Washington: Extreme summers, not unusual in the US today, will become commonplace by mid-century if the emission of greenhouses gases continues unabated.
For instance, a 100-ft drop in Lake Mead`s water level, along the Colorado river, is one of the most disturbing outcomes of the 10-year drought, thanks to climate change.
By analysing observations and results obtained from climate models, Phil Duffy of the Lawrence Livermore National Lab (LLNL), showed that previously rare summer peak temperatures are already occurring more frequently in some US regions, the Journal Climate change reports.
"The observed increase in the frequency of previously rare summertime average temperatures is more consistent with the consequences of increasing greenhouse gas concentrations than with the effects of natural climate variability," said Duffy.
"It is extremely unlikely that the observed increase has happened through chance alone," added Duffy, who led the study, according to an LLNL statement.
Duffy and colleague Claudia Tebaldi, senior scientist with Climate Central, showed that the models project that previously rare summer temperatures will occur in more than 50 percent of summers by mid-century throughout the lower 48 US regions.
Duffy and Tebaldi performed a statistical analysis showing that the increases in rare summer temperatures seen in the later period are very unlikely to have occurred through chance weather variations.