UCL Institute for Sustainable Resources


Government policies have had a discernible impact on reducing global CO2 emissions

12 October 2021

Literature survey of over 500 papers shows evidence that climate policy has had observable effects in the face of continued emissions growth.


Janna Hoppe (ETZ), Professor Michael Grubb (UCL ISR), Ben Hinder (UCL, ISR) and Professor Anthony Patt (ETZ) have produced a literature survey of over 500 papers drawing together evidence of the significance of climate policy in the face of our continued emissions growth.

Ever since the Intergovernmental Panel on Climate Change (IPCC) published its first Assessment Report in 1990, the scientific consensus on anthropogenic climate change has strengthened. It has become abundantly clear that human activity is driving climate change. In response, increasing number of governments (as well as other actors) have enacted policies to start abating their emissions – “emissions mitigation” – at first slowly, more rapidly since the mid 2000s, initially mainly in developed countries and more recently across the world. By 2017, climate policies covered about 70% of global GHG emissions. There remains an open question however as to how effective these policies have been. Research into this topic is difficult because climate change touches every part of our economy and therefore any change in one area will affect emissions, even if this wasn’t an intended outcome. 

We are however beginning to get enough evidence to discern the signal of implemented policy from the noise of these confounding factors. Stimulated by and produced in tandem with the forthcoming IPCC 6th assessment report on mitigation, a preprint literature survey of over 500 papers by Janna Hoppe (ETZ), Professor Michael Grubb (UCL), Ben Hinder (UCL) and Professor Anthony Patt (ETZ) draws together the evidence that we have on the significance of climate policy in the face of our continued emissions growth. Most of these papers were as cited in the first and second order drafts of the IPCC 6th assessment report on mitigation (WGIII), and representing a wide coverage of papers cited by leading academics from which to draw conclusions. These assessments provide evidence that mitigation policy has had a discernible effect on several different indices: on technology progress; on proximate drivers of emissions (such as national energy intensity or land use); and on emissions themselves. The review provides a first tentative quantification that combines multiple lines of evidence, to estimate that policies to date have reduced global emissions - compared to a “no policy” scenario or year on year – by several billion tonnes.

This is a significant finding, as for a long time it was an open question as to whether policy was succeeding because the signal was clouded by continued economic growth and shifts in fossil fuel prices outside of policy, among many other things. By bringing together the available evidence, this review underlines that the global effort, whilst currently still too weak to deliver the Paris targets, is not starting from nothing It demonstrates that many policies have been working to reduce the rate of emissions growth, and can help policymakers to make informed choices about how to apply mitigation policy for the greatest effect. 

Professor Grubb said:

The oft-repeated claim that governments have done nothing to tackle climate change is not true; the important question is, what if any difference have the numerous policies adopted actually made? Our estimate is that policies to date have cut the growth by a few billion tonnes of CO2 annually – maybe 5-10% of annual emissions. The impact is discernible, enough to slow but not yet turn around the global trend. More is needed, but we are not starting from nothing."