# Climate Analysis

In this unit, students focus on the phenomena of Earth’s ice as they model how glaciers shape Earth’s surface. In this lesson, they investigate how scientists use ice cores to reconstruct Earth’s past climates and environments. This page is a high-level extract of this lesson.

## Science Background for Teachers:

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.

## Science Lesson: Exploring Climate Analysis

Once students understand how glaciers store ice that can be thousands or millions of years old, they examine how glaciers store a record of past climate changes in their ice. Scientists use glacial ice core stratifications to analyze Earth’s past climate changes, and have learned that Earth has experienced at least five ice ages since it first formed.

## Science Big Ideas

• Glaciers hold clues to Earth’s past climate.
• Ice cores are like a weather report over hundreds or thousands of years, providing scientists with information about Earth’s changing temperature, climate, atmosphere, and biological activity.
• Earth’s climate has not always been the same as it is now. Scientists believe we are currently living in the warm period of Earth’s fifth ice age, which began about 10,000 years ago.
• Ice ages occur when Earth’s average temperature decreases, which is related to how the sun’s energy reaches Earth.
• The position of Earth relative to the sun is believed to be the most important factor in influencing climate because it causes uneven heating of the planet.
• Climate is very complex because it is affected by many different things. There are different possible causes for Earth’s dramatic changes in climate throughout the planet’s history.

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## Science Essential Questions

• How can glacial ice provide scientists with information about past changes to Earth’s climate?
• Why do scientists think we are currently living within a warm period of an ice age?
• What would likely happen to the distribution of water on Earth during the coldest part of an ice age?
• How would you explain the relationship between Earth’s tilt, its curved shape, and the general climate in Antarctica?
• How can scientists use ice cores to determine different seasons, as well as the length of a climate period?
• What are some longer-term causes of Earth’s climate changing in the past?
• Why do scientists believe the climate changes we are seeing today are a direct result of human activities?
• How would you explain the relationship between Earth’s temperature, glaciers, and ocean levels to analyze one effect of a changing climate on people?

## Common Science Misconceptions

Misconception: The Ice Age happened in the past.

Fact: We are currently in a warmer period within an ice age, and Earth has experienced multiple ice ages since it first formed.

## Science Vocabulary

Climate : the average weather in a location over 30 years or more

Ice age : a global climate marked by long periods of cold temperatures that cause glacial formation and expansion

Ice core : cylinder of ice drilled out of glaciers that contains layers of snow, dust, volcanic ash, atmospheric gasses, and microbes from past time periods

Season : a period of time characterized by specific weather patterns and by the length of day and night

Weather : the conditions of the atmosphere (temperature, humidity, wind speed, air pressure, and precipitation) at a particular place and time

## Lexile(R) Certified Non-Fiction Science Reading (Excerpt)

Storing Ice

The National Ice Core Laboratory in Colorado is not your typical science laboratory. Scientists inside the lab wear ski parkas, insulated gloves, and boots as they work. They need to dress warmly because the lab is kept at -23 degrees Celsius (-10 degrees Fahrenheit).

And the sound of saws buzzing is a common sound. This is because scientists measure and cut pieces of Antarctic glacier ice from massive ice cores stored in the laboratory. An ice core is a cylinder of ice drilled out of glaciers that contains layers of snow, dust, volcanic ash, atmospheric gasses, and microbes from past time periods.

Scientists from all over the country come to the National Ice Core Laboratory to study pieces of ice cores that are stored there. The laboratory holds ice cores from glaciers around the world. For example, one project includes ice cores from a giant, ancient Antarctic ice sheet that is more than 70,000 years old. A team of scientists traveled to Antarctica to drill the ice cores, and then sent them back to the laboratory.

Ice cores are important for scientists who want to learn about Earth’s changing climate. Climate is the average weather in a location over 30 years or more. Weather is the conditions of the atmosphere (temperature, humidity, wind speed, and precipitation) at a particular place and time. Dust, volcanic ash, air bubbles, and sediment trapped in glacial ice can reveal information about the climate on Earth at the time they were trapped in ice.

An Icy ‘Weather Report’

Scientists believe that Earth is 4.5 billion years old. During Earth’s history, the planet has been without glaciers longer that it has been with glaciers. Glaciers only form when the planet does not receive enough solar energy for snowfall to completely melt over the summer.

Scientists use scientific instruments to read ice cores like a weather report that includes weather data from year to year, going back hundreds or thousands of years. This is possible because ice cores contain evidence of past changes. Air bubbles contain atmospheric gasses from hundreds or thousands of years ago. Volcanic ash reveals volcanic activity. The composition of the snow in a particular layer can reveal the temperature.

Scientists can also look for patterns in the ice cores. Summer layers in an ice core are lighter than winter layers. Thicker bands indicate a longer climate period, while narrower bands indicate a shorter climate period. Warmer temperatures are often followed by increased biological activity because living things need a certain temperature to survive.

Because of ice cores, scientists know that in Earth’s history, there have been several ice ages—global climates marked by long periods of cold temperatures that cause glacial formation and expansion. Glaciers expand during the cold periods of an ice age. At the height of the last cold period, about 100,000 years ago, glaciers reached down to the city of Chicago and up to the middle of South America. This last cold period was called the Great Ice Age.

Scientists believe we are currently living in the warm period of Earth’s fifth ice age, which began about 10,000 years ago. It is a warm period because glaciers are present but retreating. There are complex variables that influence the climate at any given time and can cause it to change. For example, sudden events such as a volcanic eruption or a forest fire can impact the climate. Volcanic eruptions send ash particles into the environment, blocking sunlight from reaching Earth’s surface. This contributes to Earth’s cooling. However, volcanoes also release carbon dioxide, which causes warming over millions of years because it traps thermal energy from the sun. For this reason, carbon dioxide, along with water vapor and methane are called greenhouse gasses.

Forest fires release carbon dioxide into the atmosphere. But if a forest re- grows after the fire, the trees and other plants will remove about the same amount of carbon dioxide as was released into the environment during the burning.

Other changes can be more long-term. For example, the path of Earth’s orbit around the sun has changed over time, as has the way Earth tilts toward the sun. Both of these factors influence how much thermal energy from the sun Earth absorbs, which in turn affects Earth’s temperature and climate.

## Hands-on Science Activity

In this lesson, students create glacial ice core stratification models to investigate how ice cores form and how scientists use them to analyze climate data. Students use their observations to explain how ice core samples are extracted from ice sheets and how the ice layers can provide evidence of past climate events (volcanic eruptions, warm periods, cold periods, etc.).

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