Is it the sun?

There are some denialists who maintain that the world is getting warmer because the sun is hotter, and that rising global temperatures have nothing to do with the CO2 released into the atmosphere over the last couple of hundred years from the burning of fossil fuels.

The chart below shows how silly this claim is.  You can see the fairly regular solar cycle (yellow line) and you can also see how it coincides, more or less, with "bulges" in the upward trend of global temperatures.  Note how (a) the sun's cycle has been relatively weak over the last few years and (b) how the relationship between the solar cycle and the fluctuations around the rising temperature trend in recent years looks much less robust.  OK, I'm just looking at the chart, and not doing a statistical analysis, so I merely offer the observation.  I also offer the observation (again without doing any statistical analysis) that the temperature line (grey) appears to fit very well indeed with the CO2 lines (blue Mauna Loa, green ice core) allowing for cyclical and random fluctuations in temperature.  One obvious cycle is ENSO (El Niño/Southern Oscillation) which raised temperatures in 1998 and again last year.  With the latest El Niño over, the temperature anomaly will slip back towards the CO2 line.  And it will likely (by the looks of things) coincide with a cooler sun.  But that will be temporary only.  The slope of the CO2 line is increasing.  The fundamental driving force, rising CO2 level in the atmosphere, will dominate again, and God help us if there is another El Niño.

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