Azza said:
Volcanos - not significant compared to anthropogenic emissions (US Geological Society)
Example:
LAKI (1783) -- The eastern U.S. recorded the lowest-ever winter average temperature in 1783-84, about 4.8OC below the 225-year average. Europe also experienced an abnormally severe winter. Benjamin Franklin suggested that these cold conditions resulted from the blocking out of sunlight by dust and gases created by the Iceland Laki eruption in 1783. The Laki eruption was the largest outpouring of basalt lava in historic times. Franklin's hypothesis is consistent with modern scientific theory, which suggests that large volumes of SO2 are the main culprit in haze-effect global cooling.
TAMBORA (1815) -- Thirty years later, in 1815, the eruption of Mt. Tambora, Indonesia, resulted in an extremely cold spring and summer in 1816, which became known as the year without a summer. The Tambora eruption is believed to be the largest of the last ten thousand years. New England and Europe were hit exceptionally hard. Snowfalls and frost occurred in June, July and August and all but the hardiest grains were destroyed. Destruction of the corn crop forced farmers to slaughter their animals. Soup kitchens were opened to feed the hungry. Sea ice migrated across Atlantic shipping lanes, and alpine glaciers advanced down mountain slopes to exceptionally low elevations.
KRAKATAU (1883) -- Eruption of the Indonesian volcano Krakatau in August 1883 generated twenty times the volume of tephra released by the 1980 eruption of Mt. St. Helens. Krakatau was the second largest eruption in history, dwarfed only by the eruption of neighboring Tambora in 1815 (see above). For months after the Krakatau eruption, the world experienced unseasonably cool weather, brilliant sunsets, and prolonged twilights due to the spread of aerosols throughout the stratosphere. The brilliant sunsets are typical of atmospheric haze. The unusual and prolonged sunsets generated considerable contemporary debate on their origin.They also provided inspiration for artists who dipicted the vibrant nature of the sunsets in several late 19th-century paintings, two of which are noted here.
Azza said:
Sun flares - contentious, but generally considered not to be a factor
Climate scientist Gerald Meehl at the National Center for Atmospheric Research and his colleagues suggest that solar variability is leaving a definite imprint on climate, especially in the Pacific Ocean.
When researchers look at sea surface temperature data during sunspot peak years, the tropical Pacific showed a pattern very much like that expected with La Niña, a cyclical cooling of the Pacific Ocean that regularly affects climate worldwide, with sunspot peak years leading to a cooling of almost 1 degree Celsius (1.8 degrees Fahrenheit) in the equatorial eastern Pacific. In addition, peaks in the sunspot cycle were linked with increased precipitation in a number of areas across the globe, as well as above-normal sea-level pressure in the mid-latitude North and South Pacific.
Azza said:
Earthquakes - reference please
http://www.livescience.com/38488-earthquakes-trigger-methane-release.html
http://www.pollutionsolutions-online.com/news/air-clean-up/16/breaking_news/climate_change_could_be_affected_by_earthquakes/26370/
Azza said:
Orbital forcing - already factored-in and not relevant to current global warming
Of orbits and ice ages
Researcher confirms that axis shifts help to propel temperature changes
http://news.harvard.edu/gazette/story/2012/01/of-orbits-and-ice-ages/
Azza said:
Meteors (I presume you meant meteorites) - not relevant to current global warming
Comets also...
http://spaceinfo.com.au/2010/04/21/comet-crash-caused-climate-change/
...and how this is relevant to now is that a comet crashing and changing the 'natural cycle' of weather and temperature changes then has a domino effect on what happens over the years. A change in land formations, oceans, and interrupting a "warming cycle" with a sudden temperature drop has to have influence on future weather patterns.
Now I think the whole scenario is more complicated than the "its manmade gases" or "its natural what is happening".......I think what we are witnessing is a slow rise in Earth's temperatures caused by many variables, not one reason alone.
So I'm not a sceptic/denier...but I certainly aren't on the blaming the human race bandwagon either.
