evidence: Much like archaeologists dig up artifacts to piece together stories of ancient civilizations, climate scientists dig up natural "artifacts" to piece together stories of past climates. From fossil pollen to air bubbles trapped in ice cores, these artifacts, or "proxies," allow scientists to compare current climate change to the past. This week, NOAA released the most comprehensive database ever assembled of proxies—many available publicly for the first time—that can tell scientists about temperatures since the last ice age ended roughly 12,000 years ago. [...] Paleoclimate proxies indirectly record climate and atmospheric conditions present when they formed or grew; air bubbles in ice cores sample past carbon dioxide levels, pollen and undecayed plant matter reveal growing conditions, and the ratio of oxygen isotopes in marine fossils indicate ocean temperatures. Proxies can come from all over the world — from glaciers in Antarctica to the tropical oceans — and compiling them into datasets can help place today’s warming climate into the context of a longer history. [...] By using records from multiple proxy sources, the scientists were able to cover every continent and ocean for a more complete reconstruction of Earth’s climate over the past 12,000 years. In addition, comparing multiple proxy sources against each other allows scientists to reconstruct a more reliable and consistent story.