New report about climate change and how it could impact future Atlantic seasons

[MarioProtVI]

So as most probably know the IPCC released it’s damming report on climate change and that we are in for a bad rest of the century if we don’t curb emission now.

A few notable things that were interesting is I saw how that, if trends continue, climate change will make the tropical Atlantic drier (less precipitation). This would probably mean less active and strong MDR seasons like say 1995, 2004 and 2017 in the decades to come (some of this might already be visible considering how since 2010 the quality per year, mainly in La Ninas have seemed to become drier and weaker, like 2011 and 2019 to an extent). (graphic is here https://www.ipcc.ch/sr15/graphics/)

Another thing that was discussed was the risk of the collapse of the Gulf Stream, which has made some headlines previously. Were this to occur at some point in the future, the resulting chain effects would probably significantly weaken the THC and result in 2007- or 2013-esque seasons with significantly lower quality and weaker storms since it allegedly would disrupt the monsoon in Africa. All said it probably would cause some sort of -AMO perhaps but this is just my two cents after glancing at this. That said it is also inevitable that future seasons will see more powerful storms worldwide (Patricia was one example) and the Atlantic is probably not too far away from seeing it’s first 200+ mph storm and sub-880 storm as a result of climate change (Of course it would be in the WCarib since that’s the only place they can theoretically form).

Thoughts and how you think future seasons will be impacted by climate change?

[Shell Mound]

A few notable things that were interesting is I saw how that, if trends continue, climate change will make the tropical Atlantic drier (less precipitation). This would probably mean less active and strong MDR seasons like say 1995, 2004 and 2017 in the decades to come (some of this might already be visible considering how since 2010 the quality per year, mainly in La Ninas have seemed to become drier and weaker, like 2011 and 2019 to an extent). (graphic is here https://www.ipcc.ch/sr15/graphics/)

Another thing that was discussed was the risk of the collapse of the Gulf Stream, which has made some headlines previously. Were this to occur at some point in the future, the resulting chain effects would probably significantly weaken the THC and result in 2007- or 2013-esque seasons with significantly lower quality and weaker storms since it allegedly would disrupt the monsoon in Africa.

I have been saying the bolded for some time now, and finally the mainstream science on climate change seems to back me up. I think climate change has led to the most recent +AMO ending earlier than previous +AMO cycles. As a result, since most Category-4+ landfalls on the CONUS tend to be associated with storms that form in the MDR, a less active MDR with fewer long-lived systems and thus lower ACE would likely reduce the risk of extremely intense landfalls on the CONUS. So in this respect climate change is arguably a good thing, as it may offset warmer global SST by facilitating -AMM/-AMO development. So far there is little evidence of sea-level rise and the “negative” impacts of climate change seem to be overstated, although I do believe warming is ongoing.

[Ubuntwo]

I have been saying the bolded for some time now, and finally the mainstream science on climate change seems to back me up. I think climate change has led to the most recent +AMO ending earlier than previous +AMO cycles. As a result, since most Category-4+ landfalls on the CONUS tend to be associated with storms that form in the MDR, a less active MDR with fewer long-lived systems and thus lower ACE would likely reduce the risk of extremely intense landfalls on the CONUS. So in this respect climate change is arguably a good thing, as it may offset warmer global SST by facilitating -AMM/-AMO development. So far there is little evidence of sea-level rise and the “negative” impacts of climate change seem to be overstated, although I do believe warming is ongoing.

You can't just pick and chose the parts of science that agree with your subconscious. Little evidence for sea-level rise? Key West has reported a 9 inch increase in sea level since 1913. Satellite estimates pin it at about 3-4 inches over just the past 30 years. Coastal areas that rarely flooded historically now do so tidally. Warming (anthropogenic or not) isn't something you believe in, it is objectively and measurably occurring.

Climate change is bringing, and will continue to bring, a 'mixed bag' of impacts on the AHS. Heavy rainfall/flooding events will become more frequent. Warmer sea surface temperatures and OHC not only mean more fuel for storms, but also that the season itself is expanding, both in time through the year and geographical coverage. While the RCP simulations predict a drier (~10%) tropical Atlantic with 1.5-2C warming, the Sahel looks ~20% wetter. That would normally indicate stronger and larger tropical waves - this is not a clear cut and binary thing.

[KWT]

1: the model setup for precip/extreme temps look mighty close to el nino. Given enso is a function of *relative* temp difference not necessarily absolute temps, is it trying to say we will be in a more constant state of el nino. If so I'm truly not buying that part of it.

2: as for the Atlantic itself, my guess is the model sees the itcz moving northwards towards the southern Sahara at times. Logically this would dry the air out and promote more sal outbreaks which shows quite nicely in the drier area spread and extent. This part does make sense to me.

Edit - also agree with some points above, a warmer Atlantic means a longer season, indeed I think we already are seeing that with marginal early systems that may have not been strong enough now just about are, and in quite the glut of October canes in recent years.

I suspect we may end up with a less compact season, maybe weaker peak but higher numbers due to it being more spread out through the year than in the past.

[mitchell]

So far there is little evidence of sea-level rise and the “negative” impacts of climate change seem to be overstated, although I do believe warming is ongoing.

Little evidence for sea level rise? What?
Virtually every long record tidal station along the US coastline (many recording water level data back into the middle 19th century) show the rising seas with very good regional corroboration.

Aside from data, there is observation.

The US east coast is just littered with evidence of sea level rise. centuries old Cedar tree stumps (a species that grows a couple feet above above Mean High Water are exposed at or below current mean high water. I mean the evidence of rise is just everywhere.

[al78]

The general consensus on tropical cyclone activity globally is that storm numbers most likely will decrease, hurricane numbers will stay the same or decrease, and there will be a shift in the intensity distribution to more frequent very intense hurricanes/typhoons/cyclones (cat 4+). It is less clear what will happen in individual basins, but my take on it is that the rise in storm numbers in recent decades is an artifact of improvements in observation techniques and the NHC is calling storms more frequently than, say, 50 years ago. This is backed up in the literature which shows the incerase in storm numbers in the Atlantic is due to the increase in the number of weak short lived tropical storms that would have been missed decades ago. I think the dice will roll in favour of cat 4/5 hurricanes due to warming SSTs increasing (on average) the MPI, and I expect La Nina events will still continue in the future, the favourable atmospheric conditions that accompany them will give weak storms the opportunity to tap into that extra oceanic heat and given them more chance to intensity to cat 4/5 strength. I do not know how the atmospheric conditions are expected to involve in the future on average. If vertical wind shear is expected to increase, and/or the tropical Atlantic is expected to become drier, that will negate the effect of rising ocean temperature.

[tolakram]

Maue had a tweet about the storm numbers.

 https://twitter.com/RyanMaue/status/1425501295490764800