The trends in the number of warm days for the 30 temperature sites across New Zealand are presented from 1972 to 2022. Warm days are days with a daily maximum temperature above 25 degrees Celsius.
The number of warm days change from year to year in response to variable weather patterns and climate drivers. Climate models project we may experience more warm extremes in the future (IPCC, 2021). According to the WMO (2016) a decrease in cold days and nights and an increase in warm days and nights can have major implications for human health, agricultural production, and ecosystems.
Variables:
site: NIWA monitoring site
period_start: Start of the period for which the trend was assessed
period_end: End of the period for which the trend was assessed
p_value: P value
slope, conf_low, conf_high: Rate of change per year and their lower and upper confidence intervals
conf_level: confidence level (66% or 90% to match IPCC likelihood levels)
z: Z score
trend_method: Whether the information in this row correspond to the Sen slope or the Mann-Kendall test
n: number of observations used to calculate the trend
note: analysis note
s, var_s, tau: Mann-Kendall trend statistics
alternative: the alternative hypothesis used for the Mann-Kendall test
trend_likelihood: Likelihood categories adapted from IPCC. Indicates the likelihood that a trend is increasing, decreasing, or indeterminate
lat: Latitude
lon: Longitude
References:
Intergovernmental Panel on Climate Change. (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (V. Masson-Delmotte, P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, & B. Zhou, Eds.). Cambridge University Press.
https://www.ipcc.ch/report/ar6/wg1/
World Meteorological Organization. (2016). Hotter, drier, wetter. Face the future. WMO. https://public.wmo.int/en/resources/world-meteorological-day/previous-world-meteorological-days/hotter-drier-wetter-face
