The Forum > Article Comments > Cosmic cycles, not carbon dioxide, control climate > Comments
Cosmic cycles, not carbon dioxide, control climate : Comments
By Viv Forbes, published 20/1/2016The warm days, seasons, years and epochs have never been a deadly threat to life on Earth. Frost, snow, hail and ice are the killers.
- Pages:
-
- 1
- 2
- 3
- 4
- Page 5
-
- All
The Sun-Climate Connection
The rate at which energy from the sun reaches the top of Earth’s atmosphere is denoted by the term “total solar irradiance” (or TSI). TSI fluctuates slightly from day to day and week to week. Superimposed on these rapid short-term fluctuations is a cycle related to sunspots in the outer layers of the Sun that lasts approximately every 11 years.
The current TSI varies with season, time of day, and latitude. Yet it is thought that small changes in this relatively small amount of absorbed solar energy can make a difference to our climate. Might changes in the rate of solar absorption, called radiative forcing (RF), be influencing our climate today?
(1) Direct changes in climate due to solar output
The average increase in solar radiative forcing since 1750 is much smaller (~ 0.12 W m-2) than the increase in RF due to heat-trapping gases (~2.6 W m-2) over that same time period. [3]The slight increase in solar absorption is, moreover, more than offset by natural cooling. The twentieth century witnessed the eruption of major volcanoes— the most recent, Pinatubo, in 1991—that spewed tiny reflective particles into the atmosphere. Incoming energy from the sun that encountered these particles was reflected back into space. In other words, natural processes alone would have brought about slight late twentieth century cooling—not the warming we have experienced.