The phrase "regional scale" refers to a specific geographic area that is larger than a local or city level, but smaller than a national or global level. It focuses on a particular region or territory within a country or a continent. Full definition
They identified those sea level changes that have a large impact at regional scales in many locations, including largely populated cities. (jpl.nasa.gov)
It also looks at what is being done to mitigate climate change, and what else can be done, from a governmental scale to a more regional scale. (metlink.org)
Evolution of anthropogenic and biomass burning emissions of air pollutants at global and regional scales during the 1980 - 2010 period. (iiasa.ac.at)