HOW WARM WILL 2018 BE?

David Whitehouse
GWPF Observatory, 6 June 2018 

The start of 2018 has been warm because of unusual weather which has already subsided.

As far as global temperature goes it’s been a warmish start to the year, though not exceptional. This has led Carbon Brief in its three-monthly “state of the climate” report to predict that this year “is likely” to be as warm as the fourth warmest year since records began about 150 years ago. They say it could be as high as the second or as low as the 12th warmest.

Carbon Brief says, “The first three months of 2018 can give some sense of what to expect for the entire year.” But being based on a quarter of this year’s monthly measurements it could be described as either bold or foolish. Because the prediction is made without a good understanding of what has been happening to the global temperature in the past months it is probably more of the latter.

Nowhere in the Carbon Brief prediction is there any analysis of why 2018 got off to a warm start. Look towards the  Tasman Sea that has been adding to global temperatures since late 2017.

The water temperature in the Tasman Sea is well above normal –  6° C more than average for the start of December. New Zealand’s summer was the hottest on record, Tasmania had its hottest November-January on record. It was exceptionally warm on both sides of the Tasman, more than two degrees above average in December and part of January.



The increase is not due to climate change but to a La Nina climate system. Globally La Nina events are associated with cooling but that is not true in some regions which, because of blocking high pressure regions and sometimes a lack of storms, allows sea temperature to increase. New Zealand’s National Institute of Water and Atmospheric Research  meteorologist Ben Noll told newshub nz that the “very impressive marine heatwave” has led to the largest deviation from normal temperatures in the world. “The sea surface temperatures in the Australia-New Zealand region are presently the most anomalous on the globe…typical La Nina signature, but intensity turned up many notches.” He added that there were other factors driving the temperature higher, “La Nina sits in the background as big driver of the change, but it’s at the top of a pyramid of other factors”.

It was so warm that the Australian Government Bureau of Meteorology and New Zealand’s National Institute of Water and Atmospheric Research teamed up to release a “special climate statement”. Though why this abnormal weather merits a climate statement seems strange. The hot spot off the Tasman Sea has not been the only one in the past few months.



Recently scientists at Australia’s Commonwealth Scientific and Industrial Research Organisation produced a framework for marine heatwaves. The new classification system ranks them by intensity using four levels. A Category 1 heatwave is the lowest intensity. Under the new system, a heatwave that hit the Mediterranean Sea in 1999 would be considered a Category 1 heatwave. The NE Pacific event of 2013 – 2015 the so-called Blob is a Category 3. A marine heatwave in Western Australia in 2011 would be a Category 4.

The study of marine heatwaves is in its infancy. It is possible they are increasing in frequency and they may be linked to rising sea temperatures. Much more work is needed.

2018 has been warm because of unusual weather which has already subsided. It is not representative of the global temperature for the remainder of the year. There is evidence the oceans are cooling.