Understanding Climate Part 2: Volcanoes, Oceans, and Internal Variability

Summary

This script explores how volcanoes can temporarily cool the Earth by blocking sunlight with ash and releasing sulfate aerosols. Despite emitting CO2, their impact is minor compared to human activities. It also delves into the ocean's role in climate regulation through its circulation system, which is threatened by climate change. The script discusses phenomena like El Niño/La Niña and the Arctic Oscillation, highlighting their short-term climate effects versus the long-term warming driven by human-induced greenhouse gas emissions.

Takeaways

• 🌋 Volcanoes have a short-term cooling effect on climate by releasing dust and ash that block sunlight, and by producing sulfate aerosols that reflect sunlight.
• 🌍 The 1991 Mount Pinatubo eruption caused a temporary 0.5°C drop in global temperatures, illustrating the impact of volcanic activity.
• 💨 Volcanic emissions of carbon dioxide are less than 1% of human emissions, so volcanoes are not responsible for the current global warming trend.
• 🌊 Ocean currents play a critical role in distributing heat, regulating climate, and cycling nutrients and gases, with deep currents driven by water density differences.
• 🔄 The global conveyor belt is a 1,000-year cycle that circulates water and heat around the globe, affecting weather and climate.
• 🧊 Melting glaciers and ice sheets are introducing less dense, cold freshwater into the ocean, which can weaken ocean circulation and disrupt ecosystems.
• 🌡 Warming ocean temperatures are causing coral bleaching and affecting marine life by reducing the ocean's ability to hold gases like carbon dioxide and oxygen.
• 🌎 The El Niño/La Niña cycle temporarily affects global temperatures and weather patterns, with El Niño causing warming and La Niña causing cooling.
• 🌀 The Arctic Oscillation influences regional weather and climate by altering air pressure patterns, impacting temperatures in the Arctic and sub-polar regions.
• ☀️ Long-term global warming is primarily driven by the planet's energy imbalance, caused by excess greenhouse gases from human activities.

Q & A

What is the short-term effect of volcanic eruptions on global climate?

Volcanic eruptions can have a short-term cooling effect of about 0.1 – 0.2 degrees Celsius by releasing dust and ash that temporarily block out sunlight, and by emitting sulfur dioxide gas which forms sulfate aerosols that reflect sunlight away from the Earth's surface.

How did the eruption of Mount Pinatubo in 1991 impact global temperatures?

The eruption of Mount Pinatubo in the Philippines in 1991 caused a 0.5 degree Celsius drop in global temperature, making it the second-largest volcanic eruption of the 20th century.

Why can't volcanoes be blamed for the current rise in global temperatures?

Volcanoes emit carbon dioxide, but their average emissions are less than 1% of those from current human emissions from burning fossil fuels, which are about 100 times greater than even the maximum estimated volcanic carbon dioxide fluxes.

What factors drive ocean currents and how do they impact climate?

Ocean currents are driven by wind, tides, Earth's rotation, the sun, and water density differences caused by temperature, salinity, and depth. They play a key role in distributing heat energy, regulating weather and climate, and cycling nutrients and gases.

What is the global conveyor belt and how long does it take to circulate the globe?

The global conveyor belt is a global-scale circulation system that circulates the globe in a 1,000-year cycle, moving water horizontally and vertically on local and global scales.

How does the melting of glaciers and ice sheets affect ocean circulation?

As glaciers and ice sheets melt due to climate change, the influx of cold freshwater, which is less dense than ocean water, weakens the circulation in crucial areas like the poles where water should be sinking to drive circulation.

What happens to coral reefs when ocean waters warm?

Warming ocean waters cause coral reefs to be stressed and bleach, leading to the death of corals and leaving only skeletal remains.

How do warmer ocean waters affect the ocean's ability to hold gases?

Warmer ocean waters are less able to hold gases such as carbon dioxide and oxygen, leading to oxygen-limited or anoxic conditions in certain regions and forcing marine life to migrate to areas with higher oxygen levels.

What is the significance of the ocean's role in carbon dioxide sequestration?

The ocean is the world's largest active carbon dioxide storage center, taking in excess carbon dioxide from the atmosphere via diffusion, especially in polar regions where water is coldest and densest.

How does the El Niño/La Niña cycle affect global climate?

The El Niño/La Niña cycle can cause temporary warming and cooling, respectively, by affecting oceanic and atmospheric circulation patterns. El Niño increases global temperature while La Niña decreases it.

What is the Arctic Oscillation and how does it influence weather patterns?

