STATE OF THE CLIMATE IN 2009

• Published in: Bulletin of the American Meteorological Society 2010-07, Vol.91 (7), p.S1-S218
• Main Authors: ARNDT, D.S, BARINGER, M.O, JOHNSON, M.R, ALEXANDER, L.V
• Format: Article
• Language: English
• Subjects: Air temperature; Altimetry; Archives & records; Bgi / Prodig; Carbon dioxide; Climate change; Climate models; Climate prediction; Climatology; Glaciers; Global climate models; Hurricanes; Hydrography; Ice; Marine; Meteorology; Oceanic climates; Oceans; Ozone depletion; Physical geography; Precipitation; Rain; Satellites; Sea ice; Seasons; Surface temperature; Time series; Tropical climates; Tropical cyclones; Tropical environments; Variables; Weather forecasting
• ISSN: 0003-0007; 1520-0477; 1520-0477
• DOI: 10.1175/BAMS-91-7-StateoftheClimate

The year was characterized by a transition from a waning La Niña to a strengthening El Niño, which first developed in June. By December, SSTs were more than 2.0°C above average over large parts of the central and eastern equatorial Pacific. Eastward surface current anomalies, associated with the El Niño, were strong across the equatorial Pacific, reaching values similar to the 2002 El Niño during November and December 2009. The transition from La Niña to El Niño strongly influenced anomalies in many climate conditions, ranging from reduced Atlantic basin hurricane activity to large scale surface and tropospheric warmth. Global average surface and lower-troposphere temperatures during the last three decades have been progressively warmer than all earlier decades, and the 2000s (2000–09) was the warmest decade in the instrumental record. This warming has been particularly apparent in the mid- and high-latitude regions of the Northern Hemisphere and includes decadal records in New Zealand, Australia, Canada, Europe, and the Arctic. The stratosphere continued a long cooling trend, except in the Arctic. Atmospheric greenhouse gas concentrations continued to rise, with CO₂ increasing at a rate above the 1978 to 2008 average. The global ocean CO₂ uptake flux for 2008, the most recent year for which analyzed data are available, is estimated to have been 1.23 Pg C yr−1, which is 0.25 Pg C yr−1smaller than the long-term average and the lowest estimated ocean uptake in the last 27 years. At the same time, the total global ocean inventory of anthropogenic carbon stored in the ocean interior as of 2008 suggests an uptake and storage of anthropogenic CO₂ at rates of 2.0 and 2.3 ±0.6 Pg C yr−1for the decades of the 1990s and 2000s, respectively. Total-column ozone concentrations are still well below pre-1980 levels but have seen a recent reduction in the rate of decline while upper-stratospheric ozone showed continued signs of ongoing slow recovery in 2009. Ozone-depleting gas concentrations continued to decline although some halogens such as hydrochlorofluorocarbons are increasing globally. The 2009 Antarctic ozone hole was comparable in size to recent previous ozone holes, while still much larger than those observed before 1990. Due to large interannual variability, it is unclear yet whether the ozone hole has begun a slow recovery process. Global integrals of upper-ocean heat content for the last several years have reached values consistently higher than for all prior