Global surface temperature

This article is about the average temperature at the Earth's surface (at the present time and in the past). For records of extreme weather events, see List of weather records.

The blue line represents global surface temperature reconstructed over the last 2,000 years using proxy data from tree rings, corals, and ice cores.[1] The red line shows direct surface temperature measurements since 1880.[2]

Global surface temperature (GST) is the average temperature of Earth's surface. More precisely, it is the weighted average of the temperatures over the ocean and land. The former is also called sea surface temperature and the latter is called surface air temperature. Temperature data comes mainly from weather stations and satellites. To estimate data in the distant past, proxy data can be used for example from tree rings, corals, and ice cores.[1] Observing the rising GST over time is one of the many lines of evidence supporting the scientific consensus on climate change, which is that human activities are causing climate change. Alternative terms for the same thing are global mean surface temperature (GMST) or global average surface temperature.

Series of reliable temperature measurements in some regions began in the 1850—1880 time frame (this is called the instrumental temperature record). 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.[3] 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.[4] 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.

Through 1940, the average annual temperature increased, but was relatively stable between 1940 and 1975. Since 1975, it has increased by roughly 0.15 °C to 0.20 °C per decade, to at least 1.1 °C (1.9 °F) above 1880 levels.[5] The current annual GMST is about 15 °C (59 °F),[6] though monthly temperatures can vary almost 2 °C (4 °F) above or below this figure.[7]

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.[8]: 5  The trend is faster since the 1970s than in any other 50-year period over at least the last 2000 years.[8]: 8  Within that upward trend, some variability in temperatures happens because of natural internal variability (for example due to El Niño–Southern Oscillation).

The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch. Some temperature information is available through geologic evidence, going back millions of years. More recently, information from ice cores covers the period from 800,000 years ago until now. Tree rings and measurements from ice cores can give evidence about the global temperature from 1,000-2,000 years before the present until now.[9]

  1. ^ a b PAGES 2k Consortium (2019). "Consistent multidecadal variability in global temperature reconstructions and simulations over the Common Era". Nature Geoscience. 12 (8): 643–649. doi:10.1038/s41561-019-0400-0. ISSN 1752-0894. PMC 6675609. PMID 31372180.
  2. ^ "Global Annual Mean Surface Air Temperature Change". NASA. Retrieved 23 February 2020.
  3. ^ Brohan, P.; Kennedy, J. J.; Harris, I.; Tett, S. F. B.; Jones, P. D. (2006). "Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850". J. Geophys. Res. 111 (D12): D12106. Bibcode:2006JGRD..11112106B. CiteSeerX 10.1.1.184.4382. doi:10.1029/2005JD006548. S2CID 250615.
  4. ^ "Remote Sensing Systems". www.remss.com. Retrieved 19 May 2022.
  5. ^ World of change: Global Temperatures Archived 2019-09-03 at the Wayback Machine The global mean surface air temperature for the period 1951-1980 was estimated to be 14 °C (57 °F), with an uncertainty of several tenths of a degree.
  6. ^ "Solar System Temperatures". National Aeronautics and Space Administration (NASA). 4 September 2023. Archived from the original on 1 October 2023. (link to NASA graphic)
  7. ^ "Tracking breaches of the 1.5 °C global warming threshold". Copernicus Programme. 15 June 2023. Archived from the original on 14 September 2023.
  8. ^ a b IPCC (2021). "Summary for Policymakers" (PDF). The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. ISBN 978-92-9169-158-6.
  9. ^ Cite error: The named reference :1 was invoked but never defined (see the help page).