What is climate change? Climate change refers to long-term changes in the average conditions that shape Earth’s climate, including temperature, rainfall, winds, oceans and seasonal patterns. Earth’s climate has changed naturally throughout its history. The rapid warming observed since the industrial era is different because human activities—especially burning coal, oil and gas, deforestation and other greenhouse-gas emissions—are the dominant cause of recent long-term warming.
The simplest distinction is this: weather describes what is happening over a short period; climate describes patterns measured over many decades. One cold morning does not disprove global warming, just as one hot afternoon does not establish a climate trend. Scientists examine long records from land, oceans, ice and the atmosphere to understand how the climate is changing.
Quick notes: Climate change is broader than global warming. Global warming means the long-term rise in Earth’s average surface temperature. Greenhouse gases such as carbon dioxide and methane interact with infrared radiation. Human activity has increased their atmospheric concentrations. Impacts include rising sea levels, melting glaciers and changes in rainfall and some extreme-weather risks. Mitigation reduces causes; adaptation reduces harm.
What climate change means—and why the words matter
Climate is commonly described using statistics of weather over a long period, often a 30-year reference period. These statistics include averages, variability and seasonal patterns. Climate is not simply the average temperature of one place. It includes rainfall, humidity, winds, snow and ice, ocean conditions and patterns that affect ecosystems and human life.
Climate change can involve a shift in the average, a change in variability, a change in the frequency of extremes, or several of these at once. Some regions may become wetter in particular seasons while others become drier. A global average describes a large-scale trend; it does not mean every location warms or changes at the same rate.
Global warming is the long-term rise in Earth’s global average surface temperature. Climate change includes this warming and the wider effects on climate patterns and connected systems. The distinction matters because temperature changes influence rainfall, oceans, ice, ecosystems and human activity in different ways.
How the greenhouse effect works
Sunlight reaches Earth. Some is reflected by clouds, the atmosphere, ice and bright surfaces; the rest is absorbed by land and oceans, warming the planet. Earth then releases energy as infrared radiation. Greenhouse gases absorb and re-emit some of this outgoing infrared energy, slowing the loss of heat to space and keeping the surface warmer than it would otherwise be.
The natural greenhouse effect is essential for a habitable planet. The problem is not that greenhouse gases exist. The problem is that human activity has increased the concentration of important greenhouse gases, strengthening the warming influence and shifting Earth’s energy balance.
- Energy arrives: sunlight reaches the atmosphere and surface.
- Energy is absorbed: land and oceans warm as they absorb part of the incoming energy.
- Energy leaves: Earth emits infrared radiation toward space.
- Greenhouse gases interact: gases such as carbon dioxide, methane and nitrous oxide absorb and re-emit infrared energy at particular wavelengths.
- The balance changes: higher greenhouse-gas concentrations create an additional warming influence as the climate system adjusts.
Saying greenhouse gases ‘trap heat’ is a useful first explanation, but they do not form a physical blanket that stops all heat from escaping. The underlying process is radiative transfer: gases interact with infrared radiation and affect how energy moves through the atmosphere.
Why human activities are changing the climate
Burning fossil fuels
Coal, oil and natural gas contain carbon stored underground over geological timescales. Burning them for electricity, transport, industrial heat and other uses releases carbon dioxide. Carbon dioxide is long-lived in the climate system, so a portion of emissions affects climate over many decades to centuries.
Deforestation and land-use change
Forests store carbon in trees, roots and soils. Clearing or degrading forests can release some stored carbon and reduce the capacity of ecosystems to remove carbon dioxide from the atmosphere. Land-use change can also alter surface reflectivity, water movement and local climate.
Agriculture and industrial activity
Agriculture is associated with greenhouse-gas emissions including methane from livestock and some rice production, and nitrous oxide from fertilised soils. Industrial processes, cement production, waste management and certain refrigerants also contribute. Different gases have different atmospheric lifetimes and warming influences.
