Does “business as usual” lead to an additional 56-108 extremely hot days (over 95°F) per year by 2100? Extreme weather & sea level rise predictions by the “Risky Business” report [Fact Checking]

August 18, 2014 12:53 pm0 comments

The following graphics and block quotes are from a recent report on the economic risks of climate change by the Risky Business Project. The video toward the end of the post is from the Risky Business website. For more about the report and its authors, and the heavyweights in the financial world backing the project, check out my note at the bottom.

 

PREDICTED INCREASE IN EXTREMELY HOT DAYS

 

Increase in annual number of extremely hot days predicted by the Risky Business Report. Source: Risky Business website.

From the report:

The average resident [from Texas, Oklahoma, and Kansas] experienced 35 days per year over 95°F in the past 30 years. This number will likely increase by 26 to 56 additional extremely hot days by mid-century and 56 to 108 days per year by the end of the century—for a total of between three and four months of additional extreme hot days per year.

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Dr. John Nielsen-GammonDr. John Nielsen-Gammon: The summary of projections for the Southern Great Plains is based on what the Risky Business report calls the “business as usual” path but what is in fact the representative concentration pathway (RCP) 8.5, the highest of the pathways used in the IPCC physical climate modeling. The IPCC does not characterize this as “business as usual” and it was selected because it was near the high end (90th percentile) of various non-mitigation scenarios, all of which could be considered to be business as usual scenarios.  I’ll write more about this in a separate post. [Editor’s update: See separate post, ‘What is Business as Usual?‘ published on 8/20/2014.]

SRES and RCP scenarios

Projected radiative forcing (W ^m-2) over the 21st century from the SRES and RCP scenarios. Draft Figure 1-4 from IPCC AR5 WGII, Chapter 1.

The range of impact numbers reported as “likely” ranges encapsulate the central 2/3 of the model runs for RCP 8.5.  Thus, “likely” doesn’t mean “likely” in an absolute sense, it means “likely” if (a) business as usual turns out to produce even greater amounts of CO2 than most business as usual scenarios expect, and (b) the model spread accurately represents the uncertainty given a particular evolution of concentrations.  If one were to take all uncertainties into account, the low end of the likely range would be much lower than what is reported here, and the high end of the likely range might be lower too.

 

Dr. Andrew DesslerDr. Andrew Dessler: I disagree with John here. If you look at the standard RCP scenarios (2.6, 4.5, 6.0, 8.5), all of them assume some mitigation in their construction except the 8.5 scenario. Thus, I think it is reasonable to call the 8.5 scenario a “business as usual” scenario.

 

Dr. John Nielsen-GammonDr. John Nielsen-Gammon: I agree that RCP 8.5 can correspond to a business as usual scenario, but not “the” business as usual scenario or even a central business as usual scenario.  More to come.

 

Dr. Bart VerheggenDr. Bart Verheggen: Detlef van Vuuren, who has been intimately involved with the RCP scenarios, described it as follows: Plausible upper limit: RCP 8.5; Business as Usual: Between RCP 6.5 and RCP 8.5.

 

Dr. Scott DenningDr. Scott Denning: Of course there’s not even that much difference between the climates of RCP6 and RCP8.5 until late in the 21st Century.  There’s been considerable debate about whether the world has enough coal to actually reach RCP8.5 in the coming centuries. Another way of looking at that is whether emissions will be cut to mitigate warming or whether they will be cut because our descendants run out of coal. From the “Risky Business” point of view, either way it’s important to roll out new technologies ASAP.

 


 

PREDICTED SEA LEVEL RISE ON THE TEXAS COAST

 

Houston Ship Channel from Roy.Luck via Flickr

Houston Ship Channel from Roy.Luck via Flickr

 

From the report:

In Texas, […] where about one-third of the state’s GDP is generated in coastal counties, sea levels will likely rise by 1.5 to 2 feet by mid-century and 3.2 to 4.9 feet by the end of the century, with a 1-in-100 chance of a 7 foot rise.

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Dr. John Nielsen-GammonDr. John Nielsen-Gammon: [T]he local projections of sea level rise assume that any local processes that affected sea level over the period of record of tide gauge data will continue apace.  As coastal communities have become aware of the problems associated with groundwater depletion and coastal subsidence, the rate of local sea level rise has slowed, at Galveston at least (Paine et al., 2012, GCAGS Journal 1:13-26), so the likely sea level rise is even less than the corrections above would imply.

 


 

“EXTREME BECOMES THE NORM” VIDEO

 

People organize human society around what we think of as “normal weather.” We organize our agriculture, our cities, our transportation, our human habitat — pretty much everything around normal weather. And [in years of] normal weather, 1/3 (one in three years) are a little bit colder than usual, 1/3 are normal, and 1/3 are a little bit warmer than usual. In those circumstances, human society works perfectly. It is out on the edges that we get into real trouble, and in the edges we get incredible heat waves that kill our cities, floods that inundate our cities, and droughts that destroy agriculture.

So let’s look at the real world and see what climate change is doing to our weather patterns. As you can see, this data from NASA shows that for many years (this is starting in the 1950s) actual weather patterns matched the normal, but as time went by and climate change begins to have an impact, the whole range moves to the right. So today, only 1 in 12 winters is colder than normal. Only 2 in 12 years are normal. And 8 in 12 years are now hotter than normal. 1 in 12 [years has] extreme temperature that we have never seen.

