Want a glimpse back in time? Then try USGS’s new paleoclimate website. There, you can explore many USGS paleoclimate studies that use information from the earth’s history to better forecast, plan, and adapt to future climate change.

Sources/Usage: Some content may have restrictions. View Media Details

Paleoclimates are preserved in marine, aquatic, and land settings around the world. USGS scientists search far and wide in unusual and exotic locations for clues.

Why Study Past Climates?

Climate change and its future impacts are a critical concern worldwide. Ecosystems, water availability, ocean acidity and circulation, sea-level rise, and natural hazards all interact with or respond to climate change.

Throughout geologic time, Earth’s climate has changed in response to many different forces. Paleoclimate studies provide an essential perspective on what causes climate change and the potential range and effects of future climate change on natural systems and people who rely on them.

By collecting data on past climates and their impacts on ecosystems, scientists can test and improve climate models that are used to project future climates. Evidence on the response of past ecosystems to a changing climate provides information on their resilience and guides resource managers and other decision makers on actions to mitigate the consequences of future climate change.

How Do Scientists Study Past Climates?

Modern climate records go back only a century or so – the blink of an eye on a 4.5-billion-year old planet! So, scientists unravel past climates and environments by examining climate proxies -- physical, chemical, and biological evidence preserved in sediments, corals and other climate archives that they retrieve on land and in waters around the world.

Sources/Usage: Some content may have restrictions. View Media Details

Sediments are the most commonly studied paleoclimate archive. Their ubiquity spans marine, fresh water, and land environments and extends back nearly 4 billion years. Layers of sediment contain many clues to what the climate was like at different time scales in the past. The types of minerals, fossils, chemistry, and the size and shape of sediment grains tells scientists about the salinity, temperature, oxygen and nutrient levels, and how past landscapes looked and evolved. Charcoal preserved in sediments and ice cores helps document the frequency and magnitude of past fires.

Corals are colonial marine animals that form reefs in shallow subtropical waters. They generate annual growth bands, similar to tree rings. Scientists analyze coral chemistry to reconstruct monthly, annual, and longer records of past ocean temperature and salinity. These data help to understand how climate phenomena such as El Niño and La Niña have varied through time.

Sources/Usage: Some content may have restrictions. View Media Details

Packrats also provide paleoclimate archives. They collect artifacts near their dens, and pile them into a heap that they preserve by urinating on it. The result is a packrat midden. The oldest middens date back 45,000 years, preserving plant and animal remains dating well before the last ice age. Middens are found from Canada’s Northwest Territories to Nicaragua and are treasure troves to climate scientists. They knew we’d need it someday!

What Do Different Time Spans Reveal?

Climate reconstructions span all timescales. Studies on the last few millennia help quantify rates and impacts of natural climate variations. Research on records between ten thousand and 2.6 million years old explores rates and magnitudes of change, climate extremes like the ice ages, global sea-level rise and other changes associated with variations in Earth’s orbit, its tilt, greenhouse gas levels, and ocean circulation. Deep-time studies extend beyond 2.6 million years to examine climate change related to plate tectonics and mountain building, extreme climates, and long-term carbon dioxide and climate patterns.

What’s the Latest Research and Why is It Important?

USGS scientists are leading research projects that are relevant to future food and water supplies, to hazard mitigation, and to natural resource management. Some examples…

Arctic Paleoclimatology

USGS scientists examine tiny fossils from the Arctic Ocean’s continental shelves down to its abyss to investigate the region’s climate back to 500,000 years. Research suggests that recent warming has reversed Arctic trends during the last few millennia. Because instrumental records extend back only a few decades and large annual and decadal variability, the causes of recent warming remain unclear. Yet understanding past Arctic climates is vital because of recent rapid changes. Last year, atmospheric carbon dioxide reached 400 ppm --a level not seen in 3 million years, and the extent and thickness of summer Arctic ice has decreased substantially since 1979.

Arctic research will shed light on potential future climate change, and guide decisions on ecosystems, endangered species, energy, and transportation issues.

Sources/Usage: Some content may have restrictions. View Media Details

East Coast Sea-Level Studies

Sea-level rise and storm surge are major threats along much of the U.S. East Coast. From New Jersey to the Florida Keys, the Eastern Seaboard is dominated by features formed when sea level was higher than it is now. A complex interplay of global climate, continental subsidence and rebound from ice age glaciers, regional tectonics, and ocean dynamics controls the shore’s elevation. This USGS led research is quantifying how those factors have influenced past sea level and how much sea level has varied. The findings inform decision makers tasked with protecting property and lives along the heavily populated East Coast.    

Water in the American West

Water availability in the western U.S. is an issue of great concern due to ever-increasing demands of a growing population. Precipitation patterns in the American West are influenced by surface temperatures of the North Pacific Ocean and atmospheric circulation patterns.

USGS is developing precipitation and drought records from the western U.S. that span the last 11,500 years. These records use pollen, charcoal, and geochemical analyses from sites throughout the American West to reconstruct climate variability and its impact on land and aquatic ecosystems. Integrating these data with paleoclimate records from the Pacific Ocean and elsewhere in North America improves understanding of how different regions are affected by natural patterns of climate variability. This work will inform efforts to meet water resource demands throughout the West and other parts of our Nation.  

Learn More:

See the new USGS Paleoclimate Research website