Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

Aviation and global climate change in the 21st century.

Our current understanding of mechanisms that are, or may be, acting to cause climate change over the past century is briefly reviewed, with an emphasis on those due to human activity. The paper discusses the general level of confidence in these estimates and areas of remaining uncertainty. The effects of increases in the so-called well-mixed greenhouse gases, and in particular carbon dioxide, appear to be the dominant mechanism. However, there are considerable uncertainties in our estimates of many other forcing mechanisms; those associated with the so-called indirect aerosol forcing (whereby changes in aerosols can impact on cloud properties) may be the most serious, as its climatic effect may be of a similar size as, but opposite sign to, that due to carbon dioxide. The possible role of volcanic eruptions as a natural climate change mechanism is also highlighted.

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Radiative Forcing of Climate Change

https://elib.dlr.de/59672/1/scientdir.pdf

Transport impacts on atmosphere and climate: Aviation

The evolution of global and regional anthropogenic SO2 emissions in the last decade has been estimated through a bottom-up calculation. After increasing until about 2006, we estimate a declining trend continuing until 2011. However, there is strong spatial variability, with North America and Europe continuing to reduce emissions, with an increasing role of Asia and international shipping. China remains a key contributor, but the introduction of stricter emission limits followed by an ambitious program of installing flue gas desulfurization on power plants resulted in a significant decline in emissions from the energy sector and stabilization of total Chinese SO2 emissions. Comparable mitigation strategies are not yet present in several other Asian countries and industrial sectors in general, while emissions from international shipping are expected to start declining soon following an international agreement to reduce the sulfur content of fuel oil. The estimated trends in global SO2 emissions are within the range of representative concentration pathway (RCP) projections and the uncertainty previously estimated for the year 2005.

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The last decade of global anthropogenic sulfur dioxide: 2000-2011 emissions

Transport activity, a key component of economic development and human welfare, is increasing around the world as economies grow. For most policymakers, the most pressing problems associated with this increasing transport activity are traffic fatalities and injuries, congestion, air pollution and petroleum dependence. These problems are especially acute in the most rapidly growing economies of the developing world. Mitigating greenhouse gas (GHG) emissions can take its place among these other transport priorities by emphasizing synergies and co-benefits (high agreement, much evidence). Transport predominantly relies on a single fossil resource, petroleum that supplies 95% of the total energy used by world transport. In 2004, transport was responsible for 23% of world energy-related GHG emissions with about three quarters coming from road vehicles. Over the past decade, transportâ€™s GHG emissions have increased at a faster rate than any other energy using sector (high agreement, much evidence). Transport activity will continue to increase in the future as economic growth fuels transport demand and the availability of transport drives development, by facilitating specialization and trade. The majority of the worldâ€™s population still does not have access to personal vehicles and many do not have access to any form of motorized transport. However, this situation is rapidly changing. Freight transport has been growing even more rapidly than passenger transport and is expected to continue to do so in the future. Urban freight movements are predominantly by truck, while international freight is dominated by ocean shipping. The modal distribution of intercity freight varies greatly across regions. For example, in the United States, all modes participate substantially, while in Europe, trucking has a higher market share (in tkm1), compared to rail (high agreement, much evidence). Transport activity is expected to grow robustly over the next several decades. Unless there is a major shift away from current patterns of energy use, world transport energy use is projected to increase at the rate of about 2% per year, with the highest rates of growth in the emerging economies, and total transport energy use and carbon emissions is projected to be about 80% higher than current levels by 2030 (medium agreement, medium evidence). There is an ongoing debate about whether the world is nearing a peak in conventional oil production that will require a significant and rapid transition to alternative energy resources. There is no shortage of alternative energy sources, including oil sands, shale oil, coal-to-liquids, biofuels, electricity and hydrogen. Among these alternatives, unconventional fossil carbon resources would produce less expensive fuels mostcompatible with the existing transport infrastructure, but lead to increased carbon emissions (medium agreement, medium evidence). In 2004, the transport sector produced 6.3 GtCO2 emissions (23% of world energy-related CO2 emissions) and its growth rate is highest among the end-user sectors. Road transport currently accounts for 74% of total transport CO2 emissions. The share of non-OECD countries is 36% now and will increase rapidly to 46% by 2030 if current trends continue (high agreement, much evidence). The transport sector also contributes small amounts of CH4 and N2O emissions from fuel combustion and F-gases (fluorinated gases) from vehicle air conditioning. CH4 emissions are between 0.1â€“0.3% of total transport GHG emissions, N2O between 2.0 and 2.8% (based on US, Japan and EU data only). Worldwide emissions of F-gases (CFC-12+HFC- 134a+HCFC-22) in 2003 were 0.3â€“0.6 GtCO2-eq, about 5â€“10% of total transport CO2 emissions (medium agreement, limited evidence). When assessing mitigation options it is important to consider their lifecycle GHG impacts. This is especially true for choices among alternative fuels but also applies to a lesser degree to the manufacturing processes and materials composition of advanced technologies. Electricity and hydrogen can offer the opportunity to â€˜de-carboniseâ€™ the transport energy system although the actual full cycle carbon reduction depends upon the way electricity and hydrogen are produced. Assessment of mitigation potential in the transport sector through the year 2030 is uncertain because the potential depends on: â€¢ World oil supply and its impact on fuel prices and the economic viability of alternative transport fuels; â€¢ R&D outcomes in several areas, especially biomass fuel production technology and its sustainability in massive scale, as well as battery longevity, cost and specific energy. Another problem for a credible assessment is the limited number and scope of available studies of mitigation potential and cost. Improving energy efficiency offers an excellent opportunity for transport GHG mitigation through 2030. Carbon emissions from â€˜newâ€™ light-duty road vehicles could be reduced by up to 50% by 2030 compared to currently produced models, assuming continued technological advances and strong policies to ensure that technologies are applied to increasing fuel economy rather than spent on increased horsepower and vehicle mass. Material substitution and advanced design could reduce the weight of light-duty vehicles by 20â€“30%. Since the TAR (Third Assessment Report), energy efficiency of road vehicles has improved by the market success of cleaner directinjection turbocharged (TDI) diesels and the continued market penetration of numerous incremental efficiency technologies. Hybrid vehicles have also played a role, though their market penetration is currently small. Reductions in drag coefficients of 20â€“50% seem achievable for heavy intercity trucks, with consequent reductions in fuel use of 10â€“20%. Hybrid technology is applicable to trucks and buses that operate in urban environments, and the diesel engineâ€™s efficiency may be improved by 10% or more. Prospects for mitigation are strongly dependent on the advancement of transport technologies. There are also important opportunities to increase the operating efficiencies of transport vehicles. Road vehicle efficiency might be improved by 5â€“20% through strategies such as eco-driving styles, increased load factors, improved maintenance, in-vehicle technological aids, more efficient replacement tyres, reduced idling and better traffic management and route choice (medium agreement, medium evidence). The total mitigation potential in 2030 of the energy efficiency options applied to light duty vehicles would be around 0.7â€“0.8 GtCO2-eq in 2030 at costs

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Ron Wit

Papers

Aviation and global climate change in the 21st century.

Transportation and its Infrastructure

Chapter 5 Transportation and its infrastructure