On Solar Variability and Global Warming

It appears as though solar variability is gaining some mainstream media attention in being cited as a likely impetus for terrestrial climate change. But for confirmation of this, scientists have now begun to look beyond the Earth to other areas of our solar system. Most recently, research on the climate of Mars has confirmed warming that appears to be mirroring that of the Earth. Is my SUV destroying the climate of Mars too? As published by National Geographic, (Mars melt hints at solar, not human, cause for warming, scientist says) recent work citing solar variability as a primary cause of climate change here on Earth is gaining traction:

“Man-made greenhouse warming has made a small contribution to the warming seen on Earth in recent years, but it cannot compete with the increase in solar irradiance,” Abdussamatov said.

By studying fluctuations in the warmth of the sun, Abdussamatov believes he can see a pattern that fits with the ups and downs in climate we see on Earth and Mars.

Abdussamatov is not alone in citing solar variability – fluctuating energy output from the sun – as a major factor in the Earth’s climate. Just last month, research published by NewScientist explores evidence of a relationship between solar variability and the ice age cycles on Earth (Sun’s fickle heart may leave us cold). Work completed by George Ehrlich of Geoge Mason University concludes:

There’s a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years – exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star’s core…

The article discusses many of the oscillations that control the temperature of the sun’s surface:

Ehrlich’s model shows that whilst most of these oscillations cancel each other out, some reinforce one another and become long-lived temperature variations. The favoured frequencies allow the sun’s core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years. Ehrlich says that random interactions within the sun’s magnetic field could flip the fluctuations from one cycle length to the other.

These two timescales are instantly recognisable to anyone familiar with Earth’s ice ages: for the past million years, ice ages have occurred roughly every 100,000 years. Before that, they occurred roughly every 41,000 years.

For details, check out the full text of Ehrlich’s research. While recent work has explored a correlation between solar variability and terrestrial climate cycles, none have explored the potential mechanism until now, writes Ehrlich in his abstract:

A theory is described based on resonant thermal diffusion waves in the sun that appears to explain many details of the paleotemperature record for the last 5.3 million years. These include the observed periodicities, the relative strengths of each observed cycle, and the sudden emergence in time for the 100 thousand year cycle. Other prior work suggesting a link between terrestrial paleoclimate and solar luminosity variations has not provided any specific mechanism. The particular mechanism described here has been demonstrated empirically, although not previously invoked in the solar context.

Work published in Science Magazine in 2001 (Persistent Solar Influence on North Atlantic Climate During the Holocene) cites specific influences of solar variability on the climate of the North Atlantic:

Surface winds and surface ocean hydrography in the subpolar North Atlantic appear to have been influenced by variations in solar output through the entire Holocene.

Bond et al. confirm the likelyhood that the particular influence on the North Atlantic may have been transmitted globally:

The surface hydrographic changes may have affected production of North Atlantic Deep Water, potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally.

Given that the sun has a profound impact on the climate of the globe, it naturally follows that any solar variability to influence the Earth’s climate in one location will have its affects felt throughout the globe.