We know that 2016 was the hottest year on record - a remarkable 1.1°C above the pre-industrial period and 0.06°C above the previous record set in 2015. Unfortunately, this was not the only climate record that was shattered last year.
In its latest annual Statement on the State of the Global Climate, the World Meteorological Organization (WMO) lists multiple reasons why 2016 was a year of great significance for our climate.
“This report confirms that the year 2016 was the warmest on record ... This increase in global temperature is consistent with other changes occurring in the climate system,” said WMO Secretary-General Petteri Taalas.
“Globally averaged sea surface temperatures were also the warmest on record, global sea levels continued to rise, and Arctic sea-ice extent was well below average for most of the year,” he said.
“With levels of carbon dioxide in the atmosphere consistently breaking new records, the influence of human activities on the climate system has become more and more evident,” said Mr Taalas.
Several studies, not included in the WMO report, show that these extreme climate events have continued into 2017. “Even without a strong El Niño in 2017, we are seeing other remarkable changes across the planet that are challenging the limits of our understanding of the climate system. We are now in truly uncharted territory,” said World Climate Research Programme Director David Carlson.
Here's a closer look at some of the key environmental indicators from last year.
Parts of the world are actually getting colder
The world is getting warmer, but parts of it are actually getting colder. For example, in 2016, northern and central Argentina, Paraguay and lowland Bolivia experienced significantly cooler temperatures on land. In May, Argentina had its lowest nationwide mean maximum on record. The temperature did not rise above 20°C in Buenos Aires for 103 days from 25 April to 5 August, the longest such period on record.
Meanwhile, south-western Australia experienced its coldest winter since 1990.
Crop yields boomed
Flooding occurred in Niger and northern Nigeria, and was reported in other parts of West Africa outside the Niger basin, including Gambia, Senegal and Ghana. Significant flooding was also reported in the southern half of Sudan.
But the wet conditions led to good crop production in many parts, with record yields reported in Mali, Niger and Senegal.
Record yields were also reported in Tasmania. After the driest eight months on record from September 2015 to April 2016, Tasmania had its wettest May to December on record. The high rainfall and mild spring conditions led to record grain production with winter crop production expected to be 49% above that of 2015.
Ice melted – in winter
The 2016 autumn freeze-up of Arctic sea ice was exceptionally slow, but even stranger things were going on. In mid-November, the sea ice actually started melting. On 19 November, the extent of Arctic sea ice, shown in red here, was nearly 1 million square kilometres lower (8.633 million vs 9.504 million) than it was on that date in 2012.
The next day, the gap widened further, with 8.625 million square kilometers in 2016 versus 9.632 million in 2012.
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Snowfall in the northern hemisphere showed two extremes in 2016.
The mean annual snow-cover extent for 2016 in the Northern hemisphere was 24.6 million km2, 0.5 million km2 below the 1967–2015 average and the 12th lowest value on record. This was very similar to 2015.
But the snow cover in January was above average.
While the snow cover for February to June was well below average. The April mean snow-cover extent was the lowest on record, with March ranking second, February and June third and May fourth.
By the time Autumn came around, the snow cover was above average again.
From drought to flooding
Last year saw examples of extreme transitions from drought to above-average rainfall.
The most dramatic transition occurred in Australia.
Droughts were well established early in the year in two separate regions – inland Queensland and a region of the south-east encompassing Tasmania, western Victoria and south-east South Australia – with below-average rainfall extending back to 2012 in parts of both regions.
But then there was a marked shift to above-average rainfall from May onwards, culminating in September, when many parts of eastern Australia had record high monthly rainfall.
The subsequent extensive flooding of inland rivers caused the main highway from Melbourne to Brisbane to be closed for more than a month. Damaging flooding occurred in early June on the east coast and in northern Tasmania.
Two separate outbreaks of major hailstorms in Texas, one around Dallas–Fort Worth in March and a second centred on San Antonio in April, resulted in combined damage of more than $5 billion. The storm threw down hailstones with a diameter of 11cm in San Antonio.
Outside the United States, a notable hailstorm occurred in Brabant province of the Netherlands on 23 June, with hailstones of 5cm–10 cm in diameter and losses estimated at €500 million ($540 million).
Cyclones and hurricanes are following different paths
Whilst the global tropical cyclone activity was close to normal in 2016, there were some startling anomalies.
The total of 82 cyclones was slightly below the long-term average of 85, but activity was above average in the North Atlantic (15 cyclones, average 12) and East Pacific (21 cyclones, average 16) regions.
They were below average in the southern hemisphere, particularly the Australian region, which had its least active season since satellite records began with only three cyclones (average 10).
The North-West Pacific season was close to average with 26 cyclones, although their geographic distribution had some unusual features, such as three landfalls on the Japanese island of Hokkaido: the first time this has occurred since records began in 1951.
There was also some unusual hurricane activity. Hurricane Pali, in the central Pacific, in addition to odd timing, also reached the lowest latitude (2°N) of any western hemisphere hurricane, while Alex was the first January hurricane in the North Atlantic since 1938.