Are you searching for a science lesson that brings climate change to life in your classroom? Positive feedback loops are not just fascinating—they’re a powerful way to help students grasp the dynamics behind our warming planet. By teaching about positive feedback loops, like the relationship between sea ice, albedo, and temperature, you’ll equip your students with a deeper understanding of one of the mechanisms fueling anthropogenic climate change. Let’s explore this complex topic so you can plan an impactful and accessible lesson for your learners!
Before we dive in: If you’re an educator planning to teach positive feedback loops in climate change, having great visuals to deepen understanding is key! I think you and your students will love my positive feedback loop diagram (plus you’ll support my blog with your purchase! ❤️)
What is a Positive Feedback Loop?
In science, a positive feedback loop is a cycle that keeps reinforcing or amplifying itself. A simple example is when laughter spreads. If your friend starts laughing, it might make you laugh too, which then makes your friend laugh even harder. This cycle continues, making everyone laugh more.
A positive feedback loop is called “positive”, because each part of the cycle strengthens the next, not because it is necessarily a good thing. For example, a forest fire can create a positive feedback loop. As more trees catch fire, the fire gets bigger and hotter, which makes it easier for the flames to spread to even more trees.
What is Albedo?
Have you ever noticed that a black T-shirt feels hotter than a white one on a sunny day? This is because of something called albedo. When sunlight hits a surface, some energy reflects off while the rest is absorbed, making the surface warmer. Albedo is a measure of how much sunlight a surface reflects. Light-colored or shiny surfaces have a high albedo, meaning they reflect more sunlight. Dark surfaces, like a black T-shirt, have a lower albedo, so they absorb more energy from the sun and feel warmer.
Positive feedback loops play a role in climate change, and it begins with albedo. Sea ice in polar regions is light-colored and reflective, so it has a higher albedo than dark ocean water. When sea ice melts because of anthropogenic (human-caused) climate change and rising temperatures, the reflective ice is replaced by dark ocean water. The dark ocean absorbs more heat from the sun without the reflective ice to protect it. This causes the ocean to warm more and faster, which increases temperatures and speeds up climate change. As more sea ice melts, it creates a cycle that leads to even more melting.
A Positive Feedback Loop and Climate Change
Let’s break down a positive feedback loop step-by-step:
1. Temperatures Rise
Average global temperatures are rising. This is one of the main effects of climate change.
2. Sea Ice Melts
Ice melts at 32°F (0°C). When the average global temperatures rise, more sea ice melts.
3. Ocean’s Surface Becomes Exposed
As sea ice melts, the ocean surface is uncovered. Large areas that were once covered by light-colored ice are now dark ocean water.
4. Albedo Decreases
Light-colored sea ice reflects more sunlight than dark ocean water. When the ice melts, the ocean reflects less sunlight.
5. Ocean Water Warms
Without reflective sea ice, the ocean’s water absorbs energy from the sun. This causes the ocean to warm up. And the cycle begins again.
Why it Matters
Why should you care about ice melting in faraway places like the poles? Polar ice melting is a problem for several reasons. First, as ice melts, it raises sea levels around the world. This leads to flooding along coastlines, putting coastal and island communities at risk of disappearing underwater and displacing the people living there. Another issue is the loss of important habitats for animals in the Arctic and Antarctica.
Additionally, as polar regions warm, permafrost (frozen ground) also thaws, releasing greenhouse gases and contributing to further climate change. This is a second example of a positive feedback loop in climate change because more warming causes more gases released, which causes more warming.
Teach Positive Feedback Loops and Climate Change:
There’s no need to scramble to pull together materials for a positive feedback loop lesson – I’ve already created them for you! Support this blog when you purchase my Positive Feedback Loop Diagrams and my Albedo Lab Activity materials:
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Are you looking for a hands-on activity to teach climate change? In this lab, students will create a model of sea ice and ocean water albedo using aluminum foil and two tubs of water. Students will track the temperature in a covered and un-covered tub on a sunny day. Students will learn about albedo and the impacts of positive feedback loops in climate change.
