Because warming initially releases more CO2 from the oceans until the carbon sinks catch up and the heat trapping power of CO2 is not very strong. Mars is almost all CO2 and yet there's little to no greenhouse effect. The postulated effect of CO2 comes from the addition of water vapor which affects the weather and could cause more warming or less warming depending on that effect.
The last post brings up several points:
Regarding comparisons to other planets, Mars is cold because it has almost no atmosphere. It's true that what is there is mostly CO2, but it is such a thin layer that in aggregate, there is very little ability to trap heat. On the other hand, the atmosphere of Venus is thick (and also almost all CO2), and its surface temperature is about 460 degrees celsius because of a very strong greenhouse effect.
Climate models simulate forcing from greenhouse gases but must also simulate water vapor because it is an important component of ocean/atmosphere processes. The steady increase in temperatures that are forecast are from a steadily increasing component of greenhouse gases, not some sort of runaway cloud effect. It's true that warmer temperatures leads to more evaporation (ie. clouds) and that this water vapor can potentially cause more warming or less warming, depending on whether it blocks radiation or traps heat, but this uncertainty still does not negate the effect of a steadily increasing stew of greenhouse gases, which do trap heat. And if we're betting that increasing clouds save us by reducing temperatures, then the recent empirical evidence (near-term record temperatures, metling icecaps, etc.) suggests that we shouldn't count on it.
But forgetting the cloud problem, let's say that we are confident that the oceans can at some point reach an equilibrium as a carbon sink as you mention. If so, we would still have to reduce our emissions to a steady state (ie. something like a 1990 target), because otherwise, we are continually raising the curve ahead of the effect of a sink. But this also neglects to consider that a massive sink of carbon dioxide into oceans will cause it's own problems with increased acididity, which would likely be very bad for marine life.
The last post brings up several points:
Regarding comparisons to other planets, Mars is cold because it has almost no atmosphere. It's true that what is there is mostly CO2, but it is such a thin layer that in aggregate, there is very little ability to trap heat. On the other hand, the atmosphere of Venus is thick (and also almost all CO2), and its surface temperature is about 460 degrees celsius because of a very strong greenhouse effect.
Climate models simulate forcing from greenhouse gases but must also simulate water vapor because it is an important component of ocean/atmosphere processes. The steady increase in temperatures that are forecast are from a steadily increasing component of greenhouse gases, not some sort of runaway cloud effect. It's true that warmer temperatures leads to more evaporation (ie. clouds) and that this water vapor can potentially cause more warming or less warming, depending on whether it blocks radiation or traps heat, but this uncertainty still does not negate the effect of a steadily increasing stew of greenhouse gases, which do trap heat. And if we're betting that increasing clouds save us by reducing temperatures, then the recent empirical evidence (near-term record temperatures, metling icecaps, etc.) suggests that we shouldn't count on it.
But forgetting the cloud problem, let's say that we are confident that the oceans can at some point reach an equilibrium as a carbon sink as you mention. If so, we would still have to reduce our emissions to a steady state (ie. something like a 1990 target), because otherwise, we are continually raising the curve ahead of the effect of a sink. But this also neglects to consider that a massive sink of carbon dioxide into oceans will cause it's own problems with increased acididity, which would likely be very bad for marine life.