Adding new evidence to the attribution puzzle of the recent water shortage over São Paulo (Brazil)

Abstract

São Paulo, Brazil has experienced severe water shortages and record low levels of its water reservoirs in 2013-2014. We evaluate the contributions of Amazon deforestation and climate change to low precipitation levels using a modelling approach, and address whether similar precipitation anomalies might occur more frequently in a warming world. Precipitation records from INMET show that the dry anomaly extended over a fairly large region to the north of São Paulo. Unique features of this event were anomalous sea surface temperature (SST) patterns in the Southern Atlantic, an extension of the sub tropical high into the São Paulo region and moisture flux divergence over São Paulo. The SST anomalies were very similar in 2013/14 and 2014/15, suggesting they played a major role in forcing the dry conditions. The SST anomalies consisted of three zonal bands: a cold band in the tropics, a warm band to the south of São Paulo and another cold band poleward of 40 S. We performed ensemble climate simulations with observed SSTs prescribed, vegetation cover either fixed at 1870 levels or varying over time, and greenhouse gases (GHGs) either fixed at preindustrial levels (280 ppm CO 2) or varying over time. These simulations exhibit similar precipitation deficits over the São Paulo region in 2013/14. From this, we infer that SST patterns and the associated large-scale state of the atmosphere were important factors in determining the precipitation anomalies, while deforestation and increased GHGs only weakly modulated the signal. Finally, analyses of future climate simulations from CMIP5 models indicate that the frequency of such precipitation anomalies is not likely to change in a warmer climate.

Pacific and Atlantic Multidecadal Variability Relations with the Choco and Caribbean Low-Level Jets during the 1900–2015 Period

“…Barichivich et al [33] found an intensification of Walker's circulation during the late 1990s, associated with strong warming of the tropical Atlantic and cooling of the tropical Pacific. Furthermore, Pattnayak et al [34,35] analyzed the relationship of precipitation in northern and northwestern South America with SST anomalies in the Atlantic after 2000. Therefore, through these interbasin SST gradients, the PDO and AMO SST mean states modulated the CJ and CLLJ variations during the last three decades [30].…”

Fate of Rainfall Over the North Indian States in the 1.5 and 2°C Warming Scenarios

“…The concentrations of greenhouse gases (GHGs) must fall before 2060 to accomplish the 1.5°C warming objective, whereas to achieve the 2°C warming target, GHGs must fall before 2085 (Sanderson et al., 2016). Due to the change in the concentration of GHGs, the ocean warming pattern changes and hence show different climate response in term of precipitation in the atmosphere (Chadwick et al., 2013; Long et al., 2014; Pattnayak et al., 2018).…”

“…hence show different climate response in term of precipitation in the atmosphere (Chadwick et al, 2013;Long et al, 2014;Pattnayak et al, 2018).…”

Drivers and physical processes of drought events over the State of São Paulo, Brazil

“…Drought events in southeastern Brazil are widely publicized by the national and international news. For example, beginning from austral summer 2013/2014 to 2014/2015, southeastern Brazil suffered a 16-month drought, and by January 2015, the Cantareira reservoir, the main water storage for the metropolitan area of São Paulo, was down to 5% of capacity (Nobre et al 2016;Pattnayak et al 2018). Debate continues over whether anthropogenic effects influenced this event and the past rainfall variability.…”