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How much higher will the annual mean surface air temperature be in 2020, relative to the 1951-1980 base period?

Discussion of the human influence on global temperatures has a long history. For instance, Fourier first discussed why the Earth was warmer than expected from solely considering solar radiation reaching the planet in his On the Temperatures of the Terrestrial Sphere and Interplanetary Space in 1824. Fourier ruled out geothermal effects, considered the temperature of outer space and made allusions to the heating of a greenhouse (Fleming, 1999). Tyndall (1861) suggested a solution to this conundrum by experimentally demonstrating that gases such as carbon dioxide can effectively absorb infrared radiation, i.e. the ‘greenhouse effect’. These activities eventually culminated in the work of Callendar (1938), who used 147 land-based weather stations to show that the Earth's land temperature had increased over the previous 50 years, and produced estimates that agree remarkably well with more recent analyses (Hawkins and Jones, 2013).

Surface air temperature change is a primary measure of global climate change. The globally averaged combined land and ocean surface temperature data as calculated by a linear trend, show a warming of 0.85°C (90% CI: [0.65 to 1.06]), over the period 1880 to 2012 (IPCC, 2013). The effects of increased global surface temperatures, and the associated changes in climate include:

  • Increases in the frequency and intensity of intense precipitation (Min et al., 2011), and increases in the proportion of the global land surface in extreme drought (Burke et al., 2006),
  • Global sea level rise (Vermeer and Rahmstorf), which in turn may result in the erosion of beaches and coastal wetlands, increased flooding, and intrusion of saltwater into rivers, bays, and aquifers (Titus, 2008), and global ocean warming and acidification (Pörtner, 2008),
  • Adverse effects to human health, due to thermal stress, and the increased prevalence of infectious diseases (McMichael et al., 2006), and increased food security risk (Zhao et al., 2017; FAO, 2008),
  • Loss of terrestrial biodiversity at all system levels, including species-level reductions in range size and abundance, especially amongst endemic species (Warren et al., 2013).

According to GISS Surface Temperature Analysis data, over the 2008 to 2018 period, the mean surface air temperature was 0.76°C higher relative to the 1951 to 1980 baseline. 2016 was the hottest recorded year with the mean surface temperature being 1.02°C higher than that over the same baseline.

How much higher will the annual mean surface air temperature be in 2020, relative to the 1951-1980 base period?


This question resolves as the change in global annual mean surface air relative to the 1951-1980 base period in degrees Celsius. The data must originate from GISS Surface Temperature Analysis. The adoption of the base period amounts to scaling reported temperature changes such that the mean temperature change over the 1951-1980 period is 0.


GISTEMP v4 data may be accessed here. Data can also be found here. Please make a copy by clicking "file" and then "make a copy" if you wish to edit it. If you make useful additions to the dataset, please share the file in the comments.


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