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.