Asymmetric and heterogeneous frequency of high and low record-breaking temperatures in China as an indication of warming climate becoming more extreme

Abstract

The ratio of record highs to record lows and their rates of decay with time has emerged as a new metric for climatic warming and extremes complementing with the well-documented daily temperature range. This paper evaluates both the observed and model-projected high/low record behaviors in China, with a particular focus on an anomalous cooling region sometimes termed "warming hole." We found that the observed frequency decay over time of high (low) record temperatures occurred much slower (faster) than the theoretically expected rate (1/n) of the independently and identically distributed (i.i.d.) time series. The high to low record (H/L) ratio is 3.0 in the recent years, about 50% larger than those in the U.S. and Europe. A drifting-mean i.i.d. model mimicking warming climate represents the observed record behavior much better than the i.i.d. sequence, but it still cannot explain the full record variability, implying that either the past mean warming rate has been nonlinear (accelerating) or temperature variance has become more extreme. The H/L record ratio by the mid-2040s with respect to 2006 could reach 6.8 under the high emission RCP8.5 scenario, whereas the increase of the record magnitude in the representative concentration path scenario remains largely similar to the current climate. Record frequency is highly correlated not only to Pacific Warm Pool temperature but also to Atlantic Multidecadal Oscillation index, with significant positive correlation in northern and southeastern China. Key Points High to low record temperature ratio was 3.3 in past decade in China. Mean climatic warming was the main cause for increased record hot days. By 2050s, the high to low record temperature ratio could reach 30. © 2013. American Geophysical Union. All Rights Reserved.