# The Climate Explainer — full text

> The Climate Explainer is an independent editorial publication that translates mainstream climate science into plain English. Every explainer is grounded in the peer-reviewed consensus summarized by the IPCC and major scientific agencies — no doomism, no denialism, no invented numbers.

# Climate Change vs Global Warming: What's the Difference?

> Global warming is the long-term rise in Earth's average surface temperature, driven mainly by human greenhouse gas emissions. Climate change is the broader term: it includes that warming plus everything it triggers — shifting rainfall, rising seas, melting ice, ocean acidification, and more intense extremes. Global warming is one symptom; climate change is the whole condition. Scientists use both terms, choosing whichever fits what they are describing.

Source: https://reportingclimatescience.com/climate-change-vs-global-warming/  
Publisher: The Climate Explainer  
Published: 2026-07-19  
Updated: 2026-08-16

## Climate Change vs Global Warming: What's the Difference?

**Global warming** is the long-term rise in Earth's average surface temperature caused mainly by human emissions of greenhouse gases. **Climate change** is the broader term: it covers that warming *plus* everything the warming sets in motion — shifting rainfall patterns, rising seas, melting ice, ocean acidification, and changes in extreme weather.

In short: global warming is one symptom. Climate change is the whole condition. Every degree of global warming is climate change, but not every aspect of climate change is a temperature reading.

## The Two Terms at a Glance

| | Global warming | Climate change |
|---|---|---|
| **What it describes** | The rise in Earth's average surface temperature | Long-term shifts in the whole climate system |
| **Scope** | One variable: temperature | Temperature, precipitation, sea level, ice, oceans, extremes |
| **Main driver today** | Human greenhouse gas emissions | The same emissions, plus the ripple effects of the warming they cause |
| **Example** | Earth's average temperature has risen by more than 1°C since the late 1800s | Heavier downpours, longer droughts, shrinking glaciers, acidifying oceans |

## Global Warming: A Simple Definition

Global warming is the observed increase in Earth's global average surface temperature over decades, driven primarily by carbon dioxide, methane, and other greenhouse gases released by burning fossil fuels, deforestation, and agriculture.

The mechanism behind it is [the greenhouse effect](/what-is-the-greenhouse-effect/): these gases let sunlight in but slow the escape of heat, so the planet's energy budget tips toward warming. According to assessments by the IPCC, NASA, and NOAA, the planet has warmed by more than 1°C compared with the late 19th century, and human activity is unequivocally the dominant cause.

Two things "global warming" does *not* mean:

- **It doesn't mean every place warms equally.** The Arctic is warming several times faster than the global average, while a few regions warm more slowly.
- **It doesn't mean every year is hotter than the last.** Natural variability, such as El Niño and La Niña, makes individual years wobble around a clearly rising trend.

## Climate Change: The Bigger Picture

Climate change refers to long-term changes in the state of the climate system as a whole. Scientifically, the term can describe any persistent shift — including natural ones like ice ages. In modern usage, though, it almost always means the rapid, human-driven change underway now.

That change includes warming, but also its knock-on effects:

- **Water:** wet regions and storms tend to deliver heavier rainfall, while many dry regions face more intense drought.
- **Ice and sea level:** glaciers and ice sheets are losing mass, and seas rise as ice melts and warmer water expands.
- **Oceans:** the ocean absorbs both excess heat and a large share of our CO2, which makes seawater measurably more acidic.
- **Extremes:** heatwaves have become more frequent and more intense across most land regions.

A cold snap or a snowy winter doesn't contradict climate change — weather is what happens this week; climate is the pattern over decades.

## Why Did "Global Warming" Become "Climate Change"?

It didn't, really — **both terms have been used by scientists for decades**, and both are still in use. "Climatic change" appears in scientific papers from the 1950s, and the Intergovernmental Panel on Climate Change (IPCC) has carried "climate change" in its name since it was founded in 1988.

The shift in public language happened for two main reasons:

1. **Accuracy.** Researchers and agencies increasingly preferred "climate change" because the problem is bigger than temperature. "Global warming" undersells sea level rise, shifting rainfall, and ocean acidification.
2. **Politics and framing.** Different communicators have favored one term or the other at different times, for different audiences. But the underlying science never changed with the vocabulary.

So when someone asks whether global warming was "renamed" because the warming stopped — no. The warming has continued, and scientists simply use the more precise word for whichever thing they're describing.

## Which Term Should You Use?

Use **global warming** when you specifically mean the temperature trend. Use **climate change** when you mean the full set of changes — which is most of the time. News outlets, the IPCC, and agencies like NASA generally follow that same convention.

