Climate change fuelling rise in extreme weather events

Subject: Geography

Section : Physical geography

Context: According to IMD climate change has hampered the ability of forecasting agencies to make predictions accurately.

Analysis of the study-

An analysis of the day-to-day rainfall data since 1970 shows that the number of very heavy rainfall days had increased and that of light or moderate rainfall days had decreased.
That means if it is not raining, it is not raining. If it is raining, it is raining heavily.
The rainfall is more intense when there is a low pressure system. This is one of the most important trends found in the tropical belt, including India.
Studies have proved that this increase in heavy rainfall events and decrease in light precipitation are due to climate change.
The IMD had explained that climate change has increased the surface air temperature, which in turn has increased the evaporation rate.
Since warmer air holds more moisture, it leads to intense rainfall.

Impact of climate change on weather prediction-

Climate change has hampered the ability of forecasting agencies to accurately predict severe events.
The India Meteorological Department is installing more radars and upgrading its high-performance computing system to meet the challenge.
Though the monsoon rainfall had not shown any significant trend in the country, the number of heavy rainfall events had increased and that of light rainfall events had decreased due to climate change.
The impact-based forecast will improve to become “more granular, specific and accurate” by 2025 and the IMD will be able to provide forecasts up to panchayat-level clusters and specific areas in cities in the coming years, the IMD said.

Severity of cyclones –

Climate change has increased the instability in the atmosphere, leading to an increase in convective activity — thunderstorms, lightning and heavy rainfall.
The severity of cyclones in the Arabian Sea is also increasing.
This increase in the frequency of extreme weather events is posing a challenge to forecasters.
Studies show that the ability to predict heavy rainfall is hampered due to climate change.

Improvement in prediction model-

The IMD’s forecast accuracy had improved by about 30% to 40% for severe weather events such cyclones, heavy rain, thunderstorms, heat waves, cold waves and fog in the past five years due to an improvement in the observational network, modelling and computing systems.
The number of deaths due to cyclones and heat waves had also reduced over the years because of an improvement in the early warning lead time and preparedness, planning, prevention and mitigation approaches.
The IMD is bolstering its observational network with the augmentation of radars, automatic weather stations and rain gauges and satellites to improve predictability.
IMD has put up six radars in the northwest Himalayas and four more will be installed this year.
The procurement process is on for eight radars in the northeast Himalayan region.
There are certain gap areas in the rest of the country that will be filled up with 11 radars.
The number of radars will increase from 34 at present to 67 by 2025 the IMD has said.
Radars are preferred because they have a higher resolution and can provide observations every 10 minutes.

Climate change and Himalayas-

On climate change increasing the fragility of the Himalayas, IMD said, “Climate change is a fact and we need to plan all our activities accordingly.
A study by the Indian Institute of Tropical Meteorology, MoES says the frequency of mini-cloud bursts (five cm or more rainfall in an hour) is increasing in the Himalayas and it can also cause damage.

Deficit in north, east, and the north-east–

On the impact of climate change on monsoon, the digital data of the rainfall since 1901 shows that the parts of north, east and northeast India show a decrease in rainfall, while some areas in the west, such as west Rajasthan, show an increase.
Thus, there is no significant trend for the country as a whole.
The monsoon is random and it shows large-scale variations.

What the government has said-

At present, the IMD-MoES weather modelling system has a resolution of 12 kilometres. The target is to make it six kilometres.
The Ministry of Earth Sciences (MoES) also has plans to upgrade its high-performance computing system -from a capacity of 10 petaflops currently to 30 petaflops in the next two years- which will help assimilate more data into the model that can then be run at higher resolutions. The lower the range of a weather model, the higher its resolution and the greater the precision.
Similarly, the resolution of the regional modelling system will be improved from three kilometres to one kilometre.

State-wise analysis-

The government had told Parliament that Uttar Pradesh, Bihar, West Bengal, Meghalaya and Nagaland had shown significant decreasing trends in the southwest monsoon rainfall during the recent 30-year period (1989-2018, both years included).
The annual rainfall over these five States, along with Arunachal Pradesh and Himachal Pradesh, had also shown significant decreasing trends.