IDIOM2 · Unravelling the role of water stress in Mediterranean isoprene emissions to better project future regional climate-air quality interactions

Unravelling the role of water stress in Mediterranean isoprene emissions to better project future regional climate-air quality interactions

In response to changes in environmental conditions (e.g., temperature, radiation, water availability), plants emit reactive chemical compounds known as volatile organic compounds (BVOCs), which play an important role in atmospheric chemistry. In the large family of BVOCs, isoprene is the most abundant compound and influences the levels of ozone, a powerful greenhouse gas and air pollutant. Isoprene thus affects climate and air quality. In turn, climate change may alter isoprene emissions by increasing the occurrence and intensity of stresses that alter plant functioning (e.g., rising temperature, changing precipitation regimes). While increasing temperatures may exacerbate ozone production by enhancing isoprene emissions, the effect of water availability on isoprene emissions is more controversial and may depend on water stress intensity. Field campaigns, in-situ and laboratory experiments investigated the effect of different water stress (short- vs. long-term) on isoprene emissions. However, these studies provided geographically scattered and uneven results. To explore the relationship between isoprene emissions and water stress at larger scales, the IDIOM2 project applied: (a) global observations of climatic drivers of isoprene and of an intermediate by-product of its oxidation, (b) statistical techniques to jointly analyse observations, and (c) regional climate modelling to assess the effect of soil moisture on isoprene emissions and ozone pollution. As schematised in the figure, current air quality strategies pursue the reduction of anthropogenic emissions contributing to ozone production. In the future, benefits from air quality regulations may be offset by the evolution of isoprene and other BVOCs under climate changes that intensify favourable atmospheric conditions for ozone production and isoprene emissions (i.e., sunny, warm and stagnant days). To provide reliable projections of future air quality and design effective mitigation strategies, it is thus essential to reduce uncertainties in estimates of isoprene emissions both under present and future climates. To answer scientific and societal questions related to the relationship between isoprene emissions and water stress, the IDIOM2 project has three objectives: 1. Elucidate the effect of water stress and other drivers on isoprene emissions at a large spatio-temporal scale 2. Assess the spread in future isoprene emissions in an ensemble of regional climate projections over Europe 3. Estimate surface ozone pollution resulting from climate-driven changes in isoprene emissions The analysis of global observations confirmed the important role of temperature in modulating isoprene emissions and highlighted the contrasting effect of water stress in altering isoprene emissions in different regions. In parallel, numerical experiments performed at the European scale with a BVOC emission model, which assumes water stress reduces isoprene emissions, showed that large reductions in isoprene emissions slightly decrease surface ozone levels.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз