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Characteristics and Forms of the
Urban Climate . |
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2.12 Global
Aspects of Climate (Think Global, Act Local)
Changes in the global climate are characterized by the rise in average annual air temperature near the ground since the beginning of the 20th Century. This warming reached its first high point in the 1940s. Following a phase where it remained constant and even lessened slightly, the curve has once again risen since the beginning of the 1970s. The values since the 1980s are above those of the reference time period 1961/90. There is a tendency for the levels of warming to be higher in winter than in summer. Different methods have shown that the increase in global average temperatures near the ground trace back not only to natural causes, but also in substantial extent to the anthropological alteration of the composition of the atmosphere. The average earth surface temperature of about 15 degrees Celsius results from the natural greenhouse effect, which is produced by the strong absorption of heat radiation by water vapor, carbon dioxide, and other trace gases in the atmosphere. Since the beginning of the industrial age approximately 130 years ago, atmospheric concentrations of greenhouse gases have drastically increased. New greenhouse gases such as chlorofluorocarbons (CFCs) have been introduced. The relatively long retention period of greenhouse gases in the atmosphere leads to an enrichment of atmospheric gas levels. The main cause of ongoing climate change is the burning of fossil fuels, which at present produces (2007) about 30 billion tons of CO2 emissions per year. This value increases by 1 to 2% each year. This is in addition to roughly 5.5 billion tons of CO2 produced each year by the burning of tropical rainforests. The self-reinforcing anthropological greenhouse effect provides the impetus for broader global warming. The 20th Century was the warmest century in at least 600 years, and no century has seen such a quick alteration in temperatures. The many consequences for nature and all areas of society are so far not fully predictable (e.g. rising seas levels, changes in precipitation patterns, increases of extreme weather). Following the 1992 UN Conference for Environment and Development in Rio de Janeiro more than 170 nations ratified a climate treaty that obliges them to stabilize greenhouse gases at a level that reduces the danger of an anthropological disruption of the climate system. This goal was concretized in later conferences such as Kyoto in 1997. The signatory states to the Rio conference treaty gave their pledge to sustainable development that is oriented towards the future. They expressly obliged themselves to adopt a "local Agenda 21" at the municipal level, which when translated means: Doing what is necessary at the local level to protect the future of our children in the 21st Century. As such, the citizens of cities and communities are called to tackle the threat of greenhouse gases. The further rise of climate-damaging emissions – produced in large part by the burning of fossil energy sources – must be prevented. Cities and their inhabitants play an important role in the reduction of greenhouse gases. There is a significant potential here to minimize these gases, specifically in relation to the areas of spatial heating and traffic (Figure 2/22). As a public interest, global climate protection is to be taken into consideration within the planning interests of development law – for example in infrastructure planning (cf. § 1 (5) 7 of the German Federal Building Law). The option of a binding obligation such as a solar thermal requirement, however, does not yet exist in zoning and planning. The atmospheric environmental quality of a city is determined mainly by the thermal and air-hygienic components of the bioclimatic effect complex. It can thus be assumed in the moderate latitudes that the number of days with high summer air temperatures is increasing and the spatial distribution of areas with thermal discomfort is widening. The concentrations of ozone, the main component of summer smog, will increase. One task for urban planning will be the systematic creation of ventilation corridors that ensure as deep a penetration as possible of fresh air from the surrounding areas into the inner city. Furthermore, it would be advantageous to increase the proportion of urban green spaces (LOZAN J. L. et al., 1998). In this regard, Chapter 3 "Energy-Conscious Zoning and Planning" and Chapter 6 "Recommendations for Planning" – especially the latter’s details for green space planning – are recommended. Numerous cities have enacted climate protection concepts in recent years. The City of Stuttgart developed a Climate Protection Concept (LANDESHAUPTSTADT STUTTGART, 1997) that contains comprehensive measures for climate protection. The following are particularly relevant for planning:
Effective climate protection demands the efforts (also in a financial sense) of all participants to not only develop measures and concepts but also to see these implemented. |
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