Free Astronomy Magazine January-February 2022

JANUARY-FEBRUARY 2022 I n this global temperature graph, climate data scientist Neil R. Kaye breaks down how monthly average temperatures have changed over nearly 170 years. Temperature values have been benchmarked against pre-industrial averages. [Data: HadCRUT5 - Created by: Neil R. Kay] T his graph compares global surface temperature changes (red line) and the Sun’s energy that Earth receives (yel- low line) in watts (units of en- ergy) per square meter since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year nat- ural noise in the data, making the underlying trends more obvious. The amount of solar energy that Earth receives has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s. Over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-cen- tury. [NASA/JPL-Caltech] ters higher than they are today. In that hot period, there was also much more oxygen in the atmos- phere (about 30% versus the cur- rent 21%), the ice was completely melted even at the poles, the di- nosaurs dominated the world, and the land was covered with lush forests and was rich in evergreen tropical plants. About ten million years after the extinction of the large reptiles, the PETM began, characterized by still-high levels of atmospheric carbon dioxide and with average temperatures on the