Global surface temperature

Global surface temperature (GST) is the average temperature of Earth's surface at a given time. It combines sea surface temperature and the near-surface air temperature over land, weighted by how much of the Earth each covers. We get temperature data mostly from weather stations and satellites. In the past, scientists used proxy data like tree rings, corals, and ice cores to estimate temperatures.

Reliable temperature records began in the 1850s to 1880s. The longest temperature record comes from Central England temperature data, starting in 1659. Since 1975, the world's average temperature has been rising quickly. It is now about 1.1°C warmer than it was in 1880. This warming shows that human activities are causing climate change.

The temperature of the atmosphere and oceans has changed over many years. We can learn about temperatures from millions of years ago using clues from rocks, ice cores, and tree rings. These records help scientists understand how the Earth's temperature has changed naturally and because of humans.

Definition

The global surface temperature (GST) is the average temperature of Earth's surface. It combines the temperature of the ocean's surface and the air close to the ground over land.

This temperature helps us understand how Earth's climate is changing over time. It is different from the temperature of the air higher up, which scientists also study.

Temperature data from 1850 to the present time

Changes in Earth's temperature over the last hundred years show that our planet is warming up. This warming is linked to increases in gases in the air that trap heat. Measuring how much the world's temperature has changed helps scientists understand this big change.

Since the year 1850, the world's average temperature has gone up by about 1.09 °C. This warming has happened faster since the 1970s than at any other time in the last 2000 years. Most of this warming happened in two main times: from 1900 to 1940 and again from 1970 onward.

Land areas have warmed up faster than the oceans. From 1850 to 2020, land temperatures rose by 1.59 °C, while ocean temperatures went up by 0.88 °C. Scientists use many different tools to measure temperature, including weather stations on land and instruments on ships and buoys in the water. These measurements help us track how our climate is changing over time.

The record of temperature measurements started with simple thermometers and has grown to include electronic sensors and satellites. These tools give us a picture of how temperatures have changed around the world. By looking at temperature changes instead of exact numbers, scientists can see patterns that show the Earth is warming.

The warmest years have all happened recently, from 2015 to 2025. These warm years show the continuing trend of climate change, even though some years may be warmer or cooler than others because of natural changes in the environment.

Each decade since 1850 has been warmer than the one before. The most recent decade, from 2011 to 2020, was the warmest in at least 11,700 years.

Factors influencing global temperature

Further information: Causes of climate change and Climate variability and change

Many things can change the temperature of the Earth. One big factor is greenhouse gases. These gases trap heat in the air, which makes the land warmer too. This is called the greenhouse effect.

Another important factor is something called the El Niño–Southern Oscillation (ENSO). During El Niño, the Earth tends to get a little warmer. During La Niña, it usually gets a little cooler. Big volcanic eruptions can also cool the Earth for a few years because they send particles into the air that block sunlight. Changes in how we use land, like cutting down forests, can also affect the temperature by adding more greenhouse gases to the air. Finally, the amount of energy the Sun gives us changes a tiny bit over about 11 years, which can also influence Earth’s temperature.

Robustness of evidence

There is a scientific consensus that climate is changing and that greenhouse gases from human activities are the main reason. This idea is supported by groups like the Intergovernmental Panel on Climate Change (IPCC), which reviews existing science, and the U.S. Global Change Research Program.

The National Academy of Sciences has also agreed that Earth's average temperature rose in the 20th century. A study by the Berkeley Earth Surface Temperature group in 2011 found that land areas warmed by about 0.911 °C in the past 50 years. Their work showed that earlier studies by the Hadley Centre and NASA were correct, even when looking at things like urban heat island effects.

Sometimes people say that global warming "stopped in 1998". This isn't true because the climate can change in different ways over short periods. For example, strong events like El Niño in 1998 can make one year seem especially warm. After 2012, every year has been warmer than any year before 2015. We still expect warming to go up and down a little over the next years, but the overall trend is clear. ^{: Box 3.1}

Related research

Trends and predictions

Further information: Climate change § Future warming and the carbon budget, and Climate change scenario

The years from 2015 to 2021 were all warmer than any years before 2014, and this warming pattern is expected to continue. Scientists predict that by the end of the 21st century, the Earth’s temperature will likely rise between 1.0 °C and 1.8 °C if we reduce pollution a lot. If we keep adding pollution at a middle level, the temperature could rise between 2.1 °C and 3.5 °C. And if pollution increases a lot, the temperature could rise between 3.3 °C and 5.7 °C. These predictions come from special computer programs that help us understand how the climate works, along with real-world observations.

Regional temperature changes

See also: Effects of climate change and Climate variability and change § Variability between regions

Climate change will not affect every part of the Earth the same way. Places on land will warm up faster than oceans, and areas near the North Pole will warm up faster than places near the Equator. There are three big changes we expect from global warming: ice will melt, the way water moves through the air and land will change, and ocean currents will shift.

Temperature estimates from prior to 1850

The global temperature record shows how the temperature of the atmosphere and oceans has changed over time. We have many ways to estimate past temperatures, going back millions of years. Information from ice cores covers the last 800,000 years. A study of the paleoclimate looks at the time period from 12,000 years ago. Tree rings and measurements from ice cores can tell us about global temperatures from 1,000 to 2,000 years ago. The most detailed temperature information exists since 1850, when we began using thermometers for regular measurements.

Further information: Temperature record of the last 2,000 years

We can use different clues, called proxies, to estimate temperatures before we had thermometers. Things like tree ring widths, coral growth, and isotope variations in ice cores can help us understand past temperatures. These proxies give us information about climate changes over the last 2,000 years, mainly for the northern hemisphere.

Proxy reconstructions extending back 2,000 years have been performed, but reconstructions for the last 1,000 years have more and better data. These reconstructions show:

• global mean surface temperatures over the last 25 years have been higher than any comparable period since AD 1600, and probably since AD 900
• there was a Little Ice Age centered on AD 1700
• there was a Medieval Warm Period centered on AD 1000, but this was not a global event.

Main article: Paleoclimatology

We have many estimates of past temperatures throughout Earth's history. This article focuses on events since the end of the big cold period called the Pleistocene glaciers. The last 10,000 years, called the Holocene epoch, have seen many changes in temperature.

The World Paleoclimatology Data Center keeps records of ice core data from glaciers and ice caps around the world.

Main article: Geologic temperature record