How do we know climate change is caused by humans?

Summary

This video explains how human activities are the primary cause of climate change, supported by scientific evidence. It highlights key data, such as carbon dioxide's ability to trap heat, rising carbon emissions from fossil fuels, and the effect on ocean acidification. The video also addresses how the drop in carbon-13 levels confirms the fossil fuel origin of CO2. Additional evidence includes stratospheric cooling, which challenges alternative theories like increased solar radiation. The video concludes with a call to action to explore science further through interactive courses on Brilliant.org.

Takeaways

• 😀 Human activities have caused an increase in atmospheric gases that trap more of the sun's energy, leading to climate change.
• 🌍 Rising global temperatures, rising sea levels, ocean acidification, declining ice cover, and more extreme weather events are evidence of climate change.
• 🔬 The carbon dioxide (CO2) in the atmosphere absorbs infrared light, which is a key factor in global warming.
• 🌡️ The concentration of CO2 in the atmosphere has been increasing since measurements began, contributing to the warming of the planet.
• 🌊 Oceans absorb CO2 from the atmosphere, which increases their acidity, providing more evidence of human-driven climate change.
• 🔥 The additional CO2 in the atmosphere originates from fossil fuels, not from natural sources like rocks or volcanoes.
• 📚 Different isotopes of carbon (C-12, C-13, C-14) allow scientists to track CO2 sources, with fossil fuels contributing to a decrease in the C-13 to C-12 ratio.
• 🧪 Carbon 14 dating is less effective due to nuclear bomb tests in the 1960s, which added artificial carbon to the atmosphere.
• 📉 Stratospheric cooling is a sign that the warming is due to CO2, as it causes the upper atmosphere to shed heat more efficiently.
• 💡 Stratospheric cooling was predicted in 1967, and satellite data confirms that the stratosphere is indeed cooling, further supporting the idea that CO2 is the main cause of global warming.

Q & A

Why is it undeniable that human activities are responsible for climate change?

Human activities have released atmospheric gases, particularly carbon dioxide, which trap more of the sun's energy in the Earth's system, causing warming. This is supported by evidence from scientific measurements and observations.

What types of evidence are provided to show that climate change is happening?

Evidence includes rising global temperatures, increased seawater levels, ocean acidification, declining ice cover, and more extreme weather events.

How do scientists know that carbon dioxide is causing warming on Earth?

Carbon dioxide absorbs infrared light, which is essential for trapping heat in the Earth's atmosphere. This property is well-known from laboratory measurements, and it contributes to the greenhouse effect, which leads to global warming.

What is the relationship between oceans and carbon dioxide in climate change?

Oceans absorb carbon dioxide from the atmosphere, which lowers their pH, making them more acidic. This increased acidity aligns with observations, supporting the idea that rising carbon dioxide levels in the atmosphere are contributing to global warming.

How do scientists use isotopes to trace the source of carbon dioxide emissions?

Scientists use different isotopes of carbon (C12, C13, C14) to trace the source of carbon emissions. Fossil fuels, which come from ancient plants, have a distinct carbon isotope ratio that differs from natural sources like volcanic emissions.

Why is the carbon 13 to carbon 12 ratio important in understanding climate change?

The carbon 13 to carbon 12 ratio in the atmosphere is decreasing because fossil fuels, which contain a higher proportion of carbon 12, are being burned. This change in ratio provides evidence that fossil fuel combustion is a major source of the rising atmospheric carbon dioxide.

What does stratospheric cooling tell us about the cause of climate change?

Carbon dioxide warms the Earth's surface but causes cooling in the stratosphere, as it helps the atmosphere shed heat more efficiently. This stratospheric cooling aligns with predictions from 1967, suggesting that the warming at Earth's surface is due to increased carbon dioxide, not solar energy.

What would happen if the Sun were responsible for Earth's warming instead of carbon dioxide?

If the Sun were the main cause of warming, both the Earth's surface and the stratosphere would warm. However, stratospheric cooling is observed, indicating that the warming is caused by carbon dioxide and not by increased solar radiation.

What role does fossil fuel combustion play in climate change?

Burning fossil fuels releases large amounts of carbon dioxide into the atmosphere. This carbon dioxide is mainly derived from ancient plants (fossil fuels), which lowers the carbon 13 to carbon 12 ratio in the atmosphere, contributing to global warming.

How can platforms like Brilliant.org help people understand complex topics like climate change?

Brilliant.org offers interactive courses and visualizations in various scientific fields, including climate science, physics, and mathematics. It provides an engaging way for learners to understand and explore complex topics, making science accessible and fun.