Important: I’ve made the directions for this albedo lab activity available for free here in this post. If you would like printable directions and worksheets for this activity, you can purchase them in my Albedo Lab mini-study. These materials are also included within my complete Antarctica Unit and Polar Bundle.
Printable directions for the albedo lab activity are available in my mini-study.
Materials
Each lab group will need the following materials:
Two clear-bottomed shallow plastic tubs of equal size
Cold liquid water
A large piece of dark blue or black paper or cloth
Complete this lab on a sunny, warm day close to mid-day when the sun is overhead. This lab may not work on cold or overcast days, or in the early morning or afternoon when the sun is at a lower angle in the sky.
Students should record the water temperature in the two tubs at a 5-minute interval. If the water is warming slowly, you can instruct students to switch to a 10-minute interval.
Once students see a clear trend or pattern, you may instruct them to stop taking measurements.
Activity Structure and Emphasizing Key Concepts
Before starting the lab, ask your students if they would feel cooler wearing a black or white shirt on a sunny day. Or, ask them if they would be more comfortable standing barefoot on blacktop or grass on a hot day.
During the lab, introduce the term “albedo” to your students – the amount of solar radiation reflected by a surface. Relate this to the black vs white shirt example and the blacktop vs grass example.
After completing the lab procedure, ask your students what they think happens to ocean water at the poles when it is no longer covered in sea ice. Discuss how positive feedback loopswork.
I created this positive feedback loop diagram for you. It’s available in my shop, and you can support my blog with your purchase!
Step-by-Step Procedure
Head out to a sunny area, pass out the materials, then help your students work through the following steps:
Fill the two clear plastic tubs with equal amounts of cold liquid water.
Check the starting temperature of the water in both tubs. Record the temperatures on the worksheet. The starting temperature should be the same in both tubs.
Fully cover one tub in aluminum foil. This tub represents ocean water covered in a layer of reflective sea ice. The other tub represents uncovered ocean water.
Lay your dark fabric on the ground or table outside in direct sunlight. The dark fabric represents the dark color of ocean water.
Position your tubs on top of the dark fabric in direct sunlight.
Wait 5 minutes.
Check the temperature in both tubs, by inserting the thermometer into the water at the center of the container. Poke a small hole through the foil to insert the thermometer when you check the temperature in the foil-covered tub. Record the temperatures on your worksheet.
Continue to check and record the temperatures every 5 minutes.
Which tub is warming faster? Discuss why.
Discussion Questions
After working through the lab procedure, have your students discuss the following questions in small groups or as a whole class.
Which tub became warmer faster? Explain why.
Which would get warm faster, ocean water covered in reflective sea ice or exposed ocean water? Explain why.
What is albedo? *in your own words
What is a positive feedback loop? *in your own words
In your own words, describe a positive feedback loop involving melting sea ice and climate change.
Worksheets and Printable Directions
There’s no need to put together worksheets and handouts for this lab – I’ve already created them for you! You can purchase them in my Albedo Lab Mini Study. These materials are also found within my complete Antarctica Unit and Polar Bundle.
The albedo lab materials are also found within these products:
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If you enjoyed this post, I know you will love trying my other science and nature units in your classroom too!
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You may have noticed the unique rings that appear on tree stumps – and you might even know that you can figure out a tree’s age by counting the rings! But did you know that scientists can use tree growth rings to learn about our past climate and even estimate the date of historic volcanic eruptions? In this post, we will explore the exciting fields of dendrochronology and dendroclimatology – that is, the study of tree-ring dating and the study of past climates using tree rings!
A note for teachers: if you’re planning to teach trees, you’ll find all the printable handouts, worksheets, and activity directions that you’ll need in my complete Trees Unit. Plus, you’ll support my blog with your purchase!
Growth rings form as trees grow within temperate zones: trees grow most rapidly during the warm season when their leaves are on their branches, performing photosynthesis. But in the colder season, leaves fall from branches, causing photosynthesis and growth to stall. This recurring fluctuation in growth rate each year creates the annual ring pattern.
Because of this, thicker tree rings form in years with the longest and warmest or wettest growing seasons. Cool or dry years lead to less favorable growing conditions and consequently, a thinner tree growth ring. Scientists can use tree rings in very old trees to learn about our past climate and even estimate the dates of significant geologic events like volcanic eruptions!
