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 regions around the globe that are heavily populated and/or heavily farmed.
- Sea level rise of some 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 increasing difficulty 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 preferred 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”). Annual emissions now exceed 10 billion metric tons of carbon (~37 billions metric tons of CO2). Emissions have been rising about 3% per year for the past decade.
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 self-destructive as to ignore their science-based warnings and simply continue on its unsustainable 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 the scientific literature on what we face is much richer — as climate scientists have sobered up to their painful role as modern-day Cassandra’s (see Lonnie Thompson on why climatologists are speaking out: “Virtually all of us are now convinced that global warming poses a clear and present danger to civilization”).