AMOC strength not emerging until 1980 - a variation which remains within range of natural variability. A March 2022 review article concluded that while there may be a long-term weakening of the AMOC caused by global warming, it remains difficult to detect when analyzing its evolution since 1980, as that time frame presents both periods of weakening and strengthening, and the magnitude of either change is uncertain (in range between 5% and 25%). The review concluded with a call for more sensitive and longer-term research. Observations Direct observations of the strength of the AMOC have been available only since 2004 from the RAPID array, an in situ mooring array at 26°N in the Atlantic, leaving only indirect evidence of the previous AMOC behavior. While climate models predict a weakening of AMOC under global warming scenarios, they often struggle to match observations or reconstructions of the current. In particular, observed decline in the period 2004–2014 was of a factor 10 higher than that predicted by climate models participating in Phase 5 of the Coupled Model Intercomparison Project (CMIP5): however, some scientists attributed this to a larger-than-anticipated interdecadal variability of the circulation, rather than a climate-forced trend, suggesting that the AMOC would recover from it in only a few years. In February 2021, a study indicated that the AMOC did in fact recover from that decline, and found no evidence of an overall AMOC decline over the past 30 years. Likewise, a Science Advances study published in 2020 found no significant change in the AMOC circulation relative to 1990s, in spite of the substantial changes in the North Atlantic Ocean over the same period. 2010 and earlier In April 2004, the hypothesis that the Gulf Stream is switching off received a boost when a retrospective analysis of U.S. satellite data seemed to show a slowing of the North Atlantic Gyre, the northern swirl of the Gulf Stream. In May 2005, Peter Wadhams reported in The Times (London) about the results of investigations in a submarine under the Arctic ice sheet measuring the giant chimneys of cold dense water, in which the cold dense water normally sinks down to the sea bed and is replaced by warm water, forming one of the engines of the North Atlantic Drift. He and his team found the chimneys to have virtually disappeared. Normally there are seven to twelve giant columns, but Wadhams found only two giant