Atmospheric CO2 will reach the projected level he pointed to on his chart (about 500 ppm) by 2056.

Pending ●●●●●

“Within less than 50 years, it will be here,”

Said on: 24 May 2006 · Film An Inconvenient Truth (2006), on a scissor lift beside a CO2 graph; the level (~500 ppm) is as described by Yale Climate Connections
Source: A look back at 'An Inconvenient Truth,' 20 years later · Skeptical Science (repost of Yale Climate Connections)
Should come true: 2056
How sure they sounded: it will be (no hedge)
Categories: Climate
Importance: 4 of 5 · Global CO2 concentration drives warming worldwide.

Outcome

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History