Global climate warming is driving an increase in extreme weather events - such as intense precipitation and flooding in some regions, and droughts, water scarcity, and heightened wildfire risks in others. These climate-driven impacts represent some of the most pressing challenges currently facing both human societies and modern ecosystems. Developing a deeper understanding of the timing and magnitude of natural climate variability, along with its superimposed anthropogenic influences, is therefore critical for devising effective mitigating and adaptation strategies. While historical records offer insights into recent climate trends, they usually extend back no more than 200 years and are thus insufficient for studying climate variability on geological timescales, particularly during intervals considered as analogues of current and future climate change. To address these limitations, CYANITE investigates the potential of heterocyte glycolipids (HGs) and HG-based indices, such as the HDI26, as novel organic temperature proxies using lake archives. These components derived from heterocytous cyanobacteria, which are a common component of the phytoplankton community in lakes worldwide, have been shown previously to occur in lake sediments from polar to tropical climate regions. Their presence in late Cretaceous sediments also indicates that they preserve well over time and potentially allow the reconstruction of lake surface water temperatures worldwide across the Cenozoic and thus covering some important time periods that are considered as analogues for near future warming including the Middle Miocene Climatic Optimum (MMCO) and mid-Pliocene warm period (mPWP). CYANITE will unlock the full potential of heterocyte glycolipids for climate research and establish the first organic temperature proxy that allows reconstructing continental climate change in high resolution using lake archives.
