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Climate

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Climate is the long-term pattern of weather in a specific region. While weather describes what happens right now, climate describes what is typical over long periods. Scientists usually define climate by looking at averages over 30 years. This period is known as a climate normal. Using 30 years helps researchers filter out short-term anomalies. These anomalies include things like El Niño or unusual yearly changes. A more rigorous definition includes the mean and variability of many variables. These variables can be measured over months or even millions of years.

To understand climate, scientists measure many different meteorological variables. These are the physical properties of the atmosphere. Common measurements include temperature, precipitation, and wind. They also track humidity, atmospheric pressure, and solar radiation. Other data includes soil temperature and pan evaporation rates. Scientists even look at visibility and the number of days with thunder or hail. These measurements help describe the state of the entire climate system. This system includes the atmosphere, the hydrosphere, the cryosphere, the lithosphere, and the biosphere.

Many factors determine the climate of a specific location. Latitude and longitude are primary drivers of climate patterns. Altitude, or height above sea level, also plays a major role. The terrain and nearby water bodies affect local conditions. Ocean currents are very important for moving heat around the planet. For example, the thermohaline circulation warms the northern Atlantic Ocean by 5 °C. This is much warmer than other ocean basins. Vegetation also matters because it affects how much heat the ground absorbs. Changes in greenhouse gases, like carbon dioxide and methane, also control solar energy retention.

Scientists use classification systems to group different climates together. These systems help us understand the relationship between climate and biomes. The Köppen climate classification is the most widely used method. It was first developed in 1899 to identify climate zones based on vegetation. Another important method is the Thornthwaite system, which has been used since 1948. This system incorporates evapotranspiration, which is the process of water moving from the land to the atmosphere. It classifies climates into microthermal, mesothermal, and megathermal types. Other systems, like the Bergeron and Spatial Synoptic systems, focus on air masses.

We can also study climates from the ancient past through paleoclimatology. This field examines climate variations from the time of Earth's formation. Because people did not have thermometers millions of years ago, they use proxy variables. These are natural clues that act as substitutes for direct measurements. Non-biotic evidence includes ice cores and sediments found in lake beds. Biotic evidence includes tree rings and coral. These records help scientists identify periods of stability and change. They can show if climate changes follow regular, periodic cycles.

Climate variability refers to changes in the mean state of the climate. These variations happen on scales larger than a single weather event. Some variability is random, which scientists call noise. Other variability is periodic and follows distinct patterns. These patterns can be linked to astronomical factors. These include variations in sunlight and the Earth's orbit. However, natural cycles can be masked by other events. Volcanic eruptions or human emissions can hide these natural patterns. Modern records are now much more detailed thanks to satellite launches since the 1960s.

Today, the world is experiencing significant climate change. This refers to variations in global or regional climates over time. It can be caused by internal Earth processes or external forces. Recently, human activities have become a major driver of change. This includes the emission of greenhouse gases that cause global warming. This warming causes a redistribution of biota, which are living things. For instance, a 3 °C change in temperature can shift climate zones significantly. Species may move 300–400 km toward the poles or 500 m higher in elevation. Scientists use mathematical climate models to study these complex shifts.

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File:Change in Average Temperature With Fahrenheit.svg
Change in Average Temperature With Fahrenheit.svg
File:Global Temperature And Forces With Fahrenheit.svg
Global Temperature And Forces With Fahrenheit.svg
File:Köppen-Geiger climate classification (1980-2016).png
Köppen-Geiger climate classification...
File:ISS-48 Towering cumulonimbus and other clouds over the Earth (2).jpg
ISS-48 Towering cumulonimbus and other...
File:Cumulus clouds in fair weather.jpeg
Cumulus clouds in fair weather.jpeg
Climate-Morrisjm-18May2023.ogg
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