One of the biggest mysteries of global warming is the interaction between clouds and aerosols. It’s also the topic that Paolo Laj, recently appointed professor of atmosphere research and aerosol physics at the University of Helsinki, has studied since the late 1980s.
It’s understood that the small aerosol particles in the air influence the clouds, but the ways in which these processes link to global warming remain partially unknown.
Humans also have an impact.
“Approximately a half of the aerosols in the atmosphere are produced by humans. Based on our research we can say that these aerosols interact with the clouds. But we are not sure how these things influence the big picture,” says Laj.
Aerosols are also a controversial topic. As most of the impurities in the air are light in colour, they reflect sunlight away from the atmosphere and actually cool it down.
“Here we have to decide what we want. Is it more important to have our air be as clean as possible, or to reflect light away from the planet?” asks Laj.
“The air in cities is much cleaner today than it was, say, 30 years ago, in Europe. In many other part of the world, air quality is still deteriorating”
Aerosols have a global impact on climate change. Consequently, aerosol research requires long series of observations from different parts of the world. Aerosols typically have short lifetime and are sensitive to changes in the weather. This means that individual observations can easily be relegated to very local variation.
For the past 15 years, Laj has been contributing to create a global network for measuring aerosols and changes in the atmosphere using identical methods around the world, and for sharing the results openly.
This is why he came to Helsinki. Laj is a professor at the University of Grenoble, France, but also holds a part-time professorship at the University of Helsinki’s Division of Atmospheric Sciences, which coordinates the European observation data for the network.
Most of his own research is conducted in Bolivia, where he helped establish a research station high in the mountains.
“The station in Bolivia at more than 5 km in the Andes offers an interesting perspective on climate change. Located at an elevation of 3.6 kilometres, the city of La Paz has rapidly grown to a size of two million inhabitants. The station helps us monitor how this growth influences the aerosols and carbon in the mountain air.”
And what is the carbon footprint of the professor himself, working as he does in three different countries?
“It is too big. The same is true for almost all climate researchers. It’s unfortunate, but our work is international by nature. I could not do my job without travelling,” says Laj.