Understanding Climate Part 2: Volcanoes, Oceans, and Internal Variability
Summary
TLDRThis 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
🌋 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.
🌊 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.
Mindmap
Keywords
💡Volcanoes
💡Sulfate Aerosols
💡Ocean Currents
💡Global Conveyor Belt
💡Climate Change
💡El Niño/La Niña
💡Arctic Oscillation
💡Greenhouse Gases
💡Coral Reefs
💡Oxygen Minimum Zones
💡Internal Climate Variability
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.
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