Is climate change natural or human-caused?
Natural factors have always influenced climate. Volcanic eruptions can send particles into the atmosphere that temporarily reduce incoming sunlight. Changes in solar output affect Earth’s energy input. Slow variations in Earth’s orbit influence the distribution of sunlight over very long timescales. Ocean-atmosphere patterns can shift heat between regions and alter weather for months or years.
Scientists compare these influences with observed changes and physical evidence. The pattern of recent warming—including warming of the lower atmosphere, ocean heat accumulation, widespread ice loss and other climate indicators—matches the expected influence of increased greenhouse gases. Natural factors alone do not explain the observed long-term warming. The IPCC concludes that human influence has unequivocally warmed the atmosphere, ocean and land.
This does not mean every storm, drought or hot day is caused solely by climate change. Weather events arise from many interacting factors. Climate change alters background conditions and can change the probability, intensity or duration of some events. Attribution studies examine how much the changed climate influenced a particular event.
What evidence shows that climate is changing?
- Temperature records: land and ocean measurements show a long-term rise in global average surface temperature.
- Oceans: the ocean stores most of the excess heat in the climate system; warming contributes to thermal expansion and sea-level rise.
- Glaciers and ice sheets: widespread glacier retreat and ice-sheet mass loss provide evidence of a changing energy balance.
- Sea level: global mean sea level has risen through ocean expansion and the addition of water from melting land ice.
- Arctic sea ice: satellite observations show long-term decline in Arctic sea-ice extent, especially in late summer.
- Ecological indicators: the timing of flowering, migration and other biological patterns has shifted in many observed systems.
No single indicator carries the entire case. Scientists assess multiple independent records, investigate uncertainty and test whether the observations fit known physical mechanisms. The combined evidence is stronger than a photograph or one unusual season.
What are the effects of climate change?
Heat and health
As average temperatures rise, the probability and severity of many hot extremes increase. Heat affects health, outdoor work, electricity demand, crops and urban living. Risk depends on more than air temperature: humidity, night-time conditions, housing, access to cooling and the ability to protect vulnerable people all matter.
Rainfall, floods and drought
A warmer atmosphere can hold more water vapour, increasing the potential for intense rainfall when weather conditions produce precipitation. The effect varies by region. Flood risk also depends on drainage, land use, river management and infrastructure. Some regions face greater drought risk through higher evaporation and altered rainfall; others may become wetter.
Sea level and coastal exposure
Sea level rises as ocean water expands when warmed and as land-based ice contributes water to the oceans. Coastal flooding and erosion depend on local land movement, tides, storms, coastal ecosystems and the design of defences. Low-lying islands and urban coastlines require long-term planning.
Ecosystems, food and communities
Species respond to changing temperatures, seasons and water conditions in different ways. Some move to cooler locations or higher elevations; some adjust timing or behaviour; others face habitat loss. Agriculture can be affected by heat, water availability, pests, soil conditions and changing growing seasons. Health risks can include heat illness, food and water disruption and smoke exposure from fires.
Does climate change cause every natural disaster?
No. Earthquakes and volcanic eruptions are geophysical processes, not consequences of global warming. Tropical cyclones, floods, droughts, wildfires and heatwaves involve different mechanisms, and the influence of climate change varies by hazard and region.
For some hazards, scientists find a clear increase in intensity or likelihood under a warmer climate; for others, the evidence is more complicated or region-specific. Climate change can increase dangers associated with heat and heavy rainfall while exposure and vulnerability determine how damaging an event becomes.
What is climate mitigation?
Mitigation means reducing greenhouse-gas emissions or increasing the removal of greenhouse gases from the atmosphere. It addresses the causes of human-driven climate change. Examples include replacing high-emission energy, improving energy efficiency, reducing methane leaks, protecting ecosystems, changing industrial processes and developing lower-emission transport.
- Energy: improve efficiency and reduce emissions from electricity generation.
