 This is definitely a question that would be asked by someone in the Northern Hemisphere, since January in the Southern Hemisphere is definitely warm! From a global perspective, when the Earth is farther away from the sun in its orbit, the average temperature does increase by about 4°Fahrenheit (2.3°Celsius), even though the sunlight falling on Earth at aphelion is about 7 percent less intense than at perihelion. So why is it warmer when we are farther away from OUf star? The main reason is the uneven distribution of the continents and oceans around the globe. The Northern Hemisphere contains more land, while the Southern Hemisphere has more ocean. During July (at aphelion), the northern half of our planet tilts toward the sun, heating up the land, which warms up easier than the oceans. During January, it’s harder for the sun to heat the oceans, resulting in cooler average global temperatures, even though the Earth is closer to the sun. But there is another cause for warm temperatures in the north when the Earth is at aphelion: the duration of summers in the two hemispheres. According to Kepler’s second law, planets move more slowly at aphelion than they do at perihelion. Thus, the Northern Hemisphere’s summer is 2 to 3 days longer than the Southern Hemisphere’s summer, giving the sun more time to bake the northern continents. A season is a period of the year that is distinguished by special climate conditions. The four seasons—spring, summer, fall, and winter—follow one another regularly. Each has its own light, temperature, and weather patterns that repeat yearly. In the Northern Hemisphere, winter generally begins on December 21 or 22. This is the winter solstice, the day of the year with the shortest period of daylight. Summer begins on June 20 or 21, the summer solstice, which has the most daylight of any day in the year. Spring and fall, or autumn, begin on equinoxes, days that have equal amounts of daylight and darkness. The vernal, or spring, equinox falls on March 20 or 21, and the autumnal equinox is on September 22 or 23. The seasons in the Northern Hemisphere are the opposite of those in the Southern Hemisphere. This means that in Argentina and Australia, winter begins in June. The winter solstice in the Southern Hemisphere is June 20 or 21, while the summer solstice, the longest day of the year, is December 21 or 22. Seasons occur because Earth is tilted on its axis relative to the orbital plane, the invisible, flat disc where most objects in the solar system orbit the sun. Earth’s axis is an invisible line that runs through its center, from pole to pole. Earth rotates around its axis. In June, when the Northern Hemisphere is tilted toward the sun, the sun’s rays hit it for a greater part of the day than in winter. This means it gets more hours of daylight. In December, when the Northern Hemisphere is tilted away from the sun, with fewer hours of daylight. Seasons have an enormous influence on vegetation and plant growth. Winter typically has cold weather, little daylight, and limited plant growth. In spring, plants sprout, tree leaves unfurl, and flowers blossom. Summer is the warmest time of the year and has the most daylight, so plants grow quickly. In autumn, temperatures drop, and many trees lose their leaves. The four-season year is typical only in the mid-latitudes. The mid-latitudes are places that are neither near the poles nor near the Equator. The farther north you go, the bigger the differences in the seasons. Helsinki, Finland, sees 18.5 hours of daylight in the middle of June. In mid-December, however, it is light for less than 6 hours. Athens, Greece, in southern Europe, has a smaller variation. It has 14.5 hours of daylight in June and 9.5 hours in December. Places near the Equator experience little seasonal variation. They have about the same amount of daylight and darkness throughout the year. These places remain warm year-round. Near the Equator, regions typically have alternating rainy and dry seasons. Polar regions experience seasonal variation, although they are generally colder than other places on Earth. Near the poles, the amount of daylight changes dramatically between summer and winter. In Barrow, Alaska, the northernmost city in the U.S., it stays light all day long between mid-May and early August. The city is in total darkness between mid-November and January.
« Back to Meteorology, Climatology page Because the earth’s axis is tilted. It is all about the tilt of the Earth’s axis. Many people believe that the temperature changes because the Earth is closer to the sun in summer and farther from the sun in winter. In fact, the Earth is farthest from the sun in July and is closest to the sun in January! During the summer, the sun’s rays hit the Earth at a steep angle. The light does not spread out as much, thus increasing the amount of energy hitting any given spot. Also, the long daylight hours allow the Earth plenty of time to reach warm temperatures. During the winter, the sun’s rays hit the Earth at a shallow angle. These rays are more spread out, which minimizes the amount of energy that hits any given spot. Also, the long nights and short days prevent the Earth from warming up. Thus, we have winter! Winter in Yellowstone National Park. National Park Service Web site. Rural Alabama in the spring. Carol M. Highsmith Collection, Library of Congress. Soybean and corn fields ready for harvesting in late summer in Carroll County, Indiana. Carol M. Highsmith Collection, Library of Congress. Colorado’s Delores River Valley in autumn. Carol M. Highsmith Collection, Library of Congress. Published: 11/19/2019. Author: Science Reference Section, Library of Congress
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Why is the Northern Hemisphere hotter than the Southern Hemisphere during summer and colder than the Southern Hemisphere during winter?
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