On the heels of last week’s “climate strikes” across Canada and around the world, climate change remains a much-talked about—and hotly-debated— issue. Of course, many of the loudest advocates for aggressive government action claim the “science is settled.” Yet although climate scientists agree on the basic chemistry of the greenhouse effect, there’s no consensus on so-called “feedback effects”—and this is why some computer models predict catastrophic results whereas other projections are much more benign.

To see just how uncertain our knowledge really is, consider an article in the New York Times by physicist Sabine Hossenfelder who explains that scientists understand the equations that drive the climate system, but then admits “we don’t know how to solve them. The many factors that affect the climate interact with one another and give rise to interconnected feedback cycles. The mathematics is so complex, the only way scientists know to handle it is by feeding the problem into computers, which then approximately solve the equations.”

She adds that as the “Earth continues to warm, we face a future of drought, rising seas and extreme weather events. But for all we currently know, this situation could be anywhere between a mere annoyance and an existential threat.”

Now let’s turn to the economics literature. Last fall the UN’s Intergovernmental Panel on Climate Change (IPCC) issued a Special Report about what policymakers can do to limit global warming to 1.5°C. One of the lead authors of the report was Rachel Warren of the Tyndall Centre for Climate Change Research (located at the University of East Anglia in the United Kingdom). Suffice to say, Dr. Warren is not a “denier” or stooge for Big Oil.

It’s thus very interesting that Warren helped produced a 2018 paper, which says the “economic case for limiting warming to 1.5°C is unclear, due to manifold uncertainties. However, it cannot be ruled out that the 1.5°C target passes a cost-benefit test.”

This is quite a shocking declaration. Far from the now-popular goal of 1.5°C being a slam-dunk only “deniers” could doubt, this 2018 paper says we can’t rule out the possibility that the target provides more benefits than costs.

Finally, a recent study in Science concluded that planting trees could have enormous potential to mitigate climate change. If the study is correct, it means that standard estimates of the “social cost of carbon”—upon which carbon taxes are often based—might be far too pessimistic. For example, rather than being taxed at $50 for emitting an extra tonne of carbon dioxide in 2022—the schedule for the federal carbon tax favoured by the Trudeau government—what if instead a firm paid to have 10 new trees planted? Over a few decades, the new trees would more than absorb that additional tonne of carbon dioxide, at a cost of perhaps $5.

When it comes to climate change, the loudest advocates of aggressive government action often accuse skeptics of denying the “science.” Yet if we review the actual evidence with an open mind, we see plenty of reasons to doubt. The case for large carbon taxes and other government interventions—in the name of fighting climate change—is much weaker than the public has been led to believe.