So we are moving into an era where the extreme becomes the norm. And where people have to live with unbearably hot temperatures, extreme floods, and extreme droughts. It is Australia at 106 degrees (the average temp across the continent). It is Colorado, where they get an entire year’s rain in 3 days. This is what extremes mean, and unfortunately, climate change is driving weather in the extreme zones.

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Dr. Sean RobinsonDr. Sean Robinson:  I think [the video] does a great job of delivering its message effectively and succinctly. The data visualization of the dynamically shifting temperature distribution shown from 0:52 — 1:05 is not something I’ve seen before, but it gets close to the core of what the phrase “climate change” really means, much more so than our typical presentation of a trendline through noisy time-series data. Ultimately, the message and motive of the Risky Business project are not scientific in nature (it is perhaps more important than that!) so it would not be fair to critique this video as a science presentation. But, this is CCNF, so critique I shall! 

I have three scientific critiques:

1.) My first critique is the implicit claim that temperature distributions starting in the 1950s represent “normal” weather conditions, while today’s weather is abnormally warm. Yes, in many places on Earth, today’s temperature distribution is significantly shifted (and somewhat stretched) from what it was in the 1950s, but who is to say at which point in time we declare this constantly changing distribution “normal”? From a climatology point of view, it’s an arbitrary choice. As Mr. Harvey emphasizes, society operates with some assumptions about and dependencies on normal weather, but it is precisely these social conventions which provide the definition of “normal”. Social conventions can change — although in this case, those conventions are codified in a highly capitalized energy industry, civil infrastructure, and population distributions, so change requires more than just a simple choice to do so. Now, could one say that the few decades in the middle of the twentieth century during which temperatures were relatively stable provide a de facto normal due to certain important sectors of the US economy having taken their modern form then? Perhaps, but such a question is beyond physical science, so I can’t comment.

2.) My second critique has to do with the presented data itself and a lack of precise language that would be required if this were a scientific presentation. We are told the data are “from NASA”, but what is actually being plotted? It’s temperatures, but is it global averages? US averages? Reading between the lines, I believe this is US-only data, but I can’t be sure. Is it a distribution of annual averages? Daily averages? Or something else? The plot label says that each frame in the animation represents 10 years of data, and at a few points Mr. Harvey explicitly says that the plot shows the distribution of cold “years” versus warm “years”. That would imply that each 10-year snapshot is a histogram of 10 points. The histogram has a certain amount of raggedness to it, which is expected for a non-infinite data set. The noise in the central peak looks to be about 10% of the full height, meaning that each of these largest bins has around 100 data points. Judging from the point-to-point spacing and overall shape, I can then estimate that the whole histogram is somewhere around 4000 data points. That’s pretty close 3652, the number of days in a decade, so I’m fairly confident that the data being plotted is daily temperatures, not yearly averages. I still don’t know if it’s daily averages, daily highs, or something else, but the difference between the different measures one might choose doesn’t matter much for a discussion of climate *change*. However, when Mr. Harvey points to the data and says that it shows how some years are hotter or colder than normal, that’s not quite right. It shows that the number of hot days or cold days per decade is changing. These two things are of course related, but what he shows is technically different from what he tells.

3.) My final critique is the use of the phrase “extreme weather”. In one of the very first posts on CCNF, John Nielsen-Gammon argued persuasively that we should distinguish “statistically extreme weather” — like a hot day in December — from “extremely dangerous weather” like tornadoes. Clearly, the data plotted in this video is pertinent to statistically extreme weather but does not tell us about the number of wildfires or the severity of droughts. Yet, the language and imagery used in the video emphasizes the dangers of extreme weather events like floods. We are told “this is what ‘extremes’ mean” after being shown an image of a wildfire and a washed out roadway only about 20 seconds after being told that the data show that “the extreme becomes the norm”. The data do indeed show that the statistical extreme is slowly becoming the norm, but connecting that to a future where extremely dangerous weather becomes the norm requires an additional argument which is not nearly as well supported.

End.

About the “Risky Business: The Economic Risks of Climate Change in the United States” report: This report was released in June 2014 and is the product of the Risky Business Project, a fairly new initiative co-chaired by Hank Paulson–former CEO of Goldman Sachs and treasury secretary under President George W. Bush; Michael Bloomberg–former New York City mayor, and Tom Steyer–a hedge-fund billionaire turned climate activist.  The stated aim of the project is to “quantif[y] and publiciz[e]the economic risks of climate change.” The report’s key assessments and findings are being communicated through the Risky Business website and through various op-eds by the project’s high profile co-chairs (see Hank Paulson’s op-ed in the New York Times). According to the report, the project tasked the Rhodium Group, a finance and economic research firm, to conduct “an independent assessment on the economic risks posed by a changing climate in the U.S.” The team of researchers assembled by the Rhodium Group to actually conduct the assessments and author the report included climate scientist Dr. Robert Kopp of Rutgers University, economist Dr. Solomon Hsiang of the University of California, Berkeley, and analysts from Risk Management Solutions, which the Risky Business website describes as “the world’s largest catastrophe-modeling company for insurance, reinsurance, and investment-management companies around the world.”


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