Humanity’s Choice (via M.I.T.): Inaction (“No Policy”) eliminates most of the uncertainty about whether or not future warming will be catastrophic. Aggressive emissions reductions dramatically improves humanity’s chances.
In this post, I will summarize what the recent scientific literature says are the key impacts we face in the coming decades if we stay anywhere near our current emissions path. These include:
- Staggeringly high temperature rise, especially over land — some 10°F over much of the United States
- Permanent Dust Bowl conditions over the U.S. Southwest and many other heavily populated regions around the globe
- Sea level rise of around 1 foot by 2050, then 4 to 6 feet (or more) by 2100, rising some 6 to 12 inches (or more) each decade thereafter
- Massive species loss on land and sea — perhaps 50% or more of all biodiversity
- Unexpected impacts — the fearsome “unknown unknowns”
- Much more extreme weather
- Food insecurity — the increasingly difficult task of feeding 7 billion, then 8 billion, and then 9 billion people in a world with an ever-worsening climate.
- Myriad direct health impacts
Remember, these will all be happening simultaneously and getting worse decade after decade. Equally tragic, a 2009 NOAA-led study found the worst impacts would be “largely irreversible for 1000 years.”
The single biggest failure of messaging by climate scientists (until very recently) has been the failure to explain to the public, opinion makers, and the media that business-as-usual warming results in simultaneous, ever-worsening impacts that, individually, are each beyond catastrophic, but combined are unimaginablly horrific. For these impacts, terms like “global warming” and “climate change” are essentially euphemisms. That is why I have prefered the term “Hell and High Water.”
By virtue of their success in promoting doubt and inaction, the climate science deniers and disinformers have, tragically and ironically, turned the worst-case scenario into business as usual.
Business-as-usual typically means continuing at recent growth rates of carbon dioxide emissions, which we now know would likely take us to atmospheric concentrations of CO2 greater than 850 ppm if not above 1000 ppm (see U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories are being realised”). We are at about 8.5 billion metric tons of carbon a year (31 billions metric tons of CO2) and, until the recent global economic recession, were rising about 3% per year.
What is less well understood is that even a very strong mitigation effort that kept carbon emissions this century to 11 billion tons a year on average would still probably take us to 1000 ppm (A1FI scenario) — a little noted conclusion of the 2007 Intergovernmental Panel on Climate Change (IPCC) report (see “Nature publishes my climate analysis and solution“).
Until recently, the scientific community has spent little time modeling the impacts of a tripling (~830 ppm) or quadrupling (~1100 ppm) carbon dioxide concentrations from preindustrial levels. In part, I think, that’s because they never believed humanity would be so stupid as to ignore the warnings and simply continue on its self-destructive path. In part, they lowballed the difficult-to-model amplifying feedbacks in the carbon cycle.
So I pieced together those impacts from available studies and from discussions with leading climate scientists for my 2006 book, Hell and High Water. But now as climate scientists have sobered up to their painful role as modern-day Cassandra’s, the scientific literature on what we face is much richer.
In a AAAS presentation last year, the late William R. Freudenburg of UC Santa Barbara discussed his research on “the Asymmetry of Scientific Challenge“: New scientific findings since the 2007 IPCC report are found to be more than twenty times as likely to indicate that global climate disruption is “worse than previously expected,” rather than “not as bad as previously expected.”
This post will review the latest findings. It will be a cornerstone of the Climate Progress archive I promised. Please add links to more studies in the comments.