This document summarizes several air quality measurement and modelling methods that can be used to estimate ground-level air pollutant concentrations and presents multiple approaches to monitoring ambient air pollution at different spatial and temporal scales.

The stratosphere ozone layer is slowly recovering and the recovery will be complete in most parts of the atmosphere in the coming decades, according to the latest bulletin by the World Meteorological Organization (WMO).

The deteriorating quality of air, transboundary haze pollution and global climate change are the major problems affecting the atmospheric ecosystem. Air quality has deteriorated as a result of increasing traffic congestion, rapid industrialisation and increased energy consumption.

Science has been one of the foundations of the success of the Montreal Protocol. This assessment highlights advances and updates in the scientific understanding of ozone depletion since the 2018 Scientific Assessment of Ozone Depletion and provides policy-relevant scientific information on current challenges and future policy choices.

Air pollution is increasingly understood as a global issue, requiring an understanding of pollution sources, transport, and transformation from local to regional to global scales (IPCC, 2013).

New WHO Global Air Quality Guidelines (AQGs) provide clear evidence of the damage air pollution inflicts on human health, at even lower concentrations than previously understood.

The assessment highlights the critical role that cutting methane emissions, including from the fossil fuel industry, plays in slowing the rate of global warming. Cutting human-caused methane by 45% this decade would keep warming beneath a threshold agreed by world leaders.

Better air quality has led to a significant reduction of premature deaths over the past decade in Europe. However, the European Environment Agency’s (EEA) latest official data show that almost all Europeans still suffer from air pollution, leading to about 400,000 premature deaths across the continent.