Climate change and ozone

Map of the predicted changes in ozone concentration for the 2090s decade, relative to the 1990s. The shade of red is proportional to the increase in temperature. The map shows that by the 2090s, south-west Europe will experience an increase of ozone concentration at ground level of about six parts per billion.
Image courtesy Katragkou et al., 2011.

High up in the atmosphere, ozone protects life on Earth by absorbing almost 99% of the Sun's deadly ultraviolet light. At ground level, ozone is a pollutant capable of causing health problems even at the lowest concentrations.

Scientists know that ozone concentrations depend largely on temperature, wind and other weather parameters and so it's likely that they will be affected by climate change. But how?

Eleni Katragkou, a climate scientist based at the Aristotle University of Thessaloniki (AUTh) in Greece, accepted the challenge and used grid computing to simulate the effect of climate change on ozone concentrations in Europe and over the next 100 years.

The research, published in the Journal of Geophysical Research, suggests that the concentration of ground level ozone is likely to increase towards the end of the century, especially in south-west Europe.

With or without you

Ozone (O₃) is a compound made of three oxygen atoms (the gas we breathe, O₂, has two atoms) present in the atmosphere and especially common in the so-called ozone layer at about 30km altitude. By absorbing all but one per cent of the sun's ultraviolet light, ozone plays a fundamental role in supporting life on Earth. Without it, plants and animals would perish under the sun's radiation.

At ground level, ozone becomes the villain. Even at low concentrations, ozone is an air pollutant that may cause serious health problems. "People with lung diseases, children, older adults, and people who are active outdoors may be particularly sensitive to ozone," explains Eleni. "[Ozone] also affects sensitive vegetation and can damage crop production and ecosystems."

The concentration of ozone in the atmosphere and at ground level depends on several meteorological parameters, such as temperature and prevailing winds, and this means that climate change trends are expected to play a role.

"It is therefore important to be able to predict ozone behaviour in a changing climate, in order to be able assess the impacts on air quality, human health, agricultural production and ecosystems," says Eleni.

Simulating the past, present and future of ozone concentrations

Eleni and colleagues built a modelling system to simulate the impact of climate change on surface ozone during two future decades (2040s and 2090s), using one past decade (1990s) as control. The model takes into account chemistry-climate interactions, and assesses the impact of key meteorological parameters (temperature, solar radiation, wind, cloudiness) on atmospheric composition.

The backdrop for the simulation is the Intergovernmental Panel on Climate Change (IPCC) climate change scenario A1B, which is characterised by strong economic growth, in a world with nine billion people by 2050, where new technologies spread quickly, there are worldwide social and cultural interactions and a balanced usage of fossil and renewable energy sources.

Eleni used the grid resources provided by the AUTh computing centre to run the chemistry-climate interactions within the simulation. This is a crucial for the accuracy of the model: "Changes in climatic variables affect atmospheric composition," she explains. "For example, if you have higher temperatures and more sunlight you produce more ozone."

Grid computing allowed Eleni to perform long-term and computationally demanding chemistry simulations in a reasonable time frame. A single computer would need around 40 years to finish the same job.

Ground level ozone on the rise?

The conclusions of the study were published in the Journal of Geophysical Research. "We concluded that climate change can have a significant impact on ground level ozone over Europe - mostly in the direction of increasing it," says Eleni. The trend is especially significant over the south-western part of the continent, towards the end of the century.

The research also demonstrates the importance of grid computing for atmospheric science and climate-chemistry models: "The usual bottleneck for performing those types of simulations at a finer resolution is the huge demands on CPU time. This makes me think that grid computing may facilitate very much our future work in this direction," Eleni concludes.

This article originally appeared on the European Grid Infrastructure website.