Climate: From ‘hot’ to ‘extremely hot’

This is the second in a series of posts by Frederik Lichtenberg, PSR’s climate intern.

These days, global warming makes spring come earlier and fall later and the period in between to be hotter; summer-like conditions are protracted. For this reason, in his recent article, “Perceptions of Climate Change: The New Climate Dice,” global warming expert James Hansen focuses on changes in summer temperatures.

Hansen and his co-authors point out that it is not only the quantity of “hot” events that has risen but also the quality, which is indicated by a new category referred to as “extremely hot.” This category, which refers to weather events more than three standard deviations warmer than climatology would have predicted, did not exist in the period from 1951-1980. Yet it is quite frequent to find “extremely hot” weather events in the years 1981-2010.

The emergence of this new “extremely hot” category shows that in order to describe the climate of 1981-2010, then-existing categories were inadequate since such extreme temperatures so infrequent during 1950-1981. The land areas affected by these temperatures only covered a “few tenths of one percent” back then. The current figure for the occurrence of such anomalies is 10%, a drastic increase which shows very well just how intensely our climate has shifted towards warmer temperatures in a very short period of time.

The frequent temperatures of this magnitude suggest that well-remembered anomalies such as the summer heat in the Moscow area in 2010 or Texas in 2011 were a consequence of both global warming and specific local weather patterns at the time.

Furthermore, this trend – the climate dice loaded towards extreme heat – is expected to continue.

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