The National Academy of Sciences, an independent organization created by Congress to provide scientific guidance, has released an important new study. The AP leads with the Academy’s conclusion that the “recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia.” It’s an alarming fact, but ultimately, not the most significant. An excerpt from the study:
It should also be noted that the scientific consensus regarding human-induced global warming would not be substantively altered if, for example, the global mean surface temperature 1,000 years ago was found to be as warm as it is today.
Why is that? Because there are other things beside increased carbon dioxide emissions that can cause temperatures to rise. These factors “include volcanic eruptions, variations in the intensity of incoming solar radiation.”
Here is the really important point:
In particular, the numerous indications that recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia, in combination with estimates of external climate forcing variations over the same period, supports the conclusion that human activities are responsible for much of the recent warming.
In other words, the Academy factored in the natural variations in temperature — volcanic activity, solar radiation etc. — and concluded that these can’t explain the warming trend. What does explain it is increased carbon dioxide emissions from human activity.
Climate skeptics routinely point to other periods of time where there were temperature changes — the early 20th century, the “medieval warm period” — as “proof” that global warming isn’t real. This fundamentally misunderstands global warming science. The scientists have taken natural variations in temperature under consideration and concluded that the current warming trend is different. Human activity is driving it.
Fight back with the facts. Pledge to see An Inconvenient Truth.
(Note: Even if you’ve already seen the film, make sure to pledge and be counted.)