Topic: Climate

Scientists studied ancient Antarctic ice to learn about Earth's climate over the past 3 million years. They found a surprising pattern: while the planet cooled, greenhouse gas levels only changed slightly.

Scientists have long known that our planet was much warmer about 3 million years ago. Fossils of temperate and subtropical forests were found in places like Alaska and Greenland, and ancient shorelines along the U.S. East Coast showed that sea levels were much higher. But why this warm period happened and then cooled down has remained a mystery.

A team of researchers from Oregon State University and Princeton University analyzed ice cores from Antarctica to reconstruct Earth's climate over the past 3 million years. They found that while the planet gradually cooled, greenhouse gas levels in the atmosphere only changed slightly.

The research was led by Julia Marks-Peterson and Sarah Shackleton, who used measurements of noble gases preserved in trapped air bubbles to estimate changes in ocean temperature over time. Their findings show that average ocean temperatures have dropped by about 2 to 2.5 degrees Celsius over the past 3 million years.

The team also measured carbon dioxide and methane levels spanning the past 3 million years, finding that these levels generally stayed below 300 parts per million during this period.

Why It Matters

Understanding Earth's climate history is crucial for predicting future changes. This research can help us better understand how our planet has changed in the past and what might happen in the future.

Key Facts

• Scientists studied ancient Antarctic ice to learn about Earth's climate over the past 3 million years
• The planet cooled, but greenhouse gas levels only changed slightly during this time
• Researchers used measurements of noble gases to estimate changes in ocean temperature
• Carbon dioxide and methane levels generally stayed below 300 parts per million during this period

Key Terms

Greenhouse gases

Gases that trap heat in the Earth's atmosphere, such as carbon dioxide

Implications

Understanding Earth's climate history is crucial for predicting future changes. This research can help us better understand how our planet has changed in the past and what might happen in the future.