A quality white roof like Sika Sarnafil deflects solar radiation instead of absorbing it like the typical dark coloured roof. This helps to reduce heating costs and contributes less to warming temperatures around cities.
The urban heat island (UHI) effect describes how scientists have noticed warmer temperatures in cities vs outlying areas. This increase in temperature is attributed to the many man-made structures and infrastructure that absorb solar radiation. The thermal image below demonstrates a cool roof (blue) vs a standard roofing (red).
The UHI has many impacts on climate change and social health. The Government of Canada article on UHI provides an excellent explanation as to why choosing a cool roof is important and how UHI can be minimized.