Global surface temperature

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

We have good temperature records from the 1850s to 1880s. The longest record comes from Central England temperature data, starting in 1659. Since 1975, the world's average temperature has been rising fast. 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 air 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 mixes the temperature of the ocean's surface and the air near the ground on land.

This temperature helps us see how Earth's climate is changing. It is not the same as the temperature of the air higher up, which scientists also study.

Temperature data from 1850 to the present time

The Earth's temperature has been rising over the past hundred years. This warming is linked to gases in the air that trap heat. Measuring temperature changes helps scientists understand this big shift.

Since 1850, the world's average temperature has risen by about 1.09 °C. This warming has sped up since the 1970s, faster than any time in the last 2000 years. Most of the warming happened in two periods: 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 increased by 0.88 °C. Scientists use many 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.

The record of temperature measurements started with simple thermometers and now includes electronic sensors and satellites. These tools show us how temperatures have changed around the world. By looking at temperature changes, 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. 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

Scientists agree that the climate is changing because of greenhouse gases from human activities. This idea is supported by groups like the Intergovernmental Panel on Climate Change (IPCC), which reviews science, and the U.S. Global Change Research Program.

The National Academy of Sciences 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.

Some 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

From 2015 to 2021, every year was warmer than any year before 2014, and this warming will likely keep going. Scientists use special computer programs and real-world data to make predictions. They think that by the end of the 21st century, Earth’s temperature could rise between 1.0 °C and 1.8 °C if we cut down on pollution a lot. If pollution stays about the same, the temperature could rise between 2.1 °C and 3.5 °C. And if pollution grows a lot, the temperature could rise between 3.3 °C and 5.7 °C.

Regional temperature changes

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

Climate change does not affect all parts of Earth the same way. Land areas will warm up faster than oceans, and places near the North Pole will warm up faster than areas near the Equator. We expect three big changes from global warming: ice will melt, the movement of water in the air and on land will change, and ocean currents will shift.

Temperature estimates from prior to 1850

The global temperature record shows how the temperature of the air and oceans has changed over time. We have many ways to guess what past temperatures were like, going back millions of years. Information from ice cores covers the last 800,000 years. Studying the paleoclimate looks at the time 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 started using thermometers for regular measurements.

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

We can use different clues, called proxies, to guess 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 going back 2,000 years have been done, 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 similar time since AD 1600, and probably since AD 900
• there was a Little Ice Age around AD 1700
• there was a Medieval Warm Period around AD 1000, but this was not a global event.

Main article: Paleoclimatology

We have many guesses about past temperatures throughout Earth's history. This article talks about events since the end of a big cold time called the Pleistocene glaciers. The last 10,000 years, called the Holocene epoch, have seen many temperature changes.

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

Main article: Geologic temperature record