Parts of U.S. still defying worldwide trend — but not for long
Taking a careful look at the temperature records of the past few decades has enabled climate scientists to show that the first signs of global warming were detectable as early as the 1960s in the tropics.
The new research published in Environmental Research Letters gives an insight into the global impacts that have already been felt, even at this very early stage, and where those impacts are likely to intensify in the coming years.
“We examined average and extreme temperatures because they were always projected to be the measure that is most sensitive to global warming,” said lead author from the ARC Centre of Excellence for Climate System Science, Dr Andrew King.
“Remarkably our research shows that you could already see clear signs of global warming in the tropics by the 1960s but in parts of Australia, South East Asia and Africa it was visible as early as the 1940s.”
The reason the first changes in average temperature and temperature extremes appeared in the tropics was because those regions generally experienced a much narrower range of temperatures. This meant smaller shifts in the temperature record due to global warming were more easily seen.
The first signal to appear in the tropics was the change in average temperatures. Later extreme temperature events showed a global warming signal.
Closer to the poles, the emergence of climate change in the temperature record appeared later but by the period 1980-2000 the temperature record in most regions of the world were showing clear global warming signals.
The continental United States, particularly on the Eastern coast and up through the central states, is one of the exceptions. So far, there’s not a clear global warming signal, but according to the models, they will appear in the next decade.
As well, the general increase in global rainfall is noticeable, but doesn’t fall outside the natural range of variability yet. That’s expected to change soon, said co-author Dr. Ed Hawkins, with the National Centre for Atmospheric Science at the University of Reading, UK.
“We expect the first heavy precipitation events with a clear global warming signal will appear during winters in Russia, Canada and northern Europe over the next 10-30 years,” Hawkins said. “This is likely to bring pronounced precipitation events on top of the already existing trend towards increasingly wet winters in these regions.”