Question 1

What is permafrost, and why does thawing matter?

Accepted Answer

Ground that has remained **frozen for at least two consecutive years** — covering roughly a quarter of the northern hemisphere's land — and its thaw matters because of what has been locked inside it for tens of thousands of years.

**What is stored there.** Permafrost holds enormous quantities of **frozen organic matter**: plants and animals that died and were frozen before they could fully decompose. Estimates put the carbon in permafrost soils at roughly **twice the amount currently in the atmosphere**.

**Why thaw releases it.** Thawed organic matter resumes decomposing, and microbes convert it to carbon dioxide where oxygen is available and to **methane** where it is not — in waterlogged ground and lake beds. Methane is a far more potent greenhouse gas over short timescales, so the ratio between the two matters enormously for the impact.

**Why it is described as a feedback.** Warming causes thaw; thaw releases greenhouse gases; those cause further warming. **This is a genuine positive feedback**, and it is not fully captured in many emissions budgets, which is why it appears in discussions of tipping points.

**What is uncertain, honestly stated:** how fast, how much, and the split between carbon dioxide and methane. Gradual thaw is reasonably modelled; **abrupt thaw** — where ground collapses as buried ice melts, forming lakes and slumps — releases carbon far faster over small areas and is poorly represented in models. Increased plant growth in a warmer Arctic offsets some of it, by an amount that is debated.

**The physical consequences, which are already happening:** ground subsidence damaging roads, pipelines, airstrips and buildings across northern communities, at very substantial cost; coastal erosion as frozen shorelines thaw; and landscape change affecting hunting, travel and ways of life.

**The exhumation concerns** — ancient microbes, and contaminants and waste buried on the assumption the ground would stay frozen — are real for the latter and more speculative for the former.

**Subsea permafrost** beneath Arctic continental shelves is a separate and less well understood store.

Question 2

What is a climate tipping point?

Accepted Answer

A tipping point is a threshold beyond which a component of the climate system shifts to a qualitatively different state, and continues doing so under its own momentum even if the original forcing

Question 3

Why do peat bogs matter so much?

Accepted Answer

Because they store an extraordinary quantity of carbon in a very small area, and damaged peatland releases it — turning one of the most effective natural carbon stores into an emissions source. What

Question 4

How much of climate change comes from food and farming?

Accepted Answer

Roughly a quarter to a third of global greenhouse gas emissions depending on what is counted — and the distinctive feature is that these emissions are mostly not carbon dioxide from burning fuel,

Question 5

What are the main causes of climate change and how do they affect the environment?

Accepted Answer

Climate change is caused by human activities like burning fossil fuels, deforestation, and agriculture, leading to rising temperatures, extreme weather, and ocean acidification.

Question 6

What is a carbon sink, and how much CO₂ do the oceans absorb?

Accepted Answer

A carbon sink is any reservoir absorbing more carbon than it releases. The two dominant natural sinks are the ocean and land vegetation and soils, and together they absorb roughly half of human CO₂

Question 7

What is eutrophication and why do rivers turn green?

Accepted Answer

Eutrophication is the over-enrichment of water with nutrients — principally nitrogen and phosphorus — which triggers explosive algal growth and can ultimately strip the water of oxygen. The sequence:

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