Global warming is a widespread problem, with widespread attempts to reduce emissions and mitigate the effects of the International Panel on Climate Change’s worst-case scenario of 3.2°C warming (relative to pre-industrial levels) by 2100. Current measurements show that the Earth is warming by 1.1°C, but the polar regions are experiencing more surface warming than the rest of the planet.

The measurement of this increased warming in the Arctic (>65° North) relative to global averages and the mechanisms behind it are the subject of a new study published in 2017. Natural Geology.

Dr. from the Pacific Northwest National Laboratory in the USA. Wenyu Zhou and colleagues examined previous reports from 1979 that Arctic amplification factors ranged from two to four and determined that the factor of three was more likely based on Earth’s natural variability regulating temperature change.

Dr. “Natural variability is like noise,” Zhou explains. “Even in the absence of external influences (such as changes in greenhouse gases), the state of the climate system can fluctuate due to the combined dynamics of the ocean, atmosphere, and land. This variability can occur on different time scales (interannual, decadal, multi-decadal) with corresponding “fads.” depending on.

“Therefore, the observed Arctic amplification consists of two parts; one part is driven by external forcing and one part is due to natural variability (leading to a temporal anomaly in the degree of Arctic amplification). Dr. Zhou said: “The alarming quadrupling of the Arctic in recent years , challenges our previous beliefs and is rarely reproduced by climate models,” he says.

“It remains unclear whether this discrepancy reflects a temporary anomaly due to natural variability or whether it reflects forced Arctic warming that is systematically underestimated by the models.”

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

The Pacific Interdecadal Oscillation is a 20- to 30-year pattern of climatic and oceanographic change in both hemispheres of the Pacific Ocean; here positive phases indicate warming in the east and cooling in the west, alternating with negative phases.

The negative phase is the most important because it is associated with more frequent La Niña events (trade winds push warm water toward Asia, causing cool, nutrient-rich water to rise off the coast of the Americas, often intensifying the hurricane season there) since 2000 in the Arctic. It turned out that it has a warming-reducing effect.

Meanwhile, the internal Arctic regime has seen increasing warming since 2005. This is due to positive phases leading to warming over the Kara Sea, with anticyclonic climate patterns bringing moisture to the region, which contributes to the absorption of longwave radiation and surface warming. This causes sea ice to melt.

A strong decrease in sea ice leads to albedo feedback of the ice, which leads to further warming. This process occurs due to melting of sea ice, which reduces the amount of “white” surface that reflects solar radiation, instead increasing the surface area relative to the “dark” ocean to absorb radiation, thus warming the environment and causing more seas to form. ice melting, continuing the “connection” of the feedback loop

Overall, during the study periods 1970–2004 and 1980–2014, the Arctic amplification from observations was determined to be 2.09 and 3.98, respectively; After the Interdecadal Pacific Oscillation was removed, it changed to 2.28 and 3.33 and then to 2.85 and 2.94. After additional elimination of the influence of the Arctic internal regime.

As a result, a consistent amplification factor with a value of three was defined, which is consistent with that used in the Coupled Models Intercomparison Project (CMIP6) and confirms its reliability in predicting future climate change.

“Here we provide clear evidence that the previously reported fourfold Arctic amplification is an anomaly arising from dominant modes of natural variability, and that the magnitude of the forcing has been consistently around three throughout the historical period.”

This study is important because it highlights the precision of climate change modeling and the conclusions drawn to predict future patterns of global warming. Accounting for natural variability and setting the amplification factor at three rather than four means future mitigation strategies may not be as severe in the coming years.

Indeed, Dr. Zhou and colleagues suggest that in the coming decades, the Arctic internal regime will likely transition to a negative phase and the Pacific Interdecadal Oscillations to a positive phase, which will lead to a decrease in the Arctic expansion factor. as low as two.