We are on the natural rise after a natural ice period. Just check long term temperature curves and stop looking short term, making it look like there has ever been the same average temperature on earth.
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We've got spectrographs that can look at that radiation to see which radiation is not balanced. We can see that what is happening is radiation coming in at wavelengths that the atmosphere doesn't block heats things which reradiate much of that energy as infrared which the atmosphere blocks.
Thanks to spectroscopy we know that it is CO₂ in the atmosphere that is largely responsible for this blocking.
We know that the increase in CO₂ levels over the last couple of hundred years is largely from fossil fuels rather than things like decaying vegetation, forest fires, animal respiration and flatulence, or volcanic gases because of isotope ratios in atmospheric CO₂.
CO₂ from living things or recently living things contains ¹⁴C. CO₂ from fossil fuels and volcanoes does not contain ¹⁴C. CO₂ from volcanoes contains a higher ratio of ¹³C to ¹²C than the ratio in atmospheric CO₂. CO₂ from fossil fuels contains a lower ratio of ¹³C to ¹²C than the ratio in atmospheric CO₂.
That allows scientists to look at the isotope ratios in the atmosphere and figure out how much of the CO₂ there came from fossil fuels and how much came from volcanoes. The result is that most of the increase is from fossil fuels.
As a sanity check that result also matches well with the amount of CO₂ that we'd expect to have been released based on the amount of known fossil fuel use.
So no, it is not a natural rise.