More Intense, More Frequent, and Longer Lasting Heat Waves in the 21st Century

Abstract

U-230 Th ages are derived as described in (14). See (34) for a review of 230 Th dating in magmatic systems. The reported ages are taken to be those of crystallization because of the relatively tight packing of ions within allanite and the tetravalent charge of Th [compare (35)]. Reequilibration of Th during magmatic residence will be insignificant: Based on the predictive model of Fortier and Giletti (36), Th diffusion would only affect ϳ2 m in allanite over a period of 100,000 years at the highest reported temperature of the YT T magma (ϳ780°C). Uncertainty in the calculated ages due to possible variation of initial 230 Th/ 232 Th during magmatic evolution can be evaluated by assuming that observed eruption-age 230 Th/ 232 Th activity ratio variations of the YT T (0.358 to 0.433) are representative of the initial range of Th-isotope composition. For reported ages Ͻ120 ka, the uncertainty in age associated with the initial ratio is within the analytical uncertainty on the ages, except for the youngest allanite domains which could not have grown from melts that had Th isotope compositions significantly different from that of their host. Reported ages that are 120 to 200 ka could be at most a few percent to, for the older of these, as much as 27% older than allowed by the analytical uncertainty. Those few allanites with ages Ͼ200 ka could be substantially older. Thus, the age ranges reported here are conservative. 45. We are grateful to C. Chesner for samples; C. Coath, F. Ramos, and F. Kyte for analytical help; and especially J. Simon and G. Bergantz for insightful discussions. Anonymous referees provided very helpful reviews. show that future heat waves in these areas will become more intense, more frequent, and longer lasting in the second half of the 21st century. Observations and the model show that present-day heat waves over Europe and North America coincide with a specific atmospheric circulation pattern that is intensified by ongoing increases in greenhouse gases, indicating that it will produce more severe heat waves in those regions in the future.

Dependence of Present and Future European Temperature Extremes on the Location of Atmospheric Blocking

“…This is in agreement with earlier studies connecting blocking to an increase in colocated summer HWs, which is found to be mainly driven by increased radiative forcing at the location of the block (e.g., Meehl & Tebaldi, 2004; Pfahl & Wernli, 2012; Sousa et al, 2018). However, our results also show anticorrelation of blocking with HWs in southern Europe for most seasons and regions.…”

Effects of an extended drought period on physiological properties of grassland species in the field

“…Many global circulation models predict that temperate areas will become warmer and drier worldwide (Cao and Woodward 1998) with more extreme events such as severe heat waves and droughts (Easterling et al 2000;Meehl et al 2000), especially in Europe (Schär et al 2004). Such an increase in variability would strongly increase the occurrence of heat waves and drought (Meehl and Tebaldi 2004). It was previously demonstrated that this increase in temperature variability is clearly related to the feedbacks between the land surface and the atmosphere (Seneviratne et al 2006).…”

Long-term projections and acclimatization scenarios of temperature-related mortality in Europe

“…In particular, increasing attention has been paid to warm extremes [6][7][8][9][10] , which are expected to become more frequent, longer and more severe 11 . Europe emerges as an especially responsive area to temperature rise, particularly during the warm season 12 .…”