Read the passage below:
In 2021, dendrochronologist Dr. Soren Kjaer conducted an analysis of timber samples salvaged from the 1628 wreck of the warship Vasa. Prior to Kjaer's study, standard protocol dictated that waterlogged timber undergo chemical stabilization with polyethylene glycol—a method established in 1962 following the vessel's initial recovery from Stockholm Harbor. However, Kjaer discovered that acidic degradation had begun as early as 1988, long before conservationists noticed surface warping in 2005. To reconstruct the wood's structural degradation, Kjaer first digitized infrared scans taken during a 1995 survey. Only after cross-referencing those scans with wood-density measurements recorded in 2012 did his team establish that bacterial action had preceded chemical oxidation. Finally, in 2023, Kjaer published a revised preservation framework that abandoned the 1962 protocol.
Based on the passage, arrange the following events in chronological order from earliest (first) to latest (last).
- 1The establishment of the chemical stabilization protocol for waterlogged timber
- 2The onset of structural acidic degradation within the vessel's timber
- 3The conducting of an infrared scan survey on the ship's wood
- 4The first observation of physical surface warping by conservationists