Hot history: Tree rings show that last northern summer was the warmest since year 1

A new study finds that the broiling summer of 2023 was the hottest in the Northern Hemisphere in more than 2,000 years. When the temperatures spiked last year, numerous weather agencies said it was the hottest summer on record. But those records only go back to 1850 because they are based on thermometers. Now scientists can go back to the modern western calendar’s year 1, when the Bible says Jesus of Nazareth walked the Earth. Tuesday's study says no summer even came close to last year. The hottest summer before climate change was 246, but last year's was about 2 degrees Fahrenheit warmer.