Climate Analysis

Science background gives teachers more in-depth information on the phenomena students explore in this unit. Below is an excerpt from the science background on climate analysis through ice cores.

Earth and the Sun

Glaciers exist in Antarctica because it is the coldest continent on Earth. This is because of its location near the South Pole, which determines how much direct sunlight it receives. The sun’s rays are the most concentrated around the equator. Moving north or south of the equator, the sun’s rays are spread over a larger area, so each square meter of Earth’s surface receives less solar energy.

This is because of the angle of the sun’s rays as they reach Earth. Near the equator, the sun’s rays hit Earth at close to a 90-degree angle. This means that the sun’s radiant energy is concentrated within a small surface area. This results in warm temperatures. At higher latitudes, the angle that the sun’s rays hit Earth is smaller. This causes the sun’s energy to be spread over a larger surface area, which results in lower overall temperatures.

The amount of sunlight reaching a particular location on Earth also changes over the course of a year as Earth orbits the sun. It takes Earth 365 days to complete one orbit around the sun, equal to one year.

As Earth moves around the sun, the amount of sunlight that reaches the planet changes over a year. This causes seasons— periods of time characterized by specific weather patterns and by the length of day and night. People often believe that Earth has seasons because Earth is closest to the sun in the summer, and this is why the summer is so much hotter than the winter. However, this isn’t true. The distance between Earth and the sun is relatively constant during Earth’s orbit. The reason that Earth experiences seasons has to do with the planet’s tilt on its axis as it orbits the sun.

The axis is an imaginary line that goes from the North Pole to the South Pole. Earth is tilted 23.5 degrees on its axis. As Earth orbits the sun, its tilted axis always points in the same direction, toward the North Star. So, different parts of Earth get the sun’s direct rays throughout the year. For half of the year, Earth’s North Pole is tilted toward the sun. When the North Pole is tilted toward the sun, the sun shines more directly on the northern hemisphere. This is because the sun’s rays hit Earth at a higher angle.

This causes temperatures to be warmer. At the same time, the sun is shining less directly on the southern hemisphere. This is because the sun’s rays are hitting Earth at a lower angle. This causes the sun’s rays to spread out over more space, which results in cooler temperatures. This results in summer in the north and winter in the south. For the other half of the year, Earth’s North Pole is tilted away from the sun. This results in winter in the north and summer in the south.

Seasons on Earth

When winter comes to Antarctica, the South Pole is tilted away from the sun. As a result, many places on the continent experience “polar night,” when the sun never rises above the horizon.

Palmer Station is located far enough north that the sun rises above the horizon for a couple of hours before setting. However, the sun stays behind a glacier, so the station remains in the shadows during this time. In the summer in Antarctica, the South Pole is tilted toward the sun. Because Antarctica is so far south, it remains in sunlight for almost 24 hours a day. In some locations in Antarctica, the sun never sets and it is light for a full 24 hours. This is called midnight sun.

Climate and Weather

Seasons occur cyclically, which means they occur once in a set period of time. Each season occurs once every year because that is how long it takes the planet to complete one full orbit around the sun. Antarctica experiences two seasons every year: winter and summer.

More temperate locations experience four seasons: summer, fall, winter, and spring. Spring and fall occur during the transition between summer and winter, and they take place at opposite times in each hemisphere.

The tropical region also experiences two seasons, but unlike the polar regions, its two seasons are the wet season and the dry season. Because the sun’s rays shine directly on the equator year-round, it never gets cold enough for winter. These regions also experience about 12 hours of day and 12 hours of night all year.

The uneven heating of Earth’s surface, along with the cycling of water around the planet, are major drivers of weather and climate on Earth. Weather is the conditions of the atmosphere (temperature, humidity, wind speed, and precipitation) at a particular place and time. Climate is the average weather in a location over 30 years or more.

Scientists who study climate look at a variety of factors because Earth’s climate is complex. There are many variables that affect climate, but the position of Earth relative to the sun is believed to be the most important because the sun provides thermal energy that heats the planet.