Did climate change impact Hurricane Harvey?

[Ridgerunner]

I think much is being made of one hurricane season.

I remember a long time ago thinking about the various Olympic records for this or that; long jump, high jump, discus, 100 year dash, etc, etc, etc. A problem we have with knowing whether any of them exceeded prior human accomplishments I the lack of solid information about the past. How do we know for sure, by way of example, that the longest human jump in history wasn’t somewhere on a backwater of the Orinocco in 918 B.C.?

 

[Theo520]

Can we pretty much at least agree that a warmer ocean contributed to these devastating hurricanes?

No we can’t, because the demonstrated warming to date in quite minimal.

The models predict increased severity many decades in the future, not now.

 

[Theo520]

That CC is impacting hurricane intensity and will be continuing to increase that intensity on into the future is fairly well established. Re frequency there is some debate about it, one idea being that the more intense hurricanes will sort of take the wind out of the sail for more frequent hurricanes – the idea that while hurricanes will likely become more intense, they will be less frequent – this is under debate re frequency.

It’s well established IN THE GCM MODELS, not in historical record.

Also, the GCM models are predicting this for many decades in the future, after we have significant warming, they don’t predict it for the present sans warming.

 

[Zzyzx_Road]

Can we pretty much at least agree that a warmer ocean contributed to these devastating hurricanes?

No we can’t. We have had devastating hurricanes get started over cooler waters. Further, there is insufficient data to say what level of correlation we can expect because more accurate land-based measurements of hurricanes got started less than 100 years ago while satellite based measurements have been around less than 50 years. Would really need accurate data for hundreds of years before we can draw firmer conclusions.

 

[HarryStotle]

Not even over the past 100 years.

https://www.gfdl.noaa.gov/historical-atlantic-hurricane-and-tropical-storm-records/

There has been a very pronounced increase in the number of tropical storms and hurricanes in the Atlantic since the late-1980s. However, to gain insight on the influence of climate change on Atlantic tropical storm and hurricane frequency, we must focus on longer (> 100 yr) records of Atlantic hurricane activity since very strong year-to-year and decade-to-decade variability appears in records of Atlantic tropical cyclones. If greenhouse warming causes a substantial increase in hurricane activity, then the century scale increase in global and tropical Atlantic SSTs since the late 1800s should have been accompanied by a long-term rising trend in measures of Atlantic hurricanes activity.

Existing records of past Atlantic tropical storm numbers (1878 to present) in fact do show a pronounced upward trend, correlated with rising SSTs (see Figs. 1 and 9 of Vecchi and Knutson 2008). However, the density of reporting ship traffic over the Atlantic was relatively sparse during the early decades of this record, such that if storms from the modern era (post 1965) had hypothetically occurred during those earlier decades, a substantial number would likely not have been directly observed by the ship-based “observing network of opportunity.” We find that, after adjusting for such an estimated number of missing storms, there is a small nominally positive upward trend in tropical storm occurrence from 1878-2006. But statistical tests reveal that this trend is so small, relative to the variability in the series, that it is not significantly distinguishable from zero (Figure 2). Thus the historical tropical storm count record does not provide compelling evidence for a greenhouse warming induced long-term increase.