Solar irradiance is one of the most important factors influencing coral reefs. As a majority of their nutrients is obtained from symbiotic photosynthesizing organisms, reef-building corals need irradiance asa fundamental source of energy. Seasonally low irradiance at high latitudes may be linked to reduced growth rates in corals and may limit reef calcification to shallower depths than that observed at lower latitudes. However, high levels of irradiance can lead to light-induced damage, production of free radicals, and in combination with increased temperatures, can exacerbate coral bleaching. This layer represents the Maximum Monthly Climatological Mean of Irradiance (Einstein/m2d) from 2002 – 2013. Irradiance is actually PAR (photosynthetically available radiation), which is the spectrum of light that is important for photosynthesis. Monthly and 8-day, 4 km (0.0417 degree) spatial resolution data were obtained from the MODIS (moderate re solution imaging spectroradiometer) Aqua satellite from the NASA OceanColor Web (http://oceancolor.gs fc.nasa.gov/cms/).This layer was developed as part of a geospatial database of key anthropogenic pressures to coastal waters of the Main Hawaiian Islands for the Ocean Tipping Points project (http://oceantippingpoints.org/). Ocean tipping points occur when shifts in human use or environmental conditions result in large, and sometimes abrupt, impacts to marine ecosystems. The ability to predict and understand ocean tipping points can enhance ecosystem management, including critical coral reef management and policies to protect ecosystem services produced by coral reefs. The goal of the Ocean Tipping Points Hawaii case study was to gather, process and map spatial information on environmental and human-based drivers of coral reef ecosystem conditions.