The UN climate report: all is not well, but all is not lost

Today the United States Publication of the Intergovernmental Panel on Climate Change an alarming new report on the state of the climate: 14,000 scientific works compiled by hundreds of experts. It’s a loud statement of what scientists know about how humanity set the planet on fire: how hot it is and how hot it is going to be, how much polar ice is melting, how droughts and storms get worse, how dire the road is looking to the future, unless we take drastic and immediate action to stop loading the atmosphere with carbon.

“We have known for decades that the world is warming, but this report tells us that recent climate change is widespread, rapid and intensifying, unprecedented in thousands of years,” said Ko Barrett, vice president of the IPCC and senior climate advisor to the National Oceanic and Atmospheric Administration, at a press conference on Sunday announcing the report. “The bottom line is that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limit warming to 1.5 degrees C – or 2.7 degrees Fahrenheit – will be out of reach. “

This limit is the optimistic goal of the Paris climate agreement: to keep global average temperatures 1.5 degrees Celsius above pre-industrial levels, and to avoid 2 degrees warming. The new report notes that the temperature has already risen 1.1 degrees and is on track to hit 1.5 in the early or mid-2030s if things don’t change.

This is an important update of a previous IPCC report who predicted the planet would reach the 1.5 milestone around 2040, said Zeke Hausfather, climatologist and director of climate and energy at the Breakthrough Institute, who was not involved in the report. “Likewise, we pass 2 degrees somewhere between the early 2040s and the early 2050s as the most likely estimate in the higher emission scenarios,” he says, referring to one of the five modeled outcomes. in the new report.

Why is this half degree so important? “There is a big difference between 1.5 and 2”, in terms of worsening droughts, heat waves, storms, floods, melting ice, and the sea level risessays Janos Pasztor, executive director of the Carnegie Climate Governance Initiative and former United Nations Deputy Secretary-General for Climate Change, who was not involved in the report. “Two is much worse. And that beyond 2 gets a a lot a lot worse. And there is a chance, of course, that we are going in that direction. “

The report presents projections of what would happen in five different greenhouse gas emissions scenarios: these imagine a future in which humanity produces varying levels of carbon, from very low to very high. (In the lowest scenario, emissions fall to net zero around 2050 and continue to decline. In the highest scenario, they double that year.) In other words, it’s about predicting what The climate will look like depending on how quickly our civilization is decarbonizing.

The color-coded graphics that accompany the report also show what would happen to global temperatures and precipitation rates as a function of global warming, and indicate how many regions of the world have experienced an increase in extreme heat, precipitation and precipitation. Drought. (Hint: that’s almost all.)

Illustration: IPCC

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