Environmental Systems and Societies
How does latitude affect climate?
In general, the farther you move from the Equator, the colder the climate becomes. At 0° latitude (the Equator), the climate is warm, while at 90° latitude (the Poles), it is cold. However, climate is actually shaped by insolation (sunlight received), temperature, and precipitation, which show distinct trends as latitude increases. Let’s examine how these three factors vary at different latitudes.
At the Equator, the Sun’s rays strike the Earth almost directly throughout the year. As a result, insolation and temperatures remain high all year. The strong solar energy heats the air, increasing evaporation. The resulting water vapour leads to a humid climate with heavy rainfall. Water vapour also acts as a greenhouse gas, trapping heat and further raising temperatures. Countries such as **Ecuador, Brazil, Uganda**, and **Indonesia** all have warm tropical climates with high rainfall.
At about 30° latitude, the Sun’s rays hit directly at the height of summer but at an angle of roughly 30° in the middle of winter. This creates hot summers and cooler winters, with insolation and temperature varying by season. Due to the Hadley circulation, air descending at this latitude is dry and causes low rainfall. As a result, these regions are dominated by **deserts**, with low precipitation, dry air, and extreme day–night temperature swings.
At around 40° latitude, the Sun’s rays always strike at an angle, with the steepest angle in summer and the shallowest in winter. This creates warm summers and cold winters. Here, the Ferrell cells move heat and moisture poleward, producing moderate to high rainfall. Cities such as **Beijing, Istanbul, Madrid**, and **New York** sit at about 40° North, while **Argentina, Chile, Wellington (New Zealand)**, and **Tasmania (Australia)** lie near 40° South. These areas experience seasonal climates with significant precipitation, but local features such as proximity to oceans or mountains strongly influence the exact climate.
At around 66° latitude, we reach the Arctic Circle (North) and the Antarctic Circle (South). From here until the Poles, the tilt of the Earth creates polar days (24 hours of sunlight) at the height of summer and polar nights (24 hours of darkness) at the height of winter. The extremely low insolation results in very cold temperatures. Precipitation is also minimal because evaporation is weak, and most moisture is already released around 60° latitude by the Polar cells, effectively creating polar deserts in the Arctic and Antarctic.