Global climate change

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Lesson notes

What Is Global Climate Change?

**Global warming** refers to the rise in Earth's average surface temperature.
**Climate change** includes global warming plus its effects on weather patterns, ice, and ecosystems.
Since the Industrial Revolution (around 1850), human activities have driven most of the observed warming.
The term×anthropogenic climate change×highlights human-caused changes.

The Greenhouse Effect

The **greenhouse effect** is a natural process that keeps Earth warm enough for life.
Greenhouse gases (e.g., **carbon dioxide**, methane, water vapor) trap heat in the atmosphere.
Sunlight warms Earth's surface; the surface radiates heat; greenhouse gases absorb some of that heat and re-radiate it downward.
Without the greenhouse effect, Earth's average temperature would be about -18°C (0°F) instead of 15°C (59°F).

Human Contributions to Climate Change

Burning **fossil fuels** (coal, oil, natural gas) releases large amounts of CO₂.
**Deforestation** reduces the number of trees that absorb CO₂, increasing atmospheric CO₂.
Agriculture (e.g., livestock, rice paddies) releases **methane**; fertilizers release **nitrous oxide**.
Atmospheric CO₂ is now about **50% higher** than pre-industrial levels, a concentration not seen in millions of years.

Evidence of Climate Change

Global average temperature has risen about **1.2°C (2.2°F)** since the late 19th century.
The year **2024** was the warmest on record at +1.60°C above pre-industrial levels.
**Sea levels** are rising due to melting glaciers and ice sheets, and thermal expansion of seawater.
**Arctic sea ice** is declining; **glaciers** are retreating worldwide.
Extreme weather events (heat waves, wildfires, intense storms, droughts) are becoming more frequent and severe.

Impacts on the Environment and Society

**Ocean acidification** occurs as CO₂ dissolves in seawater, harming coral reefs and shellfish.
Many species are forced to **relocate** or face extinction due to rapid habitat changes.
Climate change threatens **food and water security**, increases **flooding** and **extreme heat**, and spreads **disease**.
Poorer communities, which contribute least to emissions, are often the **most vulnerable** to climate impacts.

Solutions and Mitigation

Transition from fossil fuels to **renewable energy** (solar, wind, hydro, nuclear) to reduce CO₂ emissions.
Improve **energy efficiency** in buildings, transportation, and industry.
**Reforestation** and **soil carbon storage** can remove CO₂ from the atmosphere.
International agreements like the **Paris Agreement** aim to limit warming to well below 2°C.

Key Terminology

**Global warming** = increase in average surface temperature.
**Climate change** = broader term including warming and its effects.
**Greenhouse gases** = gases that trap heat (CO₂, CH₄, N₂O, H₂O).
**Anthropogenic** = caused by human activities.
**Fossil fuels** = coal, oil, natural gas – major sources of CO₂.

The greenhouse effect: sunlight warms Earth, but greenhouse gases trap some outgoing heat, warming the atmosphere.

Energy pyramid in an Arctic food chain. Climate change threatens each level by altering habitats and food availability.

Human activities that increase atmospheric CO₂: burning fossil fuels, transportation, and deforestation.

Slides

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Practice questions

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1.Which gas is the main driver of global warming?
Easy
- ACarbon dioxide
- BOxygen
- CNitrogen
- DHydrogen
2.What is the term for the ongoing increase in global average temperature?
Easy
- AGlobal warming
- BClimate change
- CGreenhouse effect
- DGlobal cooling
3.Which human activity is the main cause of the modern rise in global temperatures?
Easy
- ABurning fossil fuels
- BPlanting trees
- CUsing solar panels
- DRecycling waste
4.What percentage more carbon dioxide is in the atmosphere now compared to pre-industrial times?
Medium
- AAbout 50%
- BAbout 10%
- CAbout 100%
- DAbout 25%
5.Which of the following is NOT a greenhouse gas?
Medium
- ANitrogen
- BCarbon dioxide
- CMethane
- DWater vapor
6.What was the global temperature increase in 2024 compared to pre-industrial levels?
Hard
- A+1.60 °C
- B+2.00 °C
- C+0.50 °C
- D+3.20 °C
7.Which of the following is an effect of climate change mentioned in the source?
Medium
- AIncreased flooding
- BDecreased sea level
- CMore stable weather
- DLess intense storms
8.Under the Paris Agreement, what is the target for limiting global warming?
Hard
- AWell under 2 °C
- BUnder 1 °C
- CExactly 2.8 °C
- DNo target

