The space alien's answer to the greenhouse gas/heatwave question

If you asked a scientifically advanced space alien whether current heat waves are worsened by our greenhouse gas emissions, it might take the complicated probabilistic approach humans have used to explain that our emissions have made the heat waves far more likely.  Or maybe it will do something easier.

Our space alien, Gort, sends out the Insta-Array of temperature sensors to get a reading, and then presses the "Ennaturalnate" button on the Climate Changeometer, instantly reverting all global greenhouse gas levels to their pre-industrial levels.  I'll leave the final answer to the non-lawyers here, but I think that all other things being equal, there would be a small but real drop in temperature within a few hours.  If one third of our warming to date is from direct effects of greenhouse gases, then Ennaturalnate should instantly drop temps in a heatwave between .25 and .5F.  Non-lawyers, is this right?  UPDATE:  per the initial comments, might take more like a week for a heat wave on land, and far longer over oceans or globally.

So that's the first and simplest answer for the news media that has so much trouble with this - if you could immediately remove all the human additions to the atmosphere, then temperatures would drop within hours, a small amount.  If the local television allows more than a five second soundbite, then you add that moreover there are feedback effects that make things significantly worse and add up over time.  And many of the climate denialists would have to agree about the near instantaneous effect, because many of the acknowledge climate forcing while making up nonsense about feedbacks being negative.  These denialists can add their caveats, but noone cares.

Just one lawyer's view of the issue.