Beneath its rough bark, a tree holds more history than you might realize!
Tree Rings and Climate Change
Tree rings can also provide scientists with a valuable glimpse into our planet’s past climate. The patterns of thicker and thinner rings let scientists know when regions were experiencing events like droughts or cold spells: these less favorable conditions cause thinner growth rings during those years. For example, scientists in Scotland are using tree rings to learn about the variations and past behaviors of the jet stream – narrow, fast air currents in our Earth’s atmosphere, important to global weather patterns. Increased variations in tree rings in recent times lead scientists to suspect that human-caused climate change has started making the jet stream less predictable.
Additionally, historic forest fire regimes (the timing and frequency of forest fires) can be tracked through tree rings. If a tree survives a forest fire, its ring from that year will often be marked with distinct scarring from the flames. Scientists use the scars and rings to figure out the natural timing of the fire regime for a region before humans interfered.
The inside of a tree trunk contains many working parts – as well as a wealth of information about the historic climate and conditions!
You may wonder – why do we need trees to learn about past climates? Surely humans have written records of weather events. However, some trees can live to be several hundred to 1,000 years old, or more! Scientists have even found bristlecone pines, a tree species with remarkable longevity, that have been around for multiple millennia – well before humans were able to accurately measure temperature.
The tree rings can also be counted in petrified wood! When available, preserved and petrified wood give scientists an opportunity to see even further back into the past than the oldest trees in an area – just so long as they can figure out when the ancient tree fell or was chopped down.
Some petrified wood I spotted while out hiking in Colorado!
Tree Rings and Dating Volcanic Eruptions
Severe volcanic eruptions lead to less than favorable growing conditions due to volcanic debris in the atmosphere. Less sunlight reaching the Earth and poor air quality may cause thin or irregular tree rings following an eruption. Looking at the tree rings of very old trees can be a great way for scientists to narrow down the year of a historic volcanic eruption.
One recent example of using tree rings in this way involves a volcano on the Greek island of Santorini. Based on records, scientists knew a significant eruption occurred sometime around 1,600 or 1,500 B.C.E. When looking at an event this ancient, scientists are somewhat limited by the age of trees in the surrounding area – few trees alive today are known to have been alive in 1,600 B.C.E.
However, for this study, the ancient wood used to construct a tomb was used. So long as the life of the ancient tree partially overlaps with the life of a tree living today in that area, scientists can use overlaps in the ring patterns of the living and ancient tree to approximate the date it was cut down. Then, using tree rings from the ancient wood, scientists were able to narrow down the time frame and now estimate the eruption occurred close to the year 1,560 B.C.E. This was possible because scientists could detect a chemical anomaly (or sudden change from the normal chemical make-up) in the ancient tree’s growth rings around this time, caused by a sudden change in growing conditions following the eruption.
Scientists can also look at trees growing on top of volcanic debris deposits – the eruption that formed the deposits must be at least as old as the oldest tree growing on the deposit. Scientists must be careful using this method, however. Take, for example, one well-known volcano – Mount Rainier in Washington state, USA. For a while, scientists believed that Mount Rainier had erupted sometime between 1820 and 1854, based on a study involving counting the number of rings of trees growing upon moraines (mounds of debris deposits) that were assumed to have formed from an eruption (Crandell, 1969). However, more recently, scientists have discredited the tree ring study by showing that these moraines formed from older volcanic deposits being moved around by non-volcanic avalanches (Sisson & Vallance, 2009).
Volcanic eruptions have a huge impact on both the landscape and the plants and animals of an area! Pictured here is the crater of Haleakala, on the island of Maui in Hawaii.
How Scientists Observe Tree Rings
Scientists can learn a lot from looking at tree rings – but they do not necessarily need to chop down a tree to do this! The trees that give the scientists the opportunity to see the furthest back into history are the oldest trees – it certainly would not be worth chopping down these incredible, ancient living beings, just to get a look at their insides.
