Had the climatologists predicted climate change as the deviations to both extremely cold and hot temperatures before?
The Intergovernmental Panel on Climate Change summarizes the state of scientific understanding of climate change every few years and at least as far back as 2002 has projected a range of changes in extreme weather.

In the IPCC report for 2002, the Working Group II: Impacts, Adaptation and Vulnerability summarized the existing scientific understanding in may areas, including "Climate Variability and Extreme Events":
"Most studies of climate change impacts have focused on changes in mean climate conditions. However, global climate change is likely to bring changes in climate variability and extreme events as well. This is relevant here because decisionmakers often consider hedging strategies to be prepared for the possibility of low-probability but high-consequence events -- a risk management framework.  Features of projected changes in extreme weather and climate events in the 21st century include more frequent heat waves, less frequent cold spells (barring so-called singular events), greater intensity of heavy rainfall events, more frequent midcontinental summer drought, greater intensity of tropical cyclones, and more intense El Nino-Southern Oscillation (ENSO) events." -
Climate Variability and Extreme Events

The question is also addressed in section 2.5. "Projected Changes in Climate Extremes could have Major Consequences":


  The vulnerability of human societies and natural systems to climate
  extremes is demonstrated by the damage, hardship, and death caused by
  events such as droughts, floods, heat waves, avalanches, and
  windstorms. While there are uncertainties attached to estimates of
  such changes, some extreme events are projected to increase in
  frequency and/or severity during the 21st century due to changes in
  the mean and/or variability of climate, so it can be expected that the
  severity of their impacts will also increase in concert with global
  warming (see Figure SPM-2). Conversely, the frequency and magnitude of
  extreme low temperature events, such as cold spells, is projected to
  decrease in the future, with both positive and negative impacts.