Claim: “The world is just warming back up after the ‘Little Ice Age’ - it’s been this warm before.”
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A recovery only takes you back to where you started, not far beyond it. The Little Ice Age was a cool spell that scientists think was triggered by a series of large volcanic eruptions and lower solar activity. As those effects faded, temperatures returned towards normal.
But the world is now warmer than at any time in at least 2,000 years, well above where it was before the Little Ice Age began. That extra heat needs a cause, and the evidence points clearly to our greenhouse gas emissions.
This chart (published in The Conversation) is a number of years old, and the line would now extend even further up to almost 1.5°C - very clearly a far bigger change than the Little Ice Age delivered.
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A recovery can’t explain it. Today’s temperatures have gone far past the levels that existed before the Little Ice Age, beyond anything in at least 2,000 years. A rebound does not overshoot like that. Something has to be adding the extra heat, and the evidence shows it’s greenhouse gases:
The physics has been known for over 150 years. Scientists in the 1850s showed in the lab that CO₂ traps heat. We have since raised atmospheric CO₂ by more than 50%.
Satellites measure the extra heat being trapped. Less heat escapes to space at exactly the wavelengths CO₂ absorbs.
The pattern is a fingerprint. If the Sun were responsible, the whole atmosphere would warm. Instead, the upper atmosphere is cooling while the surface warms, which is what happens when greenhouse gases trap heat lower down.
Natural causes have been ruled out. A dip in the Sun’s activity, known as the Maunder Minimum (about 1645–1715), added to the Little Ice Age cooling, and its recovery helped temperatures return towards normal. But that recovery was over long ago. The Sun’s output has been flat or slightly falling since the 1950s, while temperatures have risen fastest. And volcanoes cool the planet rather than warm it.