To look inside of a tree, scientists can use a thin, hand-operated drill to extract a thin “core” of wood. Imagine pushing a hollow straw through a layered Jello, to pull out a thin section – in that thin section you can see all the different stripes, representing each layer – or in the case of a tree, each ring! Then the stripes in the core can be counted to determine the number of rings, and the age of the tree. Trees can heal from these small puncture wounds – just like we heal after scraping a knee or getting a paper cut.
Drilling into a tree (left) then removing the core (right).
Classroom Activity: Observing Tree Rings and Tree Anatomy
As a plant anatomy learning activity, next time you see a cut log on the side of a trail, a stump, or some chopped firewood, try counting the number of rings to determine the tree’s age when it died. For additional learning fun, you can also try identifying the different parts of a tree cross-section: the bark, phloem, cambium, xylem (sapwood and heartwood), and pith:
Bark is the rough, protective outer coating. Bark helps protect the tree from insect and fungi invaders.
The phloem underlies the bark. The phloem’s function is to transport sugars. Sugars form in the leaves during photosynthesis, and the phloem moves the sugars to other parts of the plant where they are needed for growth.
The cambium is a thin layer of dividing cells between the xylem and phloem. This is where secondary (outward) growth occurs.
The sapwood underlies the cambium. The sapwood is the living part of the xylem, which actively moves water upwards through the tree. Water is drawn up through the ground via the tree’s roots. Water leaves the tree through tiny pores called stomata in the leaves, in a process called transpiration.
The heartwood is old, inactive xylem tissue. Heartwood no longer has living cells and does not move water. Heartwood provides structural support. Both living and dead xylem parts (sapwood and heartwood) contain tree rings that formed each year as the tree grew inwards from the cambium.
The pith is at the very center of the tree trunk and plays a role in the movement of nutrients. In older trees, the pith is often very tiny or diminished, relative to the size of the heartwood.
If you’re teaching this activity in an indoor classroom setting, it may help to have small wood slices to use as tree cross sections for each student to observe. (These are also really fun for kids to decorate and turn into necklaces!)
Free Worksheets: My email newsletter subscribers can download and print these free tree anatomy worksheets from my free resources page. To access the freebies, join the newsletter below:
If you enjoyed this post, I know you will love my complete Trees Unit! It has a ton of tree activities and everything you need to study trees in your classroom.
Driedger C. L. & Scott. W. E. U.S. Geological Survey. (August 28, 2008). Mount Rainier – Living safely with a volcano in your backyard. Retrieved from https://geology.com/usgs/rainier/
Pearson, C., Salzer, M., Wacker, L., Brewer, P., Sookdeo, A., & Kuniholm, P. (2020). Securing timelines in the ancient Mediterranean using multiproxy annual tree-ring data. Proceedings of the National Academy of Sciences, 117(15), 8410-8415.
This is part two of a series of posts on the water cycle. In part one, we learned how the water cycle makes life possible for land-dwelling plants and animals, including humans. The water cycle provides the constant source of freshwater that we need to survive. The sun powers the process of evaporation, which separates fresh water vapor from our oceans. This can fall as precipitation on land.
For Teachers: If you’re an educator planning to teach the water cycle, great learning resources are key to deepening understanding! That’s why I create Earth and environmental science units – packed with hands-on learning activities and engaging science diagrams made from my original watercolor artwork. I think you and your students will love my complete Water Cycle Unit(plus you’ll support my blog with your purchase! ❤️)
There is no doubt that the water cycle impacts our lives as humans. Humans, however, impact the water cycle too. Our actions as a species have effects on every step of the water cycle. In this post, let us dive deeper into the ways humans are affecting the water cycle. Although it can be overwhelming to think about the numerous ways that we impact this natural cycle – and I certainly felt a little overwhelmed in doing the research to write this post – my goal here is not to dishearten anyone about water resources. Change starts with education, and ultimately requires effort on both an individual and a larger scale. At the end of this post, I share some simple and inexpensive ways we can save water resources and reduce our impact on the water cycle. I also made a Saving Water Bingogame to help make learning about water resources fun for kids and to encourage simple steps in families’ daily routines to help save water!
Hand-drawn and labeled Water Cycle Diagram, with transpiration, runoff, infiltration, and more!
