|The main cause of climate change is:||a) emissions from factories and automobiles|
No, that is incorrect.
Climate change occurs in cycles caused mainly by changes in the Sun's output, the Sun's position over the Earth, and changes in albedo, the color of the surface of the Earth (especially variations in snow cover, seasonally and over time). When human emissions of CO2 rose at the fastest rate in history during and after World War II, the planet cooled, bringing fears of a coming global ice age. At other times, CO2 and Earth’s temperature have risen together, although CO2 levels generally lagged temperature suggesting that CO2 rise is a consequence of, not a cause of, warming.
Major Causes of Global Temperature Shifts
Cycles of solar variability (Sunspot activity):
~11 year Hale cycle
~ 22 year Schwab cycle
~75-90 yr Gleissberg Cycle
~200-500 yr Suess Cycle (includes the 206 year cycles that may have contributed to the downfall of the Mayan civilization)
~1100-1500 yr Bond Cycle
19,000 year cycle: Earth's combined tilt and elliptical orbit around the Sun (‘precession of the equinoxes’).
41,000 year cycle: Cycle of the +/- 1.5° wobble in Earth's orbit.
100,000 year cycle: Variations in the shape of Earth's elliptical orbit (‘cycle of eccentricity’)
For more information, see http://www.ngdc.noaa.gov/paleo/milankovitch.html and http://www.abc.net.au/science/news/enviro/EnviroRepublish_233658.htm
Heat retention: Due to atmospheric gases, mostly gaseous water vapor (not droplets), also carbon dioxide, methane, and a few other miscellaneous so-called ‘greenhouse gases’.
Solar reflectivity: Due to white clouds, volcanic dust, etc.
Landmass distribution: Shifting continents (continental drift) causing changes in circulatory patterns of ocean currents. It seems that whenever there is a large land mass at either one of the Earth's poles, there are ice ages.
Undersea ridge activity: "Sea floor spreading" (associated with continental drift) causing variations in ocean displacement.
Ocean circulation, both surface circulations and deep ocean circulation.
Albedo (or surface reflectivity) changes. These are generally natural (e.g. polar ice caps and seasonal snow cover changes), with a small component caused by human-induced “land-use change”.