The Arctic Oscillation is associated with changing patterns of air pressure in the northern hemisphere, bringing warmer weather to parts of Europe and North America while leaving the Arctic colder in its 'positive' phase, and the opposite in its 'negative' phase.

What is the primary cause of long-term warming trends over the past few decades?

The primary cause of long-term warming trends is the planet's energy imbalance, where more solar radiation is being received than is being released, due to the excess of greenhouse gases in the atmosphere accumulated by human activity.

Outlines

00:00

🌋 Volcanoes and Oceans' Impact on Climate

This paragraph discusses the influence of volcanoes and oceans on Earth's climate. Volcanic eruptions can temporarily cool the climate by releasing dust and ash that block sunlight, as well as sulfur dioxide that forms reflective sulfate aerosols. Despite emitting carbon dioxide, volcanic contributions are minimal compared to human activities. The ocean's circulation system, driven by factors like wind and water density, plays a crucial role in climate regulation. However, climate change-induced melting of glaciers weakens this circulation, affecting marine ecosystems and the ocean's capacity to absorb carbon dioxide.

05:05

🌊 Oceanic Variability and Its Effects

The paragraph delves into how oceanic variability, such as the El Niño/La Niña cycle and the Arctic Oscillation, affects global climate patterns. El Niño leads to temporary warming by disrupting ocean upwelling, impacting ecosystems and fisheries, while La Niña has the opposite effect. The Arctic Oscillation influences weather in the northern hemisphere without significantly affecting global temperatures. These short-term variations cannot account for the long-term warming trend, which is primarily driven by human-induced greenhouse gas emissions and the planet's energy imbalance.

Keywords

💡Volcanoes

Volcanoes are geological formations that can erupt, releasing hot lava, ash, and gases. In the context of the video, volcanoes have a short-term cooling effect on climate due to the dust and ash they emit, which can block sunlight. The 1991 Mount Pinatubo eruption exemplifies this effect, causing a temporary drop in global temperature. Despite emitting carbon dioxide, volcanoes are not a significant contributor to current global warming trends compared to human activities.

💡Sulfate Aerosols

Sulfate aerosols are tiny particles formed when sulfur dioxide gas from volcanic eruptions combines with water vapor and dust in the atmosphere. They play a crucial role in climate by reflecting sunlight away from Earth's surface, leading to a cooling effect. This concept is central to understanding the temporary climate impact of volcanic activity, as it outweighs the warming caused by greenhouse gases.

💡Ocean Currents

Ocean currents are the continuous, directed movements of seawater within the ocean. They are driven by factors such as wind, tides, and differences in water density. The video highlights that these currents play a vital role in distributing heat energy, regulating weather and climate, and cycling nutrients. Changes in ocean currents can have significant impacts on marine ecosystems and global climate patterns.

💡Global Conveyor Belt

The global conveyor belt is a term used to describe the large-scale circulation of ocean currents that transport heat around the globe. It operates on a cycle that can take up to a thousand years. This system is crucial for regulating Earth's climate, as it moves warm water towards the poles and cold water towards the equator. The video emphasizes the importance of this system in maintaining climate stability.

💡Climate Change

Climate change refers to long-term shifts in temperature and precipitation patterns. The video discusses how climate change, largely driven by human activities, is causing glaciers and ice sheets to melt, introducing less dense freshwater into the ocean and potentially disrupting the global conveyor belt. This disruption can have far-reaching effects on weather patterns and marine life.

💡El Niño/La Niña

El Niño and La Niña are phases of the El Niño-Southern Oscillation (ENSO) climate pattern, which involves irregularly periodic warming (El Niño) and cooling (La Niña) of the equatorial Pacific Ocean. These phenomena can cause temporary changes in global temperature and precipitation patterns, affecting weather and ecosystems worldwide. The video uses these examples to illustrate how internal climate variability can impact the global climate.

💡Arctic Oscillation

The Arctic Oscillation (AO) is a climate pattern involving fluctuations in atmospheric pressure between the Arctic and lower latitudes. When in its positive phase, it can lead to warmer weather in Europe and North America and a colder Arctic. Conversely, the negative phase results in a warmer Arctic and colder sub-polar regions. The video explains that while the AO does not significantly affect global temperatures, it can have noticeable impacts on regional weather patterns.

💡Greenhouse Gases

Greenhouse gases are gases in the atmosphere that trap heat, leading to the greenhouse effect. The video mentions that the current rise in global temperatures cannot be attributed to volcanoes but is instead linked to human emissions of greenhouse gases, such as carbon dioxide from burning fossil fuels. These emissions are significantly higher than those from volcanic activity.