Glaciers and Ice Sheets
Due to human-caused (“anthropogenic”) climate change, the total amount of water stored in glaciers and semi-permanent snowfields has decreased each year for more than 30 years. This means that every year the amount of new glacial ice forming is less than the amount of glacial ice melting, on average, across the planet.
Glaciers and ice sheets are the largest storage of freshwater on the planet, making up over two-thirds of all the freshwater on Earth! Glacial ice also serves an important role in regulating our planet’s temperature. Compared to water or land, ice is very effective at reflecting solar radiation.Ice’s reflectiveness helps keep the Earth’s temperatures cool. However, as glaciers melt, less radiation is reflected, which causes warming, and consequently more glaciers melt. This sort of amplifying effect is called a positive feedback cycle.
I visited Byron Glacier in Alaska, which is an example of a glacier in retreat – one that shrinks more than it grows each year
Oceans
Saltwater currently makes up about 97.5% of the water on Earth! And this amount is increasing. As glaciers, ice sheets, and semi-permanent snowfields melt, their waters often flow into the oceans, mixing with salt water. The result is sea level rise. This can cause (and already is causing) an upsetting impact on humans that live in low-lying areas near oceans, such as some island nations and coastal communities.
Rising ocean levels also threaten coastal wetlands and estuary ecosystems. These are unique marshy areas along the coast with abundant and diverse plant and animal life. In addition to providing habitat for wildlife, coastal wetlands provide a buffer to coastal communities during weather events like floods. Also, the roots of the many plants in these wetlands help prevent erosion along coasts. Losing these unique coastal ecosystems also means losing their ecosystem services – the benefits that they provide to humans.
The Outer Banks of North Carolina
Precipitation
Climate change doesn’t just impact water in glaciers – it also impacts the water that falls from the sky as precipitation. Changes to the global climate can impact when, where, and how much precipitation falls. It can also impact whether precipitation falls as rain or snow.
16 inches of snow on the Colorado Front Range, March 2021. Even though I don’t love shoveling snow, I am grateful for big snowstorms – snow melt in the spring provides an important water resource in Colorado!
Runoff
A lot of the water we use comes from diverted runoff – meaning we change the path that water takes back to the ocean so that it goes where we need it most. This can happen on a very small scale, such as diverting the water that runs off of our roofs into a rain barrel. Or on a very large scale – like the Grand Ditch in Colorado, which takes water from the west side of the Rocky Mountains and brings it to the Front Range, on the opposite side of the continental divide.
Runoff begins high in the mountains where snowmelt and rain on mountain peaks feed the headwaters of streams. Runoff ends when water flows into the oceans at estuaries and deltas. As humans, we have impacts on the runoff process from the mountains to the oceans, and everywhere in between. Warmer winter temperatures in the mountains due to climate change may cause less winter snowpack than mountain regions experienced historically. Less winter snowpack means less springtime runoff.
Building reservoirs is one of the most noticeable impacts that humans have on the runoff process. Reservoirs are necessary for mountain and arid regions to maintain a year-round water supply. In these areas, most of the runoff each year arrives in a fairly short time frame in the spring, as the snow melts in the mountains. Agriculture in these areas would not be possible without storing some of that runoff to use later during the summer and fall growing seasons. Reservoirs are the way we stop and keep that water. Reservoirs have great benefits to our ability to live in arid regions but have some downsides too. Storing water in a reservoir in an arid region means having that water open to the atmosphere. Consequently, over several months of storage, significant amounts of reservoir water are lost to evaporation.
Downstream of reservoirs, the discharge, or volume of water running through a river, will be less than normal. Downstreamaquatic ecosystems can be harmed by lower flows in rivers and streams. Changing a swift, snowmelt-fed river to a slow, reservoir outflow can impact the water quality and water temperature. Some fish species are adapted for life in cold, fast-flowing water, so changes in their home stream habitat can cause them harm.
My rain barrel diverts runoff from my roof, which I then use to water my garden.
