Climat Lab BookOpen climate ScienceIs the 1.5°C target still reachable?
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Figure 2. Global mean temperature estimates of HadCRUT4 (left) and GISTEMP (right) against the CO2 concentration on a logarithmic scale with a linear fit. Pre-industrial CO2 concentrations are usually taken to be 280 ppm.ConclusionsReaching the 1.5 degree target agreed-upon in Paris as a desirable goal i
s going to be hard. Exactly how hard depends on a couple of crucial definitions and physical effects of the order of a tenth of a degree. Millar et al. have reduced these uncertainties by moving the starting point of modelling from pre-industrial to the present, taking the observed trend as given (and attributable to human influences, a point we have not discussed). However, they also use definitions of the global mean temperature rise that are not universally accepted and estimates of committed warming for zero emissions that are at odds with older (AR4) ideas that were based on constant atmospheric composition. To aid in the understanding of the results of Millar et al., we tried to highlight differences in definitions and cancellations in temperature trends after CO2 emissions would have ceased. Whatever the final way the 1.5 degree or indeed 2 degree target is defined, it will take a huge effort to reduce greenhouse gas emissions fast enough to reach it.
Full detailed article with charts from peer reviewed scientific studieshttp://www.climate-lab-book.ac.uk/2017/is-the-1-5c-target-still-reachable/