ABSTRACT
Earth’s
climate future is in the hands of humanity. If emissions of greenhouse gases
remain unabated, Earth’s climate will return to the climate of the Late Eocene,
35 million years ago, when sea level was 73 meters (240 feet) higher than
today. Should that occur, many coastal cities around the world would be
inundated. Moreover the Global Warming of this unabated Reference case will be
comparable to the Global Warming from the Last Glacial Maximum 21,000 years ago
to the beginning of the Holocene interglacial climate 11,000 years ago.
However, this human-caused Global Warming would occur 50 times faster than that
caused by nature. Alternatively, humanity can mitigate greenhouse-gas emissions
to keep Global Warming below the 2°C maximum adopted by the United Nations
Framework Convention on Climate Change “to prevent dangerous anthropogenic
interference with the climate system”. This mitigation can either be done
rapidly, as in the “80/50” Plan to reduce greenhouse-gas emissions 80% by 2050,
or much more slowly, from 2020 to 2100, as in the Fair Plan to Safeguard Earth’s
Climate. The Fair Plan is a compromise between doing nothing, as in the
Reference case, and rapidly reducing greenhouse-gas emissions, as in the 80/50
Plan. Regardless of the Plan chosen to reduce greenhouse-gas emissions to keep
Global Warming below the UNFCCC limit of 2°C (3.6°F), it should not be
tantamount to our saying to one of our planetary spacecraft, Bon Voyage, call us when you get to your
planetary destination. Rather, as with our spacecraft, the chosen
climate-change policy should be monitored throughout the 21st century and Midcourse Corrections made thereto as needed to keep our “Climate
Spacecraft” on track to achieve its “Climate Target”.