Revision notes

## Global Climate Change - Night-Before Exam Notes ### What is Climate Change? - **Climate change** = long-term shifts in temperatures and weather patterns. - **Global warming** = the ongoing increase in Earth's average surface temperature, mainly due to human activities. - **Anthropogenic climate change** = climate change caused by humans. ### The Greenhouse Effect - Sunlight warms Earth; Earth radiates heat back toward space. - **Greenhouse gases** (CO₂, methane, water vapor) absorb some of this heat, warming the lower atmosphere. - Human activities (burning fossil fuels, deforestation, agriculture) release extra greenhouse gases, strengthening the natural greenhouse effect → **global warming**. ### Human Causes - **Fossil fuels** (coal, oil, natural gas) burned for energy since the Industrial Revolution (≈1850). - Deforestation and certain farming/industrial practices. - CO₂ is the main gas driving warming. Atmospheric CO₂ is now **~50% higher** than pre-industrial levels, reaching levels not seen for millions of years. ### Evidence of Warming - **Global temperature rise**: 2024 was the warmest year on record at **+1.60 °C (2.88 °F)** above 1850 levels. - **Arctic amplification**: melting sea ice, retreating glaciers, thawing permafrost. - **Extreme weather**: more heat waves, wildfires, intense storms, droughts. - **Sea level rise** and **ocean acidification** (CO₂ dissolving in seawater makes it more acidic). ### Impacts - **Environmental**: species extinction, coral reef loss, ecosystem disruption. - **Human**: flooding, extreme heat, food/water scarcity, disease, economic loss, migration, conflict. - **Vulnerability**: poorer communities contribute least to emissions but are most at risk. ### Solutions & Mitigation - **Paris Agreement** (2015): nations aim to keep warming **well below 2 °C**. - **Phase out fossil fuels**: switch to **renewable energy** (wind, solar, hydro, nuclear). - **Energy conservation** and efficiency. - **Carbon removal**: reforestation, soil carbon storage. - **Adaptation**: flood defenses, drought-resistant crops. ### Key Numbers - Current CO₂: ~50% above pre-industrial levels. - 2024 warming: +1.60 °C since 1850. - Paris target: well under 2 °C warming. - Current pledges: ~2.8 °C warming by 2100. ### Important Distinction - **Global warming** = only temperature increase. - **Climate change** = warming + all its effects (e.g., precipitation changes, storms).

Global warming: The ongoing increase in Earth's average surface temperature, primarily due to human activities that release greenhouse gases.
Climate change: Long-term shifts in temperatures and weather patterns; includes global warming and its effects on Earth's climate system (e.g., precipitation changes, storms).
Greenhouse effect: The process by which greenhouse gases absorb heat radiated from Earth's surface, warming the lower atmosphere.
Greenhouse gases: Gases such as carbon dioxide (CO₂), methane, and water vapor that trap heat in the atmosphere.
Fossil fuels: Coal, oil, and natural gas; burned for energy, releasing large amounts of CO₂ and other greenhouse gases.
Anthropogenic climate change: Climate change resulting from human activities.
Paris Agreement: A 2015 international treaty where nations agreed to limit global warming to well below 2 °C above pre-industrial levels.
Sea level rise: Increase in the average level of the world's oceans due to melting ice and thermal expansion of water as it warms.
Ocean acidification: Decrease in pH of ocean water caused by absorption of excess CO₂ from the atmosphere.
Climate adaptation: Adjustments to natural or human systems in response to actual or expected climate change effects (e.g., flood defenses, drought-resistant crops).

Flashcards

What is the difference between 'global warming' and 'climate change'?

Global warming refers only to the increase in global average surface temperature, while climate change includes both global warming and its effects on Earth's climate system, such as changes in precipitation.

What is the main human activity driving modern global warming?

Burning fossil fuels (coal, oil, and natural gas) since the Industrial Revolution is the main human activity driving modern global warming.

What are greenhouse gases?

Greenhouse gases are gases that absorb some of the heat that Earth radiates after it warms from sunlight, warming the lower atmosphere. Examples include carbon dioxide and methane.

How much has atmospheric carbon dioxide increased since pre-industrial times?

Earth's atmosphere now has roughly 50% more carbon dioxide than at the end of the pre-industrial era.

What is the greenhouse effect?

The greenhouse effect is the process by which greenhouse gases trap heat in the lower atmosphere, warming the planet. It is a natural process, but human activities have strengthened it.

List three human activities that release greenhouse gases.

Burning fossil fuels, deforestation, and some agricultural and industrial practices release greenhouse gases.

What was the warmest year on record as of 2024?

2024 was the warmest year on record, with global average temperature 1.60 °C (2.88 °F) above pre-industrial levels.

What are some observed impacts of climate change?

Observed impacts include more frequent heat waves and wildfires, thawing permafrost, retreating glaciers, sea ice decline, more intense storms and droughts, and rising sea levels.

How does climate change affect species?

Rapid environmental change in mountains, coral reefs, and the Arctic is forcing many species to relocate or become extinct.

What are some ways climate change threatens people?

Climate change threatens people with increased flooding, extreme heat, food and water scarcity, more disease, and economic loss.

What is the Paris Agreement?

The Paris Agreement is a 2015 international agreement in which nations collectively agreed to keep global warming 'well under 2 °C' above pre-industrial levels.

What is a tipping point in climate change?

A tipping point is a threshold beyond which changes become self-accelerating and irreversible, such as melting all of the Greenland ice sheet.

List two ways to reduce carbon dioxide emissions.

Switching to renewable energy sources (like wind, solar, hydro, and nuclear) and conserving energy can reduce carbon dioxide emissions.

How can carbon be removed from the atmosphere?

Carbon can be removed by increasing forest cover and using farming methods that store carbon in soil.

What is the difference between climate change mitigation and adaptation?

Mitigation involves reducing greenhouse gas emissions to limit future warming, while adaptation involves adjusting to the effects of climate change, such as building flood controls or using drought-resistant crops.

Why are poorer communities more vulnerable to climate change?

Poorer communities are responsible for a small share of global emissions but have the least ability to adapt and are most vulnerable to climate change impacts.

What are climate proxies?

Climate proxies are natural records like tree rings and ice cores that provide information about past climates before thermometer records existed.

How much higher were sea levels during the Last Interglacial (125,000 years ago) compared to today?

During the Last Interglacial, sea levels were 5 to 10 meters higher than today.

What is ocean acidification?

Ocean acidification is the decrease in pH of ocean water caused by increased carbon dioxide absorption, which harms marine life.

What is the term for climate change caused by human activities?

Anthropogenic climate change is the term for climate change resulting from human activities.

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