💡Coral Reefs

Coral reefs are diverse underwater ecosystems composed of corals and other marine life. The video discusses how warmer equatorial water temperatures, a consequence of climate change, are causing coral bleaching and the death of coral reefs. This not only affects the biodiversity of these ecosystems but also has implications for the human communities that rely on them for food and income.

💡Oxygen Minimum Zones

Oxygen minimum zones are areas in the ocean with very low levels of dissolved oxygen. The video explains that as ocean waters warm, they hold less oxygen, potentially leading to the expansion of these zones. This can force marine species to migrate to areas with higher oxygen levels, affecting local ecosystems and potentially leading to human conflicts over fishing territories.

💡Internal Climate Variability

Internal climate variability refers to natural fluctuations in the climate system that occur independently of external forcing, such as volcanic eruptions or changes in solar activity. The video uses examples like El Niño/La Niña and the Arctic Oscillation to illustrate how these internal processes can cause short-term climate changes. However, it clarifies that these cannot explain the long-term warming trend, which is primarily driven by human-induced greenhouse gas emissions.

Highlights

Volcanoes have a short-term cooling effect on climate by blocking sunlight with dust and ash.

Sulfur dioxide from volcanoes forms sulfate aerosols that reflect sunlight, causing a cooling effect.

The 1991 Mount Pinatubo eruption caused a 0.5 degree Celsius drop in global temperature.

Volcanic CO2 emissions are less than 1% of human emissions, not contributing significantly to current temperature rise.

Ocean currents play a key role in distributing heat energy and regulating weather and climate.

Deep ocean currents are driven by water density differences affected by temperature, salinity, and depth.

The global conveyor belt circulates water on a 1,000-year cycle.

Melting glaciers and ice sheets are weakening ocean circulation due to the influx of less dense freshwater.

Warmer ocean temperatures are causing coral bleaching and affecting marine ecosystems.

Warm ocean waters hold less carbon dioxide and oxygen, impacting marine life.

Ocean is the world's largest carbon dioxide storage center, helping to balance the climate system.

Weakening ocean circulation due to warming reduces the sequestration of carbon dioxide.

El Niño and La Niña cycles cause temporary global warming and cooling, affecting weather patterns.

El Niño disrupts cold water upwelling, affecting ecosystems and fishing communities.

La Niña brings colder water to the west coast of South America, influencing global temperature and precipitation.

Arctic Oscillation influences regional weather but has little effect on global temperatures.

Long-term warming trends are driven by the planet's energy imbalance due to excess greenhouse gases.

Human activity is the primary cause of the excess greenhouse gases in the atmosphere.

Transcripts

In the previous tutorial we began to understand what climate is, and how it is impacted by

variations in Earth’s orbit and solar activity. Now let’s look at some internal factors

that can impact climate. First up, volcanoes. We learned about these in some detail over

in the geology series. So what do they have to do with climate? Perhaps surprisingly,

in the grand scheme of things, volcanoes have a short-term cooling effect of about 0.1 – 0.2

degrees Celsius, as they pump out dust and ash which can temporarily block out sunlight.

Volcanoes also spew out sulfur dioxide gas which, when combined with water vapor and

dust in the atmosphere, forms sulfate. Sulfate aerosols actually reflect sunlight away from

the Earth’s surface, and so their cooling effect outweighs warming caused by greenhouse

gases that are also emitted during eruptions. In 1991, when Mount Pinatubo erupted in the

Philippines, it caused a 0.5 degree Celsius drop in global temperature! This cataclysmic

eruption was the second-largest volcanic eruption of the 20th century. Although volcanoes also

emit carbon dioxide, a prominent greenhouse gas in our atmosphere, the average emissions

are less than 1% of those from current human emissions. Thus, volcanoes cannot be blamed

for the current rise in temperatures. To put some numbers on it, the burning of fossil

fuels dumps billions of tons of carbon dioxide into the atmosphere each year. These emissions

are about 100 times greater than even the maximum estimated volcanic carbon dioxide

fluxes. Let’s now move on to the ocean. Ocean currents

are located at the surface as well as in deep water below 300 meters, causing water to move

horizontally and vertically, on local and global scales. The ocean has its own interconnected

current, or circulation system, powered by the wind, tides, Earth’s rotation, the sun,

and water density differences. Deep ocean currents are density-driven and they differ

