Often you will hear someone stridently stating that it is only the sun that warms the earth and the minuscule amount of carbon dioxide in the atmosphere has no effect, and therefore the increase in global temperatures is solely due to the increase in the sun’s radiance. There is only one problem with this. It is a lie.
Solar irradiance (the amount of radiation given out by the sun) has peaks around a roughly eleven-year cycle, and these peaks in recent times have been around 1980, 1991, 2002 and 2014. In between these peaks, the irradiance drops by about 0.1%. The maxima in irradiance, also roughly correspond to maxima in sunspot activity and it has an effect on the Earth’s climate, with the maxima warming the planet by about 0.18 degrees Celsius.
This does not explain the increase in average global temperature which, since 1900, has risen about 0.9 degrees C. There is also a clear decoupling of the 11-year average solar irradiance and the 11-year average temperature. That decoupling began about 1970 and has dramatically increased. Since then solar irradiance has actually decreased by about 0.5 watts per square metre, whereas the global average temperature has increased by about 0.7 degrees C.
Figure from: https://www.skepticalscience.com/graphics.php?g=5
Source
Global dimming is also thought to be a big problem. It is a by product of the use of fossil fuels which cause particulate to enter the atmosphere. The particulate absorbs and then reflects solar energy out of the Earth’s atmosphere. This artificially cools the air and surface temperature. I believe that measurements have been taken since the 1960’s using equipment such as an evaporating pan. When the jets ceased flying over the USA after 911, there was a measurable increase in the day time temperatures due to a lack of Jet contrails. Therefore global dimming is masking some of the effects of global warming….
David,
A similar thing happened when Mt Pinatubo, on the island of Luzon in the Philippines, blew its top in June 1991. It is estimated that about 20 million tons of sulphur dioxide was pumped into the stratosphere and dispersal of this around the world caused the global temperature to drop by about 0.5 degrees C for a couple of years. Inserting such things as particulates or sulphur dioxide into the upper atmosphere have been suggested as ‘engineering solutions’ to global warming, but given the volumes required, and possible side-effects, it is a risky strategy. It is safer to go with renewables and stop pumping out so much carbon dioxide and methane into the dump the atmosphere has become.