Fact Check: No, the sun does not cause global warming
In 2019, Scientific Reports—an open access journal run by Nature Research— came under intense criticism for suggesting that the rise of earth’s temperature by one degree Celsius over the past two centuries was as a result of the changing distance between the earth and the sun.
The four scientists from Northumbria University, the University of Bradford, University of Hull, and the Nasir al-Din al-Tusi Shamakhi Astrophysical Observatory in Azerbaijan, said the phenomenon would see temperatures rise a further three degrees Celsius by the year 2600.
Social media users have since posed the same question, pondering the sun’s contribution to global warming and climate change.
However, climate scientist Patricia Nyinguro of the Kenya Meteorological Department says the sun does not cause global warming.
“The sun is part of the climate system, and drives the climate system that is made up of humans, animals and plants, ice and glaciers and water, atmosphere and land surface. The sun is the centre of this. Without the sun, the climate system would collapse. The sun does not cause global warming; it is only responsible for maintaining life and providing the perfect balance,” says Ms Nyinguro.
She says that global warming and climate change is largely driven by human activities. In an ideal system, she explains, the sun’s emission of its rays into the atmosphere is perfectly balanced. Of the rays that are transmitted into the atmosphere, some are absorbed by the earth, some are reflected, and others are re-radiated out of the earth as long wave radiation.
“The greenhouse gases that are naturally occurring such as carbon dioxide and nitrous oxide are, in their proper measurements, useful for maintenance of perfect temperature on the earth. However, human activities have led to an increase in the greenhouse gases to amounts that are too high such that they trap more heat from the sun within the climate system than is useful for sustaining life on earth. That is why we are seeing global warming and climate change. Because greenhouse gases trap more solar radiation within the atmosphere , it leads to higher and higher temperatures.
“Reducing emissions of greenhouse gases into the atmosphere is the first thing that needs to be done to curb climate change. If we find ways to stop emissions or reduce the emissions, that will be useful. This includes increasing vegetation cover, which will reduce the rate at which the warming is taking place currently,” she says.
National Aeronautics and Space Administration (NASA) says that the warming we have seen in recent decades is too rapid to be linked to changes in Earth’s orbit and too large to be caused by solar activity.
It adds that since 1978, scientists have been taking account of the amount of solar energy hitting the roof of the atmosphere, but have concluded that “there has been no upward trend in the amount of solar energy reaching our planet.
“If the sun were responsible for global warming, we would expect to see warming throughout all layers of the atmosphere, from the surface to the upper atmosphere. But what we actually see is warming at the surface and cooling in the upper atmosphere. This is consistent with the warming being caused by buildup of heat trapping gases near the earth’s surface, and not by the sun getting ‘hotter’,” says NASA.