Extreme Temperature Diary-March 19, 2018/ Topic: Refining Sea Level Rise Projections

Monday March 19th… Dear Diary. The main purpose of this ongoing post will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials)😊. Here is today’s main climate change related topic: (If you like these posts and my work please contribute via the PayPal widget, which has recently been added to this site. Thanks in advance for any support.)

Refining Sea Level Rise Projections

Anytime I get wind of a new study narrowing down peer reviewed projections of climate change related events I like to relate them in simple terms on this site. Today I saw a study published just a few days ago combining average global temperature anomalies with forecast sea level rise:


Quoting a few key points from the article: 

Sea-level rise (SLR) is magnifying the frequency and severity of extreme sea levels (ESLs) that can cause coastal flooding. The rate and amount of global mean sea-level (GMSL) rise is a function of the trajectory of global mean surface temperature (GMST). Therefore, temperature stabilization targets (e.g. 1.5 °C and 2.0 °C of warming above pre-industrial levels, as from the Paris Agreement) have important implications for coastal flood risk. Here, we assess, in a global network of tide gauges, the differences in the expected frequencies of ESLs between scenarios that stabilize GMST warming at 1.5 °C, 2.0 °C, and 2.5 °C above pre-industrial levels. We employ probabilistic, localized SLR projections and long-term hourly tide gauge records to estimate the expected frequencies of historical and future ESLs for the 21st and 22nd centuries. By 2100, under 1.5 °C, 2.0 °C, and 2.5 °C GMST stabilization, the median GMSL is projected to rise 48 cm (90% probability of 28–82 cm), 56 cm (28–96 cm), and 58 cm (37–93 cm), respectively.

The Paris Accords tries to hold global average temperatures “under +2.0C” to avoid catastrophic climate change. At the low end of the target scale (+1.5C) there won’t be two many “casualties,” meaning that at that projected sea level rise of 48 cm most real estate along coasts will be spared. Quoting more from the abstract of the study:

By 2150, relative to the 2.0 °C scenario and based on median sea level projections, GMST stabilization of 1.5 °C spares the inundation of lands currently home to about 5 million people, including 60 000 individuals currently residing in Small Island Developing States.

(Extreme sea levels (ESLs) are defined as the combined height of the astronomical tide and storm surge (i.e. the storm tide) and mean sea level. )

At the conclusion of the paper: “Only considering changes to the mean local sea level, we find that, under median projections, lands currently home to 5 million people will be spared from being permanently submerged by local mean sea levels by 2150 under a 1.5 °C GMST stabilization compared to local mean sea levels under the 2.0 °C case. This includes lands in SIDS currently home to 60 000 people. The effects of GMST stabilization on ESLs varies greatly by region and by historical return period (e.g. the 10 year versus the 100 year ESL event, etc). Globally, for the historical 100 year ESL event, we find that by 2100, the Eastern and Gulf coasts of the US and Europe could experience substantial benefits from a 1.5 °C GMST stabilization relative to a 2.0 °C GMST stabilization, with ESL frequency amplification being reduced by about half. However, while fractional reductions may appear substantial in some cases, small absolute differences may warrant similar coastal flood risk management responses. For instance, for New York City, we estimate the expected number of historical 100 year ESL events per year between a 2.0 °C to a 1.5 °C GMST stabilization is only two times and one time per year, respectively.

Darker colors = substantial benefits due to reduced freq of extreme local sea level events in a 1.5 °C world vs. 2.0 °C world. Fig 3 Rasmussen et al. 2018:

Check out these maps: huge swaths of coastline looking at a “100-year” flood every 5 years by mid-century (2050)!

Also, today I see that Dr. Michael Mann and his group of researchers have come out with a Paris Accord guide:


From this article: (GMST stands for global model simulated temperatures):

“Crucially, in order for the temperature targets in the Paris Agreement to be as meaningful as possible, the amount of mitigation required to cap GMST needs to be linked to the impacts expected at that level of warming. It is here that ambiguity surrounding the definition of GMST is most problematic.”
I applaud the efforts of climatologists to both refine their forecasts and take any ambiguity away from wording in association with projections. What Dr. Mann is trying to do is clarify what is meant, for example, by “preindustrial conditions”  so that researches from the first article presented here can do a better job with global forecasts. In an extra step Dr. Mann has been open to taking any questions from audiences across the country. On March 20th here is where he will be:
Michael Mann, Distinguished Professor of Atmospheric Science at Pennsylvania State University, will discuss “The Dangers of Climate Change Denial” beginning at 6:30 p.m. Tuesday, March 20, in the Student Life Center Board of Trust Room. The talk is free and open to the public.
My new motto is “Refine, refine, refine those forecasts so there is no more need for brown energy refining.” 😉
So far March 2018 has seen very few reports of those ETs or Extreme Temps. We did get one big report for today, 3/19/18:

Today is the warmest March day ever recorded in Galveston, TX. Records go all the way back to 1874–when Galveston was the biggest city in Texas.

The Climate Guy

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