One of the points of opposition to man-made global warming is that the sun is actually getting more intense with respect to radiation. Some studies have been interpreted in the 00s by inferences that the Total Solar Irradiance (TSI) might be increasing over the last century, by 0.5 percent per decade in the period since 1978 when the measurements were made. However, it has not been definitely linked to global warming as the biggest cause, and it is not of such a proportion either. In fact, the Sun is predicted to get hotter progressively as the fusion reactions within it create increasing levels of energy leading to a point a billion years down the line where life would not be possible on earth.

The same data on solar irradiance (flow per unit area) has also been used to show the opposite in studies and inferences of the present decade (2010s), that there has actually been a reduction in TSI in the past four decades due to a weaker cycle in solar activity, which goes through 11-year cycles of minimum to maximum intensity.

The doubts have therefore been raised with the measurements and their interpretation.

Another factor that is attributed by Global-Warming Skeptics is that the circulation of warmer ocean surface waters into deeper waters might have been impacted due to some cyclic reasons. This has been raised as a probable reason for global warming and that this might naturally reverse in the coming years leading to a cooler ocean surface and therefore a cooler globe.