Scott Alexander examines the fate of 1990s environmental concerns, finding a mix of solved problems, exaggerated issues, and ongoing challenges that have faded from public attention. Longer summary

Scott Alexander reflects on the environmental concerns of the 1990s, examining what happened to issues like air and water pollution, acid rain, rainforest deforestation, endangered species, landfill space, peak resource, and whale conservation. He finds that some problems were solved, some were exaggerated, and others continue but receive less attention. The post explores why certain environmental issues fade from public consciousness, considering factors like problem-solving, alarmism, shifting focus to climate change, and changes in societal attitudes. Shorter summary

Scott Alexander explores research on how high indoor CO2 levels may impair cognition and sleep, suggesting simple solutions like better ventilation. Longer summary

Scott Alexander discusses recent research on the effects of high indoor carbon dioxide (CO2) levels on cognitive function and sleep quality. He describes how his housemates discovered high CO2 levels in their home and improved their symptoms by increasing ventilation. The post explores studies showing cognitive impairment at high CO2 levels and the potential impact on sleep quality. Scott suggests that nighttime CO2 levels in bedrooms can be particularly high and may affect sleep. He recommends simple solutions like opening windows or using certain plants to reduce CO2 levels. The post ends with a call for readers to participate in an informal experiment on nighttime air quality. Shorter summary

Scott examines the relationship between altitude and obesity, then explores and ultimately dismisses the theory that increased atmospheric CO2 could be causing the obesity epidemic. Longer summary

Scott Alexander explores the correlation between altitude and obesity rates in the US, noting that people living at higher elevations tend to be less obese. He discusses various studies on altitude anorexia and hypoxia's effect on weight loss. The post then transitions to a speculative theory about whether increased atmospheric CO2 from global warming could be causing the obesity epidemic. While intriguing, Scott ultimately concludes that this theory is likely not true, based on geographical inconsistencies, submarine studies, and the small magnitude of potential effects. Shorter summary