By Tom Harris

Earth Hour will be observed across the world on Saturday from 8:30 to 9:30 pm local time. Rather than switch off lights to show solidarity with the climate change movement, the public should switch off Earth Hour.

The event is not focussed on cost effective, achievable objectives such as reducing pollution or conserving energy. Earth Hour organizers tell citizens to “use your power to change climate change,” as if we had a global thermostat.

Climate has been changing, at times far faster than today, for billions of years, and it will continue to change no matter what we do. Yet Earth Hour spokespeople insist that all natural climate drivers such as changes in cloud cover, ocean currents and the sun are dwarfed by the impact of carbon dioxide (CO2) emissions from fossil fuels, the source of 86% of world energy consumption. They say that climate catastrophe lies ahead unless we spend vast sums to change the way we generate energy.

For this to make sense, several conditions would have to be met.

We would have to be confident that future global warming, if it occurs, will be dangerous. In the past 150 years, we have seen a warming of about 0.8 degrees Celsius despite a supposed 40% increase in atmospheric CO2 levels. This has been highly beneficial as we emerged from the Little Ice Age. So, it is only future rise that could be of concern. And for it to be worth public debate, let alone billions of dollars to try to stop, that rise would have to be dangerous.

The probability that future global warming, if occurs, will be dangerous is about 2%, according to Dr. Tim Ball, former University of Winnipeg climatology professor. His conclusion is supported by the 2015 report of the Nongovernmental International Panel on Climate Change (NIPCC) which asserted: “No evidence exists that… [a warming of 2°C, which the UN says we must avoid] would be net harmful to the global environment or to human well-being.”

But let’s be generous to Earth Hour activists and assume a 10% chance that future global warming, if it happens, will be dangerous.

We would also have to know that the cause of this change would be increasing CO2 concentrations. CO2 rise is not a concern otherwise since it is not a pollutant.

450 million years ago, CO2 levels were 11 times today’s, but the Earth was stuck in an extended cold period. At other times, it was hot when CO2 levels were high. At other times, it was neither unusually hot nor cold. There is no consistent correlation between CO2 and temperature in the geologic record.

And according to the NIPCC report, “No close correlation exists between temperature variation over the past 150 years and human-related CO2 emissions.”

Ball says that, if dangerous global warming were to occur, the odds of it being caused by rising CO2 are effectively zero. Natural factors play a far more major role, he and others assert. However, let’s assume a 10% likelihood for this step.

For Earth Hour’s goals to be rational, we would also have to know that CO2 levels will actually rise as a result of increasing emissions from fossil fuel consumption.

While most people assume CO2 concentrations have risen in recent centuries, some scientists dispute this. Ball says, “The CO2 level from pre-industrial times was completely manipulated to show a steady rise from 270 ppm to the current 400 ppm. Scientifically valid chemical measurements of 19th century CO2 levels in excess of those of today were simply ignored.”

He concludes, “we should not assume CO2 levels will rise in the foreseeable future.” Ball assigns a 20% probability that CO2 levels will rise. Let’s assume the odds are 75%.

But is this rise, if it occurs, caused mainly by human activities? Or could it come mostly from natural sources such as the ocean? Ball says there is a 2% chance that any future CO2 rises will have been caused by industrial activity. We will say there is 50% chance.

Calculating the product of our probabilities — 10% x 10% x 75% x 50% — reveals that there is only a one in 260 chance that future global warming, if it occurs, will be dangerous and caused by our CO2 emissions.

But we would still have to know that, were global warming problems ahead, it is more cost effective to reduce CO2 emissions (mitigation) than simply to adapt. Ball and others assert that there is only a slim chance that mitigation is the most cost effective approach.

So the likelihood that Earth Hour’s goals make sense are miniscule. It’s time that environmentalists kicked climate campaigners off the stage and focussed on problems we know to be real.

Tom Harris is Executive Director of the Ottawa, Canada-based International Climate Science Coalition.