Tuesday, December 6, 2022

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When will the world as we know it end with climate change?

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

If nothing is done to limit greenhouse gas emissions, temperatures are expected to rise 2.1 C to 3.5 C above pre-industrial levels by the end of the century. Earth hasn’t been this hot in over 3 million years. These temperatures are not unprecedented, but the difference now is the rate at which global temperatures are rising and the role humans have played in this process.

Normally, Earth’s climate systems exist in balance – if we give them a little push, they return to their natural state. However, after crossing a critical threshold, these changes become irreversible and self-perpetuating, with devastating effects on animals and plants. These thresholds are called tipping points.

“Once a tipping point is crossed, the ‘positive’ (i.e. amplifying) feedback loops become strong enough to continue driving changes in the tipping element until it reaches a totally new state,” David A. McKay, research consultant at Georesilience Analytics and a researcher at the Stockholm Resilience Center, said. Pleasemynews.

“For example, once the Greenland Ice Sheet loses enough height from melting ice, its top sinks into warmer air levels which cause further melting… This would block up to 7 meters of long-term sea level rise, with an additional 3 meters of the similar West Antarctic ice sheet – committing future generations to massive reshaping of the world’s 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 begins 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, a sudden and widespread thaw would severely disrupt livelihoods and infrastructure in the North and release additional greenhouse gases, gradually amplifying global warming – by [around] 5-10% – over the next few centuries,” McKay said.

McKay and his team identified 16 climate-tipping elements around the world, including tropical coral reefs, the Amazon rainforest and the polar ice caps.

“The closest tipping points are the collapse of the Greenland and West Antarctic ice sheets, widespread abrupt thawing of permafrost in northern regions, and the death of warm-water coral reefs, which we all assess as likely beyond 1.5C and can’t be ruled out at the current level of warming of around 1.2C.”

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

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

“To have the best chance of avoiding climate tipping points, global warming should be limited to 1.5°C,” McKay said.

For this to happen, the Intergovernmental Panel on Climate Change has estimated that greenhouse gas emissions would need to be halved 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 point us towards a warming of around 2.6°C by 2100, and the ambitious yet unimplemented promises made at the UN climate talks in Glasgow last year would only be about 2°C,” McKay said.

“Even limiting warming to 1.5°C, which is the lowest possible given time scales, and would require massive global social and economic transformations, would not eliminate the possibility of crossing climate tipping points.

Even a 1.5C rise would be devastating for many countries.

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

For McKay, there is only one solution.

“The more we reduce emissions now, the more we can reduce the chances of triggering climate tipping points,” he said. “1.5C is still roughly physically possible, but unfortunately at the moment politically it seems quite unlikely.

“I am hopeful, however, inasmuch as we in high-emitting communities can certainly still do much more to limit warming than our current trajectory, with every fraction of a degree avoided being crucial.”

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