Newswise — Warming during the summer months in Europe was much faster than the global average, shows a new study by Stockholm University researchers published in Journal of Geophysical Research Atmospheres. As a result of human emissions of greenhouse gases, the climate across the continent has also become drier, particularly in southern Europe, resulting in worse heatwaves and an increased risk of wildfires.
According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), warming of land areas occurs significantly faster than the oceans, with an average of 1.6 degrees and 0.9 degrees respectively. It means that the global budget for greenhouse gas emissions to stay below 1.5 degrees warming on land has already been used up. Now, the new study shows that the emissions budget to avoid 2 degrees warming over large parts of Europe during the summer semester (April-September) has also been used up. Indeed, the measurements reveal that warming during the summer months across much of Europe over the past four decades has already exceeded two degrees.
“Climate change is serious as it brings, among other things, more frequent heat waves to Europe. These, in turn, increase the risk of wildfires, such as the devastating wildfires in southern Europe in the summer of 2022,” says Paul Glantz, associate professor in Stockholm University’s Department of Environmental Sciences and lead author of the study.
In southern Europe, a clear, so-called, positive feedback from global warming is evident, i.e. warming is amplified due to drier soil and less evaporation. Additionally, there was less cloud cover over much of Europe, possibly due to less water vapor in the air.
“What we see in southern Europe is in line with what the IPCC predicted, which is that a greater human impact on the greenhouse effect would lead to dry areas on Earth becoming even drier,” says Paul Glantz.
Impact of aerosol particles
The study also includes a section on the estimated impact of aerosol particles on temperature increase. According to Paul Glantz, the rapid warming in, for example, central and eastern Europe is primarily a consequence of human emissions of long-lived greenhouse gases, such as carbon dioxide. But as emissions of short-lived aerosol particles, such as from coal-fired power plants, have declined markedly over the past four decades, the combined effect has led to an extreme rise in temperature of more than two degrees.
“Airborne aerosol particles, before they started declining in the early 1980s in Europe, masked warming caused by human greenhouse gases by just over one degree on average for the summer semester. As the aerosols in the atmosphere decreased, the temperature rose rapidly. Human emissions of carbon dioxide are still the biggest threat as they affect the climate for hundreds to thousands of years,” says Paul Glantz.
According to Paul Glantz, this effect provides a harbinger of future warming in areas where aerosol emissions are high, such as in India and China.
Background – The greenhouse effect and the aerosol effect
The burning of fossils leads to the release of both aerosol particles and greenhouse gases. While their origin is common, their effects on climate are diverse.
On the greenhouse effect
Greenhouse gases are largely insensitive to solar radiation while absorbing infrared radiation efficiently, leading to re-emission to the earth’s surface. The Earth absorbs both solar radiation and infrared radiation, which leads to heating of the lower atmosphere in particular.
Time-space: Greenhouse gases are generally long-lived in the atmosphere and this is especially true for carbon dioxide where human emissions affect the climate for hundreds to thousands of years. It also means that greenhouse gases spread evenly across the planet.
On the aerosol effect
In contrast to greenhouse gases, aerosol particles affect incoming solar radiation, i.e. they scatter part of the sunlight into space causing a cooling effect. Human emissions of aerosols can enhance this cooling effect.
Time-space: Airborne human aerosol particles have a life span of approximately one week, which means that they cool the climate mainly locally or regionally and in the short term.
According to the Paris Agreement, all parties must commit to drastically reduce their greenhouse gas emissions, but it is also important to decrease concentrations of aerosol particles as well because, in addition to their effects on the climate, aerosol particles in the air pollution cause around eight million premature deaths each year worldwide.