It is now established fact that the planet is getting warmer, and we are driving the temperature ever higher. But a small, highly vocal group of deniers still like to posit that there are other, more important factors at play here than our insignificant selves, like the massive thermonuclear reactor some 150 million kilometers (93 million miles) away.
Now, a new study hopes to put those arguments to rest, again, by showing that the activity of the Sun has had no hand in the dramatic rise in temperatures that the world has experienced over the last few decades. In fact, the research, carried out by scientists at the Max Planck Society, found that rather than increasing in activity over the last 30 to 40 years, the Sun’s activity has decreased slightly.
The Sun is intrinsically incredibly active, swirling with plasma and ejecting fountains of gas into space when it flares up. These energetic particles are constantly blown towards Earth, with storms occasionally whipping them up and threatening the armada of satellites around the planet.
However, only certain wavelengths of the Sun's radiation actually make it to the surface of the Earth and contribute to warming it up. Primarily, this includes visible light, as the remainder tends to be absorbed by other molecules. When the Sun experiences periods of intense magnetic activity, it emits more of this radiation that hurtles towards Earth. Now, researchers haved tracked these fluctuations and reconstructed the radiation intensity over time.
One such way to track the radiation was to look at the historical record to see when people observed sun spots, which denote when the star is experiencing periods of increased activity. This was coupled with the use of Carbon-14 levels that have been locked into the wood of trees. C14 is formed when cosmic rays react with molecules in the upper atmosphere of the Earth. As the Sun’s magnetic field fluctuates, so too does the production of C14.
From this, they were able to determine exactly what influence the Sun’s activity has had on the temperature of the planet. They note that over the last century alone, Earth has warmed by 1°C (1.7°F), while the last 30 years has seen the temperature rise at a rate not seen for at least 1,000 years. During this period, it is true that the Sun’s activity has fluctuated, but during the last three decades there has “certainly been no increase in the brightness of the Sun.” If anything, it has slightly dimmed.
They note, however, that there is something that has increased over the last 100 years in synch with the warming temperatures: carbon dioxide concentration.