Neither term is wrong. They're two lenses on the same, well-documented reality: humans are adding greenhouse gases to the atmosphere, the planet is warming as basic physics predicts, and the climate system is changing in response.

For more term-by-term comparisons like this one, browse our full [Climate Terms](/climate-terms/) collection.

## Frequently asked questions

**Is global warming the same as climate change?**

No, though they are closely related. Global warming refers specifically to the rise in Earth's average surface temperature. Climate change covers the full set of long-term shifts in the climate system — warming plus changes in rainfall, sea level, ice cover, ocean chemistry, and extreme weather. All current global warming is part of climate change, but climate change includes much more than temperature.

**Why did scientists switch from 'global warming' to 'climate change'?**

They didn't really switch — both terms have appeared in scientific literature for decades, and the IPCC has had 'climate change' in its name since 1988. 'Climate change' became more common in public communication mainly because it is more accurate: the problem includes sea level rise, shifting precipitation, and ocean acidification, not just warmer temperatures. The change in wording never reflected any pause in the warming itself.

**What is a simple definition of global warming?**

Global warming is the long-term increase in Earth's average surface temperature, caused primarily by greenhouse gases — mainly carbon dioxide and methane — released by burning fossil fuels, deforestation, and agriculture. These gases trap heat that would otherwise escape to space. According to the IPCC, NASA, and NOAA, the planet has warmed by more than 1°C since the late 1800s, with human activity as the dominant cause.

**Does a cold winter disprove global warming?**

No. Weather describes conditions over days or weeks in one place; climate describes patterns over decades across the globe. Cold snaps and snowy winters still occur on a warming planet, and natural cycles like El Niño and La Niña make individual years bounce around. The long-term trend in global average temperature is clearly upward even though not every year or every region sets a record.


---

# How Do Climate Models Work?

> Climate models divide the atmosphere, ocean, land and ice into a three-dimensional grid, then repeatedly solve equations describing how energy, water and matter move through the system. Scientists evaluate models against observations and past climates. For future runs, they supply different greenhouse-gas and land-use scenarios. The results are conditional projections with quantified uncertainty, not promises of exact weather on a future date.

Source: https://reportingclimatescience.com/how-do-climate-models-work/  
Publisher: The Climate Explainer  
Published: 2026-09-04  
Updated: 2026-09-07

## Climate models in one paragraph

Climate models are computer-based representations of the atmosphere, ocean, land and ice. They divide Earth into a three-dimensional grid, apply equations grounded in physics, chemistry and biology, and calculate how energy, water and matter move between cells over successive time steps. Scientists test models against observed and past climates, then run them under different assumptions about future greenhouse gases and other influences. The output is a conditional projection: what the climate would tend to do if those inputs occurred.

A model is necessarily simpler than the planet. That is not a defect concealed in the small print; simplification is what makes a model usable. The serious questions are which processes it represents, how it represents them, how it performs against observations, and whether it is fit for the question being asked.

## What is inside a global climate model?

A global climate model, often abbreviated **GCM**, couples several parts of the Earth system. NOAA's Geophysical Fluid Dynamics Laboratory describes the major components as atmosphere, land surface, ocean and sea ice. Modern Earth system models can also represent atmospheric chemistry, aerosols, vegetation and the carbon cycle.

Within each component, equations describe conservation of energy, mass and momentum, along with fluid motion and other physical or chemical processes. The components exchange quantities such as heat, water and momentum. Ocean circulation can move heat; sea ice changes how much sunlight a surface reflects; vegetation exchanges water and carbon with the atmosphere. The model calculates those interactions repeatedly as simulated time advances.

The model does not “learn” a future temperature by extending a line on a graph. It produces a response from the encoded physical system when researchers change an input, such as atmospheric greenhouse-gas concentrations, volcanic aerosols or solar output. That distinction matters: climate models are experiments with physical relationships, not elaborate trend lines.

The basic energy mechanism those equations must respect is explained in [what the greenhouse effect is](/what-is-the-greenhouse-effect/).

## Why do models divide Earth into grid cells?

No computer can calculate every air molecule, cloud droplet, leaf and ocean eddy. Models therefore divide the atmosphere, ocean and land into a three-dimensional grid. Equations are solved for variables within each cell, and the results pass to neighbouring cells at the next time step.

Grid-cell size is the model's spatial resolution. Smaller cells can represent finer geographic detail, but they multiply the number of calculations and require more computing power. Shorter time steps likewise add detail and cost. Resolution should not be confused with accuracy: a map containing smaller pixels can still inherit imperfect inputs or an imperfect representation of a process.

