Combining detailed climate records with the farm data, they were able to understand how yields and profits have changed over time. (sciencedaily.com)
The only drawback is that those measurements were taken for the purpose of measuring the weather over a finite period of time, not creating a long - term climate record. (popsci.com)
Most paleo - climate records show that the tropics had mean annual temperatures of 28 to 33 °C, which is not much warmer than today. (newscientist.com)