Urbanization has contributed to the warming trend in the Philippines, especially in major cities, a recent study by climate scientists suggested. 

The annual mean temperature increased by 0.16 °C per decade between 1951 and 2018, according to a report published by the Philippine Climate Change Assessment (PhilCCA) Working Group 1 last month. 

Metropolitan areas tend to get hotter than rural areas due to a phenomenon called urban heat island. This is because buildings, concrete, and other urban structures absorb and retain more heat than natural landscapes. 

Urban expansion also changes the land cover. As a result, the radiation and energy balance in urban areas are affected. 

There has been a significant increase in warm nights and decrease in cool nights in Metro Manila, scientists said, noting this trend is “consistent with countrywide analysis.”

Concrete and other urban structures hold onto the heat from the sun during daytime and release it slowly, causing a delay in cooling, explained John Manalo, a weather specialist at the Philippine Atmospheric, Geophysical and Astronomical Services Administration and one of study’s authors.

At night, the stored heat radiates back, but instead of immediately dissipating, it lingers. 

“This heat transfers between concrete structures, especially with the addition of air conditioning in buildings, which accumulates warm air at night. As a result, UHI intensity is often higher during nighttime than daytime,” Manalo said. 

Experts have highlighted the need for green spaces in urban areas to mitigate the impact of the urban heat island effect, provide shade and cooling effects in built-up areas, and reduce energy consumption for cooling. 

Climate scientists also found that urbanization can potentially enhance rainfall associated with southwest monsoon or habagat over the National Capital Region by 20%. 

The published report, written by Filipino scientists, assesses the state of climate science in the Philippines. It was patterned after the reports by the United Nations’ Intergovernmental Panel on Climate Change (IPCC) on the latest climate science, threats posed by climate change, and measures to limit future temperature increases and adapt to climate impacts.