Climate change

An atmospheric gas that **absorbs longwave (infrared) radiation** and re-radiates heat, warming the atmosphere — e.g. **CO₂, methane, water vapour**.

The warming of the atmosphere when **greenhouse gases absorb longwave infrared** radiation that would otherwise escape to space.

The **extra warming** caused when humans add **more greenhouse gases** (mainly CO₂) to the atmosphere.

**Carbon dioxide (CO₂)**, **methane (CH₄)** and **water vapour**.

**Carbon dioxide (CO₂)** — mainly from burning fossil fuels.

**Longwave infrared** radiation (the heat re-radiated by the warm Earth) — not incoming visible light.

Incoming **shortwave** sunlight **passes through** the gases to warm the surface; only the **outgoing longwave infrared** is absorbed.

(1) It **absorbs longwave infrared** radiation; (2) per molecule it is a **stronger absorber than CO₂**.

**Burning fossil fuels** (coal, oil and gas); deforestation also contributes.

As CO₂ rises, **more longwave infrared is absorbed**, so **less heat escapes** and **temperature rises** — both lines climb together.

No — it keeps Earth **warm enough for life**. Global warming comes from the **enhanced** effect (extra human-added gases).

**Caused by human activity** (rather than by natural processes).

**Burning fossil fuels**, **deforestation**, **agriculture**, and **cattle farming**. (Hook: FDAC.)

**Burning fossil fuels** — it releases carbon stored in coal, oil and gas for millions of years.

A **sink** removes CO₂ from the air (photosynthesis); a **source** adds CO₂ (respiration, decomposition, combustion).

It **removes a sink** (fewer trees photosynthesising) AND **releases** the stored carbon when the wood is burnt or rots.

**Deforestation / clearing forest** — it stops trees locking carbon away by photosynthesis.

Cattle release **methane** (a potent greenhouse gas) from digestion, and clearing forest for pasture **removes a sink** and releases CO₂.

Most plants **stop photosynthesising**, but **respiration and decomposition continue**, so CO₂ is added faster than it is removed.

Long-term **rise** = human activity (mainly fossil fuels); yearly **zig-zag** = photosynthesis (down in summer) vs respiration/decomposition (up in winter).

A loop where the **effect makes the original change even bigger** — it is **self-amplifying**.

A loop where the **effect opposes the change**, returning the system **toward balance** (self-correcting).

**No.** 'Positive' means the change is **amplified** — a positive climate feedback loop is **harmful** (more warming).

Warming **melts bright ice** → exposes a **darker, lower-albedo surface** → it **absorbs more heat** → **more warming** → **more melting**.

It **releases trapped methane and CO2** (greenhouse gases) → these **trap more heat** → more warming → **more thaw**.

Warm water **holds less dissolved CO2**, so CO2 is **released to the air**, trapping more heat → the ocean warms further.

How much sunlight a surface **reflects**. Bright ice = **high** albedo (reflects); dark sea/land = **low** albedo (absorbs).

A **threshold** past which change becomes **self-sustaining and irreversible** — runaway warming.

**Ice–albedo**, **permafrost methane** release, and **ocean CO2 release**.

Finish the sentence: '…and that causes **MORE** warming.' If it adds to the change, it is **positive** feedback.

**Distribution** (where species live), **ecosystem / community** change (who lives together) and **phenology** (when events happen).

The **timing of seasonal life-cycle events** — such as budburst, flowering, breeding and migration.

**Poleward** (towards the poles) and to **higher altitude**, following the cooler conditions they can tolerate.

The tree **spreads northwards / poleward** (and uphill) into newly-suitable ground, because the band of climate it can survive in has moved that way.

**Warm-tolerant species are favoured and spread; cold-adapted species decline or are lost** — so the mix and abundance of species changes.

When a consumer and its food respond to **different cues**, warming shifts their timing by different amounts, so they fall **out of step** (e.g. caterpillars peak before chicks hatch).

It responds to **day length**, which warming does **not** change, so it arrives on the same date while its temperature-cued food has already shifted earlier.

Warmer water holds **less dissolved oxygen**, stressing oxygen-demanding species and favouring warm-tolerant ones.

The fall in **seawater pH** caused by the ocean absorbing extra atmospheric **CO₂**, which dissolves to form carbonic acid.

Dissolved CO₂ forms **carbonic acid**, which releases **H⁺ ions** — more H⁺ means a lower (more acidic) pH.

There are **fewer carbonate ions (CO₃²⁻)** available, because the extra H⁺ ions react with them.

**Calcifying organisms** — corals, molluscs and some plankton — because they need carbonate ions to build **calcium carbonate** shells and skeletons.

Corals build their **calcium carbonate** skeletons **more slowly**, and existing skeletons can **dissolve**, so reefs weaken.

Weaker reefs provide **less habitat and shelter**, so **biodiversity falls** and fisheries that depend on reefs decline.

Burning **fossil fuels** and **deforestation** (which removes a CO₂ sink).

More CO₂ → dissolves → **carbonic acid** → lower **pH** → fewer **carbonate ions** → slower/dissolving **calcium carbonate**.

**Reducing the cause** — lowering greenhouse-gas emissions or **removing CO₂** from the atmosphere.

**Adaptation copes with the effects** of warming (e.g. sea walls) and does **not lower CO₂**; **mitigation reduces the cause**.

Solar, wind and hydro generate energy **without burning fossil fuels**, so **less CO₂ is added** to the atmosphere.

A store that **removes more CO₂ than it releases** — **forests, peatlands, soils and oceans**.

Living trees **remove CO₂ by photosynthesis** (sequestration) and **store carbon in wood/soil**, keeping it out of the air.

It **removes a carbon sink** (less CO₂ removed) AND **releases stored carbon** when trees are burned or rot.

**Cut methane** (fewer cattle, better landfill) or use **carbon capture and storage (CCS)**.

**Adaptation** — it copes with an effect (rising sea level) and does **not lower CO₂**.