What Is Climate Change? Definitions, Causes & Impacts

When you hear that Earth’s average temperature has climbed more than 1°C since your grandparents’ day, it’s easy to shrug — a single degree sounds small. Yet that shift is already reshaping coastlines, farming seasons, and the severity of storms you see on the news.

Average global temperature rise since 1850: 1.1°C ·
Year with highest recorded global temperature: 2024 (currently) ·
Projected global population affected by water stress by 2050: 5 billion ·
Percentage of carbon emissions from fossil fuels: ~75% ·
Global sea level rise in the 20th century: ~17 cm

Five key indicators, one worrying pattern: each metric confirms a rapidly warming planet.

What is climate change in simple words?

A straightforward definition

• Climate change refers to long-term shifts in average weather patterns that define Earth’s local, regional, and global climates (NASA Science).
• These shifts can be natural — from volcanic eruptions, orbital variations, or solar changes — but since the 1800s, human activities have become the dominant driver.
• The term “climate change” is broader than “global warming,” which specifically describes the long-term heating of Earth’s surface (NASA Science).

How it differs from weather

• Weather is what you see outside today — rain, sun, clouds — and it changes in hours.
• Climate is the average of those conditions over decades or centuries. When that average shifts, you get climate change.
• The UK government (GOV.UK) explains that climate change is already causing more frequent floods, droughts, and heatwaves.

Which best defines climate change?

Official definition from the UN Framework Convention on Climate Change

• The UNFCCC defines climate change as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods” (GOV.UK).
• This definition sets a legal benchmark: climate change is not normal fluctuation; it’s a human-driven shift.

NASA’s definition

• NASA defines climate change as “a long-term change in the average weather patterns that have come to define Earth’s local, regional, and global climates” (NASA Science).
• It adds that “these changes have a broad range of observed effects that are synonymous with the term.”

Scientific consensus

• The IPCC Sixth Assessment Report states unequivocally that “human influence has warmed the atmosphere, ocean and land” (GOV.UK).
• More than 99% of climate scientists now agree that human activities cause the current warming (NRDC).

The implication: whether you look through a legal, scientific, or policy lens, every authoritative definition points to human activity as the primary trigger.

What are the 5 main causes of climate change?

Burning of fossil fuels

• Coal, oil, and natural gas combustion for energy, transport, and industry account for roughly 75% of global greenhouse gas emissions (GOV.UK).
• Carbon dioxide (CO₂) from fossil fuels is the largest single contributor.

Deforestation

• Forests act as carbon sinks, absorbing CO₂. When trees are cut or burned, stored carbon is released and future absorption capacity is lost (GOV.UK).
• Land-use changes like deforestation contribute about 10–15% of total human emissions.

Agriculture and livestock

• Livestock produces methane, a potent greenhouse gas, through digestion and manure.
• Fertiliser use releases nitrous oxide. Together, agriculture accounts for roughly 18% of global greenhouse gas emissions (GOV.UK).

Industrial processes

• Cement, steel, and chemical manufacturing emit CO₂ and other greenhouse gases as by-products.
• Refrigeration and air conditioning release fluorinated gases — extremely potent and long-lasting (NRDC).

Waste and landfills

• Decomposing organic waste in landfills generates methane.
• Waste treatment accounts for about 3–5% of emissions, according to GOV.UK.

How to explain climate change to a kid?

Simple analogy: a blanket around Earth

• Earth has a natural blanket of gases (the greenhouse effect) that keeps it warm enough for life.
• Human activities are making that blanket thicker — trapping extra heat like a duvet you can’t kick off.

Key facts for younger audiences

• The 10 warmest years on record have all happened since 2015 (GOV.UK).
• Polar bears are losing sea ice they need for hunting because the Arctic is warming twice as fast as the rest of the planet.

Using everyday examples

• If you leave a chocolate bar in a hot car, it melts. The planet’s ice is like that chocolate — glaciers are disappearing.
• Stronger storms mean more school closings and power outages.

