Temperature Forcings

“The Sun right now is probably the most active it's been in 400 years.”-- Sallie Baliunas, Harvard Smithsonian Center for Astrophysics

“We are altering the balance of energy between our planet and the rest of the universe.” -- Al Gore

Every school kid knows that the source of the Earth’s heat and life is our magnificent Sun, never mind “the rest of the universe.” The Sun is HOT, with a surface temperature of 5785 K, and it delivers radiation power to the Earth of about 1370 Watts per square meter. If the Sun were to suddenly go out, the Earth would cool eventually to the temperature of outer space, 3 degrees Kelvin. [Question: How long would it take?]

In the last post I discussed the dynamics of the Earth’s motion that determine the variation of solar radiation hitting the Earth. The following graph is a compilation of that data, also showing the major Ice Ages.




The other major forcing factor for the temperature of the Earth is the Greenhouse Effect, the trapping of reflected heat by greenhouse gases (CO2, NO2, Methane) in the atmosphere, as influenced by continental drift, ocean currents, the carbon cycle and the silicate-carbonate cycle. Without the Greenhouse Effect the Earth would cool by about 15 C to the freezing point of water.

Over the life of the Earth the Sun’s power has increased about 30% while the Earth’s temperature has decreased due to a large decrease of the concentration of greenhouse gasses. For example, the C02 density has decreased by 95% from its peak. It’s understandable that the recent increase of CO2 has convinced many that it has caused the recent temperature increase.

There is, however, contrary evidence: Most of the 20th century warming occurred before 1940, when the CO2 concentration was much lower. Then when the human-caused CO2 increased strongly from 1940 to 1975, the global temperature actually decreased. In fact, ice cores have shown that for the last 240,000 years, the CO2 increase has come around 800 years after the temperature increase. The rising temperature heats the oceans which outgas CO2.

But there is another solar forcing that nicely accounts for the last 20 temperature oscillations during the Holocene Warming. Looking at the sun photo above, we see a large white spot on the face of the sun called “Sunspot 822.” When the photo was taken in Nov. 2005, 822’s length was 87,000 miles, about the size of Jupiter. Sami Solanki, director of the Max Planck Institute for Solar System Research in Germany, said: “The Sun has been at its strongest over the past 60 years and may now be affecting global temperatures.” The Martian South polar ice cap shrinking has been accelerating since 1999 at a prodigious rate, according to Michael Malin, Principal Investigator for the Mars Orbiter Camera. There is no anthropomorphic CO2 generation on Mars.

The details of a 1500 year solar forcing cycle have been known since the research of Gerard Bond of the Lamont-Doherty Earth Observatory. Bond and his colleagues reported that the climate of the North Atlantic has warmed and cooled nine times in the past 12,000 years in step with the waxing and waning of the sun. The process works like this.

The solar wind (charged particles) of a brighter and more active sun magnetically fends off energetic cosmic rays from space that would otherwise hit the Earth's atmosphere, ionizing air molecules that act as nuclei for cloud droplets that reflect solar radiation and cool the earth. Thus a more active sun sweeps away the cosmic rays and fewer clouds are formed. The Earth heats up. In addition, the active Sun produces more far-UV radiation which splits oxygen molecules generating ozone in the stratosphere that in turn absorbs near-UV that heats the atmosphere.

The active Sun is a double whammy. The details of the 1500 year solar cycle and the measured global temperatures are convincingly explained in a new book by S. Singer and Dennis Avery.

References

G. Bond, "Persistent Solar Influence on North Atlantic Climate during the Holocene," Science 294, 2001.

Singer and Avery, Unstoppable Global Warming: Every 1500 Years

Ward and Brownlee, The Life and Death of Planet Earth