Climate scientists have long believed that the interior of Antarctica may be less sensitive to warming, but our research published this week shows that this change is huge.
In the past 30 years, the Antarctic has been one of the fastest-changing places on the planet, and it has warmed more than three times faster than the rest of the world.
My colleagues and I believe that these warming trends cannot be the result of natural climate change alone. The effects of anthropogenic climate change appear to be synergistic with the significant impact of tropical natural variability on Antarctica’s climate. Together they make Antarctica warming one of the strongest warming trends on the planet.
Antarctica cannot avoid warming
Antarctica is located in the coldest region on earth: the Antarctic Plateau. The average temperature in winter is -60℃, and the average temperature in summer is -20℃.
Antarctica’s climate usually changes greatly in temperature over the course of a year, and regional differences are very large. In the late 20th century, most parts of the Antarctic Antarctic and Antarctic Peninsula were warming. But Antarctica-inside the remote and high-altitude continent-cooled until the 1980s.
Since 1957, scientists have been tracking the temperature of the Antarctic station, the Amundsen-Scott meteorological station at the southernmost tip of the earth. It is one of the longest complete temperature records on the Antarctic continent.
Our analysis of Antarctic weather station data shows that between 1989 and 2018, the Antarctic weather warmed by 1.8°C, which has changed more rapidly since the early 2000s. During the same period, the warming in western Antarctica suddenly stopped and the Antarctic Peninsula began to cool down.
One of the causes of Antarctic warming is the stronger low-pressure system and the stormy weather east of the Antarctic Peninsula in the Weddell Sea. With the clockwise flow around the low-pressure system, this has always sent warm and humid air to the Antarctic Plateau.
Antarctic warming is related to tropical
Our research also shows that the ocean in the tropical western Pacific and the Antarctic began to warm rapidly at the same time. We find that nearly 20% of the annual temperature change in Antarctica is related to the ocean temperature in the tropical Pacific Ocean, and the warmest years of the Antarctic in the past two decades have occurred in the western tropical Pacific Ocean, which is also extremely warm.
To study this possible mechanism, we conducted climate model experiments and found that this ocean warming produced an atmospheric wave pattern that stretched across the South Pacific to Antarctica. This leads to a stronger low-pressure system in the Weddell Sea.
From earlier research we know that the strong regional differences in temperature trends are partly due to the shape of Antarctica.
The eastern Antarctic ice sheet, which borders the South Atlantic and the Indian Ocean, extends farther north in the South Pacific than the western Antarctic ice sheet. This will result in two significantly different weather patterns and have different climatic effects.
The more stable westerly winds around Antarctica keep the local climate relatively stable, while frequent high-latitude storms in the South Pacific transport warm and humid air to parts of western Antarctica.
Scientists believe that these two different weather patterns and the mechanisms driving their changes may be the reason for the strong regional changes in Antarctica’s temperature trends.
What does this mean for Antarctica
Our analysis shows that extreme changes in Antarctic temperature can be partially explained by natural tropical changes.
To estimate the effects of human-induced climate change, we analyzed more than 200 climate model simulations from 1989 to 2018 and observed greenhouse gas concentrations. These climate models show that the recent increase in greenhouse gases may account for about 1 ℃ of total greenhouse gases. Antarctic warming 1.8 ℃.
We also used these models to compare the recent heating rate with all possible 30-year Antarctic temperature trends, which naturally occur without human influence. In the absence of human influence, the observed warming exceeds 99.9% of all possible trends-meaning that under natural conditions, the likelihood of recent warming is extremely small, although not impossible. It seems that the effects of tropical variation and the increase in greenhouse gases work together, and the end result is one of the strongest warming trends on the planet.
These climate model simulations reveal the remarkable nature of Antarctic temperature changes. The observed Antarctic temperature (which dates back to 1957) shows 30 years of temperature fluctuations, ranging from cooling above 1°C in the 20th century to warming above 18°C in the past 30 years.
This means that decades of temperature fluctuations are estimated to be three times stronger than the warming caused by human-induced climate change of about 1°C.
The temperature change in Antarctica is so great that it now masks the human influence. The interior of Antarctica is one of the few places on Earth where it is impossible to accurately determine human-induced warming, which means it is a challenge to determine how long the warming will last.
But our research shows that extreme and sudden climate changes are part of Antarctica’s internal climate. These may continue into the future, to hide human-induced warming or to exacerbate warming when the natural warming process and the human greenhouse effect cooperate.
Kyle Clem is a climate science researcher at Te Herenga Waka, Victoria University of Wellington