Die US-Klimabehörde NOAA hat ihren Jahresbericht 2017 (PDF) vorgelegt und laut diesem war 2017 das drittwärmste Jahr seit Beginn der Wetteraufzeichnungen, was die vergangenen vier Jahre zu den wärmsten seit Messbeginn macht. Dazu kommt, dass 2017 das wärmste Jahr ohne das Wetterphänomen El Niño darstellt.
Overall, 2017 was third warmest year on record, Noaa said, behind 2016 and 2015. Countries including Spain, Bulgaria, Mexico and Argentina all broke their annual high temperature records. Puerto Madryn in Argentina reached 43.4C (110.12F), the warmest temperature ever recorded so far south in the world, while Turbat in Pakistan baked in 53.5C (128.3F), the global record temperature for May.
Concentrations of planet-warming carbon dioxide continued on an upward march, reaching 405 parts per million in the atmosphere. This is 2.2ppm greater than 2016 and is the highest level discernible in modern records, as well as ice cores that show CO2 levels back as far as 800,000 years. The growth rate of CO2 has quadrupled since the early 1960s. […]
In May of last year, ice extent in the Arctic reached its lowest maximum level in the 37-year satellite record, covering 8% less area than the long-term average. The Arctic experienced the sort of warmth that scientists say hasn’t been been present in the region for the last 2,000 years, with some regions 3 or 4 degrees Celsius hotter than an average recorded since 1982. Antarctic sea ice was also below average throughout 2017.
Land-based ice mirrored these reversals, with the world’s glaciers losing mass for the 38th consecutive year on record. According to the report, the total ice loss since 1980 is the equivalent to slicing 22 metres off the top of the average glacier. Prolonged warmth in the seas helped spur a huge coral bleaching event, which is when coral reefs become stressed by high temperatures and expel their symbiotic algae. This causes them to whiten and, in some cases, die off.
A three-year stretch to May 2017 was the “longest, most widespread and almost certainty most destructive” coral bleaching event on record, the report states, taking a notable toll on places such as the Great Barrier Reef in Australia. Global average sea levels reached the highest level in the 25-year satellite record, 7.2cm (3in) above the 1993 average.