Some important processes occur at scales smaller than a grid cell. Clouds are a familiar example. Instead of resolving every cloud directly, a model uses a **parameterization**: a mathematically defined way to represent the average effect of a smaller-scale process on the larger cell. The IPCC notes that more complex parameterizations and increasing spatial and temporal resolution have accompanied advances in modelling. Parameterization is a declared approximation, not an arbitrary adjustment made after seeing the desired answer.

## How are climate models tested?

One test is a historical simulation, sometimes called a hindcast. Researchers start the model in an earlier climate state and supply known changes in external influences, including greenhouse gases, solar intensity and volcanic activity. They then compare the simulated climate with observations the model was not simply asked to reproduce value by value.

Useful evaluation goes beyond global average temperature. Researchers compare spatial patterns, seasonal cycles, ocean behaviour, rainfall, sea-level pressure and responses to major events. The IPCC's Sixth Assessment evaluated successive generations in the Coupled Model Intercomparison Project—CMIP3, CMIP5 and CMIP6—against observations for variables including surface air temperature, precipitation and sea-level pressure.

Models are also tested against climates unlike the recent present, including evidence from ancient climates. No test proves that every regional projection is exact. Testing instead reveals where models reproduce relevant behaviour, where biases persist and how much confidence is appropriate for a particular use.

It is also possible to test old projections after time has passed. The IPCC reports that climate models published since around 1970 projected global surface warming in reasonable agreement with observations when researchers account for the difference between the forcing assumed in the projection and the forcing that actually occurred. That qualifier is essential: a model cannot be marked wrong for a future emissions path that society did not follow.

## Why do scientists run many models?

Research groups build models with different resolutions and representations of unresolved processes. They then run coordinated experiments using common inputs through the **Coupled Model Intercomparison Project**, or CMIP. Comparing the results reveals both robust responses and areas where model structure matters.

An **ensemble** is a collection of simulations, not a vote in which the most popular outcome automatically becomes true. Ensembles can vary the initial conditions, the model formulation, the assumed future pathway or all three. Their spread helps researchers examine distinct sources of uncertainty.

The ensemble average can reduce some effects of random internal variability, but it does not make every model equally suitable for every task. The IPCC says no universal, robust method exists for weighting a multi-model projection ensemble in all cases; expert judgement remains part of assessment. For a regional question, researchers also consider whether the selected models represent the processes important to that region.

## What is the difference between a projection and a prediction?

A **projection** states what a model produces under specified assumptions. A **prediction** is an attempt to state what will actually happen, often initialized from current conditions. The terms sometimes overlap in public writing, but the conditional nature of a long-range climate projection should remain explicit.

Future human emissions, land use and technology are not laws of physics. Researchers therefore use scenarios: coherent possible pathways for greenhouse gases, aerosols and other drivers. If a high-emissions and a low-emissions scenario yield different late-century climates, that difference is information about consequences under different inputs. It is not evidence that the model failed to choose one future.

This is why a responsible chart names the scenario, time period, baseline and geographic scale. A single coloured line with those details removed is not a complete climate projection.

Climate models also differ from daily weather forecasts. Weather prediction tries to follow the precise evolution of the atmosphere from today's measured state. Small initial differences grow, limiting detailed forecasts far ahead. Climate projections usually ask about the statistics of the system—averages, ranges, frequencies and long-term responses to forcing. A roulette wheel cannot tell you the next number, but its long-run distribution can still be described; the analogy is imperfect, yet it captures why uncertain sequences can coexist with informative statistics.

For the vocabulary around long-term change, see [climate change versus global warming](/climate-change-vs-global-warming/) and the broader [Climate Terms](/climate-terms/) collection.

## Where does uncertainty come from?

Three broad sources recur:

1. **Internal variability.** The climate system fluctuates naturally, so simulations begun from slightly different states can trace different short-term paths.
2. **Model uncertainty.** Models simplify reality and differ in their treatment of unresolved processes.
3. **Scenario uncertainty.** Future emissions and land-use choices are not known in advance.

Observations have uncertainty too. Thermometers, satellites, ocean instruments and reconstructed past climates each have measurement or sampling limits. Model evaluation must account for those limits rather than treating an observational dataset as perfect.

The balance among uncertainties changes with the question. Internal variability can dominate some near-term regional outcomes, while scenario choice becomes more important for many long-term global outcomes. A precise-looking local number therefore deserves more scrutiny than a robust large-scale direction shared across models and lines of evidence.

## What can climate models tell us—and what can they not?

Models are strong tools for testing mechanisms, attributing observed changes and estimating conditional climate responses. Confidence is generally greater where results agree with physical understanding, observations and independent evidence, and where multiple models show a consistent large-scale response.

