Climate change has become the greatest single threat to coral reefs globally. First documented in the early 1980s, mass coral bleaching (i.e., bleaching that spans tens to thousands of kilometers) has become one of climate change's most visible marine ecological impacts. Coral bleaching has become more extensive, frequent, and intense. This can be seen in the acceleration of marine heatwaves that cause mass bleaching. It's clear that remotely monitoring coral reefs and providing actionable intelligence are critical for early detection, on-the-ground response, communication, and enhancing coral reef resilience.

In response to these, NOAA established the Coral Reef Watch (CRW) program. For more than 20 years, CRW has utilized remote sensing, modeled and in-situ data to predict, observe, and alert users globally to threats to the coral reef environment. The near real-time satellite products and modeled predictions that comprise CRW's global 5km-resolution early-warning system of coral reef environmental changes have successfully and accurately predicted and monitored all major mass coral bleaching events observed globally since 1997, and have provided other critical information to users, especially during periods of severe oceanic heat stress.

Marine resource managers, scientists, decision makers, in-water coral reef monitoring networks, and other coral reef stakeholders rely on NOAA CRW's satellite and modeled products and alerts to: predict and monitor in near real-time changes in thermal stress in the coral reef environment; prepare and prioritize resources for events (e.g., mass coral bleaching or disease) that have long-term, ecologically-significant impacts on coral and reef health and function; communicate, quickly and broadly, among agencies, the press, and the public, changes in the status of local reefs; implement timely, protective responses and adaptation actions; analyze climate change impacts (e.g., bleaching, disease, and mortality) on coral reefs; and assess when specific reefs are vulnerable or resilient to anthropogenic climate change and its impacts. Using the information the CRW team and its products provide, users not only activate their coral bleaching & disease response plans, incident action plans, and associated in-water monitoring networks, but they also reduce local stressors (e.g., by closing scuba diving and fishing areas), rescue native and rare corals, and shade/cool key nursery reefs. CRW's satellite and modeled products support conservation, restoration, and resilience-based research and management projects that aim to protect and/or restore coral reefs in a rapidly warming world. In times of low or no heat stress, users also apply CRW products to identify appropriate locations for and implement conservation and restoration initiatives, to give transplanted corals or corals grown in-situ the best chance at survival. Additionally, our work informs many national and international assessments of coral reef conditions.

CRW is part of the NOAA Coral Reef Conservation Program and the National Environmental Satellite, Data, and Information Service. CRW's satellite product suites are a key component of NOAA's monitoring efforts for coral reef ecosystems, including the National Coral Reef Monitoring Program.