HS-ESS2-2: Feedbacks Between Earth's Systems
Also called NGSS HS-ESS2-2 · Topic: Earth's Systems · Earth and Space Science
The Official Wording
Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems.
Clarification statement: Examples should include climate feedbacks, such as how an increase in greenhouse gases causes a rise in global temperatures that melts glacial ice, which reduces the amount of sunlight reflected from Earth's surface, increasing surface temperatures and further reducing the amount of ice. Examples could also be taken from other system interactions, such as how the loss of ground vegetation causes an increase in water runoff and soil erosion; how dammed rivers increase groundwater recharge, decrease sediment transport, and increase coastal erosion; or how the loss of wetlands causes a decrease in local humidity that further reduces the wetland extent.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-ESS2-2 Means in Plain English
Students analyze real geoscience data to show that one change at Earth's surface can ripple through other systems and come back around. The classic case is melting ice: less ice reflects less sunlight, the surface warms more, and still more ice melts.
No formal limit is set. Other feedbacks count too, like cleared plants leading to more runoff and erosion. It builds on human impacts on climate (MS-ESS3-5) and leads into modeling how energy flow shapes climate (HS-ESS2-4).
HS-ESS2-2 I Can Statements
- I can explain what a feedback loop is in Earth's systems.
- I can tell a reinforcing feedback from a balancing one.
- I can use data to support a claim about a feedback.
HS-ESS2-2 Worked Example
An outdoor test of dark and bright icy surfaces, then a look at real sea-ice records.
Does darkening an icy surface make it melt faster, and how could that feed back on climate?
Set It Up: Two equal trays of shaved ice, one dusted with a thin layer of charcoal powder, set in full sunshine with a measuring cup for meltwater.
- Set both trays side by side in the sunshine at the same time.Same ice, same sunshine, same start
- Pour off and measure the meltwater from each tray every 10 minutes for 40 minutes.Dusted tray gives noticeably more meltwater
- Explain the difference: bright ice bounces sunshine away while the dark dust soaks it up.Albedo: bright surfaces reflect, dark ones absorb
- Read the September Arctic sea-ice record since 1979.Late-summer ice cover trends clearly downward
- Draw the loop: warming melts sea ice, the darker ocean absorbs more sunshine, and the water warms further.A reinforcing feedback
The dusted ice melted faster, for the same reason shrinking sea ice exposes dark ocean that soaks up more energy and drives further melting.
Why it works: Ice reflects much of the sunshine that strikes it while open ocean absorbs most of it, so losing ice adds heat that removes even more ice.
Common Mistakes with HS-ESS2-2
Thinking feedback just means a response
“The feedback is that the ice melts.”
Try this: A feedback is a loop: the effect circles back and changes its own cause, either strengthening it or weakening it.
Calling a positive feedback good
“Positive feedback means a good thing for the planet.”
Try this: Positive means the loop amplifies the change, not that it helps. The ice and sunlight loop is positive and speeds warming.
Changing more than one thing
One tray in shade, the dusted tray in full sun
Try this: Keep sunlight, ice amount and start time the same for both trays so the dust is the only difference between them.
Where HS-ESS2-2 Fits
Practice HS-ESS2-2
Quick Check
- Why does losing sea ice speed up warming in the Arctic?
- Is the ice and sunlight loop a reinforcing or a balancing feedback?
- Clearing a hillside of plants increases runoff. What feedback might follow?