Warming Is Unequivocal - Four Revolutions in the Earth Sciences - page 235

or dread, take your pick. Such a wide range is next to useless for anyone trying to
decide how seriously to take global warming.
In2003,modelersatMIThadprojectedthatby2100,globaltemperatureswould
rise by 2.4°C, near the lower end of the range that AR4 would report. By 2009, the
MIT modelers had raised the projected temperature rise to 5.1°C.
The “Summary for Policymakers” from the IPCC Fifth Assessment appeared as
this topic was in the final stages of preparation. 13 As expected, AR5 offered an
even stronger confirmation of anthropogenic global warming and even more dire
predictions of its future consequences. Since the pattern has been for each suc-
cessive IPCC report to come to firmer conclusions than the one before, we would
be wise to assume that AR5 also understates the evidence and the danger to hu-
manity. The report concludes that it is now even more certain—greater than 95
percent—that humans are the dominant cause of observed global warming. Nat-
ural variations and the Sun have contributed less than 0.1°C to the warming since
1950. Validating the hockey stick chart, the previous three decades were likely
the warmest in the last 1,400 years. As for future warming, the median estimate
is 4°C (7.2°F). Sea level is rising faster than at any time in the last 2,000 years
and by 2100 could rise by more than one meter. Greenland is more vulnerable to
melting than previously thought; Arctic sea ice will disappear before midcentury.
Finally and most ominously, whatever amount of global warming has occurred by
2100 will be “irreversible for centuries to millennia.” We are putting not merely
our grandchildren at risk but also their grandchildren. One cannot read the AR5
report without recalling the words of Elizabeth Kolbert in her Field Notes from a
Catastrophe : “It may seem impossible to imagine that a technologically advanced
society could choose, in essence, to destroy itself, but that is what we are now in
the process of doing.” 14
How We Know We Are Right
The media pay little attention to plate tectonics and meteorite impact. If they hap-
pen to mention the age of the Earth, it is often in the context of young-Earth cre-
ationism. In contrast, hardly a day goes by without a media report on global warm-
ing. The stories tend to be of two types: one describes the increasing scientific
evidencethathumansarecausingdangerousglobalwarming,whichisbeingmani-
fested in various kinds of extreme weather. The other describes the rejection of
global warming by roughly half the public and, in the United States, a majority of
Republicanpoliticians.FormostelectedrepresentativesoftheRight,globalwarm-
ing has indeed become anathema. In the 2012 U.S. campaign for president, every