Just because natural variation in the amount of energy we get from the sun (called 'insolation') has driven climate change in the past, doesn't mean that's what's going on today.
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Right now insolation is going *down*, and the planet *should* be cooling, but it's not. It's not, because heating from CO2 is overwhelming the cooling from decreased insolation.
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Here’s a simple proof of global warming that doesn't depend on any assumptions or predictions:
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1st. CO2 levels have been rising sharply ever since the industrial revolution, when we started releasing massive amounts of stored carbon. This graph shows what that looks like. Note the sharp spike on the right hand side:
https://scripps.ucsd.edu/programs/keelingcurve/wp-content/plugins/sio-bluemoon/graphs/co2_10k.png
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2nd. CO2 traps heat. The more CO2, the more heat.
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You can't fight physics, if we're trapping more heat, then the planet is heating up.