The time at which the signal of climate change emerges from the ‘noise’ of natural climate variability (Time of Emergence, ToE) is a key variable for climate predictions and risk assessments.
The figure below shows the ToE for a range of GCMs. ToE occurs several decades sooner in low latitudes, particularly in boreal summer, than in mid-latitudes, because the variability tends to be far smaller in the tropics (also see Mahlstein et al.). However, there is considerable uncertainty in when ToE occurs.
Importantly, the uncertainty in ToE arises not only from inter-model differences in the magnitude of the climate change signal, but also from large differences in the simulation of natural climate variability. Narrowing the uncertainty in ToE will require better understanding of the causes of climate variability, especially as the GCMs analysed tend to have too large variability in the extra-tropical regions.
The full analysis discusses this all in more detail.
Hawkins, E., & Sutton, R. (2012). Time of emergence of climate signals Geophysical Research Letters, 39 (1) DOI: 10.1029/2011GL050087