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Looking out my window in Ottawa, where it snowed yesterday and today and we tied the record for most days with at least 10 cm of snow cover, just in time for the new carbon tax that will supposedly save us from all this warming, I found myself wondering: If you weren’t dogmatically persuaded that the Earth was heating up dangerously because of man-made CO2, how would you know unexpected cold was merely weather while expected or unexpected heat proves climate change?

For starters, how would you know the Earth is dangerously heating up? They could check temperature records, of course. Indeed it would seem the most logical thing to do. And it all seemed so clear for over a decade after James Hansen’s compelling 1988 testimony to a U.S. Senate Committee, intentionally scheduled for a hot day in a room where the air conditioning had been intentionally disabled. More CO2 means hotter temperatures. But if you did check the records you’d find them distinctly ambiguous.

They show early 20th-century warming, a cooling from around 1940 to 1970, then warming to around 2000 after which temperature flatlines except for an El Nino spike in 2016, none of which fits the theory of a simple, obvious relationship between CO2 and temperature. Worse, temperature records show cycles lasting centuries including warming from the Dark Ages until around 1200 then cooling through 1700 then warming again. How would you know the last bout of warming was natural until 1970 and man-made afterward? How would you check?

I won’t even get into the longer geological record’s absence of any hint that CO2 drives temperature. But while dogmatists speak dogmatically about global temperature when calling 2018 the 4th-hottest year ever, we have few measuring stations over much of the Earth’s surface, especially the wet bits, and little reliable historical data. Even so, what data we have says in the United States, with the best historical and current coverage, 2018 was only the 14th-warmest year since 1880 which, given a general warming trend, doesn’t suggest that we’re accelerating toward disaster.

Ah, they may say, never mind because 97 percent of the world’s scientists agree that we are. But how would you know that if you weren’t convinced a priori? How would you know how anyone managed to ask them, or when or how and what they found. Dig here and you’ll get a nasty surprise. (For details see my column last week.)

When it comes to the recent devastating cyclone in Mozambique, if you didn’t know it was due to climate change, how would you check? Presumably you’d go and look at historical records to see if Mozambique never used to have dangerous cyclones, and whether such storms seem to be increasing in frequency, intensity or both, locally or globally. They don’t.

As for the scurrilous claim that climate skeptics are in it for the money, if you didn’t already know your opponents were not just stupid but evil, how would you check? If you tallied up the government and foundation grants available to those who promote alarmist views against the amount available from those same sources or others for those who raise questions you’d rapidly discover that the David and Goliath labels were reversed and with them that of venality. (By the way, if anybody knows who these oil companies are that lavishly fund skeptics, please give me their names and phone numbers right away.)

Then there’s this business of brushing aside naifs who point out the window at the snow with the patronising claim that the issue isn’t global warming, it’s climate change. Well, if it were not holy writ for you, how would you decide whether man-made CO2 really was changing the climate? I guess you’d have to go and look at evidence, including those cyclones and snowfall patterns that keep defying model predictions, or polar bears and coral reefs that just won’t die on cue. If the indicators of climate change refuse to change you can’t blame CO2 for changing them, just as you can’t jail someone for murder if the victim insists on walking into the courtroom.

When you go looking for the killer floods unleashed by rising sea levels that wash away vulnerable Pacific islands, you won’t find them. As for more forest fires, more floods, worse droughts, and so on you’d discover that not even the United Nations’ Intergovernmental Panel on Climate Change says they’re happening. Just that they’re going to. Later. But we can’t wait for proof. We must take drastic action now because… because…

Well, how would you know it’s urgent? And how do the people claim to know who are making big decisions that affect our lives? I started the Climate Discussion Nexus website to discuss what the evidence really shows, and I hope you’ll join the conversation.