They cannot identify society's exact future emissions path, reproduce every cloud or storm, or guarantee the weather in one place on one future date. Downscaling can add useful local structure, but it does not erase uncertainty inherited from the global model, the scenario or the downscaling method.

The right reading is neither “the model is a crystal ball” nor “the model is imperfect, so it says nothing.” Ask what experiment was run, what assumptions were supplied, how the model was evaluated, what range the ensemble produced and whether the scale matches the claim. That is how climate scientists read model output too.

## Sources

- [NOAA Climate.gov: Climate Models](https://www.climate.gov/maps-data/climate-data-primer/predicting-climate/climate-models)
- [NOAA Geophysical Fluid Dynamics Laboratory: Climate Modeling](https://www.gfdl.noaa.gov/climate-modeling/)
- [IPCC AR6 Working Group I: Frequently Asked Questions](https://www.ipcc.ch/report/ar6/wg1/resources/frequently-asked-questions/)
- [IPCC AR6 Working Group I, Chapter 4: Future Global Climate](https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-4/)

## Frequently asked questions

**Are climate models based only on past temperature trends?**

No. Climate models encode physical, chemical and biological processes, including conservation of energy and mass, fluid motion and exchanges among the atmosphere, ocean, land and ice. Observations are used to initialize and evaluate them, not merely to extend a trend line.

**How do scientists test a climate model?**

They compare simulations with observations of present and past climates, including spatial patterns, seasonal cycles and responses to known influences such as volcanic eruptions and greenhouse gases. Coordinated model intercomparisons reveal both shared results and persistent biases.

**Why do climate projections show a range?**

The range reflects natural internal variability, differences among model representations and uncertainty about future emissions and land use. Those sources are studied with ensembles that vary initial conditions, models and scenarios rather than relying on one simulation.

**Is a climate projection the same as a weather forecast?**

No. A weather forecast follows the detailed evolution of the atmosphere from current conditions. A long-term climate projection describes statistical changes under stated forcing assumptions, such as shifts in averages, ranges or frequencies across decades.

**Does higher model resolution guarantee greater accuracy?**

No. Smaller grid cells can represent finer geographic detail, but accuracy also depends on observations, model physics, parameterizations and fitness for the question. Downscaled or high-resolution output can still carry uncertainty from the global model and scenario.

**Why are future emissions scenarios used?**

Human emissions, land use and technology cannot be derived from physical equations alone. Scenarios provide coherent possible inputs, allowing researchers to compare what the climate system would do under lower, intermediate or higher forcing pathways.


---

# How Earth's Climate System Works: Energy and Connections

> Earth's climate works through energy exchange: sunlight is absorbed or reflected, and the planet emits infrared energy to space. The atmosphere, ocean, ice, land and living things interact to store and redistribute energy. A persistent imbalance changes the system's heat content. Human greenhouse-gas emissions have caused global warming by changing this system's energy balance.

Source: https://reportingclimatescience.com/how-earths-climate-system-works/  
Publisher: The Climate Explainer  
Published: 2026-09-15  
Updated: 2026-09-15

## How does Earth's climate system work?

Earth's climate works through energy exchange: sunlight is absorbed or reflected, and the planet emits infrared energy to space. The atmosphere, ocean, ice, land and living things interact to store and redistribute energy. A persistent imbalance changes the system's heat content. Human greenhouse-gas emissions have caused global warming by changing this system's energy balance.

Think of two questions as you follow the system: how much energy is Earth gaining or losing, and where is that energy going? They describe different things. Moving heat from one region to another changes regional conditions; changing the planet's total energy inventory requires a net gain or loss across its boundary. The mechanisms below connect those questions. [NASA CERES describes these energy flows](https://ceres.larc.nasa.gov/science/); the [IPCC assesses human-caused warming](https://www.ipcc.ch/report/ar6/syr/summary-for-policymakers/).

## What enters and leaves the climate system?

Sunlight arriving at Earth has two possible destinations: some is reflected back to space, while the rest is absorbed by the atmosphere and surface. Earth also emits thermal infrared radiation, energy associated with its temperature. Reflected sunlight and emitted infrared are separate outgoing flows.

At the top of the atmosphere:

**Rate of energy gain = absorbed sunlight minus outgoing thermal infrared energy.**

Absorbed sunlight already excludes reflection; subtracting reflected sunlight again would count it twice. When the two sides balance over time, the system is in radiative equilibrium. A positive difference adds energy; a negative difference removes it. This balance condition does not mean Earth is currently in equilibrium. See [NASA's energy-budget explanation](https://science.nasa.gov/earth/earth-observatory/climate-and-earths-energy-budget/).

