File:RCP-projections-damage to US economy.jpg

Representative Concentration Pathway

• https://en.m.wikipedia.org/wiki/Representative_Concentration_Pathway

2018 / U.S. National Climate Assessment / U.S. Carbon Assessment

Projections of possible 'economic impact' on the US economy are represented in graphic format, as with the attached slide.

Robert Rohde's points out in a Tweet thread (here https://mobile.twitter.com/RARohde/status/1067375439415582721) that recent climate assessment projections were reported by the US media without specifying the range of possible outcomes in sufficient detail.

As Robert makes his case in his series of Tweets:

In the reporting on the National Climate Assessment, some articles (such as this by @CNN) have focused on the far end of the risk distribution and say that "the economy could lose ... more than 10% of its GDP" by 2100.

I'd like to push back a little.

In Chapter 2, (link: https://nca2018.globalchange.gov/chapter/2/), a 90% likelihood range of ~4.5 to ~9.8 F is indicated for RCP8.5, with a most likely value of about 7 F.

(review the history of RCP science and statistics)

He then refers to Ch. 29 of the report and the following:

...the high estimate comes from RCP8.5 (red dots), an emissions scenario which assumes extremely aggressive growth of CO2 emissions.

While possible, I certainly wouldn't regard RCP8.5 as a likely future.

More importantly, a close examination of the GDP figure will notice that there are many red dots associated with RCP8.5. The distribution of red dots reflects an uncertainty in the climate's response to this much CO2, and covers a very large range from 4 F to 14 F at 2100.

This presented range is huge. In fact, it is substantially larger than the response range presented elsewhere in the same report. In Chapter 2, (link: https://nca2018.globalchange.gov/chapter/2/) nca2018.globalchange.gov/chapter/2/, a 90% likelihood range of ~4.5 to ~9.8 F is indicated for RCP8.5, with a most likely value of about 7 F.

One can and should make the case, as Robert does in his widely shared Twitter thread, that current projections of climate change impacts should be seen as *a range* of possibilities and probabilities. What Robert neglects to include in his social media remarks is the inclusion of the dynamic forces at work with global climate, and the human factor.

We, as nations, communities, businesses, religions, individuals will be making decision how we consider and react to the facts of human-caused changes in our environment. If we dismiss climate reports and science, as a large swath of political voices generally from conservative business interests and tradition religious points of view are doing, and refuse to act to protect the environment essential for life, then the projections will shift, and not in a good way.

The science over time demonstrates, with a powerful case and degree of certainty, the reality of climate change/global warming. The evidence is convincing in its facts and details.

What is up for debate now is how fast the impacts will be felt on human communities, and earth systems that impact life, economics and ecology.

A "precautionary principle" and protection of "The Commons" must be kept in mind as we go forward -- together.

The future well-being of each and every one of us -- and the health of life on planet Earth -- call for new vision, wisdom and action.

Projections -- RCPs -- are signs of things to come. How we choose to act will influence which projections come to pass.

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