...while Kerry Emanuel (MIT) forecast a 10 fold increase in frequency of extreme hurricane event at the end of the century ( 10 fold increase for Harvey's rain intensity and 10 fold increase for Irma's max wind intensity). However, I don't on which RCP scenario, scientist Kerry Emanuel, calculated these projected frequencies
I find this highly speculative. Atlantic hurricane intensity has not increased over the past century, so it seems that his forecast is on rather shaky ground. Thus far, there has been no indication that major hurricanes are traveling further north. Recent rainfall increases, due to predicted atmospheric blocking, may have a better chance of occurring.
Kerry Emanuel is considered as expert in his field (hurricanes) I think he has more than 30 years of research in this field, you can look at his researchgate profile:
https://www.researchgate.net/profile/Kerry_EmanuelYou can also have a look at my post "Reply #350 on: September 13, 2018, 10:27:38 PM" on the same hurricane season 2018 thread, and you will be able to watch Kerry Emanuel presentation at the American Meteorological Society, his research tends to prove that effectively the path of hurricane is migrating up North in the Northern hemisphere and down South in the Southern, well in hand with warmer sea surface temperature. At the end of last year, there were 3 research papers from 3 unrelated research teams who issued papers on the higher rainfall intensity from Harvey and the impact of climate change on the odds of this event. It is quite easy to find these papers on google scholar.
Additional, last year hurricane Ophelia was the first hurricane so much up North East in the Atlantic, mainly due to exceptional sea surface temperature allowing the cyclone to keep its tropical hurricane status in an area where there has not been tropical storm before:
https://en.wikipedia.org/wiki/Hurricane_Ophelia_%282017%29https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/asl.813"During September 2017, the region of observed SSTs with temperatures >26.5°C extended slightly further north relative to the 1993–2015 climatology, and positive SST anomalies were recorded across the eastern tropical Atlantic and Caribbean Sea (Figure 4c). Indeed, during September 2017, SSTs in the northern Caribbean approached 30°C (Figure 4e), which, when combined with favourable remote forcing from the tropical Pacific, could favour the development and intensification of tropical cyclones (e.g., Vecchi and Soden, 2007)"
According to a NASA study, the very active 2017 hurricane seasons was driven by positive sea surface temperature anomaly, contrary to 2005 and 2010 (very active but with few landfall in the US) which were more driven by favourable atmospheric conditions.
also in:
"The Present-Day Simulation and Twenty-First-Century Projection of the Climatology of Extratropical Transition in the North Atlantic"
MAOFENG LIU et al, April 2017
https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-16-0352.1the paper results shows a trend of moving up North, whether in North West or North East Atlantic of the transition from tropical storm to extra tropical storm, with climate change going forward
ABSTRACT
This study explores the simulations and twenty-first-century projections of extratropical transition (ET) oftropicalcyclones(TCs)intheNorthAtlantic,withanewlydevelopedglobalclimatemodel:theForecastOriented Low Ocean Resolution (FLOR) version of the Geophysical Fluid Dynamics Laboratory (GFDL) Coupled Model version 2.5 (CM2.5). FLOR exhibits good skill in simulating present-day ET properties (e.g., cyclone phase space parameters). A version of FLOR in which sea surface temperature (SST) biases are artificially corrected through flux-adjustment (FLOR-FA) shows much improved simulation of ET activity (e.g., annual ET number). This result is largely attributable to better simulation of basinwide TC activity, which is strongly dependent on larger-scale climate simulation. FLOR-FA is also used to explore changes of ET activity in the twenty-first century under the representative concentration pathway (RCP) 4.5 scenario. A contrasting pattern is found in which regional TC density increases in the eastern North Atlantic and decreases in the western North Atlantic, probably due to changes in the TC genesis location. The increasing TC frequency in the eastern Atlantic is dominated by increased ET cases.
The increased density of TCs undergoing ET in the eastern subtropics of the Atlantic shows two propagation paths: one moves northwest toward the northeast coast of the United States and the other moves northeast toward western Europe, implying increased TC-related risks in these regions. A more TC-favorable future climate, evident in the projected changes of SST and vertical wind shear, is hypothesized to favor the increased ET occurrence in the eastern North Atlantic.
