Heliophysics Big Idea 1.3
The Sun's energy drives Earth's climate, but the climate is in a delicate balance and is changing due to human activity.
Expanded from question one of the big three heliophysicist investigative questions: What are the impacts of the sun on humanity? Learn more ›
The global warming trend observed on Earth since the mid-20th century is caused by human activities. Human-made emissions in the atmosphere, rapid, unsustainable deforestation, and the increases in non-reflective surfaces, like asphalt, are all examples of human activities amplifying the greenhouse effect, trapping and slowing heat loss to space. While the Sun has played a role in past climate changes, for example, a decrease in solar activity- coupled with increased volcanic activity- helped trigger the Little Ice Age, the evidence shows the current global warming of Earth’s climate cannot be explained by the Sun. Even fluctuations in solar irradiance (the Sun’s energy Earth receives), as the Sun goes through its 11-year cycle, does not cause Earth’s climate to change.
Guiding Question: How are weather and climate different?
Standards: LS4, ESS2, ESS3, PS3
- Climate describes a range of an area's typical weather. Earth has many different climates. Climates differ by location on Earth, but ultimately all of Earth's climates are driven by the amount of Sunlight reaching Earth.
- Students at this level begin to learn about how sunlight warms the Earth in grade K (K-PS3-1,2), and by grade 4 they know that sunlight can transfer energy (4-PS3-2). Stewardship of Earth is a major theme at every grade level. At the grade 3 level, students can define what climate is (3-ESS3-2) and in grade 4 they are able to identify the impact of using non-renewable resources on Earth's systems, which includes air pollution from burning fossil fuels (4-ESS3-1). At the grade 5 level students are defining Earth's systems, including the atmosphere (5-ESS2-1).
- Connect to the Sun by emphasizing that energy from sunlight heats the land, water, and air. Some of the heat is reflected back into space, some of the heat is absorbed by Earth's systems. If too much heat is reflected or absorbed, Earth's systems aren’t able to support life. By burning fossil fuels, as well as other activities, humans are changing how the Earth's systems reflect and absorb sunlight. It is important, at all levels, to distinguish the causes of long-term and short-term climate change. The Sun is the main source of energy for Earth (sunlight). This energy input has changed over long time scales (millions of years), causing natural climate change (e.g. ice ages). However, it is essential to emphasize that humans, through the disruption of Earth’s energy budget, cause climate change over a much shorter time scale (decades to centuries). The result is the biosphere cannot adapt quickly enough to overcome these rapid, artificial changes without causing extinction events for some species (3-LS4-4).
- Extend student exploration by discussing how different surfaces reflect and absorb sunlight, causing some surfaces to remain cool (snow, ice, cement), while other surfaces become hot (asphalt). Changing the surface of the land, for example by removing trees and adding more roads and buildings, can also contribute to climate change because it affects how Earth reflects sunlight.
- Support younger students by modeling making observations of how sunlight heats Earth's surface. By grade 5 students are able to understand how sunlight heats the atmosphere and how trapped greenhouse gases affect the heating of Earth’s surface.
- Challenge students at the next level by exploring data related to long-term and short-term climate change.
Featured Resource: NASA Climate Kids: Weather and Climate ›
Guiding Question: Is the Sun getting hotter?
Standards: ESS2, ESS3, PS1, PS3
- The Sun's core is more than 27 million degrees Fahrenheit and will remain at that temperature until it runs out of fuel in approximately 4.5 billion years. When it runs out of fuel, it will slowly cool to an object called a white dwarf, which is a dense, cool object that is only 90,000 degrees F. While the temperature of the Sun has changed over a time-scale of billions of years, the temperature of the Sun does not impact short-term climate change. Even though daily fluctuations in the radiation levels from the Sun may impact weather, this does not produce climate change.
- At the middle level students are beginning to differentiate between thermal motion and radiation, and learn that radiation carries energy, which can be absorbed to produce heat (MS-PS1-4, PS3-3,4). Students also explore weather, climate, and the human impact of changes on Earth's energy budget (MS-ESS2-6, ESS3-3, ESS3-5).
- Connect to the Sun by emphasizing to students that the Sun's energy gets to Earth via solar radiation and that Earth has an energy budget based on the amount of incoming and outgoing solar radiation. The Sun warms Earth's atmosphere, which drives Earth's weather systems. While the Sun is not getting hotter, the amount of radiation being trapped in Earth's atmosphere is increasing due to the burning of fossil fuels. When heat can't escape Earth's atmosphere, changes to Earth's energy budget causes rapid climate change, at a rate in which biological life has trouble adapting. At the dawn of life, at about 3.8 billion years ago, the Sun was 30% dimmer, but there were more greenhouse gases, which kept Earth from freezing.
- Extend student exploration by emphasizing that an important aspect of Earth's energy budget is how much ice is on Earth. Ice reflects solar radiation back into space, which helps cool Earth. The warmer Earth becomes, the less ice will be on Earth, and the warmer Earth becomes. This is called a positive feedback loop. Periods during Earth's history, known as ice ages, are also not caused by increased solar radiation, or from the Sun getting hotter, but from changes to Earth's atmosphere from volcanic activity (MS-ESS2-1).
- To support beginner students, ask students to explain the difference between weather and climate with examples (3-ESS3-2).
- Challenge students at the next level by exploring how Earth's orbit has changed over time, which has also affected Earth's climate.
Featured Resource: Earth's Albedo and the Sun's Brightness Affect on Climate Interactive ›
Guiding Question: How does the changing shape of the Earth's orbit over hundreds of thousands of years cause climate change?
Standards: ESS1, ESS2, PS2
- The orbits of the planets around the Sun were set into motion when the solar system was formed, 4.5 billion years ago, and subsequently altered by collisions of planetary bodies and other forces. For example, the Moon is thought to have been formed from a chunk of the Earth that broke off during a collision early in Earth's history. Changes in Earth's movement, which includes the shape of its orbit around the Sun (eccentricity), the angle of the Earth's axis with respect to Earth's orbital plane (obiquity), and the direction Earth's axis of rotation is pointed (precession or "wobble"), are called Milankovitch cycles. These cycles, or changes in Earth's orbit, cause the amount of sunlight to vary and cause the climate to oscillate over longer time scales (hundreds of thousands of years).
- At this level, Kepler's and Newton's laws are used to quantify the motion of Earth around the Sun (HS-ESS1-4, HS-PS2-4). Milankovitch cycles are directly addressed by (HS-ESS2-4). Emphasize that short-term climate change is caused by human activity, not Milankovitch cycles.
- Connect to the Sun by focusing on how these cyclical changes have altered the intensity and distribution of sunlight falling on Earth (insolation), causing cycles of ice ages and other gradual climate changes.
- Extend student exploration by comparing the time scale of climate change caused by humans (in the last 100 years, a the beginning of the Industrial Revolution) with the Milankovitch cycles. Recent rising global temperatures have caused increased frequency and intensity of storms, melting polar ice, and sea level rise. Humans, over thousands of years, have caused desertification, which changes Earth’s albedo, which alters Earth’s energy budget and climate.
- To support beginner students, make sure they understand the greenhouse effect (MS-ESS3-5).
- Challenge students at the next level by exploring the mathematical model for calculating differences in solar radiation at various Earth latitudes, along with corresponding surface temperatures. For example, the heating of Earth’s surface varies with the sine of the Sun’s elevation angle in the sky and the cosine of the latitude of the surface.
Featured Resource: Milankovitch (Orbital) Cycles and Their Role in Earth's Climate Exploration ›