- Buildings: design and operate buildings to use less energy while maintaining healthy conditions.
- Transport: improve public transport, walking, cycling, vehicle efficiency and lower-emission options where suitable.
- Industry: reduce process emissions and improve materials efficiency.
- Land and food: protect ecosystems and reduce avoidable food loss.
- Policy and finance: support investment and standards that make emissions reduction practical.
No single technology solves the problem alone. Energy systems, land use, infrastructure, affordability and social needs differ across countries. Mitigation strategies work best when designed around local circumstances and assessed for their full effects.
What is climate adaptation?
Adaptation means adjusting human or natural systems to actual or expected climate impacts, reducing harm or taking advantage of possible opportunities. Examples include heat-health plans, flood-resilient drainage, coastal protection, drought planning, early-warning systems, resilient crops and buildings suited to local conditions.
Mitigation and adaptation are not alternatives. Even strong emissions reductions cannot prevent all future changes because some warming and impacts are already in motion. Adaptation helps communities manage risks, while mitigation limits how much additional risk builds up.
Climate change in Singapore and tropical cities
Singapore’s tropical climate makes heat, humidity, heavy rainfall and coastal exposure important planning considerations. Urban heat is influenced by buildings, road surfaces, shade, vegetation, ventilation and human activity. Climate change interacts with these local factors; it is not the only influence on how hot a street or building feels.
For a low-lying coastal city, sea-level rise and extreme water levels are long-term planning issues. Rainfall and drainage planning matter because intense rain can create flood risk when water arrives faster than infrastructure can manage it. Adaptation involves land-use planning, drainage, coastal protection, building design and public preparedness.
For a neighbourhood-level look at ecology and urban green space, read How Bukit Timah Works: the Botanic Gardens Rain Forest. Green space provides valuable benefits, but tree planting alone is not a substitute for economy-wide emissions reductions.
How to judge climate claims
- Check the source: identify whether the claim comes from a scientific assessment, public agency, peer-reviewed study, news report or social-media post.
- Check the variable: is it about weather, local temperature, global average temperature, rainfall or sea level?
- Check the period: a short interval can be strongly affected by natural variability.
- Check the location: a regional observation does not automatically describe the planet.
- Check uncertainty: scientific ranges express what is known and what remains uncertain; they do not mean that nothing is known.
- Check the causal claim: distinguish a long-term trend from attribution of a particular event.
Beware of claims that use a single cold day to disprove warming, or that attribute every unusual weather event to climate change without evidence. Both replace careful analysis with a shortcut.
Frequently asked questions about climate change
What is climate change in simple words?
Climate change is a long-term shift in Earth’s climate patterns, including temperature, rainfall, oceans and other conditions. Recent global warming is mainly driven by human greenhouse-gas emissions.
What is the difference between global warming and climate change?
Global warming is the long-term rise in Earth’s average surface temperature. Climate change includes this warming and wider changes in climate patterns and related systems.
Can climate change happen naturally?
Yes. Natural factors influenced climate throughout Earth’s history. The current rapid warming trend is primarily explained by human influence.
What is the difference between mitigation and adaptation?
Mitigation reduces the causes of climate change; adaptation reduces harm from its impacts.
Can planting trees solve climate change?
Trees can store carbon and provide other benefits, but land-based carbon removal has limits and must be maintained. It cannot replace rapid reductions in fossil-fuel and other greenhouse-gas emissions.
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For the biological process that supports much of the food web, read What is Photosynthesis?. For the relationship between climate and ecosystems, see How Bukit Timah Works: the Botanic Gardens Rain Forest.
Sources and further reading
NASA’s What Is Climate Change? explains the distinction between weather, climate and global warming and summarises observed indicators. The IPCC Sixth Assessment Synthesis Report assesses human influence, impacts, adaptation and mitigation. For Singapore’s official climate information, begin with the Ministry of Sustainability and the Environment. This guide focuses on established mechanisms rather than a fast-changing daily temperature ranking.