Energy > Climate Change
Is the sun causing the earth to warm?
This article is part of our series focused on the causes and consequences of a warming planet
Is the sun causing the earth to warm? It would seem logical. The sun is the fundamental source of energy that creates heat on our planet. An increase or decrease in the sun’s output could cause the earth’s temperature to rise or fall.
Scientists believe that changes in the sun’s output may have impacted the earth’s temperature in the past. For example, studies have found that a decrease in solar output is likely to have caused the Little Ice Age between 1650 and 1850.
But studies of the current warming trend have found no similar relationship. The sun’s energy, received at the top of earth’s atmosphere, has followed a natural 11-year cycle of small ups and downs but with no long-term net increase or decrease. By comparison, global temperature has risen significantly.
Moreover, if the warming of the earth is caused by an increase in the output of the sun, then the entire atmosphere should be warming. This would include the lower atmosphere (troposphere) as well as the upper atmosphere (stratosphere). However, scientific studies have found that, while the lower atmosphere is warming, the upper atmosphere is actually cooling.
This phenomenon indicates that more heat is being trapped in the lower atmosphere and less heat is reaching the upper atmosphere. So, today’s warming is not caused by more heat overall but more heat being trapped next to the earth’s surface. Hence, the greenhouse effect is causing the warming.
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Don Hofstrand, retired extension agricultural business specialist, email@example.com
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University