Evidence - NASA Science: Climate Change

Key Takeaways

• Earth's climate has historically changed, but the current warming rate is unprecedented over the past 10,000 years.
• Human activity's influence on climate warming is now an established fact according to IPCC.
• Evidence of climate change is evident in both historical data (ice cores, tree rings) and modern technology (satellites).
• The rate of climate change since the mid-20th century is unprecedented.

Historical Climate Changes

• In the last 800,000 years, Earth experienced eight ice age cycles.
• Climate changes resulted mainly from variations in Earth's orbit affecting solar energy received.
• Current warming is human-induced, starting in the mid-1800s, with rapid atmospheric, oceanic, and biospheric changes.
• Carbon dioxide and other gases trap heat, contributing to warming.

Evidence of Rapid Climate Change

Global Temperature Rise

• Average surface temperature rose about 2°F (1°C) since the late 19th century.
• Most warming occurred in the past 40 years, with 2016 and 2020 as the warmest years.

Ocean Warming

• The ocean absorbed significant heat, particularly in the top 100 meters, warming by 0.67°F (0.33°C) since 1969.

Ice Sheets Shrinking

• Greenland and Antarctic ice sheets are losing mass rapidly.
• Greenland lost an average of 279 billion tons annually (1993-2019), Antarctica about 148 billion tons.

Glacier Retreat

• Global retreat of glaciers is observed in major mountain ranges and regions.

Snow Cover Decrease

• Northern Hemisphere spring snow cover has diminished over the last 50 years.

Sea Level Rise

• Global sea level increased about 8 inches (20 cm) in the past century, with accelerated rates in recent decades.

Arctic Sea Ice Decline

• Both extent and thickness of Arctic sea ice have decreased significantly.

Increase in Extreme Events

• Higher frequency of record high temperatures and intense rainfall events in the U.S.

Ocean Acidification

• Surface ocean water acidity increased by 30% since the Industrial Revolution.
• Oceans absorb 20-30% of human carbon dioxide emissions annually.

Conclusion

Scientific evidence from multiple sources confirms rapid climate change, primarily driven by human activities such as increased greenhouse gas emissions.