section_path: Debate/Comparison with renewable energy/Speed of transition and investment needed
section_name: Speed of transition and investment needed
paragraph_text: Speed of transition and investment needed
  
  Analysis in 2015 by professor Barry W. Brook and colleagues found that nuclear energy could displace or remove fossil fuels from the electric grid completely within 10 years. This finding was based on the historically modest and proven rate at which nuclear energy was added in France and Sweden during their building programs in the 1980s. In a similar analysis, Brook had earlier determined that 50% of all global energy, including transportation synthetic fuels etc., could be generated within approximately 30 years if the global nuclear fission build rate was identical to historical proven installation rates calculated in GW per year per unit of global GDP (GW/year/$). This is in contrast to the conceptual studies for 100% renewable energy systems, which would require an order of magnitude more costly global investment per year, which has no historical precedent. These renewable scenarios would also need far greater land devoted to onshore wind and onshore solar projects. Brook notes that the "principal limitations on nuclear fission are not technical, economic or fuel-related, but are instead linked to complex issues of societal acceptance, fiscal and political inertia, and inadequate critical evaluation of the real-world constraints facing low-carbon alternatives."
  
  Scientific data indicates that – assuming 2021 emissions levels – humanity only has a carbon budget equivalent to 11 years of emissions left for limiting warming to 1.5 °C while the construction of new nuclear reactors took a median of 7.2–10.9 years in 2018–2020, substantially longer than, alongside other measures, scaling up the deployment of wind and solar – especially for novel reactor types – as well as being more risky, often delayed and more dependent on state-support. Researchers have cautioned that novel nuclear technologies – which have been in development since decades, are less tested, have higher proliferation risks, have more new safety problems, are often far from commercialization and are more expensive – are not available in time. Critics of nuclear energy often only oppose nuclear fission energy but not nuclear fusion; however, fusion energy is unlikely to be commercially widespread before 2050.