Abstract
The puzzle of recent global warming trend slowdown has captured enough attention, though the underlying cause is still unexplained. This study addresses that area segregating the role of natural factors (the sun and volcano) to that from CO2 led linear anthropogenic contributions. It separates out a period 1976–1996 that covers two full solar cycles, where two explosive volcanos erupted during active phases of strong solar cycles. The similar period also matched the duration of abrupt global warming. It identifies that dominance of Central Pacific (CP) ENSO and associated water vapour feedback during that period play an important role. The possible mechanism could be initiated via a preferential alignment of NAO phase, generated by explosive volcanos. Inciting extratropical Rossby wave to influence the Aleutian Low, it has a modulating effect on CP ENSO. Disruption of Indian Summer Monsoon and ENSO teleconnection during the abrupt warming period and a subsequent recovery thereafter can also be explained from that angle. Interestingly, CMIP5 model ensemble, and also individual models, fails to comply with such observation. It also explores possible areas where models miss important contributions due to natural drivers.
Highlights
The global temperature has risen at an unprecedented pace since 1976/1977 (Hansen et al, 2010; Ipcc, 2013)
A positive connection between Aerosol Optical Depth (AOD) and North Atlantic Oscillation (NAO) is clearly noticed even separating out influences of ENSO, a longer-term trend and Sun Spot Number (SSN)
As the study focuses on natural influence, that includes both the sun and volcano, caution should be taken if the sun indicates reverse behavior for NAO
Summary
The global temperature has risen at an unprecedented pace since 1976/1977 (Hansen et al, 2010; Ipcc, 2013). Coupled modeling community using all forcing could successfully capture that rising trend. Associated with that abrupt hike in temperature, world experienced unusual climate patterns globally (Monsoon globally: Yim et al, 2013) as well as regionally (Indian Summer Monsoon(ISM): Yim et al, 2013; Kumar et al, 1999; Trenberth and Hoar, 1997; Ashok et al, 2001; ENSO: Qiong et al, 2008; Ashok and Yamagata, 2009; Yeh et al, 2009: North Atlantic Oscillation (NAO): Roy, 2016) etc. Existing coupling among known major climate modes suggested deviations (ISM-ENSO: Kumar et al, 1999; Ashok et al, 2001; NAO-ISM: Chang et al, 2001). As Many physical conditions in the ocean and atmosphere changed abruptly during the year 1976/77, studies (Miller et al, 1994; Meehl and Teng, 2014) indicated it as climatic ‘regime shift’
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
