300
million years ago
24
°F

Paleoclimate

Paleoclimate Timeline graphic

As planet Earth took form, agglomerated from leftover debris surrounding the newborn sun, it settled into a rather remarkable position. Our home world, about 4.5 billion years old, happened to combine the right materials with the correct distance from our host star to blossom into a hospitable planet, covered in water, vegetation and roaming wildlife of all varieties.

For some 3.7 billion years, life and the planet continued to evolve together, entwined in a mutual ebb and flow of evolutionary creation and cataclysmic devastation. Temperature records—compiled from miles-long ice cores filled with preserved gas bubbles and the remains of unicellular ocean-dwellers—can be compared to the fossil record to help scientists fill in the timeline of Earth’s history. The Cambrian explosion, for example, some 541 million years ago, saw a proliferation of complex life in the world’s oceans, possibly brought about by an increase in oxygen. The Permian extinction 252 million years ago, sparked by a rapid increase in volcanic activity and CO2 in the atmosphere, wiped out some 90 percent of all marine species and 70 percent of terrestrial species.

The planet’s ebbs and flows continue today, with one notable additional variable: humans. For thousands of years, our species has manipulated the climate through agriculture, deforestation, herding and other land use. And in just the past 100 years or so, we’ve extracted and burned exorbitant amounts of fossil fuels in the forms of coal and oil—fuels that were largely created over millions of years as dead plankton and other organic material was buried under the seafloor. Powering our rails and our cars, our factories and our homes has released hundreds of billions of tons of CO2 into the atmosphere, mirroring large-scale carbon emission events of the distant, prehistoric past.

Graph of global temperatures from the previous 20,000 years

The result, as observed and confirmed by thousands and thousands of scientific papers, is a period of rapid global warming, unprecedented in geologic history. The graph above gives a sense of temperature changes over the past 20,000 years, with a major spike in the past century, and two projections of future temperatures for the next 3,000 years that depend on whether our species manages to curb its carbon emissions.

“The history of our planet has been marked by changes in temperature” as well as “the ever-throbbing drum of evolving organisms,” says Kirk Johnson, the director of the Smithsonian’s National Museum of Natural History. “But climate change is different.” Though the planet has been hot before—hotter than it is now—today’s rate of change has never been seen in the temperature record.

By examining the 400-million-year timeline of Earth’s climate history below, compared to the last 20,000 years, we may better understand the changes we are driving and the possible futures we face as a species—and as the only known planet of living beings.

iceberg icon

Timeline Key

World Without Ice Caps


World With Ice Caps


Climate Event


Associated Event


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