The Köppen-Geiger system divides Earth’s climate into five main categories

View the 55 ECVs used to describe Earth's atmospheric conditions

Essential climate variables include physical, chemical, and biological variables that meaningfully contribute to Earth's climate and how it changes with time. Many of these variables influence one another through feedback mechanisms across Earth's atmosphere, hydrosphere, cryosphere, biosphere, and geosphere.

An overview of Earth's atmospheric cells and how they distribute Earth's uneven heating

The Hadley, Ferrel, and Polar cells are circulation patterns that act like gears, moving warmer air from the equator to the poles. The rising and falling of air currents within these patterns creates semi-persistent regions of low and high pressure, which contribute to the formation of regional climates, such as tropical zones.

Global climate models simulate Earth system interactions and how human activity impacts climate

By splitting the planet into tiny 3D grid cells, supercomputers can run thousands of equations for each cell to determine the movement of energy, moisture, and other elements across Earth. The equations can also incorporate greenhouse gases to determine how humans affect the climate.

Meteorological v. astronomical seasons, explained

Meteorologists and climatologists define seasons differently from “regular” or astronomical spring, summer, fall, and winter. Traditional seasons reflect the movement of celestial objects, known as the astronomical seasons; meteorologists mark seasonal change based on temperature averages.

A breakdown of Earth's atmospheric layers, including why it can get colder or hotter with altitude

Gases in the troposphere—the atmosphere's lowest layer—cool with increasing height as they get farther from the thermal energy emitted by Earth's warm surface. In the next layer—the stratosphere—ozone is increasingly heated by the sun's ultraviolet radiation with height. Because cooler air sinks and hotter air rises, the cooler troposphere and hotter stratosphere form a natural boundary keeping Earth's weather in the lowest layer.

Hot, semiarid, coastal, cold: An overview of the four desert types

This article describes the various characteristics of deserts, including their geography, their climate, their soil, and the wildlife and vegetation that inhabit them. All desert climates are characterized by extreme temperatures and low rainfall,...

The greenhouse effect was discovered by analyzing Earth's temperature

Using mathematical techniques developed to analyze heat transfer, Jean-Baptiste Joseph Fourier showed that Earth should be significantly cooler if solar radiation were the only contributor to its surface temperature. By considering that the atmosphere could amplify the sun's warming effect, he formulated what became known as the greenhouse effect.

The impact of greenhouse gases is assessed as a measure of Global Warming Potential

Since 1990, the Intergovernmental Panel on Climate Change has used GWP to measure how much energy 1 metric ton of a gas emits over a given period—usually 100 years—relative to 1 metric ton of carbon dioxide. By definition, carbon dioxide has a GWP of 1.

Hurricanes are classified according to their maximum sustained wind speed

The Saffir-Simpson Hurricane Wind Scale is a rating system that organizes hurricanes into one of five categories. Categories three and higher are classified as major hurricanes, but all categories can produce deadly storm surges and rain-induced floods.

The Kardashev scale measures a civilization's advancement based on energy use

Developed by Russian astrophysicist Nikolai Kardashev in 1964, the scale classifies a civilization based on the amount of energy its existing technologies can harness, ranging from a society that consumes as much energy as a single planet to one that consumes as much energy as an entire galaxy.

The three categories of photosynthesis, which each help plants survive in different environments

In the vast majority of plants, C3 photosynthesis produces three-carbon intermediate molecules in the Calvin cycle within the cells of leaves. Plants in hot, dry climates use C4 photosynthesis across two types of cells to produce four-carbon molecules before the Calvin cycle. Plants in drought conditions use CAM to store carbon dioxide as an acid at night, minimizing water loss.

The complexity of classifying a tree

It may seem obvious to us when we see a tree, but very specific characteristics cause scientists to distinguish trees from other types of plants. This video provides a visual and verbal explanation of distinctions that separate trees from other plants like shrubs or herbs. See a scientific breakdown of these traits.

Climate determinism wrongly linked human traits and societal progress to geography

Historically rooted in Greek philosophy, its ideas used the latitudes where people were located to justify racial hierarchies, casting tropical peoples as lazy or inferior. These biases still influence how media and research portray people in climatically disadvantaged regions. (Some readers may experience a paywall.)

As of 2022, just 0.5% of installed renewable energy capacity worldwide is geothermal

Despite being able to generate electricity regardless of the weather, solar (28%) and wind (27%) are far more prevalent, primarily because of their lower upfront costs. Geothermal plants use 88% less space than solar farms to produce the same energy, but have been restricted to geologically active regions.

