The World My Grandchildren Will Inherit

I went to a presentation at the University of Washington by Professor Raftery of the Statistics and Sociology Departments of a recent paper of his and colleagues (Alec Zimmer, Dargan M.W. Frierson, Richard Startz, and Peiran Liu) in the Journal Nature, entitled Less than 2 °C warming by 2100 unlikely (link behind a paywall).



Their paper is a response to a need to provide a statistical forecast for global temperatures.  What the IPCC has previously provided are "scenarios" based on "expert" thinking.  Raftery has previously developed statistical methods for estimating world-wide migration patterns that has been adopted by the United Nations.  At the presentation he presented a statistical model for forecasting global temperatures.

Their result is a 90% interval forecast of 2 to 4.9 degrees Centigrade with a median of 3.2 degrees.
Their backtesting strongly supported the median.  He also said "that the data suggested that future improvements in carbon efficiency will continue to be incremental rather than abrupt, but they will be driven in large part by technological advances."

The confidence interval from 2 to 4.9 degrees does mean that it remains likely that it could be as much as 4.9 degrees which would be catastrophic, so we can't be over-optimistic. However the analysis convinced me that my grandchildren will very possibly have a 3.2 degree future to look forward to. 



What does three degrees mean?  We have some idea from the book Six Degrees by Mark Lynas.

For 3 degrees, Lynas introduces us to the Pliocene, 3 million years ago, that mirrors what we should expect.  Both the Arctic and the Antarctic were warm enough to support forests.  There were no glaciers, sea levels 80 feet higher than now.  The likely cause, CO2, 360 to 400 ppm at that time.  The current concentration in our atmosphere right now is 409 ppm.

The Pliocene probably had a permanent El Nino.  We're in an El Nino right now.  It's 50-55 degrees Fahrenheit day and night here in Seattle in the middle of January.  Of course, the rest of the country is undergoing snow blizzards but that's due to a different cause, jet stream diversion because of the warming Arctic bringing cold weather down to the U.S. Northeast.  But the El Nino means a warm Pacific Northwest and California floods and mudslides.

A permanent El Nino would have dramatic effects elsewhere on the planet.  The Indian Monsoon will fail which will be catastrophic for their agriculture.  The Amazon rain forest will dry up.  The carbon cycle between vegetation/soil and the atmosphere will reverse, pouring carbon dioxide into the atmosphere aggravating global warming.  Australia will dry up and burn and the population will migrate to a better climate in the North.

The disappearance of glaciers in the mountains  above Pakistan will mean serious water shortages there.

The Sahara will jump the Mediterranean into Europe.  There will be alternating floods and droughts in the rest of Europe.

The Colorado River will diminish creating water shortages in Arizona and California.

There'll be increasing diseases like Zika, Chikungunya, as well as a newly discovered Zika-like virus, the Rift Valley Fever.

Most of the CO2 we are generating with our cars and electricity-generating plants is going into the oceans.  This is causing ocean acidification, and by 2100 carbonate sea life will begin to disappear, clams, oysters, shrimp.  Corals will bleach and die.

And finally, sea levels.  It will take a century or so to achieve the 80 feet that the Pliocene saw, but it will likely be at least several feet by 2100 and possibly quite a bit more, putting many coastal cities under water (goodbye Miami and New Orleans), and considerably adding to the destruction caused by hurricanes and typhoons.






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