evidence: - While the Sun has played a role in past climate changes, the evidence shows the current warming cannot be explained by the Sun. [...] But several lines of evidence show that current global warming cannot be explained by changes in energy from the Sun: [...] - If a more active Sun caused the warming, scientists would expect warmer temperatures in all layers of the atmosphere. Instead, they have observed a cooling in the upper atmosphere and a warming at the surface and lower parts of the atmosphere. That's because greenhouse gases are slowing heat loss from the lower atmosphere.