In the total absence of anthropogenic aerosols (air pollution from fossil fuels) The earth will experience (median estimate) +0.8C of warming.
Currently there is a massive amount of residual warming locked in from historic emissions of GHGs. This is determined by the Earth's energy imbalance which is now +0.9 Watts per meter-squared. This energy is primarily being absorbed by the world's oceans and is equivalent to 600,000 Hiroshima bombs' worth of energy per day being absorbed. This energy imbalance will not go away until surface temperatures have reached equilibrium. Moderate estimates of climate sensitivity to this energy show that this means we have locked in an additional +0.7C of warming to equilibrium.
We are at 1.2C now + 0.8C (aerosols) + 0.7C (energy imbalance) = 2.7C
This does not include the 3C that the aerosols are currently cooling the Arctic
This does not include the 9C (Early Fall) warming that the Arctic will necessarily experience under the ice-free conditions that an additional 3C of warming (aerosols) and 30% (from 1980) sea ice volume loss that will occur in the absence of aerosols.
This does not include the carbon cycle feedbacks that recently published field-studies show will be much worse than the current models project. This is significant especially WRT the Arctic, since the models do not include emissions from permafrost.
The difference between the actual carbon cycle emissions projected from the best science published in the last 2 years and the models working from data that is 10 years old is approximately +400GtC of emissions which is approximately 3/4th the total carbon emitted to the Earth's atmosphere by humans since 1880.
This additional emissions of carbon will likely produce at least 150 ppmv of CO2 into the earth's atmosphere between now and 2100
This figure of 150 ppmv of CO2 is a conservative estimate since it projects current carbon cycle land and ocean sinks to stay at their current rates but these carbon cycle sinks are (in the last 2 years) being observed to go into decline.
This does not include future human emissions of CO2 between now and when we stop (including land-use changes).
The additional 150 ppmv of CO2 from carbon cycle emissions will raise the earth's temperature by an additional 0.8C (forcing and warming of atmospheric CO2 follows a logarithmic, not a linear scale).
So, in the absence of ANY future CO2 emissions from humans (if we all magically stopped burning fossil fuels today we would:
Experience a massive shift of warming and circulation changes (PDO, ENSO, AMO, Amazon and Pacific tropical rainfall patters, monsoon shifts, Arctic regional warming) within 7 years
We would also experience a complete loss of Arctic sea ice within 2 years
The Earth's surface temperature would rise by 60% of the additional warming from aerosols and energy imbalances (combined total +1.5C) = +0.9C by 2030. Yielding a globally averaged surface temperature of 2.1C.
By 2100 the majority of this full warming will be achieved plus Arctic regional warming from albedo decreases and carbon cycle feedbacks producing a globally averaged warming of 3.6C.
By 2200 the full carbon cycle emissions from melting permafrost and equilibrium temperature will be close to achieved with a warming above pre-industrial of >4.5C.
Without any further human emissions of CO2 and land use changes.