EA - Climate Change and Longtermism: new book-length report by John G. Halstead

Link to original articleWelcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Climate Change & Longtermism: new book-length report, published by John G. Halstead on August 26, 2022 on The Effective Altruism Forum. Since 2021, as part of the research for What We Owe the Future, I have been working on a report on climate change from a longtermist perspective. The report aims to provide the most complete treatment of that question yet produced. The executive summary is below and the full report is here, available at the What We Owe the Future supplementary materials webpage. I am grateful to the expert reviewers of the report for their comments. Views and mistakes are my own. Executive Summary In this report, I will evaluate the scale of climate change from a longtermist point of view. Longtermism is the idea that influencing the long-term future, thousands of years into the future and beyond, is a key moral priority of our time. In economics, longtermism is embodied by the idea that we should have a zero rate of ‘pure time preference’: we should not discount the welfare of future people merely because it is in the future. Economists who embrace a zero rate of pure time preference will tend to favour more aggressive climate policy than those who discount future benefits. Climate change is a proof of concept of longtermism. Every time we drive, fly, or flick a light switch, each of us causes CO2 to be released into the atmosphere. This changes the amount of CO2 that is in the atmosphere for a very long time: unless we suck the CO2 out of the atmosphere ourselves, concentrations only fall back to natural levels after hundreds of thousands of years. The chart below shows long-term CO2 concentrations after different amounts of cumulative carbon emissions. Some of the ecological effects of climate change get worse over time. The clearest example of this is sea level rise. On current policy, the most likely sea level rise this century is 75cm. However, over 10,000 years, sea levels will rise by 10 metres. Over the long-term, the world will look very different. From a longtermist point of view, it is especially important to avoid outcomes that could have persistent and significant effects. These include events like human extinction, societal collapse, a permanent negative change in human values, or prolonged economic stagnation. If we go extinct, then that would be the end of the human story, and there would be no future generations at all. If civilisation collapses permanently, then future generations will be left much worse off than they could have been, living lives full of suffering rather than ones of flourishing. The anatomy of climate risk The overall size of climate risk depends on the following factors: Greenhouse gas emissions The climate change we get from different levels of emissions The impacts of different levels of climate change There is uncertainty about all three factors. The main findings of this report are as follows. Emissions are likely to be lower than once thought Due to recent progress on clean technology and climate policy, we look likely to avoid the worst-case emissions scenario, known in the literature as ‘RCP8.5’. The most likely scenario on current policy is now the medium-low emissions pathway known as ‘RCP4.5’. Moreover, climate policy is likely to strengthen in the future. For instance, as I was writing this report, the US Senate passed the Inflation Reduction Act, the most significant piece of climate legislation in American history. Climate change is a great illustration of how society can make progress on a problem if enough people are motivated to solve it. This does not mean that climate change is solved, but there is significant momentum, and we are at least now moving in the right direction. The amount of carbon we could burn in a worst-case scenario is also much lower than once thought. Some of the literature a...