Indigenous climate model for monsoon trends in IPCC report

Using an indigenous climate model for the first time, two Indian scientists are contributing to climate projections for the Intergovernmental Panel on Climate Change’s sixth Assessment Report (AR6), which will be released in 2020.

R Krishnan and Swapna Panickal, from the Indian Institute of Tropical Meteorology (IITM), Pune, are documenting how climate change will impact global meteorological trends and the South Asian monsoon.

It is among 33 climate models being run by scientists from different countries contributing to AR6. IPCC is the leading international body for the assessment of climate change with 195 member nations.

According to Panickal, the current global models have larger uncertainty when it comes to predicting the impact of climate change on the South Asian monsoon.

While some models have indicated that the monsoon is weakening and rainfall is diminishing, many others have indicated otherwise.

The IITM earth system model (IITM-ESM) selected for AR6 was being used for seasonal forecasts by the India Meteorological Department (IMD) and was adopted as a global climate model at IIT because of its effectiveness in computing and forecasting monsoon trends

“The data from the model will be available in the public domain by next year so that other scientists and researchers can use it to study global climatic trends,” Panickal said.

Unlike previous IPCC reports, AR6 will provide an assessment of climate impact, specific information on changes to come, and a timeline so that the government can prepare for mitigation efforts. The information on the South Asian monsoon will be of significance to the India in terms of long-term planning on agriculture, water resource management and other socio-economic activities.

The IITM-ESM projections have indicated a weakening of the Indian monsoon in recent decades, leading to an overall decrease in rainfall. This trend has been supported by long-term monsoon data from the IMD, but the model also shows that in future there will be a
perceptible enhancement in overall monsoon rainfall as well as increase in extreme weather events such as floods and droughts. “We cannot say
when visible enhancement in monsoon can be felt. It may be after 2050, it mainly depends on what is the global and regional mean temperature rise over pre-industrial levels,” he said.

The team has started the model simulation using pre-industrial conditions from 1850, including temperature, humidity, ocean temperature, and other factors that continue into the future until the end of the 21st century.These are designed to understand the response of the global climate and the regional monsoon rainfall.

“We have to provide annual values of greenhouse gases, aerosols (pollution particles), land use change to get climate response,” said Panickal.

As climate scientists, their main message to the world is to decrease fossil fuel emissions. “Human influence, primarily the burning of fossil fuels, has been the dominant cause of global warming over the past several decades...,” he said.

Led by Panickal, six other Indian climate scientists from other research organisations will work on other aspects of climate change for AR6.

“It’s a welcome step that an Indian model will be used for IPCC assessments. Many international climate models...are not able to predict trends very accurately, plus different models are suited for different regions. We needed something specific for the South Asian monsoon. IITM has data and expertise for the model,” said Manju Mohan from the Centre for Atmospheric Sciences at Indian Institute of Technology-Delhi.