There were many photographs that encapsulated the past year of weather extremes of fierce heatwaves, dangerous floods and wild winds but perhaps the most telling is a computer-coloured satellite image from space.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
A grandly named US/European Ocean Surface Topography Mission - thankfully shortened to Jason-2 - captured the imagery of the engine that has been driving the planet's weather this past year. And the driving doesn't stop at midnight, New Year's Eve.
The great and powerful El Nino event of 2015, shown below as a dagger of raised sea levels along equator striking westwards from South America far into the central Pacific symbolises the huge oceanic circulation changes that have taken place this year.
More to the point is the comparison with the monster 1997-98 El Nino that is regarded as the largest such event on record.
As US space agency NASA noted in a report this week, sea levels in the east - shown as in shades of white - are as much as 25 centimetres above normal. To the western Pacific, the drop - shown in purple - is at least as large.
The mammoth shift in water levels across the world's largest ocean shows how the usual easterly trade winds that pile water up in the west have stalled if not reversed. The result is a huge warming in the upper ocean levels to the east and a cooling in the west.
"Clouds and storms follow the warm water, pumping heat and moisture high into the overlying atmosphere," Alan Buis, from NASA's Jet Propulsion Laboratory (JPL), wrote in the posting to NASA's website. "These changes alter jet stream paths and affect storm tracks all over the world."
Wenju Cai, a CSIRO researcher of El Ninos and climate change, estimates the world's weather engine has effectively shifted about 10,000km to the east: "This is so huge in terms of the reorganisation of the atmosphere."
According to NASA, south-east Asia's rainfall was "sapped", contributing to the conditions that allowed fires to burn unhindered in the country's forests, cloaking the region in smoke. Other impacts include flooding in South America, a record-breaking hurricane season in the eastern tropical Pacific and widespread coral bleaching.
In Australia's case, it has meant conditions turning hotter and drier, particularly across the south and inland areas of the east.
Importantly, the El Nino's impact is far from done - and it may not have stopped growing.
"Although the sea surface height signal in 1997 was more intense and peaked in November of that year, in 2015, the area of high sea levels is larger," Josh Willis, a JPL project scientist, told NASA. "This could mean we have not yet seen the peak of this El Nino."
Australia's Bureau of Meteorology last week said the El Nino "remains near its peak" but may not return to neutral conditions - with the convection engine shifting back westwards - until at least May.
Agus Santoso, a senior researcher at the University of NSW-based Climate Change Research Centre, said the event while comparable with the 1997-98 one will probably fall short in its intensity.
"My feeling is that it will be the second highest in terms of sea-surface temperature anomalies," Dr Santoso told Fairfax Media.
The impacts of an El Nino typically linger long after its peak and include significant flooding in the western US.
Record heat
El Nino years are also notable for elevated global temperatures as the Pacific absorbs less heat from the atmosphere - and even gives some back.
2015 will easily be the hottest year in records going back to the 1880s, eclipsing a high mark set just a year earlier as the El Nino spike adds to the background warming caused by human activity including the burning of fossil fuels.
One element of the bizarre planetary heat has been on display this week, with a huge storm system in the North Atlantic dragging tropical warmth into the High Arctic.
By one estimate, the North Pole was briefly above freezing - despite being in the depths of its dark winter - for about six hours, according to US meteorologist Ryan Maue.
The North Pole's temperature soared about 30 degrees above normal - reaching levels more typical at the height of the northern summer in July.
That same storm, though, also brought more rainfall to parts of the UK already hard hit by flooding.
For Australia, the extra atmospheric warmth is likely to top up the summer, Dr Cai said.
Adelaide will end the year with its hottest December on record while Melbourne will post its second hottest - behind 2005. A shift in the location of the Melbourne site to a slightly cooler spot probably prevented a new record for the month being set.
The dry conditions and the heat, though, has set up a long summer of high fire risk for much of the country's south.
That outlook will be of no surprise to Victorians who face another day of severe fire danger after last week's bushfires. Temperatures will climb into the high 30s or beyond on Thursday to round out 2015.
While the El Nino's impacts will play out deep into 2016, scientists such as CSIRO's Dr Cai and UNSW's Dr Santoso expect the event to make way for its opposite - a La Nina - before the year's end.
If, as in 1998, conditions flip the other way, with the weather engine shifting back to the western Pacific, areas that have had rain shortages in 2015 may well get floods amid cooler conditions.
"Extreme La Ninas tend to follow extreme El Ninos," Dr Santoso said.
