It was warm and wet: 2022 set stage for last year's disastrous weather

Storm fronts like this one barrelling in from the Pacific in August brought still more rain to an already saturated Tairāwhiti. The water table in the district was so high it delayed or inhibited plantings of major crops like maize and meant that burials at Taruheru Cemetery were forbidden for some months. Picture by Liam Clayton

The future of Gisborne’s weather is here now, signalled by local data for 2023 and recent years.

That is the view of journalist Roger Handford, who has studied weather, astronomy and ecology for over 40 years.

“Last year was the eighth year in a row where the mean daily temperature has been over 15 degrees.

“Since official records started in 1937, this is the only run of years where this measurement has been 15 degrees plus.”

Figures produced by the National Institute of Water and Atmospheric Research (Niwa) show the 30-year average for the mean daily temperature has risen steadily, to 15.29 degrees for 2023.

The 30-year average (or “normal”) for 1991 to 2020 is 14.6 degrees, so last year was well ahead of that.

Every year from 2016 to now has been above the 15 degree annual daily mean.

The warming trend is underlined by the records showing no year before 1988 had a daily mean over 15 degrees.

This trend is also shown by 1937 to 1967 having a daily mean of 13.95, which indicates Gisborne temperatures have risen by over a degree in 85 years.

The rise would appear to have accelerated over the past decade.

Last year ended with a December that underlined the trend in Gisborne’s changing weather — hotter, wetter and cloudier.

December recorded a mean maximum daily temperature of 24.1.

This was one degree higher than the 30-year average.

The month’s mean minimum daily temperature was 14.8 degrees —  humid nights that were 1.7 degrees warmer than the 30-year average.

Combined, this gave December a mean daily temperature of 19.5 degrees, the 30-year mean being 18.1.

This was the fourth warmest December on record since 1937, the warmest being 2021 ( a mean daily of 20.3 degrees; 1995 - 19.7 and 1984 - 19.5).

Everyone knows it has been our wettest year on record. December again followed the trend with just over 100 millimetres, 36mm more than the 30-year December average.

With wetter and cloudier weather, December lost out on 21 percent of its usual sunshine — 187.6 hours against the 30-year average of 236.9.

When looking at the overall weather picture for last year, Mr Handford said it has to be taken into account that 2023 followed our fifth wettest year since 1938 and another warm year where the mean daily temperature was 15.3.

Nine months out of 12 were warmer than usual for 2022, but again it  fell short on sunshine with nine months of below-average hours of sun.

Although sunshine hours totalled 2022.0, the year fell short of the 30-year average by some 274 hours.

Looking back, March 2022 had a near-record rainfall and in many ways 2022 set the stage for last year’s disastrous and record-breaking weather.

What will 2024 bring?

“No expert can tell us, but the trend in the historical weather data gives a clear indication that this district can probably expect warmer, cloudier weather and more frequent extremes,” Mr Handford said.

These are the wettest years from MetService and harbour records going back to 1878.