From North Carolina State University and the “because our models say so“Department comes this press release that is far more predictable than the climate change it claims to predict – Anthony.
By analyzing historical climate records, observational and projection data, an international team of researchers has found a “push and trigger” mechanism that has pushed the Arctic climate system into a new state in which there is likely to be a steadily increasing frequency and intensity of extreme events in all system components – the atmosphere, the ocean and the cryosphere – this century.
“We know that average temperatures are rising, and the Arctic is widely viewed as an indicator of global change due to its greater sensitivity to disturbances from external and internal forces,” says Xiangdong Zhang, research professor at North Carolina State University and senior scientist at the North Carolina Institute for Climate Studies.
“The Arctic’s annual mean warming rate is more than three times the global average – this is called Arctic amplification,” says Zhang. “However, no systematic study of the interaction of warmer temperatures with atmosphere, ocean and sea ice dynamics during weather and climate extremes around the Arctic has been conducted.” Zhang is the lead author of the study.
The team examined historical temperature data and the record of extreme events in the Arctic system components, as well as CMIP6 model projections covering a period from today to the end of the century. Overall, they found that since 2000, extreme events—heat waves in the atmosphere and ocean, heavy precipitation, sea ice loss, and ice sheet melt—have occurred regularly across the Arctic climate system with increasing frequency and intensity. The CMIP6, or Coupled Model Intercomparison Project Phase 6, is an international project consisting of modeling centers and groups worldwide.
“We usually think of warming as a gradual, quasi-linear change in temperature over time – everything is slowly getting warmer,” says Zhang. “But nonlinear changes are occurring throughout the system. The interplay between warming and changes in atmospheric, oceanic and sea ice dynamics creates ‘push and trigger’ mechanisms that lead to a tipping point for the climate system.”
According to the researchers, these push and trigger mechanisms have led to a step change or sudden shift in the baseline of the Arctic climate system since 2000.
The mechanisms in question include changes in the large-scale atmosphere and ocean circulation that increase poleward atmospheric heat and moisture transport as well as oceanic heat transport into the Arctic. Intense hurricanes and blocking high-pressure systems that impede the movement of other systems through the upper atmosphere are further amplifying warming, increasing sea ice and ice sheet temperatures, and pushing the Arctic climate system to a tipping point, triggering further extremes.
“As soon as there is a baseline change in the climate, we also see a change in extreme events,” says Zhang.
According to the researchers’ analysis, the likelihood of atmospheric heat waves has increased by 20% since 2000; Warming of the Atlantic layer has increased by 76%; Sea ice losses have increased by 83%; and the extent of melting of the Greenland ice sheet has increased by 68%.
“Before the 21st century, these events were rare,” says Zhang. “But as warming continues, they will become the new norm, and we could see ice-free summers in the Arctic by mid-century. More work needs to be done to understand the interplay of multiscale climate drivers in the Arctic so that we can predict and plan for the future.”
The study appears in Nature Reviews Earth & Environment. Zhang is supported in part by the U.S. Department of Energy and the National Oceanic and Atmospheric Administration. The work was carried out by leading and young scientists from the United States, Australia, Canada, China, Finland, Germany, Norway, Sweden, Switzerland and the United Kingdom.
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