Thursday 07 Jun 2018: Natural Decadal Climate Variability, Droughts and Their Impacts on Water and Food Securities, and Implications for National and International Policies
Vikram Mehta - The Center for Research on the Changing Earth System
Natural decadal climate variability (DCV) is one of the oldest areas of climate research. Building on centuries-long literature, a substantial body of research has emerged in the last two to three decades, focused on understanding causes, mechanisms, and impacts of DCV. Several DCV phenomena – the Pacific Decadal Oscillation (PDO) or the Inter-decadal Pacific Oscillation (IPO), tropical Atlantic sea-surface temperature gradient variability (TAG for brevity), West Pacific Warm Pool variability, and decadal variability of El Nino-La Nina events have been identified in observational records; and are associated with variability of worldwide atmospheric circulations, water vapor transport, precipitation, and temperatures; and oceanic circulations, salinity, and temperatures. DCV phenomena also modulate interannual and intraseasonal climate and weather variabilities.
Tree-ring based drought index data going back more than 700 years show presence of decadal hydrologic cycles (DHCs) in North America, Europe, and South Asia. Some of these cycles were associated with the rise and fall of civilizations, large-scale famines which killed millions of people, and acted as catalysts for socio-political revolutions. Instrument-measured data confirm presence of such worldwide DHCs associated with DCV phenomena; and show these phenomena’s worldwide impacts on river flows, crop productions, inland water-borne transportation, hydro-electricity generation, and agricultural irrigation. Fish catch data also show multiyear to decadal catch variability associated with DCV phenomena in all oceans.
This talk will give an overview of worldwide impacts of DCV phenomena, with specific examples of socio-economic-political impacts. Prospects for decadal climate, drought, and impacts predictions will then be outlined. Then, worldwide water, food, energy, and health security implications of DHCs; and national and international security implications will be described. Finally, an outline of needed actions, including international programs and policies, to adapt to impacts of future droughts caused by combinations of natural DCV and anthropogenic climate change will be presented.