Paddy field area temperature 2 degrees lower than city area temperature: NARO and Hokkaido University

HOKKAIDO, Mar. 16 – The National Agriculture and Food Research Organization (NARO) and Hokkaido University have reported in numerical models that paddy fields contribute to lowering air temperature in summer. They confirmed in the simulations that, on sunny days in summer, the temperature in the area with paddy fields is lower by around 2 degrees than in the urban area and that paddy fields can help control the temperature in a broader area. The research scientifically explained one of the multiple functions of paddy fields. It also finds that this mercury control effect diminishes if carbon dioxide (CO2) in the air increases, and that will make us more susceptible to the climate change impact.

When rice photosynthesizes, it opens stomatal pores in the leaves to release some water. Such water evaporates, takes away heat, and lowers the temperature of the surrounding area.

The numerical models showed that, at the current CO2 concentration (400ppm), the temperature of rice paddy areas is about 2 degrees lower than urban areas. It also confirmed, when the CO2 concentration is double the current concentration, the opening of the pores becomes smaller, and the temperatures of paddy fields and urban areas rise by about 0.2 to 0.7 degrees and 0.3 degrees, respectively. As a result, the temperature of the entire area increases.

According to NARO’s Institute of Agro-Environmental Science, “Modeling has great meaning in addressing multiple functions of paddy fields. It will also give us a hint to think about what will happen to the local environment when CO2 increases.”

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