Without the sun, Earth would be a frozen, lifeless rock. Yet despite the heat the sun sends to Earth, scientists have determined that it’s not responsible for recent global warming.

The sun behind tree branches

LEAN: “The most compelling reason to conclude that the changing energy from the sun is not the cause of Earth’s warming in the past 4 decades is that we have measured the sun’s brightness since 1978 using very precise space-based instruments, and the overall trend that we’ve seen has been downwards by just a few tenths of a percent.”

That’s Judith Lean, a scientist at the Naval Research Laboratory in Washington, D.C. She says the energy from the sun is not constant – instead it fluctuates in approximately eleven year cycles.

LEAN: “The most recent 11 year solar cycle is about a factor of two weaker than the three previous cycles, and this has produced an overall net downward trend at the same time that the global surface temperature has increased.”

Solar cycle weaker while surface temperatures have increased. Click To Tweet

In other words, the Earth is warming, even though the energy it receives from the sun has decreased. Thus, scientists are confident that human activity, not the sun, is responsible for global warming.

Reporting credit: ChavoBart Digital Media.
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Earth’s Warming: How Scientists Know It’s Not the Sun

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