Climate change is a long-term shift in the statistical state of Earth's climate. The current global warming trend is primarily driven by human activities that increase heat-trapping greenhouse gases, especially carbon dioxide from fossil-fuel use.

What the science says

Earth's climate has changed naturally in the past because of orbital variations, volcanic activity, solar changes and other factors. Scientists distinguish today's trend by comparing the size, timing and physical fingerprint of those natural influences with observed greenhouse-gas increases and warming.

How the process works

The greenhouse effect itself is natural and essential for a habitable planet. Human emissions strengthen that effect by adding carbon dioxide, methane, nitrous oxide and other gases, changing the balance between incoming solar energy and heat escaping to space.

What scientists measure

Observed changes include rising global temperature, ocean heat gain, melting ice, sea-level rise and shifts in many ecosystems. Attribution studies test whether combinations of natural and human influences can reproduce these patterns; models match recent warming only when human forcing is included.

Limits and open questions

Climate change does not mean every location warms at the same rate or that weather stops varying. It changes the background conditions and probabilities on which individual weather events occur, while regional outcomes depend on circulation, geography and local feedbacks.

Why this topic matters

Understanding What Is Climate Change and What Causes It helps connect individual observations to the larger scientific framework. Reliable explanations separate measured evidence from speculation, make uncertainty visible, and give readers a basis for interpreting new research as it appears.

Sources and further reading

What causes climate change?

Climate changes when the amount of energy entering, leaving or moving through Earth’s climate system changes for long enough to alter long-term averages. Natural influences include volcanic eruptions, variations in solar output and slow changes in Earth’s orbit. These factors help explain climate changes in the distant past and can affect climate over particular time scales.

The dominant cause of the rapid modern warming trend is the increase in heat-trapping greenhouse gases from human activities. Burning coal, oil and natural gas raises atmospheric carbon dioxide, while agriculture, fossil-fuel production and waste contribute methane and nitrous oxide. Land-use change can both release stored carbon and reduce the amount removed from the atmosphere by ecosystems.

Forcing and feedback are different

A climate forcing initiates a change in Earth’s energy balance. Feedbacks then amplify or reduce the response. For example, warming can increase atmospheric water vapor, which adds further greenhouse warming, while melting snow and ice exposes darker surfaces that absorb more sunlight. Distinguishing forcing from feedback helps explain why a relatively small change in the energy balance can produce broader changes across the climate system.