Records from ancient China have revealed a link between epidemics and climate change, according to a new study. The research, which examined a period in the Middle Ages, found that long periods of cooling were associated with epidemics due to agricultural failure. However, temporary spikes in temperature may have helped disease-carrying insects and other vectors to flourish, causing temporary spikes in disease outbreaks. Scientists are increasingly concerned about the effects of global warming on disease transmission, with rising temperatures potentially enabling mosquitoes to expand their ranges into previously too cold areas.