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Paleoclimatologists study environmental evidence to understand what the Earth’s past climate was like and why. They use proxy climate records to estimate past conditions and extend our understanding of climate that existed long ago.

What Is a Paleoclimate?

Fossilized leaves

According to the AMS Glossary of Meteorology, a paleoclimate is the “climate for periods prior to the development of measuring instruments, including historic and geologic time, for which only proxy climate records are available.” Examples of proxy climate records include historical documents and data preserved within corals, pollen grains, ice cores, tree rings, and ocean and lake sediments. 

Data, Maps, and Tools

View U.S. paleoclimate data from 14002017, showing how many summers each region has been in drought. 

Drought From 1400–2017

This map shows the number of summers from 1400 to 2017 with moderate to extreme drought, based on the Living Blended Drought Product (LBDP). While the dataset extends to year 0 in some locations, full coverage of the lower 48 U.S. states is not available until 1400. The LBDP is a recalibrated data series of June-July-August Palmer Modified Drought Index (PMDI) values in the lower 48 U.S. states, blending tree-ring reconstructions and instrumental data to estimate the average summer PMDI values. Learn more.

Number of Summers Area Was in Drought

The color with the hex code #faf3ce identifies:
20 – 40
The color with the hex code #faea96 identifies:
41 – 61
The color with the hex code #ffe971 identifies:
62 – 82
The color with the hex code #f9c555 identifies:
83 – 103
The color with the hex code #f3a43f identifies:
104 - 124
The color with the hex code #a9512a identifies:
125 - 145
The color with the hex code #501011 identifies:
146 - 167

Paleoclimatology and Historical Drought


Tree-ring and lake-sediment records indicate that "megadroughts" have occurred in North America over the last thousand years. According to those proxy records, it appears that those persistent droughts lasted longer than droughts experienced since we’ve had instrumental records.


Earth’s climate is variable and always changing. For example, during the past two million years much of the northern hemisphere has been covered in glacial ice with sea levels lower by as much as 410 feet during glacial periods. In contrast, the Cretaceous Period (between 145.5 and 65.5 million years ago) saw conditions that were significantly warmer than today, with less polar ice and rising sea levels.

Research & Learn | Historical Drought

Drought is a normal climate pattern that has occurred in varying degrees of length, severity, and size throughout history. Learn more about historical drought.

Data & Maps | Historical Data and Conditions

View a collection of historical drought conditions for the U.S., including statistics, map and data archives, and time series. Explore three historical drought datasets side by side on an interactive map.


Paleoclimatology Research and Resources