Highlight articles

Using satellite measurements of N₂O to remove dynamical variability from HCl measurements

Detecting trends in short data sets of stratospheric molecules is difficult because of variability due to dynamical fluctuations. We suggest that one way around this difficulty is using the measurements of one molecule to remove dynamical variability from the measurements of another molecule. We illustrate this using Aura MLS measurements of N₂O to help us sort out issues in the determination of trends in HCl. This shows that HCl is decreasing throughout the middle stratosphere as expected.

Considering the future of anthropogenic gas-phase organic compound emissions and the increasing influence of non-combustion sources on urban air quality

Following decades of successful regulatory policies focused on combustion-related sources (e.g. motor vehicles), emissions from non-combustion sources have become increasingly important for urban air quality. Using multiple approaches, we demonstrate that emissions from consumer, commercial, and industrial products and materials have become prominent contributors to the formation of photochemical smog (i.e. secondary organic particulate matter and ozone) and its associated health effects.

Evaluation of stratospheric age of air from CF₄, C₂F₆, C₃F₈, CHF₃, HFC-125, HFC-227ea and SF₆; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials

Chemical species measured in stratospheric air can be used as proxies for stratospheric circulation changes which cannot be measured directly. A range of tracers is important to understand changing stratospheric dynamics. We demonstrate the suitability of PFCs and HFCs as tracers and support recent work that reduces the current stratospheric lifetime of SF₆. Updates to policy-relevant parameters (e.g. stratospheric lifetime) linked to this change are provided for O₃-depleting substances.

HFC-125, HFC-227ea and SF₆; implications for the calculations of halocarbon lifetimes, fractional release factors and ozone depletion potentials">Read more

Results from the Fourth WMO Filter Radiometer Comparison for aerosol optical depth measurements

Aerosol optical depth measured from ground-based sun photometers is the most important parameter for studying the changes in the Earth’s radiation balance due to aerosols. Representatives for various sun photometer types belonging to individual institutions or international aerosol networks gather every 5 years, for 3 weeks, in Davos, Switzerland, in order to compare their aeorosol optical depth retrievals. This work presents the results of the latest (fourth) filter radiometer intercomparison.

WMO Filter Radiometer Comparison for aerosol optical depth measurements">Read more

The maintenance of elevated active chlorine levels in the Antarctic lower stratosphere through HCl null cycles

This paper revisits the chemistry leading to strong ozone depletion in the Antarctic. We focus on the heart of the ozone layer in the lowermost stratosphere in the core of the vortex. We argue that chemical cycles (referred to as HCl null cycles) that have hitherto been largely neglected counteract the deactivation of chlorine and are therefore key to ozone depletion in the core of the Antarctic vortex. The key process to full activation of chlorine is the photolysis of formaldehyde.

Long-term series and trends in surface solar radiation in Athens, Greece

The National Observatory of Athens has been collecting solar radiation, sunshine duration, and cloud and visibility data/observations since the beginning of the 20th century. In this work we present surface solar radiation data since 1953 and reconstructed data since 1900. We have attempted to show and discuss the long-term changes in solar surface radiation over Athens, Greece, using these unique datasets.

Total ozone trends from 1979 to 2016 derived from five merged observational datasets – the emergence into ozone recovery

This paper commemorates the 30-year anniversary of the initial signing of the Montreal Protocol (MP) on substances that deplete the ozone layer. The MP is so far successful in reducing ozone-depleting substances, and total ozone decline was successfully stopped by the late 1990s. Total ozone levels have been mostly stable since then. In some regions, barely significant upward trends are observed that suggest an emergence into the expected ozone recovery phase.

Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery

Using a robust analysis, with artefact-corrected ozone data, we confirm upper stratospheric ozone is recovering following the Montreal Protocol, but that lower stratospheric ozone (50° S–50° N) has continued to decrease since 1998, and the ozone layer as a whole (60° S–60° N) may be lower today than in 1998. No change in total column ozone may be due to increasing tropospheric ozone. State-of-the-art models do not reproduce lower stratospheric ozone decreases.

Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

We made airborne measurements of aerosol particle concentrations and properties over the Amazon Basin. We found extremely high concentrations of very small particles in the region between 8 and 14 km altitude all across the basin, which had been recently formed by gas-to-particle conversion at these altitudes. This makes the upper troposphere a very important source region of atmospheric particles with significant implications for the Earth’s climate system.

Response to marine cloud brightening in a multi-model ensemble

Marine cloud brightening (MCB) has been proposed to help limit global warming. We present here the first multi-model assessment of idealized MCB simulations from the Geoengineering Model Intercomparison Project. While all models predict a global cooling as intended, there is considerable spread between the models both in terms of radiative forcing and the climate response, largely linked to the substantial differences in the models’ representation of clouds.

News & press Highlight articles

Highlight articles

Information for

External links