The researchers used satellite images to study how the temperature of the land in Beijing changed over time, showing the city's urban heat island effect. They found that between 2008 and 2011, Beijing experienced a significant heat island effect, with temperatures rising in urban areas. The strongest heat island effect was in summer, followed by spring and autumn, while winter had the least impact. The study also showed that increasing green and water areas in the city can help reduce the heat island effect.