Evidence of the
Warming Globe

Scientists measure temperatures at thousands of weather stations, ocean buoys, and satellites around the world. They combine all those readings into a single number: Earth's global average surface temperature.

Today, Earth's average surface temperature is roughly \( 15\,^\circ\text{C} \) (about \( 59\,^\circ\text{F} \)). Even small changes to that average: a shift of \( 1\text{--}2\,^\circ\text{C} \): can have enormous effects on weather, ecosystems, and sea level.

Scientists don't just report the raw temperature. Instead they use a temperature anomaly: how much a year's temperature differs from a long-term baseline average.

A single degree may sound tiny, but Earth's climate is an enormous, interconnected system. A small average shift can trigger large changes across the planet.

Scientists rely on multiple independent data sources that all point to the same conclusion: the globe is warming. No single line of evidence stands alone.

NASA and NOAA datasets show that Earth's average temperature has risen roughly \( +1.1\,^\circ\text{C} \) since the late 1800s. The warming has accelerated sharply since the 1970s.

Earth's two great ice sheets: Greenland and Antarctica: contain enough frozen water to raise sea levels by over 65 meters if fully melted. Satellite measurements show both are losing mass at accelerating rates.

Global sea level has risen about 21-24 cm since 1880. Two processes drive this:

One of the most important distinctions in Earth science: these terms describe different time scales of atmospheric conditions.

When you encounter a claim about global temperature change, follow these steps to decide whether it counts as strong scientific evidence.

A student reads the following statement: "NASA reports that global average temperature has risen by \( +1.1\,^\circ\text{C} \) since 1880, based on data from thousands of surface stations and ocean buoys."

A neighbor says: "We had the snowiest winter in 20 years in our town. Global warming can't be real."

A report states: "Satellite data from 1979 to 2023 show that Arctic summer sea ice extent has declined by about 13% per decade."

The ocean has absorbed more than 90% of the extra heat trapped by greenhouse gases. This makes ocean heat content one of the most important indicators of warming.

Which of the following is the strongest evidence that Earth's global temperature is increasing?

A student says: "It snowed a lot this winter, so the Earth can't be warming." What is the main problem with this reasoning?

What are the two main causes of rising global sea levels?

What does a positive temperature anomaly of \( +0.8\,^\circ\text{C} \) mean?

Why do scientists use multiple independent sources (satellites, buoys, ice cores, tide gauges) when studying global temperature change?