Holocene Indian Summer Monsoon variability from the core monsoon zone of India, a pollen-based review.

Palaeoclimatic reconstructions from sediment cores of the Arabian Sea, Bay of Bengal, and other terrestrial ecosystems including lakes, peatlands and proglacial areas from the Indian subcontinent have been used to understand the past Indian Summer Monsoon (ISM) variability. The core monsoon zone (CMZ) of India is one of the most important regions to understand past ISM dynamics. Pollen based palaeoclimatic reconstructions in the CMZ of India suggest a progressive increase in the ISM during the Holocene. However, the results suggesting a weak ISM after the Younger Dryas (YD) cooling event are contrary to the observations made in other parts of the country. Besides this, the minor climatic fluctuations are difficult to find in most of the reconstructions. This may be attributed to poor sample resolution and chronological control. These limitations make it difficult to ascertain whether the response of vegetation to climatic change has been insignificant or whether this change is not reflected in the proxy (proxy response). As a consequence, we argue that pollen based palaeoclimatic reconstructions are one of the most widely used proxies and will be meaningful as backbone for climate models only if the reconstructions become more quantitative. [ABSTRACT FROM AUTHOR]