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Table 1 Estimates of the remaining carbon budgets for early 2018 for different mitigation targets. Units: GtCO2

From: Two decades of Earth system modeling with an emphasis on Model for Interdisciplinary Research on Climate (MIROC)

Target AR5 SR1.5
1.5 °C 110 (*1, GSAT-based, lower end) 420–580 (*3, GSAT-based)
570–770 (*4, GMST-based)
2.0 °C 720–830 (*2, GSAT-based) 1320–1690 (*4, GMST-based)
  1. Lower and upper bounds correspond to 66%- and 50%-tile values, respectively. (*1) This value is based on Chapter 2 of the Special Report on Global Warming of 1.5 °C (SR1.5) (IPCC 2018), which only provides the 66%-tile value from the beginning of 2011. This was converted to a value for the beginning of 2018 by using a medium estimate of annual anthropogenic emission of 42 GtCO2, as adopted in SR1.5. (*2). These values are based on the Summary for Policymakers (SPM) of the 5th Assessment Report (AR5) (IPCC 2013). Estimates of the 66%- and 50%-tile values given for the beginning of 2011 in the SPM were converted to values for the beginning of 2018, as above. (*3) These values are taken from Table 2.2 of SR1.5, in which historical warming is defined by global mean surface air temperature (GSAT). (*4) As for *3, but in this case, historical warming is defined by global mean surface temperature (GMST). See text for the definitions of GSAT and GMST