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From the same journal

Global temperature definition affects achievement of long-term climate goals

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Publication details

JournalEnvironmental Research Letters
DateAccepted/In press - 1 Mar 2018
DateE-pub ahead of print - 1 Mar 2018
DatePublished (current) - 1 May 2018
Issue number5
Number of pages8
Pages (from-to)1-8
Early online date1/03/18
Original languageEnglish


The Paris Agreement on climate change aims to limit 'global average temperature' rise to 'well below 2 °C' but reported temperature depends on choices about how to blend air and water temperature data, handle changes in sea ice and account for regions with missing data. Here we use CMIP5 climate model simulations to estimate how these choices affect reported warming and carbon budgets consistent with the Paris Agreement. By the 2090s, under a low-emissions scenario, modelled global near-surface air temperature rise is 15% higher (5%-95% range 6%-21%) than that estimated by an approach similar to the HadCRUT4 observational record. The difference reduces to 8% with global data coverage, or 4% with additional removal of a bias associated with changing sea-ice cover. Comparison of observational datasets with different data sources or infilling techniques supports our model results regarding incomplete coverage. From high-emission simulations, we find that a HadCRUT4 like definition means higher carbon budgets and later exceedance of temperature thresholds, relative to global near-surface air temperature. 2 °C warming is delayed by seven years on average, to 2048 (2035-2060), and CO2 emissions budget for a >50% chance of <2 °C warming increases by 67 GtC (246 GtCO2).

Bibliographical note

2018, The Author(s).

    Research areas

  • carbon budgets, climate change, global warming, observational temperature records, Paris agreement

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