evidence: The issue of whether or not a change in global temperature is outside the range of "normal natural variability" depends on the timescale being considered. It is true that some physical climate models (and some statistical climate models based on historically observed variability) indicate that it is possible for a warming episode as large as that seen from 1979-2000 to come about from unforced (internal) variability. However, when an unforced warming episode occurs, it is typically followed by an unforced cooling episode (if that wasn’t true, the climate would be fundamentally unstable and it would have run away to a snowball or hothouse state a long time ago). This means that the longer the sustained change in temperature, the less likely it is that the change could be due to "normal natural variability". This is why the IPCC used a period almost 3 times longer in their attribution statement that "It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together." [...] This is a falsely constructed argument by limiting the time range to 1979 to 2000. One can cherry pick an interval and show that it’s not especially different from the past, however if one takes the full reliable record of the last 140 years the warming is unequivocal.