In [this page](https://www.princeton.edu/news/2013/11/24/even-if-emissions-stop-carbon-dioxide-could-warm-earth-centuries) it says “scientific consensus is temperature would remain constant or decline if emissions were suddenly cut to zero”. There are scenarios in page 74 of this [IPCC report](https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdf). We can see that in some scenarios CO2 levels are high but temperature remains same or declines. Also, we know that when we cut the emissions CO2 levels in the atmosphere will remain high for centuries. How do these projections work?
I thought earth was getting warmer because of the high levels of CO2 in our atmosphere. In the scenario that we cut emissions, there will still be high levels of CO2 in our atmosphere but many scientists says temperature won’t go up. What am I missing?
Edit: I believe I haven’t made my point clear. Of course CO2 levels [will start to decrease](https://ei.lehigh.edu/learners/cc/readings/ifemmision.pdf) when we cut emissions. However, in the last century, temperature on earth’s atmosphere were increasing due to the greenhouse gases(ghg) in our atmosphere. And when we stop emitting these gases, we will still be having too much ghg in our atmosphere. They will **slowly** be captured by plants and ocean. However, the claim is that even with this high levels, [temperature will stop increasing](https://www.nature.com/articles/ngeo813). What is the difference between having high ghg percentage on atmosphere while also emitting, and having high amount of ghg while not emitting?
In: Earth Science
The claim that as soon as we stop increasing CO2 emissions the temperature will also **immediatelly** stop increasing is false. It will help but the effect will take a while to appear.
You can simplify and think of the planet as a whole system that both receives energy from the sun and re-emits energy to space. The ammount of energy is in equilibrium for any given temperature. (This is a very naive aproximation)
In general having more CO2 makes the planet keep more of that sun energy because CO2 prevents it from being re-emited to space and hence temperatures increase, relative to the ammount of CO2 in the atmosphere. The thing is as the planet gets hotter it also increases the ammount of energy it emits to space up to the point that if the CO2 stops increasing, the temperature will also stop increasing, and remain constant (for a given ammount of CO2) because both absorbtion and emission are in equilibrium.
BUT, this asumes that the effect of the CO2 on global temperature is immediate, and this is not the case. The planet has what we call a temperature inertia in the form of the seas and landmass that generally require much more energy to change the temperature than the air. This is why the increase of the sea temperature is such a worrisome thing. In a sense the temperature will keep increasing until those “heatsinks” reach equilibrium consistent with the energy that the planet retains. They have yet to do so.
The really big danger is that there are huge ammounts of CO2 and methane trapped under ice both on land and on the ocean and as temperatures rise and that ice melts that CO2 and methane (wich is much stronger than CO2 at making the planet keep it’s energy) will escape and far outstrip the effect that humans have. This will cause temperatures to rise further and cause even more gasses to be released. Also, at higer temperatures all those processes that absorb CO2 (plants) will also start to become less and less effective. This is a doomsday scenario because there is nothing we can do to stop it, once it starts to really get going.
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