GEOGRAPHY

Small warming can lead to irreversible ecosystem changes


A new study has found that global warming may have caused the Greenland ice sheet to melt irreversibly. Image credit: FELIPE DANA/AP IMAGES

From melting ice sheets to giant coral reefs, global warming is changing our world in clear ways. However, there is a certain controversy in determining the “tipping point”, that is, beyond this critical point, this transformation becomes irreversible. Some researchers argue that emphasizing imminent but uncertain, irreparable moments fuels public apathy rather than inspires efforts to curb climate change.

Recently, a study published in Science on climate tipping points synthesized the latest evidence that global temperatures can rise by more than 16 tipping points after rising by more than 16, triggering polar glacier collapse, permafrost melting, monsoon destruction, and the death of forests and coral reefs. The study found that many of Earth’s systems are already under pressure from rising temperatures, and that even under the most ambitious schemes to limit global warming, the planet will still undergo dramatic changes.

Chris Jones, a climate scientist at the MET’s Hadley Centre, believes it is a “timely and thorough work”. He said the findings were broadly consistent with previous studies, but the data were updated and more detailed. But he and other climate scientists caution against making “catastrophic” explanations for the findings.

To estimate the tipping point, the team of Earth system scientist David Armstrong McKay at the University of Exeter in the UK gathered evidence from ancient climate records, modern observations, model predictions and current best assessments, studying ecosystems, atmospheric systems and other systems to identify those most prone to sudden, irreversible or self-sustaining changes as the planet warms. They then estimated the minimum amount of warming that could trigger a tipping point in each system, and the maximum amount of warming a system might withstand before a catastrophic shift was inevitable. The researchers also made the best estimates of the location of each tipping point.

Overall, the study found that the current level of global warming (a 1.1°C rise in temperature since pre-industrial era) puts the Earth above the low-end risk estimates at 5 tipping points, putting coral reefs, permafrost and polar ice at risk. A mere 0.8°C warming could have accelerated the degradation of the Greenland ice sheet, while a mere 1°C warming could have led to the collapse of the West Antarctic ice sheet.

Nelile Abram, a climate scientist at the Australian National University, said: “Once the ice sheet starts to collapse, it will push itself into a more unstable structure, leading to global sea level rise. ”

The study also found that limiting global warming to 1.5 °C to 2 °C (a rough target of the Paris Agreement) could mean more than 7 tipping points, which would lead to the loss of alpine glaciers and disruption of key ocean currents. While the 1.5°C target was initially just “some convenience” from diplomatic mediation, Armstrong McKay said the study reinforces the risk of failing to achieve it.

Abram agrees, arguing that the paper synthesizes a wealth of evidence that makes it easier for policymakers and others to see how social choices can help avoid or accelerate tipping points.

Bob Kopp, a climate scientist at Rutgers University in the United States, warned that focusing too much on specific temperature thresholds could spark controversy that there is nothing in place to keep warming at safer levels. “I’m afraid the tipping point will fuel the idea that there’s a threshold below which we’re fine, and above that threshold we can’t,” he said. On the contrary, every warming up creates additional risks. ”

To gain more certainty, the researchers began comparing tipping point projections produced by different climate models. But Thomas Stocker, a climate scientist at the University of Bern in Switzerland, believes that comparisons should be made after the next generation of climate models appear, because the next generation of climate models is expected to produce more detailed results. However, a growing number of scientists have recognized that, for now, a risk assessment of some kind of tipping point is very necessary. (Source: China Science Daily Xin Yu)

Related paper information:https://doi.org/10.1126/science.abn7950



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