heathers and some juniper bushes. Within a decade, trees – birch, oak, elm and pine – were established in the area. John Haslett is the statistician for the project. He is quoted as saying, ‘the speed at which this happened (climate change) is gobsmacking. It may not have happened in 24 hours, like in (the film) The Day After Tomorrow but the science in the film is correct. (A major climate change) had to do with the Gulf Stream switching on and Off.’ (18)
In Chapter two we will see that the current situation in Greenland is very similar to what it was in Wicklow, 11,500 years ago. Could we be witnessing abrupt climate change happening at this point in history?
1. In this section I repeat some of what I have already written in Greening the Christian Millennium, Dominican Publications, Dublin, 1999, pages 62-84.
2. Tim Flannery, The Weather Makers: The History and Future Impact of Climate Change, Allen Lane (Penguin), London, 2005, page 20 -21.
3. Tim Flannery, op. cit., pages 41-42.
4. Martin Rees, Our Final Century; Will The Human Race Survive the Twenty-First Century? William Heinemann, London, 2003, page 106.
5. Stuart Clark, ‘Saved by the SUN’, Newscientist, 16 September 2006,
6. Elizabeth Kolbert, ‘The Climate of Man -1’, The New Yorker, 25 April 2005, page 67.
7. Robin Mckie, ‘Condemned to death by degrees if we fail to act’, The Observer, 26 June 2005, AI.
8. Elizabeth Kolbert, ‘The Climate of Man – 2’, The New Yorker, 2 May
2005, page 67.
9. Ibid 68.
10. Andrew C. Rivkin, ‘Studies Portray Tropical Arctic in Distant Past’, The New York Times, 1 June 2006, www.nytimes.com/2006/06/01/science / earthOlclimate.html page 1-3.
11. Tim Flannery, The Weather Makers, op cit, page 77.
12. Steve Connor, ‘World is at its warmest for a millennium’, The Independent, February 10, 2006. www.news.independent.co.uk/ environment / article344513 11 / 02 / 2006
13. John Haughton, 2004, Global Warming, CUP, page 44.
14. Ian Sample, ‘Global warming predictions are underestimated say scientists’, The Guardian, 23 May 2006, page 3.
15. Tim Flannery, op. cit, page 60.
16. Elizabeth Kolbert, The New Yorker, 25 April 2005, page 64.
18. Jan Battles, ‘How Wicklow went from artic to mild in seven years’, The Sunday Times, 25 June 2006, page 6.
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