Projecting mid-term growth of wind and solar power growth under empirically-grounded policy assumptions

There is no consensus on the policy effort required to accelerate the growth of wind and solar power for the climate goals. Some point out that the declining costs assure future expansion even without strong policies. Others document increasing opposition and non-cost barriers and argue that policy interventions should intensify, not abate, over time.

Here, we propose empirically-grounded methods and synthesise evidence to understand the balance of declining costs and increasing opposition in order to assess the policy effort needed for accelerating solar and wind power growth. In contrast to dominant approaches, we use national- rather than global-level evidence and account for both cost and non-cost factors.

We show that the growth of renewables in many front-running countries is fast but no longer accelerating and that it does not become faster in late-comers. This indicates persistent barriers which dampen the positive effect of technological learning. We develop a model for projecting global growth of technologies based on evidence from front-running countries. Our results show that under optimistic yet realistic assumptions and without a radical policy or market change solar and wind power could grow in line with 2°C-compatible scenarios, but 1.5°C-trajectories as well as the global renewables pledge would likely remain out of reach.

We also show that a scenario where the recent EU renewable targets are replicated worldwide is in line with the 1.5°C goal. The global growth of renewables in this case would be as fast as the policy-driven growth of nuclear power in Western Europe in the 1970s-1980s. Thus it is feasible to expand renewables fast enough for ambitious climate goals, but it requires massive policy effort and new strategies to address the very real barriers.

Our empirically grounded technology projections can be used to assess and inform policies accelerating the uptake of mature climate mitigation technologies.