Abstract
Abstract. We use the EMAC (ECHAM/MESSy Atmospheric Chemistry) global model with the aerosol module MADE (Modal Aerosol Dynamics model for Europe, adapted for global applications) to quantify the impact of transport emissions (land transport, shipping and aviation) on the global aerosol. We consider a present-day (2000) scenario according to the CMIP5 (Climate Model Intercomparison Project Phase 5) emission data set developed in support of the IPCC (Intergovernmental Panel on Climate Change) Fifth Assessment Report. The model takes into account particle mass and number emissions: The latter are derived from mass emissions under different assumptions on the size distribution of particles emitted by the three transport sectors. Additional sensitivity experiments are performed to quantify the effects of the uncertainties behind such assumptions. The model simulations show that the impact of the transport sectors closely matches the emission patterns. Land transport is the most important source of black carbon (BC) pollution in the USA, Europe and the Arabian Peninsula, contributing up to 60–70% of the total surface-level BC concentration in these regions. Shipping contributes about 40–60% of the total aerosol sulfate surface-level concentration along the most-traveled routes of the northern Atlantic and northern Pacific oceans, with a significant impact (~ 10–20%) along the coastlines. Aviation mostly affects aerosol number, contributing about 30–40% of the particle number concentration in the northern midlatitudes' upper troposphere (7–12 km), although significant effects are also simulated at the ground, due to the emissions from landing and take-off cycles. The transport-induced perturbations to the particle number concentrations are very sensitive to the assumptions on the size distribution of emitted particles, with the largest uncertainties (about one order of magnitude) obtained for the land transport sector. The simulated climate impacts, due to aerosol direct and indirect effects, are strongest for the shipping sector, in the range of −222.0 to −153.3 mW m−2, as a consequence of the large impact of sulfate aerosol on low marine clouds and their optical properties.
Highlights
Emissions from the land transport, shipping and aviation sectors have an important effect on atmospheric composition, which results in significant impacts on air quality and climate
The greenhouse gas emissions from the transport sectors have increased more rapidly than those of other energy-consuming sectors in the recent decade: the contribution from transport to the total CO2-equivalent emissions grew by 32 % from 1990 to 2007 in the EU-15 countries, total anthropogenic CO2-equivalent emissions decreased by 5.5 % in these countries (Sausen, 2010)
The quantification of the impacts on particle number concentration suffers from uncertainties that derive from microphysical transformations in the fresh exhaust, which cannot be resolved with the coarse spatial resolution of global climate models
Summary
Emissions from the land transport, shipping and aviation sectors have an important effect on atmospheric composition, which results in significant impacts on air quality and climate. According to the IPCC Fourth Assessment Report (Kahn Ribeiro et al, 2007), transport was responsible for 23 % of global energy-related (mainly energy production, industry, transport, residential and services) CO2 emissions in 2004 (6.3 Gt CO2) and road transport shared the dominant part (74 %) of this value. According to Kahn Ribeiro et al (2007), the energy use by global transport is expected to grow further, by about 80 % until 2030 with respect to 2007 levels, at a rate of more than 2 % per year. Developing countries and growing economies will experience the strongest increase, shifting their share from 36 to 46 % between 2007 and 2030 (non-OECD countries). The effects of transport-related emissions on atmosphere and climate deserve closer attention
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