Search

Tropospheric ozone (O3) pollution is known to damage vegetation, reducing photosynthesis and stomatal conductance, resulting in modified plant transpiration to the atmosphere. We use an Earth system model to show that global transpiration response to near‐present‐day surface tropospheric ozone results in large‐scale global perturbations to net outgoing long‐wave and incoming shortwave radiation. Our results suggest that the radiative effect is dominated by a reduction in shortwave cloud forcing in polluted regions, in response to ozone‐induced reduction in land‐atmosphere moisture flux and atmospheric humidity. We simulate a statistically significant response of annual surface air temperature of up to ~ +1.5 K due to this ozone effect in vegetated regions subjected to ozone pollution. This mechanism is expected to further increase the net warming resulting from historic and future increases in tropospheric ozone. Plain Language Summary: Ozone is a pollutant near the Earth's surface, where it is harmful to health and vegetation. Ozone is formed by chemical reactions in the atmosphere driven by the action of sunlight on emissions from fossil fuel combustion and other sources. Ozone harms vegetation by entering leaves through small pores on leaves called stomata. These stomata are also the route by which gases such as water vapor and CO2 are naturally exchanged between plants and the atmosphere. Ozone damage to vegetation affects the efficiency with which gases pass through plant stomata, typically reducing both photosynthesis and stomatal conductance due to biochemical damage. This results in a change in the amount of water vapor that plants put into the atmosphere. In this study we use a computer model to estimate for the first time how this modification in plant water vapor source to the atmosphere changes climate. We show widespread surface warming and changes in clouds due to the impact of ozone on plants. This has important implications for policies aimed at limiting global and regional temperature increases in the presence of ozone pollution and provides evidence for an additional climate benefit to reducing ozone pollution. Key Points: We make the first estimate of global radiation balance and surface temperature response to vegetation damage by ozoneRadiative changes are dominated by atmospheric moisture and cloud response to ozone‐induced changes in plant transpirationOzone‐vegetation‐hydrology interactions should be considered in future climate scenarios and simulations [ABSTRACT FROM AUTHOR]