. . . . Some people blame the Sun for climate change. But, says NASA, several lines of evidence show that current global warming cannot be explained by changes in energy from the Sun. These include:
- Since 1750, the average amount of energy from the Sun either remained constant or decreased slightly.
- If a more active Sun caused the warming, scientists would expect warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere and a warming at the surface and lower parts of the atmosphere. That’s because greenhouse gasses are slowing heat loss from the lower atmosphere.
- Climate models that include solar irradiance changes can’t reproduce the observed temperature trend over the past century or more without including a rise in greenhouse gasses.
The above graph compares global surface temperature changes (red line) and the Sun’s energy that Earth receives (yellow line) in watts (units of energy) 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 natural 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 1880. 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-century,” NASA scientists say. Source: Evidence Shows That Current Global Warming Cannot Be Explained by Solar Irradiance (NASA – Vital Signs of the Planet)