## Why can a small persistent imbalance matter?

Distinguish a rate from an accumulated amount. A watt is one joule per second: watts measure power, while joules measure energy. Climate diagrams often express power per square metre, written W/m².

Here is an **illustrative calculation, not an estimate of Earth's present imbalance**. Suppose an area gains one extra joule each second for a full day:

- Assumed net gain: 1 W/m².
- Duration: 24 × 60 × 60 = 86,400 seconds.
- Accumulated energy: 1 × 86,400 = 86,400 joules per square metre.

For comparison, an assumed 10 W/m² gain lasting one hour adds 36,000 joules per square metre. The smaller rate operating longer adds more energy in this example. Neither calculation gives a temperature rise: that would also require knowing what absorbs the energy and how its state changes. The arithmetic illustrates why both the magnitude and duration of an imbalance matter.

## What does the atmosphere do besides move air?

Greenhouse gases, including carbon dioxide and water vapour, absorb and emit infrared radiation. Together with clouds, they alter energy exchange between the surface, atmosphere and space. Their presence keeps the surface warmer than it would otherwise be. Energy still escapes to space; the greenhouse effect does not mean that every outgoing ray is permanently confined.

Clouds affect both sides of the radiation balance: they reflect sunlight and interact with infrared radiation. Their net effect depends on their properties, including height. A cloud therefore cannot be classified as warming or cooling simply because it contains water. These processes are explained by [NASA's CERES science team](https://ceres.larc.nasa.gov/science/). Our [greenhouse-effect explainer](/what-is-the-greenhouse-effect/) follows that mechanism in more detail.

## How does atmospheric circulation redistribute heat?

Uneven solar heating helps drive large-scale air movement. **Atmospheric circulation** is the recurring pattern of that movement, which transfers heat and moisture. The familiar three-cell diagram describes Hadley, Ferrel and Polar cells in each hemisphere; it summarises average circulation rather than tracing every day's weather.

In the Hadley circulation, trade winds converge toward the equator, where air rises in a zone of frequent thunderstorms. Higher up, air moves poleward before sinking in the subtropics. That pattern helps explain the contrast between equatorial rainfall and subtropical dry regions.

Earth's rotation also matters. The **Coriolis effect** deflects moving air to the right in the Northern Hemisphere and left in the Southern Hemisphere. High-altitude jet streams help guide weather systems. Heat transport consequently follows structured, changing routes rather than flowing straight from the equator to each pole. The [Met Office describes these circulation patterns](https://weather.metoffice.gov.uk/learn-about/weather/atmosphere/global-circulation-patterns).

## Why is the ocean central to climate?

The ocean stores heat and transports it through currents. Surface winds are an important driver of currents; temperature and salinity differences, Earth's rotation and tides also contribute. **Salinity** means the amount of dissolved salt in water. Water moving between regions carries heat with it, helping moderate the uneven heating of the planet. [NOAA describes the ocean's climatic role](https://oceanexplorer.noaa.gov/ocean-fact/climate/).

Water has a high **heat capacity**, meaning it can absorb substantial energy without the temperature response being the same as in air. Ocean heat content therefore supplies information that a surface-air temperature reading cannot provide. Warming seawater also expands, contributing to sea-level rise. [NASA's ocean-warming indicator](https://science.nasa.gov/earth/explore/earth-indicators/ocean-warming/) explains heat storage and thermal expansion.

The IPCC's assessment assigns **91% of the observed energy increase during 1971–2018 to ocean warming**. That is a share of the climate system's accumulated energy increase, not a claim that the ocean warmed by 91% or received 91% of all sunlight. The period and denominator matter. See [IPCC Working Group I, Chapter 7, Section 7.2.2 and Table 7.1](https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-7/).

## How does the water cycle carry energy?

**Evaporation** changes liquid water into water vapour. It requires energy and removes heat from the surroundings. Oceans, lakes, rivers and other wet surfaces supply water to the atmosphere this way; boiling is not required. The [US Geological Survey explains evaporation and its cooling effect](https://www.usgs.gov/water-science-school/science/evaporation-and-water-cycle).

When vapour becomes liquid again, **condensation** releases heat into the atmosphere. Rising air can cool enough for cloud droplets to form. Water changing state therefore transfers energy as well as moving moisture. This energy associated with a change of state is called latent heat. The [USGS condensation explanation](https://www.usgs.gov/water-science-school/science/condensation-and-water-cycle) describes the release of heat as droplets form.

Follow the sequence carefully: taking energy from a wet surface during evaporation and releasing it during condensation are different stages. A statement that evaporation itself heats the surface reverses the local effect. Likewise, water vapour is a gas; the visible droplets in a cloud are liquid water, a different state of the same substance.

