Opinion | Humanity Can Still Take a Stand on Climate. It Must.

The report’s main points are these: First, nations have waited so long to curb emissions that a hotter future is essentially locked in, as are more droughts, more forest fires, more crippling heat waves, more sea level rise, more floods. The greenhouse gases that have already been pumped into the atmosphere are going to stay there a long time, inflicting misery for years to come.

This summer has already produced huge floods in Central Europe, Nigeria, Uganda and India, blazes in Greece and Siberia, wildfires erasing entire towns in California and Canada, murderous heat waves in the Pacific Northwest, the drying up of Colorado River reservoirs. “What more can numbers show us that we cannot already see?” asked one U.N. climate official. Fair question. But what the numbers show is that these meteorological calamities will become routine unless the world takes dramatic steps to get a grip on emissions.

In their analysis of the new report, the Times reporters Henry Fountain and Brad Plumer offer this illustration. Humans have already heated the planet by roughly 1.1 degrees Celsius, or 2 degrees Fahrenheit, since the 19th century. If global warming rises to around 1.5 degrees Celsius in the next 20 years, heat waves that would have occurred once every 50 years can be expected to show up once every 10 years. At 4 degrees of warming, they’ll show up every year.

Point two: Humanity can still take a stand. It must. If countries make a coordinated effort to stop adding carbon dioxide to the atmosphere by, say, midcentury, and undertake through reforestation and other means to remove carbon from the air, global warming might level off at around 1.5 degrees. This in turn means mustering the will to stave off a darker future than the one the world has already locked itself into. It also means, in policy terms, a rapid shift away from fossil fuels; big investments in wind, solar and nuclear power; a rebuilt electric grid; more efficient homes and buildings — in short, a wholly different energy delivery system.

Earlier this month, Mr. Biden announced a strategy to shift Americans from gasoline-powered cars to electric vehicles, thus resurrecting an Obama initiative Mr. Trump had canceled. This is an important step. But Mr. Biden is not going to get the energy transformation he wants via regulation any more than Mr. Obama could. For this, he will need Congress.

Can Congress deliver? No small question. The Senate, split evenly between the parties, took forever to approve an infrastructure bill, which has only modest climate-related measures in it and should not have been all that controversial. Ahead lies something a lot more difficult — winning approval of a giant $3.5 trillion budget reconciliation bill that can be approved with only 51 votes (all the Democrats and the vice president), thus avoiding a Republican filibuster and opening a legislative pathway for a range of big-ticket social programs and Mr. Biden’s climate policies.

Of these, two are of paramount importance and are essential to honoring Mr. Biden’s campaign promise to cut America’s emissions in half by 2030, eliminate fossil fuel emissions from power plants by 2035 and zero out all greenhouse gases by midcentury — pretty much what the I.P.C.C. wants. One is billions in incentives for electric vehicles and for clean energy sources like wind, solar and nuclear power. The other is a clean electricity standard that, as currently envisioned, would reward power producers that reduce emissions and penalize those that don’t. There are likely to be add-ons from individual senators, like Chris Van Hollen’s proposal, unveiled this month, to tax Exxon, Chevron and a handful of other major oil and gas companies to get them to pay for floods, fires and other disasters linked to the fossil fuels they have produced over the years.