Climate system from IPCC AR4

How Climate Works

Learn about climate, why it is changing, and how scientists are studying it.



The climate where you live is called regional climate. Global climate is a description of the climate of a planet as a whole, with all the regional differences averaged.

Why Earth Is Warming

Over the past century, the global average temperature has warmed. Learn the science of why this has happened, and what the future holds.

The Greenhouse Effect

Without the greenhouse effect, Earth’s temperature would be below freezing. It is, in part, a natural process. However, Earth’s greenhouse effect is getting stronger as we add greenhouse gases to the atmosphere. That is warming the climate of our planet.

History of Climate Science Research

How has our knowledge about Earth's climate grown over time? Use our interactive timeline to explore important and interesting scientific milestones, including when carbon dioxide was first discovered and when we learned about the heat-trapping ability of gases.

Why Does Climate Change?

Factors that have the power to change global climate can be natural, like volcanic eruptions and changes in solar energy, or caused by humans, like the addition of greenhouse gases to the atmosphere.

The Biosphere

The biosphere includes all life on our planet. Scientists study how biological processes, like photosynthesis, affect other parts of the Earth system. Humans are only a small fraction of Earth's biosphere, but our actions have a large impact.

El Niño-Southern Oscillation

Learn how the El Niño-Southern Oscillation (ENSO) climate fluctuation affects weather around the world.

Drought: When Water Is Scarce

Drought can occur anywhere in the world and harm people and ecosystems. Drought is becoming more frequent and more severe due to climate change.

Climate Variability

When climate conditions, such as temperature and precipitation, vary from the expected averages this is called climate variability. Natural changes in the Earth system can cause climate variability, but scientists are concerned about climate variability resulting from human-caused climate change. 

How the Geosphere Rocks Climate

How has the geosphere impacted Earth’s climate? Typically, the geosphere reacts on geologic timescales, affecting climate slowly and over millions of years. However, the burning of fossil fuels over the last 150 years has sped the impact of the geosphere on climate.

Indirect Evidence of Climate Change

Both direct and indirect measurements are important for understanding the true scale of climate change. Learn how scientists use indirect evidence to study both modern and past climate change.

Investigating Past Climates

To understand how and why the climate has changed in the past scientists study evidence such as ice cores, coral reefs, and more. Learn about different types of paleoclimate proxies and how they tell the story of Earth's past climate.

Researching Climate Change

Climate change research involves numerous disciplines of Earth system science as well as technology, engineering, and programming. To have a complete picture of how the climate changes we rely on direct measurements, proxy data, and computer modeling. 

The Energy Budget

Accounting for all the energy that enters and leaves the Earth system helps us understand how the planet maintains a habitable temperature. This accounting of energy is known as Earth’s radiation budget.