The catch: explaining climate change to a child isn’t just about science — it’s about giving them a reason to feel hopeful without hiding the truth.

What will Earth look like in 2050?

Projected temperature rise

• Under current policies, global warming is likely to exceed 1.5°C by the early 2040s and could reach 2.7°C by 2100 (GOV.UK).
• The NRDC notes that even at 1.5°C, coral reefs would largely disappear and heatwaves would become far more intense.

Sea level rise and coastal impacts

• Sea levels have already risen ~21 cm since 1900 and could rise another 0.5–1 meter by 2100 (NASA Science).
• Low-lying cities like Miami, Shanghai, and Venice face routine flooding even with 0.5 meters of rise.

Effects on food and water security

• Up to 5 billion people could face water stress by 2050 as glaciers shrink and rainfall patterns shift.
• Crop yields for staple grains like wheat and maize could drop 10–20% across the tropics (GOV.UK).

Why this matters: 2050 is not a far-off scenario — it’s closer than the year the Paris Agreement was signed (2015). The choices made in the next five years will determine whether those projections become reality or an avoided future.

Why is 2030 the point of no return?

IPCC carbon budget

• The IPCC’s latest reports calculate that to have a 50% chance of limiting warming to 1.5°C, the world can emit no more than about 500 billion tonnes of CO₂ from 2020 onward.
• At current emission rates, that budget will be exhausted around 2030 (GOV.UK).

Emissions reduction targets

• To stay within the budget, global emissions must peak by 2025 and fall 43% by 2030 compared to 2019 levels (GOV.UK).
• Current national pledges put the world on track for a 10–15% reduction — far short of the target.

Irreversible tipping points

• Exceeding the carbon budget increases the risk of crossing tipping points: disintegration of the Greenland ice sheet, Amazon rainforest dieback, and collapse of the Atlantic Meridional Overturning Circulation.
• Once triggered, these changes become self-sustaining even if emissions stop.

Timeline of key climate milestones

• 1850–1900 — Pre-industrial baseline period for temperature measurements (NASA Science)
• 1896 — Svante Arrhenius calculates that doubling CO₂ could raise Earth’s temperature by 5–6°C
• 1988 — IPCC established by UNEP and WMO
• 2015 — Paris Agreement adopted, aiming to limit warming to well below 2°C (GOV.UK)
• 2024 — Record hottest year globally recorded (1.1°C above pre-industrial)
• 2050 (projected) — Global temperatures projected to exceed 2°C if emissions continue at current rate

The timeline shows a clear acceleration: from scientific discovery in 1896 to an international agreement in 2015, and now to a record-breaking year in 2024.

What we know — and what remains uncertain

Confirmed facts

• Global average temperature has risen ~1.1°C since pre-industrial times (GOV.UK)
• Human activities (especially fossil fuel burning) are the dominant cause (NASA Science)
• Greenhouse gas concentrations are at highest levels in 800,000 years (NRDC)

What remains unclear

• Precise timing of specific tipping points (e.g., collapse of West Antarctic ice sheet)
• Exact regional impacts of sea-level rise at local scales
• Whether global warming will exceed 2°C or 3°C by 2100 — depends on future emissions

The pattern: scientists are highly certain about the direction of change but less certain about the exact timing and regional details.

Voices on the front line

The era of global boiling has arrived.

— UN Secretary-General António Guterres (2023)

Climate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional, and global climates.

— NASA Goddard Institute for Space Studies

It is unequivocal that human influence has warmed the atmosphere, ocean and land.

— IPCC Sixth Assessment Report (2021)

What this means for you

Climate change is not a distant problem — it’s already reshaping health, homes, and budgets. Warmer air means longer allergy seasons and greater mold exposure in humid regions. Colder winters may bring more colds as indoor gatherings increase. For the average household, the choice is clear: invest in weather adaptation and renewable energy now, or pay far more for disaster recovery later.

Related reading

• Home Remedies for Cold: How Weather Changes Affect Your Health
• Symptoms of Mold Exposure: Climate Change and Indoor Air Quality