Answer: Immigration is one of the major reasons for cities to expand in size.
The greenhouse effect is related to the increase in the average surface temperature which is considered "global warming". Global warming is the result of an increase in gases like methane, carbon dioxide, and other factors that lead to a rise in the planet's temperature.
Eastern boundary currents are associated with the cooling off of the ocean waters. These currents originate from both of the poles, they bring cold, shallow, slow water towards the lower latitudes and cools of the water near the Equator. Once there they are warming up and move in the opposite direction as westward warm currents.