## How do ice and snow affect absorbed sunlight?

The **cryosphere** is the frozen part of the Earth system. Its bright surfaces matter because of **albedo**, the proportion of incoming sunlight a surface reflects. Sea ice reflects more sunlight than the darker ocean exposed when it melts.

This creates a feedback: initial warming can reduce sea ice; the exposed water absorbs more sunlight; that additional absorption contributes to further warming. **Positive feedback** means amplification of the initial change. The word positive describes the direction of the response, not whether the outcome is desirable.

The [National Snow and Ice Data Center explains this ice–albedo feedback](https://nsidc.org/learn/parts-cryosphere/sea-ice/why-sea-ice-matters). The important connection is that ice responds to temperature while also changing how much sunlight is absorbed. Treating ice only as an indicator of warming misses its active role in the energy budget.

## What roles do soil, vegetation and carbon play?

Land cover changes the way the surface exchanges energy and moisture with the atmosphere. Vegetation and soil influence reflection, infrared emission and evaporation. Soil moisture affects surface temperature, while the shape and roughness of the land influence wind. These are physical connections, even before considering carbon. The [Met Office's account of the climate system](https://weather.metoffice.gov.uk/climate/what-affects-global-climate) explains how the atmosphere, water, frozen regions, land and biosphere interact. **Biosphere** means living organisms and their place in that system.

The **carbon cycle** adds another connection. Plants take in carbon dioxide through photosynthesis, using sunlight to build organic material. Respiration, decomposition and burning return carbon to the atmosphere. Carbon also moves between the atmosphere and ocean and is stored in soils, organisms and rocks.

Burning fossil fuels transfers carbon from long-standing geological stores into the active cycle. Clearing forests also changes stored carbon. Vegetation is consequently neither a passive backdrop nor an unlimited solution to added carbon dioxide: plant growth also requires water and nutrients. [NASA's carbon-cycle explanation](https://science.nasa.gov/earth/earth-observatory/the-carbon-cycle/) follows those transfers and constraints.

## What changes the system, and what responds to change?

A **radiative forcing** is a disturbance to the radiation balance, such as one caused by changing greenhouse-gas concentrations. A feedback is part of the system's response that changes the subsequent energy balance. Keeping these concepts separate helps distinguish an initiating influence from an amplifying or damping response.

Warming also increases the planet's emission of infrared energy, a stabilising response. Other responses, including changes in water vapour, ice and clouds, modify how much warming follows a given forcing. The IPCC assesses these processes together; recognising an amplifying feedback does not establish unlimited warming. See [Chapter 7's assessment of forcing and feedbacks](https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-7/).

The existence of natural processes does not make the cause of recent global warming unresolved. The [IPCC's 2023 Synthesis Report](https://www.ipcc.ch/report/ar6/syr/summary-for-policymakers/) identifies human activities, chiefly the release of greenhouse gases, as the unequivocal cause of global warming. Its assessment distinguishes warming from greenhouse gases, cooling from other human influences, natural drivers and internal variability. These influences can operate together; they are not interchangeable explanations. Our [climate-change and global-warming guide](/climate-change-vs-global-warming/) clarifies the terminology.

## How do scientists check that these connections are real?

Different measurements address different parts of the system. NASA's [CERES observations](https://ceres.larc.nasa.gov/science/) track radiation flows and help evaluate climate models. Ocean observations track stored heat; [NASA describes combining in-water instruments, satellite measurements and models](https://science.nasa.gov/earth/explore/earth-indicators/ocean-warming/) to study the ocean. Our [climate-model guide](/how-do-climate-models-work/) explains how observations test simulations.

When reading a climate claim, ask three specific questions. Does it describe an energy flow or an accumulated amount? Is it about the whole planet or one region? Does the reported number include a time period and a clearly named quantity? Those checks help distinguish a circulation change, an energy imbalance and a measured warming trend without confusing one for another.

## Sources

- [NASA: Climate and Earth's Energy Budget](https://science.nasa.gov/earth/earth-observatory/climate-and-earths-energy-budget/).
- [NASA CERES: Science](https://ceres.larc.nasa.gov/science/).
- [Met Office: Global Circulation Patterns](https://weather.metoffice.gov.uk/learn-about/weather/atmosphere/global-circulation-patterns).
- [NOAA: Ocean, Climate and Weather](https://oceanexplorer.noaa.gov/ocean-fact/climate/).
- [NASA: Ocean Warming](https://science.nasa.gov/earth/explore/earth-indicators/ocean-warming/).
- [IPCC AR6 Working Group I: Chapter 7](https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-7/).
- [USGS: Evaporation](https://www.usgs.gov/water-science-school/science/evaporation-and-water-cycle).
- [USGS: Condensation](https://www.usgs.gov/water-science-school/science/condensation-and-water-cycle).
- [NSIDC: Why Sea Ice Matters](https://nsidc.org/learn/parts-cryosphere/sea-ice/why-sea-ice-matters).
- [Met Office: What Affects Global Climate?](https://weather.metoffice.gov.uk/climate/what-affects-global-climate).
- [NASA: The Carbon Cycle](https://science.nasa.gov/earth/earth-observatory/the-carbon-cycle/).
- [IPCC AR6 Synthesis Report: Summary for Policymakers](https://www.ipcc.ch/report/ar6/syr/summary-for-policymakers/).

