Air Sourced Heat Pump.

Yes some plants grow better with higher CO2, it's not always true because in many cases the growth rate is limited by some other factor (sunlight, water, etc.). That doesn't mean that just because high CO2 in a polytunnel can be good then high CO2 in the atmosphere more generally is automatically beneficial to all plants. If that high CO2 adversely affects temperature, rainfall patterns, pollinator or pest lifecycles or anything else that those plants depend on then it can have a negative impact on that plant. If that plant is a staple crop that humans depend on then that can be very serious for us.

Thinking of climate change only as an increase in average global temperature also misses a lot of important detail. Local temperatures can vary more than that including in both directions, rainfall patterns can change dramatically, sea water expands 0.13%/degree C with obvious implications, etc.

I find the assertion that the atmospheric CO2 level is a noiseless straight line to be inconsistent with the measurements. Here the black line is measurements at Mauna Loa and the orange at the South Pole. In both, though to a greater extent in the black line there is a clear seasonal variation - about 5 ppm pk-pk at Mauna Loa, with some fine structure visible within the yearly cycle. Additionally whilst one could make a reasonable linear fit to it, it is clearly not straight - the slope around 1970 is about half the slope around 2010.

https://royalsociety.org/-/media/Royal_Society_Content/policy/projects/climate-evidence-causes/figb2-large.jpg?la=en-GB&hash=8E044446B61F89CAEB986B7E7318BB63
 

@Sparkingchip yes the gas fitter thing is very weird.

Yes some plants grow better with higher CO2, it's not always true because in many cases the growth rate is limited by some other factor (sunlight, water, etc.). That doesn't mean that just because high CO2 in a polytunnel can be good then high CO2 in the atmosphere more generally is automatically beneficial to all plants. If that high CO2 adversely affects temperature, rainfall patterns, pollinator or pest lifecycles or anything else that those plants depend on then it can have a negative impact on that plant. If that plant is a staple crop that humans depend on then that can be very serious for us.

Thinking of climate change only as an increase in average global temperature also misses a lot of important detail. Local temperatures can vary more than that including in both directions, rainfall patterns can change dramatically, sea water expands 0.13%/degree C with obvious implications, etc.

I find the assertion that the atmospheric CO2 level is a noiseless straight line to be inconsistent with the measurements. Here the black line is measurements at Mauna Loa and the orange at the South Pole. In both, though to a greater extent in the black line there is a clear seasonal variation - about 5 ppm pk-pk at Mauna Loa, with some fine structure visible within the yearly cycle. Additionally whilst one could make a reasonable linear fit to it, it is clearly not straight - the slope around 1970 is about half the slope around 2010.

https://royalsociety.org/-/media/Royal_Society_Content/policy/projects/climate-evidence-causes/figb2-large.jpg?la=en-GB&hash=8E044446B61F89CAEB986B7E7318BB63
 

@Sparkingchip yes the gas fitter thing is very weird.