Northern Hemisphere
The Northern Hemisphere is the half of Earth that lies north of the equator. This simple line divides our planet into two distinct halves, yet it carries profound implications for life on this side of the globe. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole. This definition anchors all subsequent discussions about climate, geography, and human settlement patterns within this vast region.
Due to Earth's axial tilt of 23.439281°, there is a seasonal variation in the lengths of day and night across the Northern Hemisphere. There is also a seasonal variation in temperatures, which lags behind the variation in day and night duration. Conventionally, winter in the Northern Hemisphere is taken as the period from the December solstice, typically occurring around December 21 UTC, to the March equinox, usually falling near March 20 UTC. Summer follows as the period from the June solstice through to the September equinox, often landing on September 23 UTC. These dates vary each year due to the difference between the calendar year and the astronomical year. Within the Northern Hemisphere, oceanic currents can change weather patterns that affect many factors along the northern coast. Such events include El Niño, Southern Oscillation, which influences global climate systems.
Trade winds blow from east to west just above the equator. The winds pull surface water with them, creating currents that flow westward due to the Coriolis effect. The currents then bend to the right, heading north toward higher latitudes. At about 30 degrees north latitude, a different set of winds, known as the westerlies, push the currents back to the east, producing a closed clockwise loop. In the Northern Hemisphere, objects moving across or above the surface of Earth tend to turn to the right because of this same Coriolis effect. As a result, large-scale horizontal flows of air or water form clockwise-turning gyres. These are best seen in ocean circulation patterns within the North Atlantic and North Pacific oceans. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere. Conversely, air rising from the northern surface tends to draw air toward it in a counterclockwise pattern. Hurricanes and tropical storms, massive low-pressure systems, spin counterclockwise in the Northern Hemisphere.
During the 2.5 million years of the Pleistocene, numerous cold phases called glacials occurred at intervals of approximately 40,000 to 100,000 years. Significant advances of continental ice sheets took place in Europe and North America during these periods. The long glacial periods were separated by more temperate and shorter interglacials that lasted about 10,000 to 15,000 years. The last cold episode of the last glacial period ended about 10,000 years ago. Earth is currently in an interglacial period of the Quaternary, known as the Holocene. The glaciations that occurred during the glacial period covered many areas of the Northern Hemisphere. The setup of 3 to 4-kilometer thick ice sheets caused a sea level lowering of about 120 meters.
The Arctic is a region around the North Pole, located at 90° latitude. Its climate is characterized by cold winters and cool summers. Precipitation mostly comes in the form of snow. Areas inside the Arctic Circle, which lies at 66°34′ latitude, experience some days in summer when the Sun never sets, and some days during winter when it never rises. The duration of these phases varies from one day for locations right on the Arctic Circle to several months near the Pole. Between the Arctic Circle and the Tropic of Cancer, which sits at 23°26′ latitude, lies the Northern temperate zone. Changes in these regions between summer and winter are generally mild rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather. Tropical regions lie between the Tropic of Cancer and the Equator at 0° latitude. They are generally hot all year round and tend to experience a rainy season during summer months and a dry season during winter months.
As of 2015, the Northern Hemisphere is home to approximately 6.4 billion people, representing around 87.0% of Earth's total human population of 7.3 billion people. Calculated from World Population Yearbook 2019 data, the Northern Hemisphere contains about two-thirds of Africa and a small part of South America. The continents of North America and mainland Eurasia are located entirely within this region. Countries with land that straddles the equator are divided into half populations in each hemisphere. Entirely northern countries include Algeria, Benin, Burkina Faso, Cameroon, Cape Verde, Central African Republic, Chad, Djibouti, Egypt, Eritrea, Ethiopia, Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Libya, Mali, Mauritania, Morocco, Niger, Nigeria, Senegal, Sierra Leone, South Sudan, Sudan, Togo, and Tunisia. Most of these nations lie north of Libreville in Gabon in the west to south of Mogadishu in Somalia in the east.
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Common questions
What is the Northern Hemisphere?
The Northern Hemisphere is the half of Earth that lies north of the equator. This region contains 87.0% of the total human population as of 2015.
When does winter occur in the Northern Hemisphere?
Winter in the Northern Hemisphere runs from the December solstice around December 21 UTC to the March equinox near March 20 UTC. Summer follows this period and extends from the June solstice through to the September equinox on September 23 UTC.
How do weather systems spin in the Northern Hemisphere?
Hurricanes and tropical storms spin counterclockwise in the Northern Hemisphere due to the Coriolis effect. Conversely, high pressure weather cells exhibit clockwise air circulation patterns within this region.
Where are the ice sheets located during glacial periods?
Significant advances of continental ice sheets took place in Europe and North America during the Pleistocene glacials. These 3 to 4-kilometer thick ice sheets caused a sea level lowering of about 120 meters.
Which countries are entirely within the Northern Hemisphere?
Entirely northern countries include Algeria, Benin, Burkina Faso, Cameroon, Cape Verde, Central African Republic, Chad, Djibouti, Egypt, Eritrea, Ethiopia, Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Libya, Mali, Mauritania, Morocco, Niger, Nigeria, Senegal, Sierra Leone, South Sudan, Sudan, Togo, and Tunisia. Most of these nations lie north of Libreville in Gabon in the west to south of Mogadishu in Somalia in the east.