Question to the Department for Business, Energy and Industrial Strategy:

To ask Her Majesty's Government, further to the report Prolonged Siberian heat of 2020, published on 15 July, what assessment they have made of whether the report's sample size is large enough to justify the use of a GEV asymptotic approximation when analysing the Verkhoyansk temperatures.

The report’s sample size is large enough to justify the fitting method used in the analysis as daily temperature data at approximately one-year intervals are not significantly correlated from year to year over continental regions. The maximum daily temperature in a particular month or season in a particular year in a continental region does not serve as a good predictor of the maximum daily temperature in the same month or season in the following year (over and above the long-term effect of climate change) due to natural variability of the climate system. The June-July daily maximum temperature data over timescales from 1 day upwards shows no significant autocorrelation (correlation with itself across a period of time) above 1 week timescales and confirms that the 94 data points used in the report are independent, a sufficiently large number to justify the fitting method used in the analysis. The analysis in the report is based on peer reviewed methodology as set out in a paper by Van der Wiel et al. referenced in the report, which applied this fitting method to a dataset of a comparable size.