Researchers generally group gut bacteria into six different categories

The trillions of bacteria in the gut microbiome can be grouped into six categories: firmicutes, actinomycetota, pseudomonadota, fusobacteriota, bacteroides, and a broad miscellaneous category. The functions of each are complex but range from breaking down food and producing vitamins to fighting pathogens.

Scientists quantify how far from the poles auroras will be visible using the G-scale

The Geomagnetic Storm scale indicates the expected severity of the deformation of Earth's magnetic field based on the amount of energy injected by the solar wind. Solar activity is monitored using various satellites to forecast these storms, which can also be used to anticipate damage and disruption to power systems, radio communications, and satellite navigation.

How is the climate like baseball?

A two-minute video taking a lighthearted look at an unexpected analogy, explaining why some people call carbon dioxide (and the other greenhouse gases) the steroids of the climate system.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Mapping how the El Niño-Southern Oscillation affects weather patterns around the world

In the warm episode (El Niño), summers in India, Indonesia, Australia, and the Caribbean are drier than normal, while winters bring wetter, cooler conditions to the US Gulf Coast and warmer conditions to the Pacific Northwest. During the cold episode (La Niña), these are reversed, with India, Indonesia, and the southern Caribbean experiencing greater rainfall in the summers.

Even in nature reserves, climate change is driving rapid ecological collapse

Studies show a dramatic decline in insect populations, resulting in cascading global biodiversity losses across non-insect species. The balances in tropical ecosystems are the most affected by climate change.

Ice ages are periods of glaciation that last tens of millions of years

During these periods, Earth grows cold and is covered in massive continental ice sheets. Scientists have outlined at least five major ice ages, which result from the alignment of complex factors, like the flow of ocean currents and the movement and location of tectonic plates.

As of 2025, scientists at B2 study the heat tolerance of cacao and coffee trees

The research at Biosphere 2 has led to the development of low-cost plant monitors, which can be provided to farmers worldwide to enable more precise monitoring of crops. Geodesic domes built within the ocean biome are used to investigate the best architectural structures for repopulating degraded reefs.

Wine is divided between Old World and New World

The distinction stems from both geography and winemaking technique and tradition. This video breaks down how different viticultural regions fit into each category and the common traits of both Old World and New World wines. It also provides helpful tips for reading Old World wine labels.

The 'Goldilocks zone' is the region around a star where liquid water can exist

Also referred to as the habitable zone, this region varies based on the properties of a planetary system's host star, including its size and luminosity, which measure the rate at which the star radiates energy per unit area.

Asia's agriculture-focused set of 24 'small seasons'

In contrast to the four broad seasons and their basis in astronomy and climate, ancient farmers in China and Japan had many more and varied seasons (or "sekki). Take Keichitsu (March 6 to 21), for example: this means "going-out of the worms" when bugs come out from hibernation.

Roughly half of the world's nations are (relatively young) electoral democracies

Classifying countries by governance type involves leaning into technical systems like the Regimes of the World classification. In this data dive, see a map of the world's oldest and youngest electoral democracies, as well as liberal democracies (which are measured by the protection of minorities and checks on executive power from the legislature).

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Visualize the path of every solar eclipse from 1900 to 2099 and see what each looks like when observed from different locations on Earth.

Explore the history, structure, and species of Australia's Great Barrier Reef with this interactive journey narrated by Sir David Attenborough.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

Ebola species have historically been named after where they were discovered, stigmatizing residents who live there, including Bundibugyo, in Uganda.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

View the ten deadliest tornadoes in US history.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

When you complete a CAPTCHA on a website to prove you are human, you may be unknowingly training algorithms for self-driving cars, whose systems require training data to help identify crosswalks, bicycles, and other outdoor objects.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

The term 'algorithm' originated from the Latinized name of al-Khwārizmī, a 9th-century mathematician whose works introduced Arabic numerals and the decimal-based numeral system to Europe and whose treatise 'Al-Jabr' gave algebra its name.

Georgia O'Keeffe's flower paintings are often assumed to be sexual, though the artist claimed she was simply interested in highlighting the beauty of flowers that most people neglect

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

The Brothers Grimm were lawyers before they were storytellers, but became interested in fairy tales as they began investigating how rules and customs had been passed down through cultures.

See photos of Meteora, a mountainous site in central Greece, home to 14th-century monasteries perched atop soaring outcroppings.