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| Edited By: M Dinesh Kumar |Source: DNA |Updated: Aug 28, 2018, 07:10 AM IST
Many uncertainties are involved in climate change predictions for countries like India which experience monsoon weather pattern. The predictions of climate trends for India by various climate models differ widely vis-à-vis the magnitude of change in rainfall and temperature and the nature of change itself. The degree of uncertainty is likely to be even higher when these model outputs are used for further predictions of river flows and crop yields. While these issues related to climate predictions are widely discussed, a critical issue which was left unattended is the implications of climate variability for the utility of model predictions. Yet, the governments are preoccupied complying international protocols to reduce carbon emissions and measures to reduce the impacts of climate change. Little attention is paid to the implications of climate variability on hydrology and water flows in river basins and crop yields.
There is a tendency among ‘Climate Crusaders’ to run roughshod on those confronting them with data on the more visible phenomenon of ‘climate variability’, and how this phenomenon is systematically ignored by the climate modellers. The subcontinent is known for its climatic variability for several millennia. Analysis also showed that lower the amount of mean annual rainfall in a region, higher the yearly variation, and vice versa. Also, lower the rainfall, higher the aridity. The climate models do not capture such nuances in their predictions. The result is that the values of the predicted change in temperature and rainfall are much lower than the actual year to year variability in them.
Climate modellers come with ‘doomsday prophecies’ vis-à-vis the impact of climate change. They would essentially include such things as: the river would have lesser stream flows or more frequent floods! Unfortunately, these are all based on aggregate figures. When we know that the annual discharge of Godavari river is found to vary from 29,000 MCM to 1,83,000 MCM, what purpose it serves if the climate change-hydrology model just predicts that the average run-off in Godavari basin would increase by 10 per cent in 50 years?
The model predictions on the impact of climate change on crop yields also suffer from such inadequacies. The models sometimes compute the yield impacts for a time scale of say, 50 or 80 years. These predictions are absurd, when we consider the fact that the crop yield is determined by a complex function, with solar radiation, micro climate, and ecology playing a key role. But, most crop models seem to function in a linear fashion and the complex interactions between climate parameters at the ‘local scale’ are conveniently ignored.
Internationally, scholars highlighted the importance of studying the impact of climate variability on biological systems and examined the impact of rainfall patterns and temperature stress on crop yields. Both intra- and inter-seasonal changes in temperature and precipitation are found to influence cereal yields. Increased rainfall variability will have substantial impacts on primary productivity and ecosystem services provided by forests and agroforestry.
Temperature rise beyond a threshold can have a negative effect on yield for many crops. But this can alter the local temperature for a few days by causing increase in precipitation. Instead of running crop models to predict the impact of climate change on yields, we just need to see how the yield of a particular crop fluctuates between years, by sharp differences in daily/weekly/monthly rainfall, average temperature, humidity etc., within the same agroclimatic zone. Analysis of meteorological data shows that the temperature and humidity can fluctuate widely on the same day or between two consecutive days, and such fluctuations are even higher than the difference between highest and lowest daily values experienced in a year.
It is possible to estimate the effect of changes in mean weekly or monthly temperatures and humidity between two years on crop yields, provided we have proper controls on other parameters affecting crop yield such as variety, seed quality, irrigation requirements and soil nutrient regime. India has 15 agroclimatic and 17 agroecological zones. It is unrealistic to assume that in a country with so many agroclimatic and agroecological zones and with a myriad of crops grown, the impact of temperature change on other weather parameters would be uniform, and the impacts of those changes on yields would be negative for all crops.
To understand the impacts of climate change on water, we should have long-term records of weather, hydrology and biophysical systems, so as to ascertain how hydrological conditions change with changes in weather parameters and land use and land cover. Crop models for analysing the effect of climate change on crop yields need to capture the effect of variability in weather parameters too, and this will be possible only if we do continuous monitoring of biophysical systems and weather parameters. We should design reservoirs which can absorb extremely variable flows for multi annual storage. Research is required on the development of drought-resistant crop varieties in semi-arid/arid regions, and flood resistant crop varieties in high-rainfall, sub-humid/humid regions.
Unfortunately, the priorities of our ‘climate action’ are presently misplaced, and significant investments are being made in water and agriculture sectors without having an integrated understanding of the likely impact of climate change on these sectors. The research on climate change impacts and adaptation strategies do not consider the reality of the monsoon climate in India which is ‘high year to year variation in weather parameters’. This has significant adverse implications on accuracy of models predicting climate change on hydrology and crop yields; and effectiveness of water management interventions for reducing climate change impacts on society.
The author is Executive Director of Institute for Resource Analysis and Policy. He is the author of six books and five edited volumes on water, energy and agriculture. Views are personal.
