This analysis replicates and examines the assessment from reference [8] concerning whether wind and solar power are progressing adequately to meet Paris climate targets. The original study utilized logistic curves, anchored to 2010 values and projected to saturate at the ‘2050 Paris benchmarks’—median 2050 values for 1.5 °C scenarios. These benchmarks, indicated by purple diamonds, also represent median scenario values for 2030. This replication employs ‘emergence rates’ (initial year-on-year growth rates) from reference [8]: 15%, 20%, 25% for wind, and 25%, 30%, 35% for solar. For each technology, a central growth case is marked in black, with high and low cases in grey.
Panels (a) and (c) of the original figure detail yearly growth rates (G) at the inflection points of these curves, normalized against the global electricity system size. These G values significantly exceed the estimated maximum growth rates observed in any major country. In contrast, orange and blue lines represent Gompertz and logistic model fits (with inflection points) applied to empirical time series of global wind and solar power deployment, using the methodology of this paper. These models project considerably lower values for 2030 and 2050 compared to the projections from reference [8].
Panels (b) and (d) provide a closer view of the same curves and data from 2010-2020, including the Residual Sum of Squares (RSS) for replicated curves and our model fits against 2010-2018 empirical data. The RSS values for the replicated logistic curves are substantially larger than those of our best fits: 10 to 280 times greater for wind, and 400 to 1000 times greater for solar. This indicates that the replicated curves from reference [8] align with empirical data with significantly less accuracy than our models, particularly when solar power compared to actual deployment is considered. Our analysis suggests a more conservative, data-driven approach to projecting the growth of solar and wind energy in the context of global climate targets.
