S. 23 Earth’s Climate & Global Warming

A collection of flashcards based on lecture notes covering Earth's climate and global warming, focusing on theories, greenhouse gases, CO₂ emissions, and related phenomena.

What distinguishes a scientific theory from a hypothesis?

A theory explains many related phenomena and is supported by evidence.

Why is Earth ~30°C warmer than expected for its distance from the Sun?

Greenhouse gases absorb and reradiate heat.

Which gases are major contributors to the greenhouse effect?

Water vapor, carbon dioxide, methane.

What was the typical CO₂ range over the last 800,000 years before 1850?

180–280 ppm.

What are present-day atmospheric CO₂ levels approximately?

425 ppm.

What evidence shows that rising CO₂ is from fossil fuel combustion and not natural sources?

O₂ levels are dropping in sync with rising CO₂.

Which countries currently produce the most CO₂ emissions?

China, USA, India.

What is the approximate sea level drop during the last glacial maximum?

125 m.

What does the 'Keeling Curve' show?

CO₂ levels measured at Mauna Loa since the 1950s.

Why does CO₂ dip every summer in the Keeling Curve?

Plant growth in the Northern Hemisphere.

During glacial episodes, why does sea level fall?

Water is stored in large ice sheets.

Which region has the highest per capita CO₂ emissions?

USA and Canada.

What is the observed historical CO₂ threshold for maintaining polar ice caps?

280 ppm.

Which sector is NOT a major contributor to CO₂ emissions?

Marine biology.

What is the best estimate for global temperature increase by 2050–2059 under the high-emissions scenario?

2.0°C.

How much colder was Earth during the last glacial maximum (20,000 years ago)?

5–7°C colder.

How much colder is required to trigger a new glaciation?

4°C colder.

What was the CO₂ level around 70 million years ago?

800 ppm.

When were CO₂ levels highest during the last 70 million years?

Paleocene–Eocene Thermal Maximum (PETM).

Which country was the largest CO₂ emitter in the 1800s?

United Kingdom.

Which country was the largest CO₂ emitter in the 1900s?

USA.

Which country became the largest CO₂ emitter in the 2000s?

China.

Which activities are the primary sources of CO₂ emissions?

Electricity, agriculture, and industry.

Describe the temperature trend over the last 150 years.

Temperatures have risen rapidly, about +1.5°C since the 1880–1910 average.

What major human activities contribute to CO₂ emissions?

Electricity generation, agriculture, and industry.

What happens to sea level during glacial periods and why?

Sea level drops (up to ~125 m) because large amounts of water are stored in ice sheets.

Why does the Keeling Curve show seasonal CO₂ variation?

Because Northern Hemisphere plants absorb CO₂ during spring and summer.

Why does falling O₂ confirm that rising CO₂ is from fossil fuel combustion?

Because burning fossil fuels consumes O₂ and produces CO₂.

How much colder would Earth be without the greenhouse effect?

30°C.

What CO₂ range characterizes the last 10,000 years before industrialization?

255–285 ppm.

What is the primary cause of the rapid CO₂ increase since 1850?

Fossil fuel combustion.

Which countries have historically been the largest CO₂ emitters over time?

UK → USA → China.

What key evidence shows CO₂ rise is human-caused?

O₂ levels are dropping in step with CO₂.