Is history made by powerful individuals or by long-term changes in technology, population, climate, and other deep factors? As world leaders gather this week in Hamburg for the G-20 summit, we are at a moment when a few individuals are playing an outsized role to our mutual peril. Global survival depends on us limiting the discretion of powerful politicians and instead strengthening national and global political systems directed toward the common good.

Individual politicians can make a difference when they sit atop powerful military forces and can deploy those forces at their personal discretion. Thus have single individuals plunged the world into paroxysms of violence. Kings and princes of the past, invoking divine powers, launched wars of brazen destructiveness, while in modern history, demagogues of unusual charisma and narcissism, including Napoleon, Hitler, Stalin, and Mao, used propaganda, terror, and personality cults to lead millions to their deaths. One hundred years ago, a few powerful generals in the German military high command pushed Europe into a war of choice with little political oversight.

I write of such portentous issues because of the bizarre circumstances of this moment. The United States has a president who is unhinged psychologically and unprepared professionally. Such a leader should be heavily constrained by Congress and other democratic checks and balances. Yet those constitutional constraints have been whittled away by corruption, notably the absurdly large role of a few billionaires in determining our political fate, and by the secrecy of the military-security state, which engages in non-stop wars with little oversight by Congress or the public.

Current circumstances have led as well to outsized roles of other powerful leaders. North Korea’s nuclear threat is in the hands of utterly unaccountable strongmen, including leader Kim Jong Un and his generals. President Vladimir Putin dominates the Russian state with few institutional checks and balances. President Xi Jinping is also China’s strongest leader in decades, though arguably with more institutional limits than Putin or Trump. Turkey’s Recep Tayyip Erdogan is another leader with few institutional constraints.

The G-20 summit on Friday looks set to be dominated by geostrategic conflicts rather than by the global economy and environment. At a time when the world should be harnessing new technologies to curb human-induced climate change, end extreme poverty, and bring epidemics likes AIDS, TB, and malaria to an end, this G-20 will be dominated by existing conflicts and risks of new wars. North Korea’s testing of an ICBM this week puts that country into the very center of the G-20, no doubt as the North Korean leaders intended. The Syrian war continues to rage. The US and Saudi Arabia have recently taunted Iran and upped the stakes in the Middle East.

And all of these threats will be dominated by a few personalities — Trump, Putin, Xi, Erdogan, Kim, and others. We will be hearing breathless reports of what these few individuals — with their whims and narrow interests — plan for the rest of us. This is a stark political failure. Nations have laboriously built up constitutional systems and the United Nations at the global level, yet we still hang on the actions and even whims of a tiny number of individuals.

Rather than leaving dangerous crises in the hands of these few leaders, global crises of war and peace should be the work of global diplomacy in the UN Security Council. The United States would have saved trillions of dollars, avoided millions of refugees, and spared hundreds of thousands of people from violent deaths, if only it had heeded the collective caution of the UN Security Council before the United States launched the Iraq and Libyan wars. Similarly, the Syrian war could have been ended five years ago through peaceful negotiation, if only the US had agreed with the other UN major powers.

US pundits have claimed that Russia and China are “intransigent” when those countries use their vetoes in the UN Security Council to oppose US belligerency. In fact, they were simply being pragmatic, calling for less war and more talk. And recall the importance of the UN Security Council in making it possible to negotiate the agreement for Iran to cease its nuclear activities and to ship its enriched uranium out of the country.

This year’s G-20 is shaping up to be a warning more than an opportunity. It is a warning of the urgency to strengthen the UN in order to avoid disastrous wars on the whims of one or more leaders. It is a reminder that unless we do so, we will continue to squander our energies on deadly conflicts while missing the remarkable opportunity to bring global prosperity and environmental sustainability to a world yearning for solutions.

http://www.bostonglobe.com/opinion/2017/07/05/warning-eve-summit/TL2az8LWtbMYkNGklqjhPP/story.html?event=event25

Jeffrey D. Sachs is university professor and director of the Center for Sustainable Development at Columbia University, and author of “The Age of Sustainable Development.”