Climate Change: Global Temperature

August 14, 2020

Given the size and tremendous heat capacity of the global oceans, it takes a massive amount of heat energy to raise Earth’s average yearly surface temperature even a small amount. The 2-degree increase in global average surface temperature that has occurred since the pre-industrial era (1880-1900) might seem small, but it means a significant increase in accumulated heat. That extra heat is driving regional and seasonal temperature extremes, reducing snow cover and sea ice, intensifying heavy rainfall, and changing habitat ranges for plants and animals—expanding some and shrinking others.  

History of global surface temperature since 1880

Explore this interactive graph: Click and drag to display different parts of the graph. To squeeze or stretch the graph in either direction, hold your Shift key down, then click and drag. The graph shows average annual global temperatures since 1880  (source data) compared to the long-term average (1901-2000). The zero line represents the long-term average temperature for the whole planet; blue and red bars show the difference above or below average for each year.

Conditions in 2019

According to the 2019 Global Climate Report from NOAA National Centers for Environmental Information, 2019 began with a weak-to-moderate El Niño event underway in the tropical Pacific Ocean. Temperatures were warmer than average across most global land and ocean areas during most of the year. 

animated gif of monthly temperature maps for 2019 plus annual average at end

This animation shows monthly temperatures for January–December 2019 compared to each month's 1981-2010 average. The final frame of animation shows where annual temperatures were warmer (red) or colder (blue) than average. NOAA Climate.gov, based on data from NCEI. 

Record high annual temperatures over land surfaces were measured across parts of central Europe, Asia, Australia, southern Africa, Madagascar, New Zealand, North America, and eastern South America. Record high sea surface temperatures were observed across parts of all oceans, including the North and South Atlantic Ocean, the western Indian Ocean, and areas of northern, central and southwestern Pacific Ocean. No land or ocean areas were record cold for the year, and the only substantial pocket of cooler-than-average land temperatures was in central North America. For regional details and more 2019 climate statistics, see the 2019 Annual Climate Report from NOAA National Centers for Environmental Information. 

Change over time

Though warming has not been uniform across the planet, the upward trend in the globally averaged temperature shows that more areas are warming than cooling. According to the NOAA 2019 Global Climate Summary, the combined land and ocean temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880; however, the average rate of increase since 1981 (0.18°C / 0.32°F) is more than twice as great.

Global map of Earth's surface temperature trends from 1990-2019 in red (warming trends) and blue (cooling trends)

Changes in global average surface temperature from 1990-2019. Places that  warmed by up to 1° Fahrenheit over the past 30 years are red, places that have cooled by up to 1° F are blue, and places where we don't have enough observations to calculate a trend are light gray. NOAA Climate.gov map, based on NCEI data.

The 10 warmest years on record have all occurred since 1998, and 9 of the 10 have occurred since 2005. The year 1998 is the only year from the twentieth century still among the ten warmest years on record. Looking back to 1988, a pattern emerges: except for 2011, as each new year is added to the historical record, it becomes one of the top 10 warmest on record at that time, but it is ultimately replaced as the “top ten” window shifts forward in time.

By 2020, models project that global surface temperature will be more than 0.5°C (0.9°F) warmer than the 1986-2005 average, regardless of which carbon dioxide emissions pathway the world follows. This similarity in temperatures regardless of total emissions is a short-term phenomenon: it reflects the tremendous inertia of Earth's vast oceans. The high heat capacity of water means that ocean temperature doesn't react instantly to the increased heat being trapped by greenhouse gases. By 2030, however, the heating imbalance caused by greenhouse gases begins to overcome the oceans' thermal inertia, and projected temperature pathways begin to diverge, with unchecked carbon dioxide emissions likely leading to several additional degrees of warming by the end of the century.

About surface temperature

The concept of an average temperature for the entire globe may seem odd. After all, at this very moment, the highest and lowest temperatures on Earth are likely more than 100°F (55°C) apart. Temperatures vary from night to day and between seasonal extremes in the Northern and Southern Hemispheres. This means that some parts of Earth are quite cold while other parts are downright hot. To speak of the "average" temperature, then, may seem like nonsense. However, the concept of a global average temperature is convenient for detecting and tracking changes in Earth's energy budget—how much sunlight Earth absorbs minus how much it radiates to space as heat—over time.

To calculate a global average temperature, scientists begin with temperature measurements taken at locations around the globe. Because their goal is to track changes in temperature, measurements are converted from absolute temperature readings to temperature anomalies—the difference between the observed temperature and the long-term average temperature for each location and date. Multiple independent research groups across the world perform their own analysis of the surface temperature data, and they all show a similar upward trend. 

Satellite image of full disc of Earth on June 24, 2019, from the EPIC camera, with an overlay graph of yearly temperature anomalies since 1900

Temperature records from NOAA, NASA, and the University of East Anglia all show an increase from the start of the 20th-century through 2019. The year 2019 counted among the top three warmest years on record. Background image from NOAA DISCOVR/EPIC. Graph by NOAA Climate.gov based on data from the Bulletin of the American Meteorological Society's State of the Climate 2019.

Across inaccessible areas that have few measurements, scientists use surrounding temperatures and other information to estimate the missing values. Each value is then used to calculate a global temperature average. This process provides a consistent, reliable method for monitoring changes in Earth's surface temperature over time. Read more about how the global surface temperature record is built in our Climate Data Primer.

References

Sánchez-Lugo, A., Berrisford, P., Morice, C., and Argüez, A. (2018). Temperature [in State of the Climate in 2018]. Bulletin of the American Meteorological Society, 99(8), S11–S12.

NOAA National Centers for Environmental Information, State of the Climate: Global Climate Report for Annual 2019, published online January 2020, retrieved on January 16, 2020 from https://www.ncdc.noaa.gov/sotc/global/201913.

IPCC, 2013: Summary for Policymakers.  In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group 1 to the 5th Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Interactive graph data

Annual global temperature anomalies for land and ocean combined, expressed as departures from the 1901-2000 average. National Climatic Data Center.

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