Over the past 50 years, polymer manufacturing has been increasing at a very fast pace, from 15 million tons in 1964 to 381 million tons in 2015 and is expected to double again over the next 20 years. Although plastic has widespread applications because of its favorable mechanical properties, thermal properties, stability and durability, it is still vulnerable to weathering and degradation processes. During these processes, plastic reacts with its environment and releases additives and polymer degradation products throughout its lifetime. Here we demonstrate that most commonly used plastics emit methane and ethylene when exposed to solar radiation at ambient temperatures. Polyethylene, which is globally the most produced and discarded synthetic polymer, is the most prolific emitter for both gases. Through an extensive time series of 212 days, we also show that emissions of methane, ethylene, ethane and polypropylene from virgin pellets of low-density polyethylene increase with time. Moreover, environmentally aged low-density polyethylene debris collected in the North Pacific Subtropical Gyre also emitted hydrocarbon gases when exposed to ambient solar radiation. Due to the longevity of plastics and the large amounts of plastic that persist in the environment, gas production may occur throughout the degradation lifetime of plastic and may represent a source of climate-relevant trace gases for an extended period of time. Dr Sarah-Jeanne Royer is an oceanographer and a specialist on plastic degradation in the oceanic environment. She is currently working on this problematic at Hawai’i Pacific University on the Island of Oahu in collaboration with Scripps Institution of Oceanography at the University of California, San Diego. Her research focuses on common polymers including synthetic microfibers and their degradation times in the environment. She also investigates the different sources and sinks that connect plastic to the ocean such as the impact of the fishing industry with respect to the total mass balance of plastic discarded in the ocean. Prior to this work, she investigated the emissions of greenhouse gases from plastics in the environment at the Center for Microbial Oceanography, Research and Education. She also worked on marine debris at the International Pacific Research Center at the University of Hawaii. For more than a decade now, she has been working with several organizations (such Sustainable Coastlines Hawaii, Parley for the Oceans and The Ocean Cleanup) to share her science, bring awareness to the growing issue of plastic in the environment and organized several educational workshops. Her goal is to pursue plastic research to better understand the degradation and fragmentation processes of plastic and fate in the ocean in addition to the plastic accumulation on the different islands of Hawai’i. Her long-last objective is for policymakers to use data from scientists and volunteers to design better laws and policies to reduce plastic production & consumption.