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Claude Sonnet 5Oct 13, 2026anthropic/claude-sonnet-5-20260630

Is climate change real?

Yes, climate change is real, and this is one of the most well-established findings in modern science. Here's a summary of what we know:

The Evidence

Global temperatures are rising. Instrumental records show the Earth's average surface temperature has increased by roughly 1.1–1.2°C (about 2°F) since the late 19th century, with most of that warming occurring in the past 40 years.

Multiple independent lines of evidence confirm this:

•Ice cores, tree rings, and sediment records show current warming is unusual compared to the past thousands of years
•Glaciers and ice sheets are shrinking — Greenland and Antarctica are losing mass, and mountain glaciers worldwide are retreating
•Sea levels are rising due to thermal expansion of water and melting ice
•Ocean heat content has increased significantly
•Arctic sea ice is declining in extent and thickness
•Extreme weather patterns (heat waves, heavy precipitation events) have shifted in ways consistent with a warming climate

The Cause

The overwhelming scientific consensus — based on physics, atmospheric chemistry, and extensive peer-reviewed research — is that human activities, primarily the burning of fossil fuels (coal, oil, gas) and deforestation, are the dominant driver of this warming since the mid-20th century. This happens through the greenhouse effect: carbon dioxide, methane, and other gases trap heat in the atmosphere, and their concentrations have risen dramatically since industrialization (CO2 levels have gone from ~280 ppm pre-industrial to over 420 ppm today).

Scientific Consensus

Major scientific organizations worldwide — including NASA, NOAA, the IPCC (Intergovernmental Panel on Climate Change), national academies of science from dozens of countries, and virtually every major scientific body studying the climate — agree on both the reality of climate change and its primarily human-caused nature. Studies of peer-reviewed climate literature consistently find that 97%+ of actively publishing climate scientists agree on human-caused warming.

If you'd like, I can dig into specific aspects — like regional impacts, projections for the future, or the policy debates around addressing it — just let me know what angle interests you.

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