What we knew already

Star-Telegram | Don Erler:

“Science gives, and depending on our political perspectives, it also takes away. As we've learned in recent days, the "world's leading climate scientists, in their most powerful language ever used on the issue, said global warming is 'very likely' caused by humans." ... This is a revelation? Aren't you glad that hundreds of scientists and representatives of 113 governments have solved a non-mystery?”

Ed Cognoski responds:

Mr Erler uses a neat rhetorical trick in response to this alarming report by the United Nations' Intergovernmental Panel on Climate Change (IPCC). He pretends it doesn't matter. He neatly turns from denial to d'oh, asking sarcastically why human involvement in climate change comes as a revelation to anyone. After years of denial, Mr Erler now says, of course, we knew that all the time. Non-mystery. Self-evident. No big deal. Doesn't change a thing.

The global warming deniers have used three lines of defense in their battle against environmental science. First, that global warming is a myth. Second, that it's not caused by humans. Third, that it's no big deal, maybe not even bad for humans, and certainly not worth combatting.

Gradually, but inevitably, those lines of defense have crumbled, one by one. Hardly anyone denies anymore that the globe is warming. With this latest update by the IPCC, it looks like human causation is now impossible to deny any longer, too. But don't count out Mr Erler.

• "Thirty years ago, many climate scientists predicted that human activity would soon create a new ice age."

  No, some scientists predicted that the Earth may be entering another cyclical, natural ice age. That may still be true. We'll know in a few thousand years whether they are right. In the meantime, human-induced global warming is likely to exact huge dislocations on humans in a matter of decades. We'll know in the lifetimes of many people alive today.

• "On the IPCC's own showing, there is no 'scientific consensus' on anything except the nearly self-evident proposition that human activity affects climate."

  Science can't predict exactly how much the sea level will rise. But it doesn't need to know whether it's going to be exactly 7 inches or 23 inches for fair-minded observers to accept that there is a scientific consensus that global warming is leading to a disastrous rise in sea levels. 1250 authors and 2500 expert scientific reviewers contributed to the report. That's scientific consensus.

• "Huge variations in temperature and sea levels have occurred and continue to happen without human intervention."

  Yes, they have, and the environmental disruptions were enormous. The current climate changes threaten to be worse than these natural cycles. Whereas ice ages come and go in periods of 10,000 to 20,000 years (with major ice ages every 100,000 years or so), what we're looking at now is temperature change as great or greater in a period of only decades or centuries. Why would we want to cause such disasters through deliberate human behavior?

Mr Erler concedes that the Earth is warming, and he's willing to admit that humans play a role, even pretending that we knew that all along, but he's still stuck on the belief that what we're witnessing is mostly natural, just another in a long cycle of climate change. The IPCC report makes that line of defense untenable any longer. The debate now leaves the likes of Mr Erler behind and turns to what to do about global warming and its human causes.