ABSTRACT Mawdsley, R.J., Haigh, I.D., Wells, N.C., 2014. Global changes in tidal high water, low water and range. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 343–348, ISSN 0749-0208. Impacts of extreme sea levels are increasing as the population and infrastructure in coastal zones increases. Extreme high sea levels generally increased at a similar rate to mean sea level through the twentieth century at most sites around the world, suggesting that the same mechanisms are driving both increases. However, the simplicity of this conclusion belies the fact that many mechanisms known to act on the different components of sea level, have been observed to change in local and regional studies. Using a ‘quasi-global’ dataset of sea level records, this paper investigates changes in the tidal component of sea level and shows that changes in mean high and low waters, and hence tidal range, are...