Infiltration
As water travels across the earth’s surface, naturally some of it seeps into the tiny pore spaces of the underground rocks and sediments, in a process called infiltration. In cities, large areas of the ground are covered in pavement, which is less permeablethan soils – it does not allow water to pass through as easily. This prevents infiltration from occurring in these areas. Consequently, flooding may occur because there is no place for the water to go, so it stays on the surface. Water may also become contaminated as it flows across paved surfaces, carrying pollution into nearby lakes and streams.
Groundwater
Groundwater provides much of the water we use in our homes, for irrigating crops, and for livestock drinking water. We get groundwater out of aquifers, which are underground geologic units containing water in their pore spaces. To extract the water from an aquifer to the surface, we install wells that are pumped. Pumping can have many impacts on the water cycle’s groundwater movement and storage. In some cases, pumping will lead to lowering the water table and depleting aquifers – in other words, taking groundwater out of aquifers faster than water can infiltrate into aquifers. Because this type of use will eventually lead to a groundwater well running dry, it is unsustainable water use.
Ideally, groundwater is pumped at slower, more sustainable rates, allowing time for aquifers to replenish and refill with water. Even so, pumping can have impacts on the water cycle. Any amount of pumping can change the way that water flows underground, impacting the amount of water that feeds springs and gaining streams. This can have both ecological impacts and impacts on downstream human water users.
A groundwater monitoring well extends tens of feet below the ground and allows scientists to track changes in the water table at a location of interest
Transpiration
Transpiration is the process of plants taking up liquid water through their roots and releasing water vapor through their leaves. Transpiration is an important part of the water cycle, moving water from the soil to the atmosphere. Humans tend to change the natural plant communities of an area – whether by replacing plants with buildings and pavement, by removing natural plant communities to grow food crops, or by introducing invasive plant species. A change in the plant community will change the amount of transpiration.
It is difficult to imagine that transpiration has much of an impact on the water cycle because it is a process that we cannot see – water vapor is invisible to us. However, a single tree can transpire thousands of gallons of water each year. Furthermore, the amount of water used by different plants varies significantly. Growing a high-water-use crop in an arid region can deplete the local water resources of an entire area! One recent example of this is in Harney County, Oregon, USA, where hay farming is a main industry, despite the difficulties of growing this high-water-use crop in a naturally dry environment. Since the region’s precipitation does not provide enough water for hay to grow, groundwater is pumped to irrigate the hay fields at a rate the aquifer cannot sustain. (See further reading and references at the bottom of this article to read more about Harney County’s water resources).
From tiny wildflowers to towering trees, all plants must transpire water to perform photosynthesis!
Everyone needs clean, fresh water every day – to drink, clean with, and grow food. Clean water is a human right, but something that not everyone has access to. If you do have access to plentiful, clean water, you have the great opportunity to start considering some ways to use less water and lessen your impact on the water cycle. There are many creative ways to reduce water use while still having enough water for our basic needs. Small actions are the first steps towards lessening our impacts on the water cycle and conserving water resources.
Time your shower, then commit to decreasing your shower time by two minutes.
Reuse drinking glasses to decrease the number of dishes to be washed.
If emptying a water bottle, consider dumping the water out on a houseplant, using it to soak dishes, etc.
Research your food – find out how much water it takes to grow the different plant and animal foods that you eat.
Inspect your home’s faucets and hoses for leaks.
Consider areas of your yard where you do not really need grass, like the margins next to sidewalks – even replacing a small area with low-water-use plants, gravel, or wood chips can help decrease water usage in the yard. Yard improvement projects can also be done in a way that improves your backyard’s wildlife habitat.
Turn off the tap while scrubbing dishes.
Turn off the tap while brushing your teeth.
Consider flushing the toilet every other time (for #1s only).
Talk to your family and friends about the importance of using less water!.
Free Printable Learning Resources for the Water Cycle
My free resources page includes several water and water-cycle related free printable learning resources, including a Saving Water Bingo game, my hand-drawn Water Cycle Diagram, and a Freshwater Visualization activity. My email newsletter subscribers can access my full collection of free resources.
Find this game on the free resources page.
Find this diagram on the free resources page.
Try this freshwater visualization activity from my free resources page.
Are you a teacher, homeschool parent, or other educator? If you liked this post on the water cycle, then I think you will enjoy using these water-related learning materials with your students:
