The Impact of Trees on the Process of Cloud Formation
Within the scope of the CLOUD project at CERN’s nuclear research center, scientists at PSI have pinpointed sesquiterpenes, which are gaseous hydrocarbons emitted by plants, as a significant contributor to cloud formation. This discovery holds the potential to minimize uncertainties in climate models and enhance the precision of climate predictions. The research findings have been documented in the Science Advances journal.
According to the latest IPCC projections, global temperatures are expected to rise between 1.5 to 4.4 degrees Celsius by 2100 compared to pre-industrial levels. This range depends on various scenarios of future greenhouse gas emissions. In the best-case scenario, significant and rapid emissions reduction could still meet the Paris Agreement’s 1.5-degree target.
Tackling Climate Uncertainties with the CLOUD Project
However, in the worst-case scenario, temperatures could surpass that target. The uncertainty in these projections is due to our incomplete understanding of atmospheric processes, particularly the interactions between various gases and aerosols. The CLOUD project, an international collaboration involving atmospheric researchers at CERN, aims to address these uncertainties.
One significant aspect that remains unclear is how cloud cover will evolve in the future. Clouds play a crucial role in climate predictions, as they reflect solar radiation, cooling the Earth’s surface. Cloud droplets form when water vapor condenses on condensation nuclei, which are tiny solid or liquid particles in the atmosphere. These particles can come from natural sources like sea salt and desert sand or human activities such as industrial emissions and traffic pollutants.
However, roughly half of these nuclei form in the air when gaseous molecules combine and transform into solids, a process known as nucleation or new particle formation (NPF). Initially, these particles are extremely small, just a few nanometers in size, but they can grow over time through the condensation of gaseous molecules and serve as condensation nuclei.
Scented Molecules Impact Cloud Formation and Climate Predictions
Greenhouse gases that have distinct odors play a significant role in cloud formation. Sulfur dioxide, primarily from coal and oil combustion, is the key anthropogenic gas contributing to particle formation. On the natural front, isoprenes, monoterpenes, and sesquiterpenes, released by vegetation, are crucial. These compounds are responsible for the familiar scents we encounter when grass is cut or during walks in the woods. When these compounds interact with ozone in the atmosphere, they form aerosols.
Sulfur dioxide concentrations in the air have decreased due to stricter environmental regulations, but terpenes, especially sesquiterpenes, are on the rise as plants release more under stressful conditions like rising temperatures and droughts.
Unveiling the Role of Sesquiterpenes in Particle Formation
The challenge in climate predictions lies in understanding how these factors affect cloud formation. To achieve this, we need to unravel how each substance contributes to particle formation. While sulfuric acid and certain terpenes have been extensively studied, sesquiterpenes have been overlooked due to their scarcity and rapid reaction with ozone.
Despite their limited presence (24 million metric tons compared to 465 million metric tons of isoprenes and 91 million metric tons of monoterpenes released annually), sesquiterpenes are shown to play a significant role in cloud formation. In fact, they generate ten times more particles than the other two organic substances at equivalent concentrations.
Researchers conducted experiments in the unique CLOUD chamber at CERN, simulating pre-industrial conditions when anthropogenic sulfur dioxide emissions were absent. These experiments revealed that the oxidation of a natural mixture of terpenes and sesquiterpenes in pure air produces ULVOCs (Ultra-Low-Volatility Organic Compounds) that efficiently form particles, eventually becoming condensation nuclei.
A Powerful Catalyst for New Particle Formation
The study highlighted the profound impact of sesquiterpenes. Even a mere two percent addition of sesquiterpenes to a mixture of isoprenes and monoterpenes doubled the rate of new particle formation, attributed to sesquiterpenes’ larger carbon atom content.
This research underscores the role of vegetation in influencing weather and climate. Moreover, it advocates for including sesquiterpenes as a distinct factor in future climate models, alongside isoprenes and monoterpenes, to enhance prediction accuracy. Given the decreasing sulfur dioxide and increasing biogenic emissions due to climate stress, understanding these compounds is crucial for our future climate.
Future studies will delve into the impact of anthropogenic gases on the natural atmosphere during industrialization. Researchers are already planning further investigations to improve cloud formation predictions at the Laboratory for Atmospheric Chemistry.
Read the original article on: Phys org
Read more: Fighting Flat-Earth Theory
