GC: Lesson - Global Climate Change (Topic 9.5) 📖

⏳ Estimated Reading/Watching Time: 15 - 17 minutes

Explain how changes in climate, both short- and long-term, impact ecosystems.

Historical Climate Change

A collection of fossilized trilobites, which are ancient marine arthropods, embedded in sedimentary rock. — **Some areas used to be covered with oceans. We know this because we can see oceanic fossils preserved in terrestrial environments.**

It’s interesting to think about how climate and other physical factors have changed over the course of Earth’s existence. In what is now the Sahara Desert, you can dig down deep under the sand and find fossils of organisms that used to live in a marine environment. If you travel to the highest reaches of the Himalayan Mountains, you can find fossils of ammonite organisms that used to live under seawater.

In the distant past, drifting continents made a big difference in climate over millions of years by changing ice caps at the poles and altering ocean currents, which transport heat and cold throughout the ocean depths. Additionally, natural changes in greenhouse gas (GHG) concentrations and changes in solar radiation influenced Earth’s climate. For example, the sun’s energy output increased about 0.1% from 1750 to 1950, increasing temperatures by 0.1^oC in the first part of the 20th century. However, we’ve been taking solar radiation measurements from space since 1979, and the data show no long-term change in total solar energy.

Past temperatures have been higher (and lower) than today, and CO₂ concentrations have also varied.

Between 1100 and 1300 the Earth experienced a warming period.
From 1400 to 1850, we experienced what is known as the “Little Ice Age,” a relatively cool period.

Explore the graph below. You can see that while global temperatures have fluctuated, the average overall global temperature has been increasing since the Industrial Revolution:

Over the past 50 years, in the United States alone....

the average temperature has risen more than 2^oF,
precipitation has increased by an average of about 5%,
extreme weather events have increased,
sea level has risen 2-5 inches,
Arctic sea ice is rapidly declining,

and the heaviest rains have increased by 20% on average in the past 100 years.

From what we’ve seen, the CO₂ is triggering the increase in temperatures that we’ve seen. Today, CO₂ released by human activities is far above the amounts in the previous 800,000 years. Explore the graph below. Notice that CO₂ concentrations were relatively constant before the mid-1800s when they started increasing during the Industrial Revolution:

Now, let's combine the temperature and carbon dioxide graphs and see what we get:

A graph illustrating the upward trend of global temperatures and CO2 concentrations from 1880 to 2010. All lines exhibit an increasing trend, with significant rises after the mid-20th century, indicating a correlation between CO2 levels and global warming.” — When carbon dioxide (CO₂) concentrations in the atmosphere are overlaid with average global temperatures since the industrial revolution, a pattern emerges. The CO₂ data in pink was taken from ice cores and the CO₂ data in yellow was taken at the Mauna Loa Observatory in Hawaii.

This evidence helps us to understand the link between increasing carbon dioxide concentrations and global temperatures is well-supported. Earth is getting warmer by virtually every measure we know (oceanic temperatures, atmospheric temperatures, ice core data, etc.) and the temperature has been well above normal for more than 25 years. Regardless of the source of global climate change, the evidence is clear: global temperatures are increasing. In this lesson, we focus on the impacts of climate change on Earth's atmosphere, lithosphere, biosphere, and hydrosphere.

Essential Knowledge

The Earth has undergone climate change throughout geologic time, with major shifts in global temperatures causing periods of warming and cooling as recorded with CO₂ data and ice cores.

Albedo and Reflectivity

The Earth from space with the sun to the left, casting rays of sunlight. Two of the sun’s rays are labeled, indicating that 15% of sunlight is absorbed by the Earth’s atmosphere and 93% is absorbed by the Earth’s surface. — **Ice is more reflective than the oceans, which are more reflective than the land.**

Before we can discuss the effects of climate change on Earth's spheres, we need to learn more about albedo and reflectivity.

Albedo is the amount a surface reflects. Lighter surfaces reflect more than darker surfaces. Planetary albedo is sunlight that is reflected away to space before it reaches the ground. Clouds, since they are white, also have a very high albedo. Globally, about 33% of the sun’s radiation is reflected back to the sun by clouds. In general, ice has a higher albedo than the ocean. And the oceans have a higher albedo than the land.

