Highlights of Global Climate 2016

The warmest year on record: +0.83 °C +/− 0.10 °C warmer than the average for the 1961–1990 reference period, +1.1 above the pre-industrial period. The 2015/2016 El Niño is one of the three strongest events since 1950.

Sea Level
On timescales longer than about a year, the vast majority (more than 90%) of the Earth’s energy imbalance goes into heating the oceans. As the oceans warm, they expand, resulting in both global and regional sea-level rise. Globally, sea level has risen by 20 cm since the start of the 20th century, due mostly to thermal expansion of the oceans and melting of glaciers and ice caps. Some regions are experiencing greater sea-level rise than others. The tropical western Pacific observed some of the highest rising sea-level rates over the period 1993–2015, which was a significant factor in the enormous devastation in parts of the Philippines when Typhoon Haiyan caused a massive storm surge in November 2013.

EL Niño 2015/2017
The year began with a strong El Niño event, near peak levels in the tropical Pacific Ocean with sea-surface temperatures still more than 2 °C above average in the east-central equatorial Pacific region in January. Conditions cooled steadily through the early months of the year, consistent with typical El Niño decay patterns, and ocean temperatures had fallen below El Niño thresholds by May. The 2015/2016 El Niño event reached a peak Oceanic Niño Index (ONI) value of +2.3 °C for the three-month period November 2015 to January 2016, making it one of the three strongest events since 1950 together with those of 1997/1998 and 1982/1983. (Learn more about El Niño)
Indian Ocean Dipôle
The Indian Ocean Dipole (IOD) describes a mode of variability that affects the western and eastern parts of the ocean. Indian Ocean Dipole index values fell below −1 °C in both July and September, making it one of the strongest negative episodes since records began. Negative IOD phases are associated with above-average rainfall in many parts of Australia and Indonesia and dry conditions in equatorial east Africa.

Greenhouse Gases
Comprehensive global greenhouse data for 2016 will not be available until later in 2017. The increase of CO2 from 2014 to 2015 was larger than that observed from 2013 to 2014 and that averaged over the past 10 years, despite no significant change in emissions from the fossil-fuel source. The El Niño event contributed to the increased growth rate in 2015, both through increased emissions from terrestrial sources (e.g. forest fires) and decreased uptake of CO2 by vegetation in drought-affected areas.

Arctic sea-ice
Arctic sea-ice extent was well below average and was at record low levels for large parts of the year. The seasonal maximum of 14.52 million km2 on 24 March was the lowest seasonal maximum in the 1979–2016 satellite record, just below that of 2015. The annual minimum summer sea-ice extent was equal to the second lowest on record in 2007. The autumn freeze-up was exceptionally slow. The mean November extent of 9.08 million km2 was 0.8 million km2 below the previous record low.

Antarctic sea ice
Antarctic sea-ice extent was close to the 1979–2015 average for the first eight months of the year, reaching a seasonal maximum of 18.44 million km2 on 31 August. However, the spring melt was exceptionally rapid, resulting in a November mean extent of 14.54 million km2 – by far the lowest on record (1.0 million km2 below the previous record). The reasons for the rapid collapse of Antarctic sea ice in late 2016 are not yet completely understood.

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