The delayed response is because the temperature rise isn't merely caused by the carbon we've emitted this year, but by all the carbon that has been accumulating in the atmosphere over the past 100 years. Carbon isn't instantly removed from the atmosphere when we stop burning it, so it's going to stay around for a long time. Plants absorb it, but we've been burning more carbon than plants can absorb for a long time.

And for all the time that there's more CO2 in the atmosphere, the atmosphere will continue to trap more heat from the sun, and temperatures will continue to rise.