## Frequently asked questions

**Why do ocean temperatures matter for climate?**

The ocean stores substantial heat and moves it through currents. Its heat content adds information beyond air temperature at the surface. Warming water also expands and contributes to sea-level rise. Measuring ocean heat therefore helps reveal changes in the wider climate system, including energy that is stored below the surface.

**Why is melting sea ice a climate feedback?**

Sea ice reflects more sunlight than the darker ocean beneath it. When warming reduces that reflective cover, exposed water absorbs more sunlight and contributes to further warming. This is a positive feedback because it amplifies the initial change; positive describes the direction of the response, rather than a beneficial outcome.

**How can condensation affect the atmosphere?**

Condensation changes water vapour into liquid water and releases heat into the atmosphere. It helps connect the movement of water with the transfer of energy. When rising air cools and droplets form, water changes state; the visible droplets are different from the invisible water vapour that preceded them.

**Are plants an unlimited sink for carbon dioxide?**

No. Plants take up carbon dioxide through photosynthesis, but growth also depends on water and nutrients. Carbon returns to the atmosphere through respiration, decomposition and burning. Understanding the carbon cycle requires following both uptake and release, rather than assuming that every addition to atmospheric carbon dioxide will be absorbed by vegetation.

**Does natural climate variability explain global warming?**

Natural variability is part of the climate system, but it does not overturn the assessed cause of global warming. The IPCC identifies human activities, chiefly the release of greenhouse gases, as the unequivocal cause of global warming. Its assessment separates human influences from natural drivers and internal variability instead of treating all changes as the same phenomenon.


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# What Is the Greenhouse Effect? How It Warms the Planet

> The greenhouse effect is the process by which gases in Earth's atmosphere — mainly water vapor, carbon dioxide, and methane — trap heat near the surface. Sunlight warms the ground, the ground radiates infrared heat back toward space, and greenhouse gases absorb and re-emit much of that heat downward. This natural effect keeps Earth about 33 °C warmer than it would otherwise be; human emissions are now strengthening it, driving modern global warming.

Source: https://reportingclimatescience.com/what-is-the-greenhouse-effect/  
Publisher: The Climate Explainer  
Published: 2026-07-19  
Updated: 2026-08-16

## What Is the Greenhouse Effect?

The greenhouse effect is the process by which certain gases in Earth's atmosphere trap heat near the surface. Sunlight passes through the atmosphere and warms the ground; the warm surface then radiates that energy back toward space as infrared heat. Greenhouse gases — mainly water vapor, carbon dioxide, and methane — absorb much of that outgoing heat and re-emit it in all directions, including back down. The result is a planet significantly warmer than it would otherwise be.

That last part is worth underlining: the greenhouse effect is not inherently a problem. It is the reason Earth is habitable at all. Without it, the planet's average surface temperature would sit around −18 °C (0 °F) — a frozen world. With it, the average is roughly 15 °C (59 °F). The problem is not the effect itself but the fact that human activity is strengthening it.

## How Does the Greenhouse Effect Work?

The mechanism runs in four steps. None of them requires exotic physics — just the well-measured behavior of light and gases.

### Step 1: Sunlight reaches the surface

The Sun delivers energy mostly as visible light, which the atmosphere is largely transparent to. Some of it reflects off clouds, ice, and bright surfaces, but the majority reaches the ground and oceans and is absorbed.

### Step 2: The warm surface radiates heat

Anything warm gives off infrared radiation — the same invisible heat you feel near a radiator. Earth's surface, warmed by sunlight, constantly radiates infrared energy upward.

### Step 3: Greenhouse gases intercept that heat

Here is the crucial asymmetry. Nitrogen and oxygen — about 99% of the dry atmosphere — let infrared radiation pass straight through. But molecules with three or more atoms, like carbon dioxide (CO₂), water vapor (H₂O), and methane (CH₄), vibrate in ways that let them absorb infrared energy. They catch a large share of the heat heading for space.

