News Update: Brazil rejected the $22 million in Amazon aid pledged at the G7.

At the Group of 7 summit, aides to President Trump complained that the French president, Emmanuel Macron, was focusing the summit not on the global economy but on “niche issues” — among them climate change. At the same time, fires continued to burn in the Amazon rainforest on a level not seen in nearly a decade.

Mr. Macron sought to present himself as a leader in the effort to quench the Amazon fires. In doing so, he positioned himself as a foil to the far-right president of Brazil, Jair Bolsonaro, whose policies encouraging deforestation of the rainforest have contributed to the blazes. After Mr. Macron threatened to pull support for a major trade deal between the European Union and some South American nations, including Brazil, over Mr. Bolsonaro’s inaction, the Brazilian president seemingly changed course, mobilizing the country’s military to tackle the fires.

The Amazon fires are a test case of sorts for how the climate crisis will strain the usefulness of seemingly simple concepts — like national sovereignty. Before calling up the military, Mr. Bolsonaro accused countries donating money to preserve the rainforest of wanting to “interfere with our sovereignty.” He also declared that the international condemnation he faced spoke to a “colonialist mentality,” criticizing what he saw as Mr. Macron’s encouragement for the G7, which does not include Brazil, to grapple with the problem on its own. These remarks speak to Mr. Bolsonaro’s nationalist politics — he came to power in part by decrying globalism — and they are overly simplified. But it would be a mistake to write them off completely.

The traditional understanding of the nation-state demands that — up to a certain limit — each nation has control over its own affairs. Climate change poses a problem for this framework: The burning Amazon affects not just Brazil but the whole world. (The portion of the Amazon in next-door Bolivia, for example, is also burning.) Does it really make sense, then, to defer to the sovereignty of the Brazilian government in addressing the problem?