We already know that it’s the orbit of the earth around the sun that causes our seasons to change from summer to winter, and back to summer again, every year.

Astronomers also tell us that the amount of energy we receive from the sun varies over an eleven-year cycle, by about one tenth of a percent. Sometimes solar activity can temporarily shut down for decades at a time. This was the situation from about 1645 to 1715. This period also coincided with the coldest part of the Little Ice Age over Europe.

And over thousands and thousands of years, Earth’s orbit undergoes slow, predictable changes in shape. The pathway that the earth follows around the sun becomes first more circular, and then more oval. The earth tilts more toward the sun, and then away from it. Together, these changes affect the amount of solar energy that Earth receives, as well as the time and place that energy is received.

These long- term, cyclical changes in the energy that the earth receives from the sun are the reason for the largest natural cycles the earth experiences. So it’s entirely logical, when we see unusual change in global temperature, to look first to the sun as our prime suspect. But when we dig deeper, we encounter solid evidence that doesn’t support our allegations.

That’s because, for the last few decades, the sun has a perfect alibi. For the first part of the last century— up until about the mid- seventies— both temperature and energy from the sun were increasing. Scientists estimate the sun is responsible for about 7 percent of the warming over that time.

But, for the last three decades, Earth’s temperature has been increasing even more rapidly than before. And this has happened at the exact same time that solar energy has been holding constant or even going down.

Yes, that’s right. Solar activity has been going down since the late 1980s as global temperatures continued to rise. So if our temperature were being primarily controlled by the sun right now, then over the last few decades we should actually have seen temperatures cooling, not warming.

Here’s a comparison of the earth’s temperature and energy from the sun:

Increases in energy from the Sun likely contributed to warming over the first half of the 1900s. However, if the Sun were controlling the Earth's temperature today, our temperatures would have decreased over the last few decades. Instead, they have increased.

And here’s where you can get the data for temperature, solar radiation, solar magnetic field, and sunspots.

Want more? Here's the latest on solar trends and global warming from the Journal of Geosphysical Research.