The city's growing size and people are making cities hotter than the surrounding areas due to changes in surfaces and human-made heat. To understand this urban heat island effect, researchers looked at how cities become hotter using three methods: checking ground weather, using satellites to see from up high, and making computer models. They found that current methods have limitations and need improving. To study this better, they say they need high-quality satellite images and consider how small particles affect the sun's heat in cities.