The study found that Arctic warming is triple that of global patterns

Global warming is a pervasive problem, with extensive initiatives to reduce emissions and mitigate against the International Panel on Climate Change’s worst-case scenario predictions of 3.2°C warming by 2100 (compared to pre-industrial levels). Current measurements show a warming of 1.1°C on Earth, but the polar regions are experiencing increased surface warming compared to the rest of the planet.

Quantifying this warming enhancement in the Arctic (>65°N) compared to global means and the mechanisms behind it is the subject of new research published in Nature Geoscience.

Dr. Wenyu Zhou of the Pacific Northwest National Laboratory, USA, and colleagues examined previous reports of Arctic amplification factors two through four since 1979 and determined that factor three was more likely based on Earth’s natural variability modulating temperature changes.

“Natural variability is like noise,” explains Dr. Zhou. “Even in the absence of external forcing (such as changes in greenhouse gases), the state of the climate system can fluctuate due to its coupled ocean-atmosphere-land dynamics. Such variability can occur on different time horizons (interannual, decadal, multi-decadal) depending on corresponding “mode”.

“Therefore, the observed Arctic amplification consists of two parts – a part that is forced by external forcing and a part due to natural variability (which leads to a temporal anomaly in the degree of Arctic amplification).

“The alarming fourfold Arctic amplification in recent decades challenges our previous beliefs and is rarely reproduced by climate models,” says Dr. Zhou.

“Whether this discrepancy reflects a temporary anomaly caused by natural variability or a forced state of Arctic warming systematically underestimated by the models remains elusive.”

To investigate, the research team compared observational data with model simulations and found that the difference in amplification factor between the two could be explained by natural variability, specifically certain oceanic and climate patterns associated with the region. This includes the Pacific Interdecadal Oscillation and the Arctic Internal Mode.

The Interdecadal Pacific Oscillation is a 20- to 30-year pattern of climate and oceanographic change in both hemispheres of the Pacific Ocean, where positive phases see warming in the east and cooling in the west, with an exchange during negative phases.

The negative phase is most important because it is associated with a higher frequency of La Niña events (the trade winds push warm water into Asia, leading to the upwelling of cold, nutrient-rich water along the U.S. coast, often increasing the severity of the hurricane season here), and has been found to have from 2000 reduction effect on Arctic warming.

Meanwhile, the internal Arctic regime is determined to have increased warming since 2005. This refers to the positive phases leading to warming over the Kara Sea, with anticyclonic climate patterns bringing moisture to the area that favors the absorption of longwave radiation and surface warming. , leading to the melting of sea ice.

A strong decrease in sea ice results in an ice-albedo feedback that leads to further warming. This process occurs due to the melting of sea ice, reducing the amount of “white” reflective surface for incoming solar radiation, instead increasing the surface area of ​​the relatively “dark” ocean that absorbs the radiation, warming the surrounding environment and causing further melting of the sea ice. continues to feedback.

Overall, the Arctic amplification is found to be 2.09 and 3.98 from the observational data for the 1970–2004 and 1980–2014 study periods, changing to 2.28 and 3.33 after removing the interdecadal Pacific Oscillation, and after another 2, 94 removal of the arctic internal mode effect.

Subsequently, a consistent amplification factor of three is identified that matches that used in the Coupled Model Intercomparison Projects (CMIP6), supporting its reliability for predicting future climate change.

“Here we provide clear evidence showing that the previously reported four-fold Arctic amplification is an anomaly caused by dominant modes of natural variability, and the rate of forced amplification is consistently around three over the historical period.”

This research is important because it highlights the sensitivity of climate change modeling and the conclusions drawn to predict future patterns of global warming. Allowing for natural variability and specifying an amplification factor of three instead of four means that future mitigation strategies may not be as stringent in the coming decades.

Dr. Indeed, Zhou and colleagues suggest that the Arctic internal regime is likely to shift to a negative phase and the interdecadal Pacific Oscillation to a positive one in the coming decades, which would lead to a reduction in the Arctic Arctic amplification factor, perhaps even as low. like two

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