When Will the World As We Know It End From Climate Change?

The climate crisis is already here. Extreme weather has become more common across the globe, and estimates suggest that current levels of warming may have already crossed the threshold for irreversible change in several of the Earth's key climate systems.

If nothing is done to curb greenhouse gas emissions, temperatures are likely to rise by 2.1 C to 3.5 C compared with pre-industrial levels by the end of the century. Earth has not been this hot for over 3 million years. These temperatures are not unprecedented, but the difference now is the speed at which global temperatures are rising and the role humans have played in this process.

Normally, Earth's climate systems exist in equilibrium—if we give them a small push, they return to their natural state. However, after a critical threshold is crossed, these changes become irreversible and self-sustaining, with devastating effects on animals and plants. These thresholds are called tipping points.

"Once a tipping point is crossed, 'positive' (i.e. amplifying) feedback loops become powerful enough to keep driving change in the tipping element until it reaches a totally new state," David A. McKay, a research consultant at Georesilience Analytics and a researcher at the Stockholm Resilience Center, told Newsweek.

"For example, once the Greenland ice sheet loses enough height from ice melt, its top sinks in to warmer air levels that drive further melting…This would lock in up to 7 meters of long-term sea level rise—with another 3 meters from the similar West Antarctic ice sheet—committing future generations to massively reshaped global coastlines and displaced populations."

Once a tipping point has been crossed, the climate system it represents will continue to change even if global warming stops or even starts to reverse. It can have immediate effects on the local environment as well as long-term effects on global ecosystems and natural cycles.

"In permafrost regions, widespread abrupt thaw would severely disrupt livelihoods and infrastructure in the North and release additional greenhouse gasses, gradually amplifying global warming—by [around] 5 to 10 percent—over the coming centuries," McKay said.

McKay and his team have identified 16 climate tipping elements around the world, including tropical coral reefs, the Amazon rain forest, and the polar ice sheets.

"The nearest tipping points are the collapse of the Greenland and West Antarctic ice sheets, widespread abrupt permafrost thaw in northern regions, and the die off of warm-water coral reefs, all of which we assess as being likely beyond 1.5 C and can't be ruled out at the current warming level of around 1.2 C."

From their estimates, the lowest critical temperatures for these tipping point thresholds may have already been crossed.

Predictions like these are based on mathematical models that simulate how Earth's systems will respond to rising temperatures. These models incorporate huge data sets and consider a wide range of variables, but no one knows for sure how things will end. And even if we take action now, the changes caused by past and future greenhouse gas emissions could be irreversible for centuries to come.

"For the best chance at avoiding climate tipping points, global warming would have to be limited to 1.5 C,"McKay said.

For that to happen, the Intergovernmental Panel on Climate Change has estimated that greenhouse gas emissions would need to be cut by half by the end of this decade. We would then need to reach "net-zero" by 2050. So far, we are not on that trajectory.

"Current international policies are taking us towards around 2.6 C of warming by 2100, and the ambitious but so far not enacted promises made at the U.N. climate talks in Glasgow last year would only just about make 2 C," McKay said.

"Even limiting warming to 1.5 C—which is the lowest possible given the timescales, and would require massive global social and economic transformations—wouldn't eliminate the possibility of passing climate tipping points."

Even an increase of 1.5 C would be devastating for many nations.

"The difference between 1.5 C and 2 C is a death sentence for the Maldives," Ibrahim Mohamed Solih, the president of the Maldives, said at the U.N. General Assembly in September 2021.

For McKay, there is only one solution.

"The more we cut emissions now, the more we can reduce the chances of triggering any climate tipping points," he said. "1.5C is still just about physically possible, but unfortunately at the moment it's looking pretty unlikely politically.

"I have hope though, in that we in high-emitting communities can definitely still do a lot more to limit warming than our current trajectory, with every fraction of a degree avoided being crucial."