Increased variability could increase impacts to vulnerable regions
By Summit Voice
SUMMIT COUNTY — Regions affected by the Asian monsoon are heavily dependent on the seasonal rains for crop production, and are also extremely susceptible to impacts from the torrential downpours, so climate scientists have looked hard at how global warming will affect the pattern.
According to new research from the Potsdam Institute for Climate Impact Research, the daily variability of the Indian monsoon may very well increase.
“Increased variability – this rather technical term translates into potentially severe impacts on people who cannot afford additional loss,” said Anders Levermann, one of the study’s authors and co-chair of PIK’s research domain Sustainable Solutions.
“The fact that all these different models agree is a clear message that adaptation measures can be built on.”
Even if seasonal mean precipitation would remain unchanged, impacts could be substantial, Levermann said. “
Focusing on the average is not always useful. If rainfall comes in a spell and is followed by a drought, this can be devastating even if the average is normal. This requires the right kind of adaptation measures that account for this variability – such as intelligent insurance schemes, for example.”
If greenhouse gas emissions continue unabated, monsoon variability could increase by 13 to 50 percent. But even if warming capped at 2 degrees Celsius, day-to-day variability could increase by 8 to 24 percent above the pre-industrial level, according to the analysis.
“So limiting global warming is key to reduce day-to-day monsoon variability, adaptation cannot replace but rather complement it,” Levermann said.
Using a conservative approach, the researchers focused on ten models with a most realistic monsoon pattern. The other ten models showed higher rates of change. The scientists used the latest ensemble of climate models, prepared for the 5th assessement report of the International Panel on Climate Change. All of them show increased variability.
Taking into account all 20 models, the spread of results reduces when the scientists looked at the rainfall changes per degree of global warming independent of the exact time path of the warming. The consistent result is that 4 to 12 percent variability change of daily monsoon rainfall in India are to be expected per degree Celsius of warming.
“This is a robust indicator,” said Arathy Menon, lead-author of the study. “This is not about exact percentages. It is the clear trend that conveys the message,” he said.
About 80 percent of annual rainfall in India occur during the monsoon season from June through September. Factors that could perturb rainfall regularity include the higher holding capacity of moisture of the warmer air, but also more complex phenomena like cooling in the higher atmosphere which changes current pressure and thereby rainfall patterns.