Жер климат жүйесінің температурасын тікелей өлшеулер және өзгерістері

In situ measurements that provide the temperature of Earth's climate system
temperature changes on other time scales

The instrumental temperature record is a record of temperatures within Earth's climate based on direct measurement of air temperature and ocean temperature. Instrumental temperature records do not use indirect reconstructions using climate proxy data such as from tree rings and marine sediments. Instead, data is collected from thousands of meteorological stations, buoys and ships around the globe. Areas that are densely populated tend have a high density of measurements points. In contrast, temperature observations are more spread out in sparsely populated areas such as polar regions and deserts, as well as in many regions of Africa and South America. In the past, thermometers were read manually to record temperatures. Nowadays, measurements are usually connected with electronic sensors which transmit data automatically. Surface temperature data is usually presented as anomalies rather than as absolute values. A temperature anomaly is presented compared to a reference value, also called baseline period or long term average). For example, a commonly used baseline period is the time period from 1951 to 1980. The longest running temperature record is the Central England temperature data series, which starts in 1659. The longest running quasi global records start in 1850. For temperature measurements in the upper atmosphere a variety of methods can be used. This includes radiosondes launched using weather balloons, a variety of satellites, and aircraft. Satellites can monitor temperatures in the upper atmosphere but are not commonly used to measure temperature change at the surface. Ocean temperatures at different depths are measured to add to global surface temperature datasets. This data is also used to calculate the ocean heat content. The data clearly shows a rising trend in global average surface temperatures (i. e. global warming) and this is due to emissions of greenhouse gases from human activities. The global average and combined land and ocean surface temperature show a warming of 1.09 °C (range: 0.95 to 1.20 °C) from 1850–1900 to 2011–2020, based on multiple independently produced datasets.]] Instrumental temperature records are based on direct, instrument based measurements of air temperature and ocean temperature, unlike indirect reconstructions using climate proxy data such as from tree rings and ocean sediments.

The period for which reasonably reliable instrumental records of near surface temperature exist with quasi global coverage is generally considered to begin around 1850. Earlier records exist, but with sparser coverage, largely confined to the Northern Hemisphere, and less standardized instrumentation. The temperature data for the record come from measurements from land stations and ships. On land, temperatures are measured either using electronic sensors, or mercury or alcohol thermometers which are read manually, with the instruments being sheltered from direct sunlight using a shelter such as a Stevenson screen. The sea record consists of ships taking sea temperature measurements, mostly from hull mounted sensors, engine inlets or buckets, and more recently includes measurements from moored and drifting buoys. The land and marine records can be compared. Land and sea measurement and instrument calibration is the responsibility of national meteorological services. Standardization of methods is organized through the World Meteorological Organization (and formerly through its predecessor, the International Meteorological Organization). Most meteorological observations are taken for use in weather forecasts. Centers such as European Centre for Medium Range Weather Forecasts show instantaneous map of their coverage; or the Hadley Centre show the coverage for the average of the year 2000. Coverage for earlier in the 20th and 19th centuries would be significantly less. While temperature changes vary both in size and direction from one location to another, the numbers from different locations are combined to produce an estimate of a global average change.

Records of global average surface temperature are usually presented as anomalies rather than as absolute temperatures. A temperature anomaly is measured against a reference value (also called baseline period or long term average). For example, a commonly used baseline period is 1951 1980. Therefore, if the average temperature for that time period was 15 °C, and the currently measured temperature is 17 °C, then the temperature anomaly is +2 °C. Temperature anomalies are useful for deriving average surface temperatures because they tend to be highly correlated over large distances (of the order of 1000 km). In other words, anomalies are representative of temperature changes over large areas and distances. By comparison, absolute temperatures vary markedly over even short distances. A dataset based on anomalies will also be less sensitive to changes in the observing network (such as a new station opening in a particularly hot or cold location) than one based on absolute values will be. The Earth's average surface absolute temperature for the 1961–1990 period has been derived by spatial interpolation of average observed near surface air temperatures from over the land, oceans and sea ice regions, with a best estimate of 14 °C (57.2 °F). The estimate is uncertain, but probably lies within 0.5 °C of the true value.

One of the issues that has been raised in the media is the view that global warming "stopped in 1998". This view ignores the presence of internal climate variability. An example of internal climate variability is the El Niño–Southern Oscillation (ENSO). The El Niño in 1998 was particularly strong, possibly one of the strongest of the 20th century, and 1998 was at the time the world's warmest year on record by a substantial margin. Cooling over the 2007 to 2012 period, for instance, was likely driven by internal modes of climate variability such as La Niña. The area of cooler than average sea surface temperatures that defines La Niña conditions can push global temperatures downward, if the phenomenon is strong enough.

The most recent climate model simulations give a range of results for changes in global average temperature. Some models show more warming in the troposphere than at the surface, while a slightly smaller number of simulations show the opposite behaviour. There is no fundamental inconsistency among these model results and observations at the global scale. The satellite records used to show much smaller warming trends for the troposphere which were considered to disagree with model prediction; however, following revisions to the satellite records, the trends are now similar.

The U. S. National Weather Service Cooperative Observer Program has established minimum standards regarding the instrumentation, siting, and reporting of surface temperature stations. The observing systems available are able to detect year to year temperature variations such as those caused by El Niño or volcanic eruptions. Another study concluded in 2006, that existing empirical techniques for validating the local and regional consistency of temperature data are adequate to identify and remove biases from station records, and that such corrections allow information about long term trends to be preserved. A study in 2013 also found that urban bias can be accounted for, and when all available station data is divided into rural and urban, that both temperature sets are broadly consistent.

Each of the seven years in 2015 2021 was clearly warmer than any pre 2014 year, and this trend is expected to be true for some time to come (that is, the 2016 record will be broken before 2026 etc.). A decadal forecast by the World Meteorological Organisation issued in 2021 stated a probability of 40% of having a year above 1.5 C in the 2021 2025 period. Global warming is very likely to reach 1.0 °C to 1.8 °C by the late 21st century under the very low GHG emissions scenario. In an intermediate scenario global warming would reach 2.1 °C to 3.5 °C, and 3.3 °C to 5.7 °C under the very high GHG emissions scenario.

The changes in climate are not expected to be uniform across the Earth. In particular, land areas change more quickly than oceans, and northern high latitudes change more quickly than the tropics. There are three major ways in which global warming will make changes to regional climate: melting ice, changing the hydrological cycle (of evaporation and precipitation) and changing currents in the oceans.