Claim: “The world is just warming back up after the ‘Little Ice Age’, a natural cold spell centuries ago, and 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 triggered mainly by a series of large volcanic eruptions, and it hit different regions at different times. 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. At around 1.4°C, this is not a slight rise: the last ice age was only about 5–6°C colder.
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A recovery can’t explain it. When the volcanic cooling of the Little Ice Age faded, temperatures returned towards their earlier level. But today’s temperatures have gone far past that level, beyond anything in at least 2,000 years. A rebound can’t 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. The Sun’s output has been flat or slightly falling since the 1950s, and volcanoes cool the planet rather than warm it.