Reflectivity is how much light is reflected off of a surface. In general, the smoother the surface, the higher the reflectivity. Ice and mirrors have high reflectivity. Asphalt roads and landmasses have low reflectivity. With these two terms in mind, let’s see how they fit into the discussion of climate change in this course.

The more smooth, light-colored surfaces we have on Earth, the more of the sun’s radiation will be reflected back to space, mediating our climate.

A diagram illustrating the positive feedback loop of sea ice melting due to warming temperatures: Temperatures warm, leading to Ocean waves absorb more solar radiation than highly reflective sea ice, which causes ‘Sea ice cover melts and shrinks,’ and in turn leads to further warming temperatures. — **The relationship between rising temperatures and sea ice represents a positive feedback loop.**

Albedo and reflectivity are important to our study of climate change because if temperatures increase, ice WILL melt. The more ice that melts, the more land that is exposed, which reduces the reflectivity of the Earth as a whole, further increasing the temperature of the planet. As the temperatures continue to get warmer, more ice will melt, exposing more land, and continuing to reduce the albedo of the planet. Positive feedback loops drive systems further and further from normal so if this trend continues, we can expect more and more sea ice to melt as temperatures increase.

NASA has been instrumental in measuring albedo and reflectivity for nearly two decades through its Clouds and the Earth’s Radiant Energy System, also known as CERES. NASA scientists are asking questions such as, “Is the Earth absorbing more or absorbing less of the Sun’s energy?” and, “If the Earth is absorbing more of the Sun’s energy, why is this happening?” CERES uses space-based sensors to measure albedo and reflectivity and NASA continues to evaluate their findings in the hopes of spotting trends that may impact Earth’s climate system.

Albedo and reflectivity are important concepts to understand when discussing climate change. Some of Earth’s heat gain over the past century has been attributed to decreasing high-albedo surfaces on Earth, mainly ice, snow, and ice sheets.

Explore the graph below to see how the mass of Antarctic and Artic ice sheets has decreased since 1992:

Having a good handle on these two concepts is imperative to understanding the changing dynamics of Earth’s climate system.

Essential Knowledge

Earth's polar regions are showing faster response times to global climate change because ice and snow in these regions reflect the most energy back out to space, leading to a positive feedback loop.

As the Earth warms, this ice and snow melts, meaning less solar energy is radiated back into space and instead is absorbed by the Earth's surface. This in turn causes more warning of the polar regions.

Effects of Climate Change on Earth's Spheres

Let's discuss the effects of climate change on Earth's spheres. You might see some effects in several spheres - this is because some effects, like rising temperatures, affect biodiversity (biosphere), ecosystems (lithosphere), rainfall (hydrosphere), and wind conditions (atmosphere).

Explore the tabs below. Can you think of any other impacts we left out?

Global Effects of Climate Change 🌎

Open each tab below to learn about global effects of climate change:

Increased concentrations of greenhouse gases can lead to global warming, disrupting atmospheric circulation. Our winds, which are generated by atmospheric circulation, help transport heat throughout the atmosphere.

Climate change has the potential to change the normal circulation patterns as Hadley cells may be impacted and disrupted.

🌡 Climate Changes (click to reveal)

Earth’s atmospheric circulation pattern, focusing on the Hadley Cell, explaining how solar heating at the equator causes warm air to rise, cool at higher altitudes, and then descend in cooler regions, creating deserts. — In this satellite image of Earth, you can see the green areas in the tropics, and the dry areas on either side of the tropics, caused by Hadley cells. These established ecosystems could change as the climate changes.

Oceanic currents often help determine the climate of coastal landmasses. Changes to ocean circulation could have drastic impacts on the climate. The transport of heat associated with the ocean conveyor belt partially moderates the cold temperatures in the North. As the poles warm due to climate change, melt water from ice and glaciers enters the ocean. This fresh melt water has the potential to slow or even shut off ocean circulation, which is dependent on temperature and salinity. The density of the fresh melt water is less than that of salty ocean water. This causes the fresh melt water to form a layer on the surface that can block the warm, salty ocean water from transporting heat to the atmosphere. The effect would be a cooling of the higher latitudes. If the warm water is not able to give off heat, it cannot cool and sink to the bottom of the ocean. This would disturb the circulation of the entire ocean conveyor belt and have a noticeable impact on the climate in the northern latitudes. For example, the Gulfstream mediates the temperature along the East Coast of the United States by bringing warm water up the coast. Major ocean currents can be seen in the graphic below:

Increasing carbon dioxide levels in the atmosphere can be absorbed into the ocean as the ocean is a carbon dioxide sink. This can also result in ocean acidification. We will talk more about ocean acidification in another lesson.

