São Paulo Metropolitan Area, jointly tracking climate change and air quality - METROCLIMA-MASP

Abstract

Urban areas are expanding in all parts of the world, and are recognized as important atmospheric sources of greenhouse gases (GHG) and of short-lived climate pollutants (SLCP). The SLCP are the gases and particulates that are also responsible for global warming not caused by the CO2 and that have atmospheric lifetime of less than 20 years. The emissions, fate and atmospheric concentrations of these species will be affected by the climate change (expected modification of temperature and humidity), and specifically by the atmospheric temperature, and by extreme hydrometeorological events. A drastic reduction of greenhouse gas and other climate pollutants emission is required to attain the objectives highlighted by the COP21 agreement. The impact on climate of the megacities and urban conglomerates is well established since a large fraction of emissions takes place in these populated areas. In fact, urban areas constitute also a major source of air pollutants (related to energy production and consumption, transport and waste disposal). One of the challenges is to find win-win strategies by which one improves air quality while limiting anthropogenic climate forcing. São Paulo is the most important megacity in South America and can therefore be considered as a laboratory for an integrated assessment of the impact on the atmosphere of the sources of GHG (CO2, N2O, CH4) and of other radiative active species, the SLCP. Here, we will focus our attention on the black carbon, methane and tropospheric ozone, constituents of the SLCP and on the feedback of the climate change on air quality. To evaluate the climate impacts of the São Paulo Megacity emissions, the first step is to assess the sources of GHG and SLCP. All current information on GHG emissions is based on bottom-up estimates performed from the extrapolation of limited flux observations and economic information. These estimated emissions have never been verified or reconciled with surface observations of species concentrations and/or with remote sensing atmospheric data. To achieve the objectives of developing an emission inventory of GHG and SLCP, surface measurements, flux measurements and satellite data will be used to evaluate the impact of the São Paulo Megacity. (AU)