### Step 4: The heat is re-radiated in all directions

Those energized molecules quickly re-emit the energy — but randomly, in every direction. Roughly half of it heads back toward the surface instead of escaping. That returned heat keeps the lower atmosphere and surface warmer than sunlight alone could.

A quick honesty note about the name: a real greenhouse works mainly by physically blocking warm air from rising away. The atmosphere works by absorbing and re-radiating infrared energy. The metaphor is imperfect, but the label has stuck for over a century.

## What Gases Cause the Greenhouse Effect?

Only a small fraction of the atmosphere participates, which is exactly why human emissions can move the needle.

| Gas | Main sources | Key characteristics |
|---|---|---|
| Water vapor | Evaporation | The largest contributor overall, but it cycles through the atmosphere in days and responds to temperature rather than driving it directly — a feedback, not a control knob |
| Carbon dioxide (CO₂) | Fossil fuels, deforestation, natural carbon cycle | The main driver of modern warming; stays in the atmosphere for centuries |
| Methane (CH₄) | Agriculture, fossil fuel operations, wetlands | Traps far more heat per molecule than CO₂ but breaks down within decades |
| Nitrous oxide (N₂O) | Fertilizers, agriculture | Potent and long-lived |
| Fluorinated gases | Industrial products, refrigerants | Entirely human-made; extremely potent per molecule |

Water vapor's role confuses many readers, so it deserves one clear sentence: warming caused by CO₂ lets the air hold more water vapor, which adds further warming — an amplifying feedback, not an independent cause.

## Natural vs Enhanced Greenhouse Effect

Scientists distinguish two versions of the same mechanism:

- **The natural greenhouse effect** is the baseline warming that has operated for billions of years, keeping Earth's average temperature in the comfortable liquid-water range.
- **The enhanced greenhouse effect** is the extra warming caused by human additions of greenhouse gases — chiefly from burning coal, oil, and gas, plus deforestation and agriculture.

The evidence for enhancement is direct. Before the Industrial Revolution, atmospheric CO₂ sat near 280 parts per million, a level confirmed by air bubbles trapped in ancient ice. Today it has passed 420 parts per million — roughly a 50% increase — and instruments have tracked the rise continuously since the 1950s. More CO₂ means more outgoing heat intercepted, which shifts Earth's energy balance and warms the surface. Global average temperature has already risen by more than 1 °C since the late 1800s, in line with what the physics predicts.

This strengthening of the greenhouse effect is the engine behind both global warming and the broader shifts in weather patterns, ice, and sea level. If you have ever wondered how those two terms differ, our companion explainer on [climate change vs global warming](/climate-change-vs-global-warming/) sorts out the vocabulary.

## Why This One Mechanism Matters So Much

Almost every other topic in climate science builds on the greenhouse effect. Ocean heat uptake, melting ice sheets, feedback loops, climate sensitivity — each is a downstream consequence of more energy being retained in the system. That is why we treat it as the foundation of our [How Climate Works](/how-climate-works/) collection.

The core takeaway fits in two sentences. The greenhouse effect is natural, well-understood physics that keeps Earth livable. Humanity is now amplifying it faster than at any point in the historical record, and that amplification — not the effect itself — is what climate science is warning about.

## Frequently asked questions

**Is the greenhouse effect good or bad?**

The natural greenhouse effect is essential: without it, Earth's average surface temperature would be around −18 °C instead of roughly 15 °C, and the planet would be frozen. The problem is the enhanced greenhouse effect — the extra warming caused by human emissions of carbon dioxide, methane, and other gases. It is the strengthening of the effect, not the effect itself, that drives modern climate change.

**What gases cause the greenhouse effect?**

The main greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, ozone, and human-made fluorinated gases. Nitrogen and oxygen, which make up about 99% of the dry atmosphere, do not trap infrared heat. Water vapor is the largest contributor overall, but it acts as a feedback that responds to temperature; carbon dioxide from fossil fuels is the main driver of current warming.

**Why is it called the greenhouse effect if it doesn't work like a greenhouse?**

The name is an imperfect metaphor that stuck. A real greenhouse warms mainly by physically stopping warm air from rising away, while the atmosphere warms the surface by absorbing outgoing infrared radiation and re-emitting part of it back down. The outcome is similar — heat retained near the ground — but the mechanism is different, which is why scientists sometimes note the analogy's limits.

**How do we know humans are strengthening the greenhouse effect?**

Multiple independent lines of evidence agree. Air bubbles in ancient ice show pre-industrial carbon dioxide near 280 parts per million; direct instrument records show it has now passed 420 — roughly a 50% rise. The isotopic fingerprint of the added carbon matches fossil fuels, and the observed warming pattern matches what greenhouse physics predicts, according to IPCC assessments.


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