Reacción a "The summer of 2023 the warmest in 2,000 years in the northern hemisphere, according to a study"

The paper published by Esper and colleagues in Nature concludes that the summer of 2023 was the warmest summer of the past 2,000 years in the extratropical regions of the Northern Hemisphere. To reach this conclusion, they used a combination of observational data (from the mid-19th century) and reconstructions based on proxy data (over the entire period) to analyse surface air temperatures from June to August.  

Perhaps, more than the conclusion as to the exceptional nature of the temperature of the year 2023 and in particular its boreal summer - which other studies with different methods, time periods and geographical areas had already established - what is really interesting is the combination of different data sources to cover the entire 2,000-year period and at the same time compare the limitations and biases of each data source. Within these limitations, it is perhaps worth highlighting the systematic bias in the first instrumental observations in the period 1850-1900 compared with a set of reconstructions, which could alter some of the quantitative aspects of the estimates of the current warming that take this period as a reference for the pre-industrial climate. 

It is also worth noting the coincidence in 2023 of an event due to natural variability such as an El Niño episode -which tends to increase temperatures globally- with the general warming trend induced by the increase in the concentration of greenhouse gases, which the authors conveniently highlight in their article.