It's Not the Sun
Solar levels have not changed significantly over the past two hundred years, showing how the sun is not responsible for climate change.
Solar radiation levels haven't changed
Solar radiation levels have not changed significantly since the 1970s. Furthermore, the small increases that have occurred since the 1600s have been offset by a more recent decrease in the late 1900s.
Scientists use satellites for constant and accurate measurements
To make sure that their measurements are accurate, scientists use state-of-the-art satellites that take measurements from the top of the atmosphere. Their location ensures that scientists get the most direct readings of solar radiation levels.
What We Know
The sun is not responsible for climate change. While there are some claims that increases in solar radiation are the cause of climate change, these are false. There are primarily two distinct ways scientists know that solar radiation levels are not the cause of climate change. The first way is by measuring the amount of solar radiation that has hit the upper atmosphere. Since 1978, scientists have found that there has been no increase in solar energy reaching the earth.
The second way is through the distribution of heat in the atmosphere. Because climate change is caused by trapping gases in the atmosphere, it is primarily warming the lower atmosphere. If the sun was responsible for climate change, then all layers of the atmosphere would be warming because the warming would be coming from above instead of below. Instead, only the lower atmosphere has experienced warming. The graph below from the National Oceanic and Atmospheric Administration (NOAA) shows how solar levels have not increased, while temperatures have.
How We Know
Since the 1970s, scientists have used satellites to directly measure incoming sunlight levels. These satellites measure the total incoming sunlight at the top of the earth's atmosphere, before it is filtered through the atmosphere. These measurements ensure a complete understanding of how the sun's energy has changed. Scientists have used their research and knowledge of historical conditions to estimate solar levels since the 1600s.
Climate Change: Vital Signs of the Planet. “Is the Sun Causing Global Warming?” Accessed September 9, 2021. https://climate.nasa.gov/faq/14/is-the-sun-causing-global-warming.
Rebecca Lindsey. “Climate Change: Incoming Sunlight.” NOAA Climate.gov, August 24, 2021. https://www.climate.gov/news-features/understanding-climate/climate-change-incoming-sunlight.