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TEACHING EARTH SCIENCES ● Volume 31 ● Number 4, 2006 The Science of Global Warming PROFESSOR COLIN PRENTICE Peter Kennett’s notes on the lecture at Bristol Conference Changes in the Earth System are approached at three levels: ● Detection i.e. it can be demonstrated that a change has happened. ● Attribution i.e. the cause of the change can be demonstrated. ● Prediction at three levels; a deduction can be drawn that should be true in general; a statement that if x happens then y will follow; a statement that x will happen, i.e. a forecast. The media do not always distinguish between these different levels in reporting changes to the Earth! Evidence for carbon dioxide content of the atmosphere: ● Carbon dioxide levels at Mauna Loa and at the South Pole are rising in parallel. ● Ice cores from the Antarctic show stable levels of CO 2 from 1000 A.D. to the start of the Industrial Revolution around 1800, followed by a rapid rise. ● The Vostok (Antarctica) ice cores show an oscillation in CO 2 content which can be correlated with glacial and interglacial epochs. Carbon stores in the Earth system are vast, but by far the greater part lies in the lithosphere, and not simply in fossil fuels. In the surface carbon cycle, on average, every molecule of CO 2 goes through a plant every 6 years! The amount of CO 2 in the atmosphere roughly correlates with fossil fuel emissions, but not completely. Carbon flux between ocean and atmosphere and between land and atmosphere must also be taken into account, although the factors are difficult to quantify exactly at present. The conclusion is that the rise in CO 2 since the Industrial Revolution has been detected: It can largely be attributed to rise in emissions from the burning of fossil fuels: Predictions for the future are dubious. Gases other than CO 2 also contribute to climate change. They include methane, nitrogen oxides, CFCs, water vapour and tropospheric ozone etc. Although less in quantity, their radiation efficiency is very much higher than CO 2 , so a little goes a long way in affecting the average temperature of the Earth. Aerosols (tiny particles in the atmosphere) also have an effect on global temperatures. Dust and soot absorb heat, but sulphates, sea salt and some organic compounds reflect it back into the upper atmosphere, thus having a cooling effect. A reconstruction of past global temperatures from 1000 A.D. shows a generally level graph, with perturbations attributable to solar events and to volcanic eruptions, but since the 1980s it shows a dramatic rise. The resultant shape of the curve is referred to as a “hockey stick” graph. So, temperature rise since the 1980s has been detected and it has been attributed to human “forcing” (accepted by the Intergovernmental Panel on Climate Change in 2001). Predictions are very difficult to make with any confidence, because of the uncertainty about the effects of aerosols. For example, governments are encouraging the reduction in emissions of sulphates for other good reasons, and yet it is sulphates in the atmosphere which help to keep down rises in temperature. Conclusions ● In order to stabilise climate, CO 2 emissions must be reduced to very low levels. ● Large uncertainties arising from the other factors outlined above must be reduced. ● The consequences of climate change need to be better quantified – we still do not really know how much global warming is dangerous for the vast range of ecosystems and human activities on the planet. A copy of the PowerPoint presentation that Professor Prentice used to illustrate his lecture with at the ESTA Conference is available on the ESTA website. Peter Kennett peter.kennett@tiscali.co.uk www.esta-uk.org 18
TEACHING EARTH SCIENCES ● Volume 31 ● Number 4, 2006 Geodiversity, Geoconservation and GeoValue PROFESSOR PETER W. SCOTT, DR ROBIN SHAIL, DR CLIVE NICHOLAS AND DAVID ROCHE There is a much increased awareness of geodiversity and its fundamental contribution to Britain’s natural heritage. Geodiversity Action Plans (GAPs) are being introduced at local and county level. But how do you set about deciding which sites are the best for observing particular geodiversity features and, once you’ve done that, are there ways to try and improve access for geological groups? The GeoValue project hopes to help out. The Geodiversity Profile, developed as part of the GeoValue project, is a new procedure for describing and valuing geodiversity. As well as having a wider application in providing a methodology for gathering data for stakeholders, such as quarry operators, planners, conservation groups and others, it is suitable for use by educational groups as part of raising awareness of the differences in the geodiversity between sites. The data are recorded on a two-page form that summarises the geological features, records prior knowledge from literature, and values the site by comparing it with others in the area having similar characteristics. A second component of GeoValue has been addressing the legal, safety and practical issues of visiting sites on public and private land to study the geology, including active and former quarries. Even if a site is apparently open, an automatic right of access does not necessarily exist, and there are potential liability problems for both the visitor and landowner. The Geodiversity Profile The profile is a standardised quantitative procedure, with clearly defined criteria that is based on elements of best practice adopted by many Regionally Important Geological and Geomorphological Sites (RIGS) and County Geology groups. It is intended as an assessment tool to allow comparisons to be made between any sites of broadly similar geology. It is not intended as a site designation in its own right, but could be used to inform such decisions. It has been developed specifically for application to rock exposures in working, disused and abandoned quarries (Figure 1), although it can be applied to most geological sites. The profile is presented as a fully justified open-book statement. Data for the profile are gathered through a desk study supported by fieldwork at the site and surrounding area. The site’s geodiversity is summarised and then valued in terms of its scientific and educational importance within the context of the number of sites with similar geology that display the same features. Any applied geology features of the site, which could be mineral resources, engineering or environmental geology, hydrogeology or applied geomorphology, are also valued for both their scientific and educational importance. Historical, cultural and aesthetic attributes of the site are rated as having local, countywide, national or international importance. The profile assigns numerical values, typically 1-4, with clearly defined criteria that promote reproducibility between different assessors, and links these to justifying statements. Obvious links between geodiversity and biodiversity are recognised within the profile. The main use intended for the Geodiversity Profile is as a standardised procedure to help inform the decision-making process on a site’s future management, for example in forward development of an active quarry, in considering a former quarry for restoration, or for conservation of its geological features. It can be used to resolve conflict between stakeholders on the relative merits of a site, and as a way for establishing the best site for illustrating specific aspects of geology. It will aid in the drawing up of Geodiversity Action Plans (GAPs) by local government and other groups, and Company Continued on page 20 Figure 1 Sand quarry in Lower Cretaceous Lower Greensand and overlying Gault Clay, Bedfordshire, with high value geodiversity for science and education. 19 www.esta-uk.org
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