🪸 Ocean Changes (click to reveal)

Additionally, melting permafrost has the capability of releasing additional carbon dioxide and methane (another greenhouse gas) into the atmosphere as organic matter previously trapped in ice is exposed, warms, and decomposes, exacerbating the greenhouse effect.

🧊 Melting Permafrost (click to reveal)

As the Earth warms, ocean water warms. When ocean water warms, the molecules move farther and farther apart due to thermal expansion. This thermal expansion results in higher sea levels worldwide. Low-lying islands such as the Maldives are already seeing some of the impacts of this rise as are some coastal areas of the world.

Explore the graph below to see how sea levels have increased since 1880:

Sea ice and ice masses on land melt during global warming adding to the volume of water in the oceans. This increases sea level worldwide as well which results in changing abiotic conditions for species and displacing human populations in low-lying areas.

An insidious aspect of the melting of snow and ice is that the loss of reflectivity associated with high-albedo surfaces (such as snow and ice) results in more of the sun’s heat being absorbed and retained. This causes increased melting of snow and ice as it sets up a positive feedback loop.

🌊 Rising Sea Levels (click to reveal)

Environmental Effects of Climate Change 🏞️

Open each tab below to learn about ecosystem-level effects of climate change:

Climate change can affect soil through changes in temperature and rainfall, which can impact soil viability (ability to support life) and potentially increase erosion. If this happens, valuable farmland could lose its ability to support a burgeoning population of humans. Species that depend on that soil will also be impacted.

While wildfires occur naturally, more frequent and more intense fires can significantly disrupt ecosystems, damage property, put people and communities at risk, and create air pollution problems even far away from the source.

The timing of natural processes such as flower blooms could also be impacted by warming temperatures. Changes that disrupt the functioning of ecosystems may increase the risk of harm or even extinction for some species. As sea levels rise, there will be less land available for terrestrial organisms to live on. Coastal ecosystems will be underwater and new areas will become our coasts. If those plants and animals are not adapted to exposure to seawater, they will have the same three choices: adapt, move, or die.

🏜 Terrestrial Ecosystem Changes (click to reveal)

As the oceans absorb more and more carbon dioxide from the atmosphere, they will continue to increase in acidity. The organisms in the ocean have the same three options: move, adapt, or die, if they are not already adapted to increased acidity. Corals especially are unable to move when conditions change, which can cause coral bleaching. If corals die due to bleaching, these highly productive ecosystems can collapse. Ocean acidification can also dissolve mollusk shells and other calcareous formations in the ocean.

🪸 Aquatic Ecosystem Changes (click to reveal)

While plants and animals have adapted to environmental change for millions of years, the climate changes we are experiencing now could require adaptation on larger and faster scales than current species have successfully achieved in the past, thus increasing the risk of extinction or severe disruption for many species.

Some organisms that have fast reproductive times, like bacteria, viruses, and insects may be able to adapt to the changing climate, but those organisms that have longer generation times, like large mammals, may not be able to adapt quickly enough to the changing climate to survive.

If animals try to move to new habitats, they must find a way to fit in that ecosystem. They must find a niche that is not already occupied or take someone else’s niche. If they take someone else’s niche, then that organism has to find another niche, and so on.

And, of course, if an organism can neither adapt nor migrate, it will die if it cannot survive the new climate.

Birds are easy to identify and count, and thus there is a wealth of scientific knowledge about their distribution and abundance. People have kept detailed records of bird observations for more than a century. There are many different species of birds living in a variety of habitats, including water birds, coastal birds, and land birds.

We have a wealth of evidence suggesting how birds are impacted by global climate change. Each species of bird has adapted or evolved to favor certain habitat types, food sources, and temperature ranges. In addition, the timing of certain events in their life cycles—such as migration and reproduction—is driven by cues from the environment. Changing conditions can influence the distribution of both migratory and non-migratory birds as well as the timing of important life cycle events.

A graph depicting the northward shift in bird populations over time, indicating a general trend of birds moving northward, with fluctuations in the distance moved each year, highlighting the impact of climate change on bird migration patterns. — Birds are migrating farther and farther north as time goes on. 305 widespread North American bird species were studied and the average center of abundance for these species was more than 40 miles. 48 of the species moved their wintering grounds more than 200 miles northward!

