The effect of carbon dioxide on mountain climate systems
source: Earth’s future
Mountains create their own weather or climate systems by changing airflow and precipitation patterns. Orographic or mountain-influenced precipitation occurs as moisture-laden air rises over high terrain; The air cools, condenses, and releases water. The atmosphere is heated by latent heat. But as the world warms and emissions of greenhouse gases such as carbon dioxide (CO2), predicting changes in precipitation in mountains is becoming more complex.
In a new study, Cadd et al. Fill the knowledge gap by predicting how precipitation in mountains will change with global warming in response to rising carbon dioxide2. In previous research, rainfall in mountains was expected to increase with global warming, because atmospheric humidity rises with temperature. However, observations in many regions over the past few decades have shown varying weather patterns in mountainous regions.
Global climate models divide the Earth’s surface into a three-dimensional grid, and the smaller the grid cells, the more accurate the results. In order to better account for complex mountain precipitation changes with increasing CO22The researchers used the Community Earth System Model (version 1.2.2), which has a high resolution of 25 km (which means the grid cells are 25 km horizontally wide). This allowed the team to input details about local conditions, including topography and surface roughness — along with information about wind patterns, moisture sources and temperature — to run global simulations spanning the next century. Their projections found that mountainous regions warm in response to carbon dioxide2 Of the global average, carbon dioxide has doubled2 The levels would result in a temperature increase of 3.44 degrees Celsius compared to today, while carbon dioxide would quadruple.2 Levels will lead to an increase of 7.35 degrees Celsius.
The researchers discovered that changes in precipitation patterns are more pronounced over mountains in low latitudes, especially over their peaks and steep terrain. They focused on five low-latitude mountain ranges, in New Guinea, East Africa, the Himalayas, Central America, and the Central Andes. New Guinea, East Africa, the eastern Himalayas and the leeward side of the central Andes saw more rainfall in response to increased carbon dioxide2 Levels. Drier conditions occurred in the mountains of Central America and the leeward side of the central Andes.
The researchers suggest that the mixed precipitation patterns are due to a feedback mechanism. High humidity levels in mountainous terrain cause air to move upward, promoting heating and precipitation, which then leads to more humidity. Conversely, a lack of humidity means less upward air movement, less precipitation, and a persistent lack of moisture. They add that further investigations into mountain meteorology will likely add additional insights into mountain hydrology, and that this research has far-reaching implications for ecosystem and community health over the next century. (Earth’s future(https://doi.org/10.1029/2023EF003886, 2023)
—Sarah DeRwin (@Sarah_Derwin), science writer