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Warming trend clear

Letter

My analysis of our weather records going back to 1905 shows conclusively the Gisborne-East Coast region is undergoing gradual climate change.

Data from the national weather archive shows the average temperature for the year has risen slowly but steadily, with 2021 continuing the last decade's run of warm years.

2021 had a mean daily temperature of 15.1 degrees — that is, the highs and lows of each day averaged out over the year.

The rise to above 15 degrees began in earnest after the 1997/98 El Nino event, with Gisborne's MetService station at the airport recording an annual daily mean of 15.7 degrees in 1998. That was the highest on record since intermittent local records began in 1905.

In the past seven years, every year but 2014 has had a daily mean of over 15 degrees.

To put this into historical context, the annual daily mean has risen from lows of 13.3 in 1976 and 13.4 degrees in 1940.

1909 was an unusual year with land clearance by fire one of the major factors altering the climate, and producing an annual daily mean of 15.1 for that year.

It took another 79 years for another warm year with a daily mean of 15.1 in 1988.

The 30-year averages which started in the 1960s show the steady rise in temperature:

1941-1970 — 13.5

1951-1980 — 13.6

1961-1990 — 13.75

1971-2000 — 14.3

1981-2010 — 14.5

To sum it up, this district has seen an average rise in temperature of over one degree in the past 100 years, in line with national figures recorded by the Department of Statistics.

Rainfall and sunshine patterns have also changed from a summer/winter seasonal separation to more rain spread out over the year, and more sun.

Another notable change from distinct cold and wet winters and hot and droughty summers is the increase of sudden, extreme events, such as the November rainstorm, and several other short but heavy downpours of 40-50mm, and more frequent dry winters.

Roger Handford