The Expanding Indian Desert: Evidence from a Weighted Epochal Trend Ensemble Analysis
IR@C-MMACS: CSIR-Centre for Mathematical Modelling and Computer Simulation, Bangalore
View Archive Info| Field | Value | |
| Title |
The Expanding Indian Desert: Evidence from a Weighted
Epochal Trend Ensemble Analysis
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| Creator |
Goswami, P
K V, Ramesh |
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| Subject |
Climate Modelling
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| Description |
One of the biggest challenges in climate research is to arrive at reliable future projections. However, while there
now exists a firm scientific basis and procedure for climate forecasts, numerical climate models still suffer from
large uncertainties. Observed local trends do reflect combined effect of both anthropogenic forcings and natural
variability over a location; however, projections based on a linear trend may have considerable error as the
trends are generally significantly non-linear owing to low frequency natural variability and the resultant changes
(second derivatives) in the trends. In this work we adopt a weighted epochal trend ensemble (WETE) approach
to assess the stability of the Indian desert with enhanced reliability. Ensemble techniques have generally helped
to reduce uncertainties in forecasts and the weighted epochal trend ensemble proposed here takes into account
the inherent non-linearity in the trend by considering a piece (epoch)-wise linear trend and its weighted
contributions to construct more reliable future projections of local climate change. We first show that epochal
trend ensemble provides better estimates of future projections by comparing observed rainfall over India during
1990-2003 with rainfall projected from a simple linear trend and an epochal trend ensemble. We then compute
projections of desert area over India based on annual rainfall and show that the Thar Desert in western India is
expanding in a south-east direction. A local desertification time-scale is defined as timescale over which the
annual rainfall over the location becomes persistently below the annual rainfall over Thar if the present trends
continue; many areas show desertification timescales less than hundred years, which may get downwardly
revised due to negative impact of increase in global warming. Both the simple linear trend and the epochal trend
ensemble projections indicate significant increase in the desert area over India over the next hundred years;
however, there are also significant differences between the two projections. The results of the validation are used
to choose the more reliable projection, which shows a sharp increase in the size of the Indian desert in the next
hundred years. While long-term climate projections have their inherent limitations, these can be used with due
care to develop policy decisions for least-regret scenarios.
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| Publisher |
CSIR Centre for Mathematical Modelling and Computer Simulation
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| Date |
2007-06
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| Type |
Monograph
NonPeerReviewed |
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| Format |
application/pdf
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| Identifier |
http://cir.cmmacs.ernet.in/182/1/rrcm0708.pdf
Goswami, P and K V, Ramesh (2007) The Expanding Indian Desert: Evidence from a Weighted Epochal Trend Ensemble Analysis. Technical Report. CSIR Centre for Mathematical Modelling and Computer Simulation, C-MMACS,Bangalore 560037,India. (Unpublished) |
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| Relation |
http://cir.cmmacs.ernet.in/182/
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