It is no longer politically popular to pretend, despite decades of evidence to the contrary, that global warming is a hoax or a phenomenon unconnected to human activities. Unfortunately, it is still popular, particularly but not exclusively among Republicans, to pretend that the climate crisis can be sufficiently mitigated without reducing our dependence on fossil fuels. The latest report from the U.N.’s Intergovernmental Panel on Climate Change (IPCC) underscores just how dangerous this fantasy is. The report confirms, with a new degree of certainty, that reaching net-zero carbon emissions is “a requirement to stabilize human-induced global temperature increase at any level.” It describes five potential warming scenarios, ranging from the least severe (a 1.5-degree Celsius increase over pre-industrial levels) to the most severe (a 4.5-degree increase). Whether we will be able to limit global warming to a relatively manageable 1.5 to 2 degrees or will have to face more drastic changes depends on our ability—and willingness—to eliminate most carbon emissions within the next twenty years.
The IPCC’s report includes charts that show the likely effects of each of its five scenarios on oceans, ice sheets, and weather patterns. But we shouldn’t need these dire predictions. The current effects of climate change are bad enough: rising sea levels, surface temperatures, and acidification; rapid melting of Arctic ice; increases in the frequency and intensity of heat waves, heavy precipitation, droughts, and tropical cyclones. And with the IPCC’s increasingly accurate modeling, the evidence that these are all attributable to human actions has become only more conclusive.