We can then think of birds as true “canaries in the coal mine” in that they tell us a lot about what’s going on not only with their own species but many other species as well.

Some bird species can adapt to generally warmer temperatures by changing where they live—for example, by migrating farther north in the summer but not as far south in the winter, or by shifting inland as winter temperature extremes grow less severe. Non-migratory species might shift as well, expanding into newly suitable habitats while moving out of areas that become less suitable. Other species might not be able to adapt to changing conditions and could experience a population decline as a result. Climate change can also alter the timing of events that are based on temperature cues, such as migration and breeding (especially egg-laying).

Birds are migrating farther and farther north as time goes on. This increased move northward is closely related to increasing winter temperatures. While scientists have learned a lot about climate shifts and the impacts on bird species, other species that migrate are still being studied. It’s likely that they, too, have been impacted by increasing climate shifts.

As the Earth warms and climate patterns shift, some species will be left out and others may benefit. Unfortunately, we are not able to totally predict the full impacts of climate shifts on living organisms, but we can make projections about possible impacts. Only time will reveal the full impact of climate shifts.

🦅 Biodiversity Changes (click to reveal)

Economic Effects of Climate Change 💵

A bar chart illustrating the escalating cost and death toll from billion-dollar disasters over four decades, indicating a significant increase in both cost and deaths over time, with the 2010s showing a cost of $807.3 billion and 5217 deaths. — **Damages from extreme weather events are increasing as they increase in frequency and intensity.**

The global economy could lose up to 18% of its total economic value by 2050 due to climate change if global temperatures rise significantly.

- Extreme weather can damage property and critical infrastructure, impacting economic productivity and increasing insurance premiums.
- Changing soil and rainfall patterns can negatively affect agriculture, forestry, fisheries, and tourism, leading to food supply disruptions.
- The demand for energy may increase as more air conditioning is needed and power generation becomes less reliable, and water supplies are stressed.
- Coastal areas where humans live could be covered by ocean water as sea levels rise, resulting in billions of dollars in lost real estate.

Societal Effects of Climate Change 🏙️

The aftermath of a building’s destruction, showcasing a pile of debris with broken wooden planks, shattered walls, and scattered insulation material. — **Extreme weather events damage personal, government, and commercial properties.**

As the planet warms, the effective range of warm weather adapted diseases and their vectors can increase, escalating the spread of diseases. For example, mosquitos are adapted to warm and wet conditions. If this climate type increases, the range of the mosquito (and its associated diseases, such as Zika and West Nile) could spread.

The changing climate can disrupt food and water supplies, leading to conflicts and displacement of populations. This can intensify political tensions, unrest, and conflict, fueling violent extremism and breaking down government security systems.

Extreme weather events can damage essential infrastructure, impacting communities.

There are many, many other potential impacts of global climate change. As scientists learn more about these potential impacts, more steps must be taken to try to mitigate them. Taking a “wait and see” attitude might prove to be dangerous and trying to mitigate the impacts later might prove to be impossible.

Essential Knowledge

Effects of climate change include rising temperatures, melting permafrost and sea ice, rising sea levels, and displacement of coastal populations.

Winds generated by atmospheric circulation help transport heat throughout the Earth. Climate change may change circulation patterns, as temperature changes may impact Hadley cells and the jet stream.

Climate change can affect soil through changes in temperature and rainfall, which can impact soil's viability and potentially increase erosion.

Global climate change response time in the Arctic is due to positive feedback loops involving melting sea ice and thawing tundra, and the subsequent release of greenhouse gases like methane.

One consequence of the loss of ice and snow in polar regions is the effect on species that depend on the ice for habitat and food.

Marine ecosystems are affected by changes in sea level, some positively, such as in newly created habitats on now-flooded continental shelves, and some negatively, such as deeper communities that may no longer be in the photic zone of seawater.

Oceanic currents, or the ocean conveyor belt, carry heat throughout the world. When these currents change, they can have a big impact on global climate, especially in coastal regions.

AP Exam Tip

You should know how albedo and reflectivity affect Earth's climate.

You should know some impacts of climate change. The AP exam will likely ask you about economic (💵), environmental (🌱), or societal (🏙) effects of climate change.

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