The Sun’s energy drives Earth’s climate, but the climate is in a delicate balance and is changing due to human activity.

The global warming trend observed on Earth since the mid-20th century is caused by human activities. This 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. Human-made emissions in the atmosphere, rapid, unsustainable deforestation, and the increases in non-reflective surfaces, like asphalt, are all examples of human activities amplifying the greenhouse effect, trapping and slowing heat loss to space. While the Sun has played a role in past climate changes, for example, a decrease in solar activity- coupled with increased volcanic activity- helped trigger the Little Ice Age, the evidence shows the current global warming of Earth’s climate cannot be explained by the Sun. Even fluctuations in solar irradiance (the Sun’s energy Earth receives), as the Sun goes through its 11-year cycle, does not cause Earth’s climate to change.

Topics: atmosphere, climate change, energy, greenhouse effect, radiation

NGSS: PS1, PS2, PS3, LS4, ESS2, ESS3

Image Credit: NASA-JPL/Caltech