The UN’s 10,000-page red alert on climate change

by Amélie Bottollier-Depois

Accelerating global warming is driving a rising tide of impacts that could cause profound human misery and ecological disaster, and there is only one way to avoid catastrophe: drastically reduce greenhouse gas emissions.

Spread across 10,000 pages, these are the main takeaways from a trio of UN reports on climate change published in August 2021, February 2022 and on Monday. The three tomes—each with its own roster of hundreds of authors—focus on physical science, impacts and the need to adapt, and finally how to slash carbon pollution.

This will be the sixth such trilogy since the Intergovernmental Panel on Climate Change (IPCC) delivered its first report in 1990 and positioned itself as the final word on the science behind global warming.

Here are five key findings from the three reports:

Beyond a doubt

Whatever climate sceptics might say, scientific evidence has removed any lingering doubt that human activity is “unequivocally” responsible for global warming, which has seen the planet heat up an average of 1.1 degrees Celsius above preindustrial levels.

The atmospheric concentration of CO2—the main driver of warming, emitted mainly by burning fossil fuels—rose at least 10 times faster between 1900 and 2019 than any time in the last 800,000 years, and is at its highest in two million years.

Bye bye 1.5C?

The 2015 Paris Agreement calls for capping global warming “well below” 2C, and 1.5C if possible. A crescendo of deadly impacts already being felt and a slew of new science has led most countries to embrace the more ambitious aspirational goal.

But that ship may have sailed.

In every IPCC projection for a liveable future, Earth’s average surface temperature increases by 1.5C or 1.6C by around 2030—a decade earlier than estimates made only a few years ago.

In theory, it will be possible to cap temperature increases to below the 1.5C threshold by the end of the century, but even a temporary “overshoot” could cause irreversible damage to fragile ecosystems at the poles, in the mountains, and in coastal areas.

Continue reading at the source (Phys.org.)