A new study published in BioScience questions claims that jellyfish are increasing worldwide, and suggests that such claims currently are not supported with any hard evidence or scientific analyses to date. Increased speculation and discrepancies about current and future jellyfish blooms by the media and in climate and science reports formed the motivation for this Working Group to convene at NCEAS to examine available data. Over 30 researchers have contributed to this research, assembling globally distributed jellyfish data to examine global jellyfish trends for the first time.