Global warming — Science definition

The rise in Earth's average surface temperature over the past century-plus, linked to human-caused increases in greenhouse gases.

Where it is taught

In use

More greenhouse gas means more outgoing heat gets caught near the surface, and the result is global warming — the steady rise in Earth's average temperature measured over the past hundred-plus years.

Climate & the Greenhouse Effect

Questions using global warming

Problem 1

What is the key difference between the natural greenhouse effect and the human-caused concern often called global warming?
  1. The greenhouse effect itself is natural and necessary; the concern is that human activity is increasing greenhouse gas concentrations, enhancing the effect and raising temperatures further.
  2. There is no difference; they are the same process.
  3. The greenhouse effect only happens at the poles.
  4. Global warming is caused by too much oxygen in the atmosphere.
Answer and explanation

The greenhouse effect itself is natural and necessary; the concern is that human activity is increasing greenhouse gas concentrations, enhancing the effect and raising temperatures further.

The natural greenhouse effect keeps Earth livable. The concern is that burning fossil fuels and other activities have added extra greenhouse gases, intensifying the natural effect and pushing global average temperatures higher.

Problem 2

A cold winter in one country is weak evidence against global warming because
  1. winters are always cold
  2. a single place over one season is not a global average over decades
  3. temperature cannot be measured
  4. warming only affects summers
Answer and explanation

a single place over one season is not a global average over decades

Climate claims are about long-term global averages, so local short-term variation does not test them.

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