Every global climate summit to date has featured lots of tough talk but little action. The United Nations confab in New York that is wrapping up is no different. Nor will anything change in the future unless climate change warriors stop insisting that the world go on an energy diet — and start offering cheaper and cleaner energy options that don't require a lifestyle where transcontinental travel means a boat like the one that the 16-year-old Greta Thunberg took from Sweden to deliver her rebuke to world's leaders.

Human-caused global warming is real, but activists have to get real. They think that they can spur action by simply exaggerating the urgency of climate change. Thunberg insisted that if drastic action to cut emissions isn't taken now, basically the planet as we know it will cease to exist. Likewise, Green New Dealers like Rep. Alexander Ocasio-Cortez (D-N.Y.) have been saying that the planet has an "expiration date."

But anyone who has watched Game of Thrones knows that dialing up apocalypse talk alone can't overcome the collective action problem preventing action on climate change. In that drama, Queen Cersei, chooses to free ride rather than join other kingdoms in fighting the forces of Armageddon.

Climate change activists are confronting the same problem — and the more they exaggerate the sacrifices required, the more they'll exacerbate it.

The 6th Intergovernmental Panel on Climate Change concluded that preserving the planet as we know it will require keeping the global mean surface temperature at no more than 1.5 degrees Centigrade above the average temperature in the 19th Century before the industrial revolution. This is a more stringent target than that set during the 2015 Paris accords whose goal was to hold the temperature increase to 2 degrees Centigrade. Allowing them to rise more than that would mean planetary change and disruptions, to be sure. For example, coral reefs would be damaged, storms may be worse, and Arctic ice may melt in summers — but not necessarily planetary catastrophe with fiercer cyclones and droughts causing mass death, a distinction that climate warriors refuse to make.

In order to hold temperature to the 1.5 degrees threshold, the IPCC calculated that the world would have to cut carbon dioxide emissions by 40 to 50 percent by 2030 and completely by 2050. This will mean a total transition from fossil fuels to renewables like wind and solar by 2050, a goal that AOC has whole-heartedly embraced for the United States.

What would the price tag for this be?

As per the IPCC's own calculations, around $2.4 trillion annually between 2016 and 2035 in 2010 dollars — or about 2.5 percent of the global GDP. To understand just how daunting that is consider that the total energy investments in the world amount to only around $1.7 trillion right now — which means that the world is being asked to make an additional $45 trillion in investments over 19 years to generate the same amount of energy and improve energy efficiency. The higher costs will mean scaling back First World lifestyles, of course. But they will also mean forcing Third World countries where many people don't even have electricity to stay stuck in poverty for many more decades to help out generations a hundred years from now.

This may be a good long-term investment but the upfront costs — both monetary and human — are formidable which makes the politics of climate change intractable. That's why the New York conference didn't go anywhere. The UN Secretary General Antonio Gueterres asked countries to up the commitments they'd made four years ago in Paris. Only 65 countries obliged; the biggest polluters just shrugged.

America didn't even request a speaking slot at the event because that would have meant laying out concrete plans for actual cuts. The Australian prime minister was in town but didn't bother showing up. China failed to announce new targets and renewed its calls that developed countries go first — no doubt because it doesn't want to put an anchor around its already limping economy. Likewise, India's Prime Minister Narendra Modi, Trump's new best friend, outlined more investments in renewables but remains committed to coal projects for the foreseeable future. And the European Union, historically a leader in pushing for emission cuts, didn't signal any intention to reach carbon neutrality by 2050.

Climate activists are blaming much of this on Trump's Paris pullout. But that's head-in-the-sand evasion because even if Trump were the Joan of Arc of climate change, he couldn't ensure results. America enthusiastically led the way for the 1997 Kyoto Treaty that convinced many countries to pledge cuts, but almost none delivered before George Bush bailed. And the reason is those that dutifully made the cuts would end up harming their economy for no gain if others didn't follow through. So it was more expedient to promise and leave.

Climate activists are now counting on woke capital to bring these countries to heel by withholding investments from polluting nations. And several asset fund managers indeed did commit to net-zero emission portfolio by 2050. But the investor community as a whole is going to face the same collective action problem that the international community is confronting, namely, that if one of them foregoes lucrative investments, there will be just that much more temptation for others.

The better way might be offering clean fuel options that are so attractive that consumers simply can't turn them down. Phone users did not switch from landlines to cell phones because they were forced to do so. They did so automatically and voluntarily because the new technology offered massive advantages relative to the costs that the old one didn't.

Something equivalent needs to happen on the energy front to make fossil fuels obsolete. The most promising alternative on the horizon so far isn't renewables but nuclear. Yet environmentalists are mostly opposed to it. This was reasonable when nuclear's upfront capital costs — namely to build layers of safety in reactors — were astronomical and options to safely dispose spent radioactive fuel weren't great. But the new generation of nuclear reactors is overcoming at least some of these problems. For example, Bill Gate's Terrapower, a traveling wave reactor, is experimenting with using depleted uranium, a waste product leftover from conventional reactors.

The most revolutionary fuels are ones that no one can even imagine yet. But they will only come about if today's young environmental activists don't skip school to spend two weeks boating across the ocean to attend a summit. Rather than lecturing world leaders, they'd help more if they stayed in class and listened to their teachers with the goal of becoming future innovators.

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