Sun & climate: moving in opposite directions
What the science says...
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The sun's energy has decreased since the 1980s but the Earth keeps warming faster than before.
Over the last 35 years the sun has shown a cooling trend. However global temperatures continue to increase. If the sun's energy is decreasing while the Earth is warming, then the sun can't be the main control of the temperature.
Figure 1 shows the trend in global temperature compared to changes in the amount of solar energy that hits the Earth. The sun's energy fluctuates on a cycle that's about 11 years long. The energy changes by about 0.1% on each cycle. If the Earth's temperature was controlled mainly by the sun, then it should have cooled between 2000 and 2008.
The solar fluctuations since 1870 have contributed a maximum of 0.1 °C to temperature changes. In recent times the biggest solar fluctuation happened around 1960. But the fastest global warming started in 1980.
Figure 2 shows how much different factors have contributed the warming. It compares the contributions from the sun, volcanoes, El Niño and greenhouse gases. The sun adds 0.02 to 0.1 °C; volcanoes cool the Earth by 0.1-0.2 °C; natural variability (like El Niño) heats or cools by about 0.1-0.2 °C; and greenhouse gases have heated the climate by about 0.8 °C.
Some people try to blame the sun for the current rise in temperatures by cherry picking the data. They only show data from periods when sun and climate data track together. They draw a false conclusion by ignoring the last few decades when the data shows the opposite result.
Basic rebuttal written by Larry M, updated by Sarah
Update July 2015:
Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial
Last updated on 28 November 2016 by Sarah. View Archives