from surface currents in scale, speed, and energy. Water density, in turn, is affected

by the temperature, salinity, and depth of the water. The colder and saltier the water

is, the denser it is. The greater the density differences between different layers in the

water column, the greater the mixing and circulation. This global-scale circulation system is called

the global conveyor belt – which circulates the globe in a 1,000-year cycle. While warm

surface currents carry less dense water away from the Equator and towards the poles, cold

deep ocean currents carry dense water away from the poles and towards the equator. The

ocean’s global circulation system plays a key role in distributing heat energy, regulating

weather and climate, and cycling vital nutrients and gases to organisms that call its waters

home. As climate change is causing a lot of glaciers and ice sheets to melt, cold fresh,

water is being increasingly pumped into the ocean system. Since this new water is fresh,

it is less dense than ocean water. Thus, in crucial places where water should be sinking

and driving circulation, like near the poles, freshwater inputs are weakening the circulation

instead. This will have global impacts and disrupt sensitive ocean ecosystems. Already,

coral reefs are being affected by warmer equatorial water temperatures. They’re stressed and

bleaching as a result, a phenomenon we discussed over in the zoology series. Where there were

once beautiful colorful reefs, there are now only skeletal remains.

As ocean waters warm, they are also less able to hold gases such as carbon dioxide and oxygen.

This has led certain regions to become oxygen limited or even anoxic, meaning they contain

no oxygen. Species of marine life reliant on oxygen will be forced to migrate to waters

that can support them with higher oxygen levels. And while the ocean is vast, this represents

issues in regards to local carrying capacity of oceanic regions where species may migrate

to, and even human conflict when it comes to fishing territories and international governance.

We mentioned that warm ocean waters can hold on to less carbon dioxide. This is major,

considering the fact that the ocean is the world’s largest active carbon dioxide storage

center. Typically, the cold water of the ocean allows it to take in excess carbon dioxide

from the atmosphere via diffusion. In polar regions where water is coldest, densest, and

taking up the most carbon dioxide, deep water formation allows it to be transported to depths

where it can be stored for at least the thousand years that ocean circulation requires. This

is a powerful way that the ocean acts to balance the internal climate system and slow the effects

of global warming. However, as ocean waters warm and ocean circulation weakens, less carbon

dioxide can be removed from the atmosphere and sequestered to the deep ocean.

Let’s look at some more examples of internal climate variability. Many times these can

involve positive feedbacks, or processes in which the end products of an action cause

more of that action to occur in a feedback loop. One example is the El Niño/La Niña

cycle, which can cause temporary warming and cooling. Both phenomena affect oceanic and

atmospheric circulation patterns, and influence global climate. While El Niño increases

global temperature, La Niña decreases it. When El Niño occurs, it impacts the west

coast of South America and southwestern portions of North America. El Niño disrupts the cold

water upwelling to the surface of the ocean, which typically brings with it nutrients and

ample fishing opportunities. Instead, warm water pools at the surface of the ocean, suppressing

the upwelling, and often distrupting the ecosystem and fishing community. Actually, these effects

are felt globally. If you ever hear “it’s an El Niño year” during a weather report

on your local TV news show, now you know why – it will affect global temperature and

precipitation. In a La Niña year, colder than usual water appears off the west coast

of South America instead, also affecting global temperature and precipitation patterns. This

cycle repeats itself on a timescale of about five years, and while the changes are short-term,

they have the ability to hinder human food production and availability internationally.

Another example of internal variability is the Arctic Oscillation, or AO, which is associated

with changing patterns of air pressure in the northern hemisphere. This phenomenon brings

warmer weather to parts of Europe and North America, leaving the Arctic colder than usual

when it’s in its “positive” phase. The “negative” phase of the AO brings the

opposite conditions, resulting in a warmer-than-usual Arctic and colder weather in the sub-polar

regions. Because of this seesaw effect, the AO has little effect on global temperatures,

but can significantly influence local and regional weather, still impacting species

and habitats on a large-scale, including humans. Thus, while internal variability in the form

of these various oscillations show close correlation with global temperatures over the short-term,

they cannot explain the long-term warming trends over the past few decades. Research

instead shows that long-term trends in sea surface temperatures are driven predominantly

by the planet’s energy imbalance, in which more solar radiation is being received by

the planet than is being released. This imbalance is due to the excess of greenhouse gases in

our atmosphere, which trap outgoing heat and which have accumulated due to human activity.

With climate now better understood, let’s shift gears back to living organisms and their

evolution.