COPENHAGEN – The United Nations Climate Change Conference in Paris later this month is being billed as an opportunity to save the planet. It is no such thing. As I show in a new peer-reviewed paper, even if successful, the agreement reached in Paris would cut temperatures in 2100 by just 0.05° Celsius. The rise in sea level would be reduced by only 1.3 centimeters.

This may seem surprising: we constantly hear how every country has made important commitments to reduce CO2 emissions – the so-called "Intended Nationally Determined Contributions,” or INDCs. According to the UN’s climate chief, Christiana Figueres, "the INDCs have the capability of limiting the forecast temperature rise to around 2.7ºC by 2100, by no means enough but a lot lower than the estimated four, five, or more degrees of warming projected by many prior.”

Figueres suggested that the Paris agreement will cut almost 2°C of warming, from 4.5°C to 2.7°C. Though her wording was crafted to avoid actually saying this, it was, predictably, what most people heard. But the reduction consists almost entirely of made-up numbers and wishful thinking.

The expected rise of 4.5°C is based on almost 10,000 gigatons (Gt, or billion tons) of CO2 emitted during this century, with all other greenhouse gasses converted to CO2 equivalents. But nobody actually believes this figure – even the UN Environment Programme estimates that with absolutely no climate policies, we would emit 7,750Gt, which might lead to a 3.8°C rise. So, the extra 0.7°C rise is simply made up: climate policies can’t take credit for reducing it, because it was never going to happen in the first place.

Keeping temperature rises to 2.7°C will require the world to restrict emissions to about 4,700Gt. So, in order to live up to Figueres’ promise, we should expect Paris to cut about 3,000Gt. It will not.

Figueres’s own organization estimates that the total reduction promised from 2016 to 2030 will amount to 29-33Gt, or 1% of what is needed to get to 2.7°C. Achieving the other 99% is based on the aspiration that, while little will happen from 2016-2030, right after that countries will step up and begin dramatic emissions cuts. Recent history renders this implausible.

Back in 1997, when the world signed the Kyoto Protocol, almost everyone expected that it would be just the first step toward deep emissions reductions. Yet the cuts envisioned in Paris by 2030 are just one-third higher than what was promised in Kyoto. And the Kyoto treaty, which required no action from developing counties, was repeatedly renegotiated to the point where it didn’t require any cuts at all. The United States dropped out, and Canada, Russia and Japan eventually abandoned it as well. Just 12 years later, great expectations were met with utter failure at the 2009 climate summit in Copenhagen.

It is only slightly less far-fetched to hope that countries won’t just live up to their Paris promises in 2030, but will extend these cuts throughout the twenty-first century. After all, that is certainly not what governments are offering. The US, for example, clearly says that its "target is for a single year: 2025.” We could even assume that countries trying to cut their emissions won’t just move energy-intensive production to other countries. (Under the Kyoto Protocol, about 40% of emissions leaked this way, with the EU’s entire reduction circumvented through higher imports just from China.) And we could believe that every single country will fulfill every single promise.

Yet, even with these heroic assumptions, the total temperature reduction would be a very modest 0.17°C. A simple model of sea-level rise reveals that we would avoid perhaps 2.6cm. And, though more than 500Gt of emissions would be cut, we would still be 2,500Gt short of Figueres’s promise.

Many environmental campaigners are outraged by my scientific analysis showing how little Paris will matter. Their anger is surprising, because the math is simple: we’re hoping for 3,000Gt but only committing to 30Gt, and history strongly suggests that even those promises are unlikely to be met.

But, along with much of the climate-policy establishment, campaigners have invested two decades in pushing for the Kyoto-Copenhagen-Paris process that has so far delivered so little. Wishful thinking, it seems, is easier than acknowledging the flaws in their approach.

Just as we saw in Kyoto, many argue that countries will go far beyond their promises in coming decades. The US has suggested it might cut emissions by 80% by 2050. Yet the average of all the top energy-economic models suggest that such a cut would cost more than one trillion present-day dollars annually, with realistic annual costs approaching $2.5 trillion.

Similarly, the EU has vowed to cut at least 80% by 2050; but, again, the average cost estimated by seven models runs to €3-6 trillion annually – possibly almost a quarter of Europe’s GDP. Such costs indicate that, given current technological expectations, the proposed reductions are merely wishful thinking.

Much has been made of China’s promise to reach peak emissions around 2030. I did not include this promise in my calculations, because for now it is mostly political grandstanding, being at least 15-20 years away from having any real-world impact. I did include China’s promise to cut about 2Gt by 2030, which will cost about $200 billion annually.

Models indicate that reaching peak emissions in 2030 could end up costing China about 500 billion to one trillion present-day dollars every year by 2050. With the EU and the US unlikely to inflict economic self-harm to achieve their hand-waving targets after 2030, it strains credibility to expect China to do so. Nonetheless, China’s peak is not the holy grail, as it will reduce emissions only about 300Gt, or a little less than 0.1°C, by the end of the century.

Our approach to climate change is broken. The Paris agreement will likely cost the world at least a trillion dollars each year, yet deliver only a tiny reduction in temperature by the end of the century. We should accept that trying to make fossil fuels too expensive to use will never work. Instead, we should make green energy so cheap that nobody can resist it.

The writer is a visiting professor at the Copenhagen Business School.

Copyright: Project Syndicate