Short-lived atmospheric species and their impact on climate

摘要

Not only long-lived greenhouse gases (GHGs), such as CO_2 and non-CO_2 GHGs, controlled by the Montreal Protocol, the Climate Convention and the Kyoto Protocol, have an impact on climate. Also short-lived atmospheric species, such as various types of aerosols and ozone and its precursors, may contribute significantly to human induced climate change. The radiative forcing of these species is complicated and not well understood. Various types of aerosols may cause direct and indirect radiative forcing of the climate system with a highly inhomogeneous horizontal and vertical distribution. Tropospheric ozone, an important GHG, is determined by human emissions of precursors such as CO, NOx, methane and other hydrocarbons and volatile organic compounds, and is affected by many highly non-linear interactive chemical and physical processes. Through its chemistry it in turn influences the lifetime of other GHGs. Policy responses to human induced climate change, such as the Kyoto protocol, are based on the ability to express the relative contribution of various species to climate change. The Global Warming Potential (GWP) is a politically accepted, but not necessarily only way to achieve this. However, the determination of GWPs of radiatively inactive precursors, or other unevenly distributed short-lived species is not straightforward. If control measures of such gases would be envisaged in future climate negotiations, a quantitative understanding and representation of their potential to change climate is needed. In this Report we attempt to briefly summarise the progress in these areas presented at the Third International Symposium on Non-CO_2 Greenhouse Gases (NCGG-3).