Whither climate change post-Paris?

Abstract

The Paris Climate Agreement has been welcomed by many as providing a remarkably strong basis for global action on anthropogenically mediated climate change, by underpinning a highly ambitious, very clever and forward-looking political process. On the other hand, the sum total of the fresh emission reductions pledged is very small. A new climate-economics model is explored to help focus on two key points remaining at issue post-Paris, namely where are we now and where are we headed? The output reinforces the unpalatable finding that in the absence of even stronger carbon-pricing policies, temperatures and sea-level will, this century, rise significantly beyond what are currently deemed to be ‘dangerous’ levels. Pigouvian taxes have long been championed by economists as providing a simple, down-to-earth corrective remedy for market failures, such as excessive carbon emissions. The Wilsonian modification, or ‘feebate’, provides an attractive modern variant that could easily be implemented post-Paris.

Croll, feedback mechanisms, climate change and the future

“…4) are biased high. On the other hand, the high sensitivities of the CMIP6 models are, nevertheless, in fair agreement with those derivable from the two other main (observation-based) approaches to sensitivity estimation: calibration using the temperature-CO2 relationship of ice ages and tuning using the post-1750 instrumental temperature trend (Thompson 2015(Thompson , 2017.…”

“…A sizeable subset of the CMIP6 models are finding that a doubling of CO2 could lead to over 5 °C of warming (Flynnn & Mauritsen 2020;Zelinka et al 2020). Thus, they are questioning whether the central goals of the Paris Agreement (to keep global temperature rise this century to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 °C) are feasible (Thompson 2017;Nijsse 2020). In a similar vein Sherwood et al (2020) stress how consistency between three other lines of evidence (the palaeoclimate record, the historical warming record and knowledge about physical processes) point to a 90% (5-95%) range of 2.3-4.7 K. They note how at the low end of the range "it now appears extremely unlikely that the climate sensitivity could be low enough to avoid substantial climate change … under a high-emission future scenario", but at the high end "we remain unable to rule out that the sensitivity could be above 4.5°C per doubling of carbon dioxide level" [Sherwood et al 2020, p. 1].…”

International climate targets are achievable, but only in models, not in the real world

“…Immediate progress towards meeting this alternative challenge could be the deployment of a smart carbon tax (a progressive tax involving a recycling of tax revenues to refund low carbon consumption). If communicated carefully to the public a well-designed, revenue-neutral carbon tax would promote a judicious balance between adaptation and mitigation measures through a consideration of costs and damages avoided and/or benefits gained (Nordhaus, 1977; Pigou, 1920; Thompson, 2017).…”