Forests cover a third of Earth's land surface, and are pivotal both in carbon storage and the water-cycle.

A new study now provides further insights into the complex role forests play in the planetary climate system, drawing on data from forests in Finland and Brazil. The research highlights the intricate relationship between emission of organic gases from trees, and the formation of reflective clouds that could influence global temperatures.

Forests release substantial amounts of organic gases, which can be detected as the distinctive scent of pine on a warm day. These gases, once released into the atmosphere, contribute to particle formation.

Clouds are composed of minuscule water droplets and each of these droplets nucleate around a particle in the air. An increase in atmospheric particles results in clouds with more droplets, enhancing their reflectivity of sunlight and leading to cooler surface temperatures.

As climate change raises temperatures, forests are anticipated to emit more of these gases, thereby creating more particles and potentially more reflective clouds.

Scientists from five countries, including Sweden, the UK, Finland, Germany and Brazil, were involved in the study, which uniquely focuses on both boreal and tropical forests. A boreal climate is characterised by long winters and cool short summers, while tropical forests are found where temperatures are high temperatures throughout the year without a notable winter season.

Boreal forests constitute 27% of Earth's forested area, while tropical forests cover some 45 percent. The researchers say these ecosystems differ in their emissions and cloud formation processes, leading to varying impacts on the forest-cloud-climate feedback loop.

Sara Blichner, postdoctoral scientist at the department of environmental sciences at Stockholm University. says, "This study, utilising long-term data from diverse forest environments in Finland and Brazil, marks the first time observational evidence has been presented for these interactions in tropical rainforests. Our findings suggest that current models may underestimate the impact of forests on cloud formation and climate, especially in tropical regions, which are crucial due to high amount of solar radiation these areas receive at these latitudes."

The study emphasises the need for improved climate models to accurately represent these complex interactions. However, Blichner stresses that while the study highlights areas for improvement in climate modelling, it does not undermine the overall reliability of these models."Climate models are highly trustworthy in representing the main processes of climate change. Our research aims to refine these models, reducing uncertainties in future climate projections," she asserts.

The research also points out that as manmade particle emissions decrease due to air quality policies, the natural particles from forests become increasingly significant. These feedback loops are more potent in cleaner air environments and could play an important role in moderating global warming.

This collaborative study underscores the need for continued research and improvement in climate modelling to better predict future climate scenarios. Additionally, the findings highlight that these types of effects must be considered when assessing forest conservation as a key strategy in climate change mitigation.

The study was published in Nature Communications journal.